4167 lines
221 KiB
Java
4167 lines
221 KiB
Java
/*
|
|
* Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
|
|
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
|
|
*
|
|
* This code is free software; you can redistribute it and/or modify it
|
|
* under the terms of the GNU General Public License version 2 only, as
|
|
* published by the Free Software Foundation. Oracle designates this
|
|
* particular file as subject to the "Classpath" exception as provided
|
|
* by Oracle in the LICENSE file that accompanied this code.
|
|
*
|
|
* This code is distributed in the hope that it will be useful, but WITHOUT
|
|
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
* version 2 for more details (a copy is included in the LICENSE file that
|
|
* accompanied this code).
|
|
*
|
|
* You should have received a copy of the GNU General Public License version
|
|
* 2 along with this work; if not, write to the Free Software Foundation,
|
|
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
*
|
|
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
|
|
* or visit www.oracle.com if you need additional information or have any
|
|
* questions.
|
|
*/
|
|
|
|
package java.lang.invoke;
|
|
|
|
import java.lang.reflect.*;
|
|
import java.util.*;
|
|
|
|
import sun.invoke.util.ValueConversions;
|
|
import sun.invoke.util.VerifyAccess;
|
|
import sun.invoke.util.Wrapper;
|
|
import sun.reflect.CallerSensitive;
|
|
import sun.reflect.Reflection;
|
|
import sun.reflect.misc.ReflectUtil;
|
|
import sun.security.util.SecurityConstants;
|
|
import java.lang.invoke.LambdaForm.BasicType;
|
|
|
|
import static java.lang.invoke.MethodHandleStatics.*;
|
|
import static java.lang.invoke.MethodHandleImpl.Intrinsic;
|
|
import static java.lang.invoke.MethodHandleNatives.Constants.*;
|
|
import java.util.concurrent.ConcurrentHashMap;
|
|
import java.util.stream.Collectors;
|
|
import java.util.stream.Stream;
|
|
|
|
/**
|
|
* This class consists exclusively of static methods that operate on or return
|
|
* method handles. They fall into several categories:
|
|
* <ul>
|
|
* <li>Lookup methods which help create method handles for methods and fields.
|
|
* <li>Combinator methods, which combine or transform pre-existing method handles into new ones.
|
|
* <li>Other factory methods to create method handles that emulate other common JVM operations or control flow patterns.
|
|
* </ul>
|
|
*
|
|
* @author John Rose, JSR 292 EG
|
|
* @since 1.7
|
|
*/
|
|
public class MethodHandles {
|
|
|
|
private MethodHandles() { } // do not instantiate
|
|
|
|
private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();
|
|
|
|
// See IMPL_LOOKUP below.
|
|
|
|
//// Method handle creation from ordinary methods.
|
|
|
|
/**
|
|
* Returns a {@link Lookup lookup object} with
|
|
* full capabilities to emulate all supported bytecode behaviors of the caller.
|
|
* These capabilities include <a href="MethodHandles.Lookup.html#privacc">private access</a> to the caller.
|
|
* Factory methods on the lookup object can create
|
|
* <a href="MethodHandleInfo.html#directmh">direct method handles</a>
|
|
* for any member that the caller has access to via bytecodes,
|
|
* including protected and private fields and methods.
|
|
* This lookup object is a <em>capability</em> which may be delegated to trusted agents.
|
|
* Do not store it in place where untrusted code can access it.
|
|
* <p>
|
|
* This method is caller sensitive, which means that it may return different
|
|
* values to different callers.
|
|
* <p>
|
|
* For any given caller class {@code C}, the lookup object returned by this call
|
|
* has equivalent capabilities to any lookup object
|
|
* supplied by the JVM to the bootstrap method of an
|
|
* <a href="package-summary.html#indyinsn">invokedynamic instruction</a>
|
|
* executing in the same caller class {@code C}.
|
|
* @return a lookup object for the caller of this method, with private access
|
|
*/
|
|
@CallerSensitive
|
|
public static Lookup lookup() {
|
|
return new Lookup(Reflection.getCallerClass());
|
|
}
|
|
|
|
/**
|
|
* Returns a {@link Lookup lookup object} which is trusted minimally.
|
|
* It can only be used to create method handles to
|
|
* publicly accessible fields and methods.
|
|
* <p>
|
|
* As a matter of pure convention, the {@linkplain Lookup#lookupClass lookup class}
|
|
* of this lookup object will be {@link java.lang.Object}.
|
|
*
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* The lookup class can be changed to any other class {@code C} using an expression of the form
|
|
* {@link Lookup#in publicLookup().in(C.class)}.
|
|
* Since all classes have equal access to public names,
|
|
* such a change would confer no new access rights.
|
|
* A public lookup object is always subject to
|
|
* <a href="MethodHandles.Lookup.html#secmgr">security manager checks</a>.
|
|
* Also, it cannot access
|
|
* <a href="MethodHandles.Lookup.html#callsens">caller sensitive methods</a>.
|
|
* @return a lookup object which is trusted minimally
|
|
*/
|
|
public static Lookup publicLookup() {
|
|
return Lookup.PUBLIC_LOOKUP;
|
|
}
|
|
|
|
/**
|
|
* Performs an unchecked "crack" of a
|
|
* <a href="MethodHandleInfo.html#directmh">direct method handle</a>.
|
|
* The result is as if the user had obtained a lookup object capable enough
|
|
* to crack the target method handle, called
|
|
* {@link java.lang.invoke.MethodHandles.Lookup#revealDirect Lookup.revealDirect}
|
|
* on the target to obtain its symbolic reference, and then called
|
|
* {@link java.lang.invoke.MethodHandleInfo#reflectAs MethodHandleInfo.reflectAs}
|
|
* to resolve the symbolic reference to a member.
|
|
* <p>
|
|
* If there is a security manager, its {@code checkPermission} method
|
|
* is called with a {@code ReflectPermission("suppressAccessChecks")} permission.
|
|
* @param <T> the desired type of the result, either {@link Member} or a subtype
|
|
* @param target a direct method handle to crack into symbolic reference components
|
|
* @param expected a class object representing the desired result type {@code T}
|
|
* @return a reference to the method, constructor, or field object
|
|
* @exception SecurityException if the caller is not privileged to call {@code setAccessible}
|
|
* @exception NullPointerException if either argument is {@code null}
|
|
* @exception IllegalArgumentException if the target is not a direct method handle
|
|
* @exception ClassCastException if the member is not of the expected type
|
|
* @since 1.8
|
|
*/
|
|
public static <T extends Member> T
|
|
reflectAs(Class<T> expected, MethodHandle target) {
|
|
SecurityManager smgr = System.getSecurityManager();
|
|
if (smgr != null) smgr.checkPermission(ACCESS_PERMISSION);
|
|
Lookup lookup = Lookup.IMPL_LOOKUP; // use maximally privileged lookup
|
|
return lookup.revealDirect(target).reflectAs(expected, lookup);
|
|
}
|
|
// Copied from AccessibleObject, as used by Method.setAccessible, etc.:
|
|
private static final java.security.Permission ACCESS_PERMISSION =
|
|
new ReflectPermission("suppressAccessChecks");
|
|
|
|
/**
|
|
* A <em>lookup object</em> is a factory for creating method handles,
|
|
* when the creation requires access checking.
|
|
* Method handles do not perform
|
|
* access checks when they are called, but rather when they are created.
|
|
* Therefore, method handle access
|
|
* restrictions must be enforced when a method handle is created.
|
|
* The caller class against which those restrictions are enforced
|
|
* is known as the {@linkplain #lookupClass lookup class}.
|
|
* <p>
|
|
* A lookup class which needs to create method handles will call
|
|
* {@link MethodHandles#lookup MethodHandles.lookup} to create a factory for itself.
|
|
* When the {@code Lookup} factory object is created, the identity of the lookup class is
|
|
* determined, and securely stored in the {@code Lookup} object.
|
|
* The lookup class (or its delegates) may then use factory methods
|
|
* on the {@code Lookup} object to create method handles for access-checked members.
|
|
* This includes all methods, constructors, and fields which are allowed to the lookup class,
|
|
* even private ones.
|
|
*
|
|
* <h1><a name="lookups"></a>Lookup Factory Methods</h1>
|
|
* The factory methods on a {@code Lookup} object correspond to all major
|
|
* use cases for methods, constructors, and fields.
|
|
* Each method handle created by a factory method is the functional
|
|
* equivalent of a particular <em>bytecode behavior</em>.
|
|
* (Bytecode behaviors are described in section 5.4.3.5 of the Java Virtual Machine Specification.)
|
|
* Here is a summary of the correspondence between these factory methods and
|
|
* the behavior of the resulting method handles:
|
|
* <table border=1 cellpadding=5 summary="lookup method behaviors">
|
|
* <tr>
|
|
* <th><a name="equiv"></a>lookup expression</th>
|
|
* <th>member</th>
|
|
* <th>bytecode behavior</th>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findGetter lookup.findGetter(C.class,"f",FT.class)}</td>
|
|
* <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findStaticGetter lookup.findStaticGetter(C.class,"f",FT.class)}</td>
|
|
* <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findSetter lookup.findSetter(C.class,"f",FT.class)}</td>
|
|
* <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findStaticSetter lookup.findStaticSetter(C.class,"f",FT.class)}</td>
|
|
* <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findVirtual lookup.findVirtual(C.class,"m",MT)}</td>
|
|
* <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findStatic lookup.findStatic(C.class,"m",MT)}</td>
|
|
* <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findSpecial lookup.findSpecial(C.class,"m",MT,this.class)}</td>
|
|
* <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findConstructor lookup.findConstructor(C.class,MT)}</td>
|
|
* <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectGetter lookup.unreflectGetter(aField)}</td>
|
|
* <td>({@code static})?<br>{@code FT f;}</td><td>{@code (FT) aField.get(thisOrNull);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectSetter lookup.unreflectSetter(aField)}</td>
|
|
* <td>({@code static})?<br>{@code FT f;}</td><td>{@code aField.set(thisOrNull, arg);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflect lookup.unreflect(aMethod)}</td>
|
|
* <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflectConstructor lookup.unreflectConstructor(aConstructor)}</td>
|
|
* <td>{@code C(A*);}</td><td>{@code (C) aConstructor.newInstance(arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#unreflect lookup.unreflect(aMethod)}</td>
|
|
* <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>
|
|
* </tr>
|
|
* <tr>
|
|
* <td>{@link java.lang.invoke.MethodHandles.Lookup#findClass lookup.findClass("C")}</td>
|
|
* <td>{@code class C { ... }}</td><td>{@code C.class;}</td>
|
|
* </tr>
|
|
* </table>
|
|
*
|
|
* Here, the type {@code C} is the class or interface being searched for a member,
|
|
* documented as a parameter named {@code refc} in the lookup methods.
|
|
* The method type {@code MT} is composed from the return type {@code T}
|
|
* and the sequence of argument types {@code A*}.
|
|
* The constructor also has a sequence of argument types {@code A*} and
|
|
* is deemed to return the newly-created object of type {@code C}.
|
|
* Both {@code MT} and the field type {@code FT} are documented as a parameter named {@code type}.
|
|
* The formal parameter {@code this} stands for the self-reference of type {@code C};
|
|
* if it is present, it is always the leading argument to the method handle invocation.
|
|
* (In the case of some {@code protected} members, {@code this} may be
|
|
* restricted in type to the lookup class; see below.)
|
|
* The name {@code arg} stands for all the other method handle arguments.
|
|
* In the code examples for the Core Reflection API, the name {@code thisOrNull}
|
|
* stands for a null reference if the accessed method or field is static,
|
|
* and {@code this} otherwise.
|
|
* The names {@code aMethod}, {@code aField}, and {@code aConstructor} stand
|
|
* for reflective objects corresponding to the given members.
|
|
* <p>
|
|
* The bytecode behavior for a {@code findClass} operation is a load of a constant class,
|
|
* as if by {@code ldc CONSTANT_Class}.
|
|
* The behavior is represented, not as a method handle, but directly as a {@code Class} constant.
|
|
* <p>
|
|
* In cases where the given member is of variable arity (i.e., a method or constructor)
|
|
* the returned method handle will also be of {@linkplain MethodHandle#asVarargsCollector variable arity}.
|
|
* In all other cases, the returned method handle will be of fixed arity.
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* The equivalence between looked-up method handles and underlying
|
|
* class members and bytecode behaviors
|
|
* can break down in a few ways:
|
|
* <ul style="font-size:smaller;">
|
|
* <li>If {@code C} is not symbolically accessible from the lookup class's loader,
|
|
* the lookup can still succeed, even when there is no equivalent
|
|
* Java expression or bytecoded constant.
|
|
* <li>Likewise, if {@code T} or {@code MT}
|
|
* is not symbolically accessible from the lookup class's loader,
|
|
* the lookup can still succeed.
|
|
* For example, lookups for {@code MethodHandle.invokeExact} and
|
|
* {@code MethodHandle.invoke} will always succeed, regardless of requested type.
|
|
* <li>If there is a security manager installed, it can forbid the lookup
|
|
* on various grounds (<a href="MethodHandles.Lookup.html#secmgr">see below</a>).
|
|
* By contrast, the {@code ldc} instruction on a {@code CONSTANT_MethodHandle}
|
|
* constant is not subject to security manager checks.
|
|
* <li>If the looked-up method has a
|
|
* <a href="MethodHandle.html#maxarity">very large arity</a>,
|
|
* the method handle creation may fail, due to the method handle
|
|
* type having too many parameters.
|
|
* </ul>
|
|
*
|
|
* <h1><a name="access"></a>Access checking</h1>
|
|
* Access checks are applied in the factory methods of {@code Lookup},
|
|
* when a method handle is created.
|
|
* This is a key difference from the Core Reflection API, since
|
|
* {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
|
|
* performs access checking against every caller, on every call.
|
|
* <p>
|
|
* All access checks start from a {@code Lookup} object, which
|
|
* compares its recorded lookup class against all requests to
|
|
* create method handles.
|
|
* A single {@code Lookup} object can be used to create any number
|
|
* of access-checked method handles, all checked against a single
|
|
* lookup class.
|
|
* <p>
|
|
* A {@code Lookup} object can be shared with other trusted code,
|
|
* such as a metaobject protocol.
|
|
* A shared {@code Lookup} object delegates the capability
|
|
* to create method handles on private members of the lookup class.
|
|
* Even if privileged code uses the {@code Lookup} object,
|
|
* the access checking is confined to the privileges of the
|
|
* original lookup class.
|
|
* <p>
|
|
* A lookup can fail, because
|
|
* the containing class is not accessible to the lookup class, or
|
|
* because the desired class member is missing, or because the
|
|
* desired class member is not accessible to the lookup class, or
|
|
* because the lookup object is not trusted enough to access the member.
|
|
* In any of these cases, a {@code ReflectiveOperationException} will be
|
|
* thrown from the attempted lookup. The exact class will be one of
|
|
* the following:
|
|
* <ul>
|
|
* <li>NoSuchMethodException — if a method is requested but does not exist
|
|
* <li>NoSuchFieldException — if a field is requested but does not exist
|
|
* <li>IllegalAccessException — if the member exists but an access check fails
|
|
* </ul>
|
|
* <p>
|
|
* In general, the conditions under which a method handle may be
|
|
* looked up for a method {@code M} are no more restrictive than the conditions
|
|
* under which the lookup class could have compiled, verified, and resolved a call to {@code M}.
|
|
* Where the JVM would raise exceptions like {@code NoSuchMethodError},
|
|
* a method handle lookup will generally raise a corresponding
|
|
* checked exception, such as {@code NoSuchMethodException}.
|
|
* And the effect of invoking the method handle resulting from the lookup
|
|
* is <a href="MethodHandles.Lookup.html#equiv">exactly equivalent</a>
|
|
* to executing the compiled, verified, and resolved call to {@code M}.
|
|
* The same point is true of fields and constructors.
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* Access checks only apply to named and reflected methods,
|
|
* constructors, and fields.
|
|
* Other method handle creation methods, such as
|
|
* {@link MethodHandle#asType MethodHandle.asType},
|
|
* do not require any access checks, and are used
|
|
* independently of any {@code Lookup} object.
|
|
* <p>
|
|
* If the desired member is {@code protected}, the usual JVM rules apply,
|
|
* including the requirement that the lookup class must be either be in the
|
|
* same package as the desired member, or must inherit that member.
|
|
* (See the Java Virtual Machine Specification, sections 4.9.2, 5.4.3.5, and 6.4.)
|
|
* In addition, if the desired member is a non-static field or method
|
|
* in a different package, the resulting method handle may only be applied
|
|
* to objects of the lookup class or one of its subclasses.
|
|
* This requirement is enforced by narrowing the type of the leading
|
|
* {@code this} parameter from {@code C}
|
|
* (which will necessarily be a superclass of the lookup class)
|
|
* to the lookup class itself.
|
|
* <p>
|
|
* The JVM imposes a similar requirement on {@code invokespecial} instruction,
|
|
* that the receiver argument must match both the resolved method <em>and</em>
|
|
* the current class. Again, this requirement is enforced by narrowing the
|
|
* type of the leading parameter to the resulting method handle.
|
|
* (See the Java Virtual Machine Specification, section 4.10.1.9.)
|
|
* <p>
|
|
* The JVM represents constructors and static initializer blocks as internal methods
|
|
* with special names ({@code "<init>"} and {@code "<clinit>"}).
|
|
* The internal syntax of invocation instructions allows them to refer to such internal
|
|
* methods as if they were normal methods, but the JVM bytecode verifier rejects them.
|
|
* A lookup of such an internal method will produce a {@code NoSuchMethodException}.
|
|
* <p>
|
|
* In some cases, access between nested classes is obtained by the Java compiler by creating
|
|
* an wrapper method to access a private method of another class
|
|
* in the same top-level declaration.
|
|
* For example, a nested class {@code C.D}
|
|
* can access private members within other related classes such as
|
|
* {@code C}, {@code C.D.E}, or {@code C.B},
|
|
* but the Java compiler may need to generate wrapper methods in
|
|
* those related classes. In such cases, a {@code Lookup} object on
|
|
* {@code C.E} would be unable to those private members.
|
|
* A workaround for this limitation is the {@link Lookup#in Lookup.in} method,
|
|
* which can transform a lookup on {@code C.E} into one on any of those other
|
|
* classes, without special elevation of privilege.
|
|
* <p>
|
|
* The accesses permitted to a given lookup object may be limited,
|
|
* according to its set of {@link #lookupModes lookupModes},
|
|
* to a subset of members normally accessible to the lookup class.
|
|
* For example, the {@link MethodHandles#publicLookup publicLookup}
|
|
* method produces a lookup object which is only allowed to access
|
|
* public members in public classes.
|
|
* The caller sensitive method {@link MethodHandles#lookup lookup}
|
|
* produces a lookup object with full capabilities relative to
|
|
* its caller class, to emulate all supported bytecode behaviors.
|
|
* Also, the {@link Lookup#in Lookup.in} method may produce a lookup object
|
|
* with fewer access modes than the original lookup object.
|
|
*
|
|
* <p style="font-size:smaller;">
|
|
* <a name="privacc"></a>
|
|
* <em>Discussion of private access:</em>
|
|
* We say that a lookup has <em>private access</em>
|
|
* if its {@linkplain #lookupModes lookup modes}
|
|
* include the possibility of accessing {@code private} members.
|
|
* As documented in the relevant methods elsewhere,
|
|
* only lookups with private access possess the following capabilities:
|
|
* <ul style="font-size:smaller;">
|
|
* <li>access private fields, methods, and constructors of the lookup class
|
|
* <li>create method handles which invoke <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a> methods,
|
|
* such as {@code Class.forName}
|
|
* <li>create method handles which {@link Lookup#findSpecial emulate invokespecial} instructions
|
|
* <li>avoid <a href="MethodHandles.Lookup.html#secmgr">package access checks</a>
|
|
* for classes accessible to the lookup class
|
|
* <li>create {@link Lookup#in delegated lookup objects} which have private access to other classes
|
|
* within the same package member
|
|
* </ul>
|
|
* <p style="font-size:smaller;">
|
|
* Each of these permissions is a consequence of the fact that a lookup object
|
|
* with private access can be securely traced back to an originating class,
|
|
* whose <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> and Java language access permissions
|
|
* can be reliably determined and emulated by method handles.
|
|
*
|
|
* <h1><a name="secmgr"></a>Security manager interactions</h1>
|
|
* Although bytecode instructions can only refer to classes in
|
|
* a related class loader, this API can search for methods in any
|
|
* class, as long as a reference to its {@code Class} object is
|
|
* available. Such cross-loader references are also possible with the
|
|
* Core Reflection API, and are impossible to bytecode instructions
|
|
* such as {@code invokestatic} or {@code getfield}.
|
|
* There is a {@linkplain java.lang.SecurityManager security manager API}
|
|
* to allow applications to check such cross-loader references.
|
|
* These checks apply to both the {@code MethodHandles.Lookup} API
|
|
* and the Core Reflection API
|
|
* (as found on {@link java.lang.Class Class}).
|
|
* <p>
|
|
* If a security manager is present, member and class lookups are subject to
|
|
* additional checks.
|
|
* From one to three calls are made to the security manager.
|
|
* Any of these calls can refuse access by throwing a
|
|
* {@link java.lang.SecurityException SecurityException}.
|
|
* Define {@code smgr} as the security manager,
|
|
* {@code lookc} as the lookup class of the current lookup object,
|
|
* {@code refc} as the containing class in which the member
|
|
* is being sought, and {@code defc} as the class in which the
|
|
* member is actually defined.
|
|
* (If a class or other type is being accessed,
|
|
* the {@code refc} and {@code defc} values are the class itself.)
|
|
* The value {@code lookc} is defined as <em>not present</em>
|
|
* if the current lookup object does not have
|
|
* <a href="MethodHandles.Lookup.html#privacc">private access</a>.
|
|
* The calls are made according to the following rules:
|
|
* <ul>
|
|
* <li><b>Step 1:</b>
|
|
* If {@code lookc} is not present, or if its class loader is not
|
|
* the same as or an ancestor of the class loader of {@code refc},
|
|
* then {@link SecurityManager#checkPackageAccess
|
|
* smgr.checkPackageAccess(refcPkg)} is called,
|
|
* where {@code refcPkg} is the package of {@code refc}.
|
|
* <li><b>Step 2a:</b>
|
|
* If the retrieved member is not public and
|
|
* {@code lookc} is not present, then
|
|
* {@link SecurityManager#checkPermission smgr.checkPermission}
|
|
* with {@code RuntimePermission("accessDeclaredMembers")} is called.
|
|
* <li><b>Step 2b:</b>
|
|
* If the retrieved class has a {@code null} class loader,
|
|
* and {@code lookc} is not present, then
|
|
* {@link SecurityManager#checkPermission smgr.checkPermission}
|
|
* with {@code RuntimePermission("getClassLoader")} is called.
|
|
* <li><b>Step 3:</b>
|
|
* If the retrieved member is not public,
|
|
* and if {@code lookc} is not present,
|
|
* and if {@code defc} and {@code refc} are different,
|
|
* then {@link SecurityManager#checkPackageAccess
|
|
* smgr.checkPackageAccess(defcPkg)} is called,
|
|
* where {@code defcPkg} is the package of {@code defc}.
|
|
* </ul>
|
|
* Security checks are performed after other access checks have passed.
|
|
* Therefore, the above rules presuppose a member or class that is public,
|
|
* or else that is being accessed from a lookup class that has
|
|
* rights to access the member or class.
|
|
*
|
|
* <h1><a name="callsens"></a>Caller sensitive methods</h1>
|
|
* A small number of Java methods have a special property called caller sensitivity.
|
|
* A <em>caller-sensitive</em> method can behave differently depending on the
|
|
* identity of its immediate caller.
|
|
* <p>
|
|
* If a method handle for a caller-sensitive method is requested,
|
|
* the general rules for <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> apply,
|
|
* but they take account of the lookup class in a special way.
|
|
* The resulting method handle behaves as if it were called
|
|
* from an instruction contained in the lookup class,
|
|
* so that the caller-sensitive method detects the lookup class.
|
|
* (By contrast, the invoker of the method handle is disregarded.)
|
|
* Thus, in the case of caller-sensitive methods,
|
|
* different lookup classes may give rise to
|
|
* differently behaving method handles.
|
|
* <p>
|
|
* In cases where the lookup object is
|
|
* {@link MethodHandles#publicLookup() publicLookup()},
|
|
* or some other lookup object without
|
|
* <a href="MethodHandles.Lookup.html#privacc">private access</a>,
|
|
* the lookup class is disregarded.
|
|
* In such cases, no caller-sensitive method handle can be created,
|
|
* access is forbidden, and the lookup fails with an
|
|
* {@code IllegalAccessException}.
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* For example, the caller-sensitive method
|
|
* {@link java.lang.Class#forName(String) Class.forName(x)}
|
|
* can return varying classes or throw varying exceptions,
|
|
* depending on the class loader of the class that calls it.
|
|
* A public lookup of {@code Class.forName} will fail, because
|
|
* there is no reasonable way to determine its bytecode behavior.
|
|
* <p style="font-size:smaller;">
|
|
* If an application caches method handles for broad sharing,
|
|
* it should use {@code publicLookup()} to create them.
|
|
* If there is a lookup of {@code Class.forName}, it will fail,
|
|
* and the application must take appropriate action in that case.
|
|
* It may be that a later lookup, perhaps during the invocation of a
|
|
* bootstrap method, can incorporate the specific identity
|
|
* of the caller, making the method accessible.
|
|
* <p style="font-size:smaller;">
|
|
* The function {@code MethodHandles.lookup} is caller sensitive
|
|
* so that there can be a secure foundation for lookups.
|
|
* Nearly all other methods in the JSR 292 API rely on lookup
|
|
* objects to check access requests.
|
|
*/
|
|
public static final
|
|
class Lookup {
|
|
/** The class on behalf of whom the lookup is being performed. */
|
|
private final Class<?> lookupClass;
|
|
|
|
/** The allowed sorts of members which may be looked up (PUBLIC, etc.). */
|
|
private final int allowedModes;
|
|
|
|
/** A single-bit mask representing {@code public} access,
|
|
* which may contribute to the result of {@link #lookupModes lookupModes}.
|
|
* The value, {@code 0x01}, happens to be the same as the value of the
|
|
* {@code public} {@linkplain java.lang.reflect.Modifier#PUBLIC modifier bit}.
|
|
*/
|
|
public static final int PUBLIC = Modifier.PUBLIC;
|
|
|
|
/** A single-bit mask representing {@code private} access,
|
|
* which may contribute to the result of {@link #lookupModes lookupModes}.
|
|
* The value, {@code 0x02}, happens to be the same as the value of the
|
|
* {@code private} {@linkplain java.lang.reflect.Modifier#PRIVATE modifier bit}.
|
|
*/
|
|
public static final int PRIVATE = Modifier.PRIVATE;
|
|
|
|
/** A single-bit mask representing {@code protected} access,
|
|
* which may contribute to the result of {@link #lookupModes lookupModes}.
|
|
* The value, {@code 0x04}, happens to be the same as the value of the
|
|
* {@code protected} {@linkplain java.lang.reflect.Modifier#PROTECTED modifier bit}.
|
|
*/
|
|
public static final int PROTECTED = Modifier.PROTECTED;
|
|
|
|
/** A single-bit mask representing {@code package} access (default access),
|
|
* which may contribute to the result of {@link #lookupModes lookupModes}.
|
|
* The value is {@code 0x08}, which does not correspond meaningfully to
|
|
* any particular {@linkplain java.lang.reflect.Modifier modifier bit}.
|
|
*/
|
|
public static final int PACKAGE = Modifier.STATIC;
|
|
|
|
private static final int ALL_MODES = (PUBLIC | PRIVATE | PROTECTED | PACKAGE);
|
|
private static final int TRUSTED = -1;
|
|
|
|
private static int fixmods(int mods) {
|
|
mods &= (ALL_MODES - PACKAGE);
|
|
return (mods != 0) ? mods : PACKAGE;
|
|
}
|
|
|
|
/** Tells which class is performing the lookup. It is this class against
|
|
* which checks are performed for visibility and access permissions.
|
|
* <p>
|
|
* The class implies a maximum level of access permission,
|
|
* but the permissions may be additionally limited by the bitmask
|
|
* {@link #lookupModes lookupModes}, which controls whether non-public members
|
|
* can be accessed.
|
|
* @return the lookup class, on behalf of which this lookup object finds members
|
|
*/
|
|
public Class<?> lookupClass() {
|
|
return lookupClass;
|
|
}
|
|
|
|
// This is just for calling out to MethodHandleImpl.
|
|
private Class<?> lookupClassOrNull() {
|
|
return (allowedModes == TRUSTED) ? null : lookupClass;
|
|
}
|
|
|
|
/** Tells which access-protection classes of members this lookup object can produce.
|
|
* The result is a bit-mask of the bits
|
|
* {@linkplain #PUBLIC PUBLIC (0x01)},
|
|
* {@linkplain #PRIVATE PRIVATE (0x02)},
|
|
* {@linkplain #PROTECTED PROTECTED (0x04)},
|
|
* and {@linkplain #PACKAGE PACKAGE (0x08)}.
|
|
* <p>
|
|
* A freshly-created lookup object
|
|
* on the {@linkplain java.lang.invoke.MethodHandles#lookup() caller's class}
|
|
* has all possible bits set, since the caller class can access all its own members.
|
|
* A lookup object on a new lookup class
|
|
* {@linkplain java.lang.invoke.MethodHandles.Lookup#in created from a previous lookup object}
|
|
* may have some mode bits set to zero.
|
|
* The purpose of this is to restrict access via the new lookup object,
|
|
* so that it can access only names which can be reached by the original
|
|
* lookup object, and also by the new lookup class.
|
|
* @return the lookup modes, which limit the kinds of access performed by this lookup object
|
|
*/
|
|
public int lookupModes() {
|
|
return allowedModes & ALL_MODES;
|
|
}
|
|
|
|
/** Embody the current class (the lookupClass) as a lookup class
|
|
* for method handle creation.
|
|
* Must be called by from a method in this package,
|
|
* which in turn is called by a method not in this package.
|
|
*/
|
|
Lookup(Class<?> lookupClass) {
|
|
this(lookupClass, ALL_MODES);
|
|
// make sure we haven't accidentally picked up a privileged class:
|
|
checkUnprivilegedlookupClass(lookupClass, ALL_MODES);
|
|
}
|
|
|
|
private Lookup(Class<?> lookupClass, int allowedModes) {
|
|
this.lookupClass = lookupClass;
|
|
this.allowedModes = allowedModes;
|
|
}
|
|
|
|
/**
|
|
* Creates a lookup on the specified new lookup class.
|
|
* The resulting object will report the specified
|
|
* class as its own {@link #lookupClass lookupClass}.
|
|
* <p>
|
|
* However, the resulting {@code Lookup} object is guaranteed
|
|
* to have no more access capabilities than the original.
|
|
* In particular, access capabilities can be lost as follows:<ul>
|
|
* <li>If the new lookup class differs from the old one,
|
|
* protected members will not be accessible by virtue of inheritance.
|
|
* (Protected members may continue to be accessible because of package sharing.)
|
|
* <li>If the new lookup class is in a different package
|
|
* than the old one, protected and default (package) members will not be accessible.
|
|
* <li>If the new lookup class is not within the same package member
|
|
* as the old one, private members will not be accessible.
|
|
* <li>If the new lookup class is not accessible to the old lookup class,
|
|
* then no members, not even public members, will be accessible.
|
|
* (In all other cases, public members will continue to be accessible.)
|
|
* </ul>
|
|
*
|
|
* @param requestedLookupClass the desired lookup class for the new lookup object
|
|
* @return a lookup object which reports the desired lookup class
|
|
* @throws NullPointerException if the argument is null
|
|
*/
|
|
public Lookup in(Class<?> requestedLookupClass) {
|
|
Objects.requireNonNull(requestedLookupClass);
|
|
if (allowedModes == TRUSTED) // IMPL_LOOKUP can make any lookup at all
|
|
return new Lookup(requestedLookupClass, ALL_MODES);
|
|
if (requestedLookupClass == this.lookupClass)
|
|
return this; // keep same capabilities
|
|
int newModes = (allowedModes & (ALL_MODES & ~PROTECTED));
|
|
if ((newModes & PACKAGE) != 0
|
|
&& !VerifyAccess.isSamePackage(this.lookupClass, requestedLookupClass)) {
|
|
newModes &= ~(PACKAGE|PRIVATE);
|
|
}
|
|
// Allow nestmate lookups to be created without special privilege:
|
|
if ((newModes & PRIVATE) != 0
|
|
&& !VerifyAccess.isSamePackageMember(this.lookupClass, requestedLookupClass)) {
|
|
newModes &= ~PRIVATE;
|
|
}
|
|
if ((newModes & PUBLIC) != 0
|
|
&& !VerifyAccess.isClassAccessible(requestedLookupClass, this.lookupClass, allowedModes)) {
|
|
// The requested class it not accessible from the lookup class.
|
|
// No permissions.
|
|
newModes = 0;
|
|
}
|
|
checkUnprivilegedlookupClass(requestedLookupClass, newModes);
|
|
return new Lookup(requestedLookupClass, newModes);
|
|
}
|
|
|
|
// Make sure outer class is initialized first.
|
|
static { IMPL_NAMES.getClass(); }
|
|
|
|
/** Version of lookup which is trusted minimally.
|
|
* It can only be used to create method handles to
|
|
* publicly accessible members.
|
|
*/
|
|
static final Lookup PUBLIC_LOOKUP = new Lookup(Object.class, PUBLIC);
|
|
|
|
/** Package-private version of lookup which is trusted. */
|
|
static final Lookup IMPL_LOOKUP = new Lookup(Object.class, TRUSTED);
|
|
|
|
private static void checkUnprivilegedlookupClass(Class<?> lookupClass, int allowedModes) {
|
|
String name = lookupClass.getName();
|
|
if (name.startsWith("java.lang.invoke."))
|
|
throw newIllegalArgumentException("illegal lookupClass: "+lookupClass);
|
|
|
|
// For caller-sensitive MethodHandles.lookup()
|
|
// disallow lookup more restricted packages
|
|
if (allowedModes == ALL_MODES && lookupClass.getClassLoader() == null) {
|
|
if (name.startsWith("java.") ||
|
|
(name.startsWith("sun.") && !name.startsWith("sun.invoke."))) {
|
|
throw newIllegalArgumentException("illegal lookupClass: " + lookupClass);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Displays the name of the class from which lookups are to be made.
|
|
* (The name is the one reported by {@link java.lang.Class#getName() Class.getName}.)
|
|
* If there are restrictions on the access permitted to this lookup,
|
|
* this is indicated by adding a suffix to the class name, consisting
|
|
* of a slash and a keyword. The keyword represents the strongest
|
|
* allowed access, and is chosen as follows:
|
|
* <ul>
|
|
* <li>If no access is allowed, the suffix is "/noaccess".
|
|
* <li>If only public access is allowed, the suffix is "/public".
|
|
* <li>If only public and package access are allowed, the suffix is "/package".
|
|
* <li>If only public, package, and private access are allowed, the suffix is "/private".
|
|
* </ul>
|
|
* If none of the above cases apply, it is the case that full
|
|
* access (public, package, private, and protected) is allowed.
|
|
* In this case, no suffix is added.
|
|
* This is true only of an object obtained originally from
|
|
* {@link java.lang.invoke.MethodHandles#lookup MethodHandles.lookup}.
|
|
* Objects created by {@link java.lang.invoke.MethodHandles.Lookup#in Lookup.in}
|
|
* always have restricted access, and will display a suffix.
|
|
* <p>
|
|
* (It may seem strange that protected access should be
|
|
* stronger than private access. Viewed independently from
|
|
* package access, protected access is the first to be lost,
|
|
* because it requires a direct subclass relationship between
|
|
* caller and callee.)
|
|
* @see #in
|
|
*/
|
|
@Override
|
|
public String toString() {
|
|
String cname = lookupClass.getName();
|
|
switch (allowedModes) {
|
|
case 0: // no privileges
|
|
return cname + "/noaccess";
|
|
case PUBLIC:
|
|
return cname + "/public";
|
|
case PUBLIC|PACKAGE:
|
|
return cname + "/package";
|
|
case ALL_MODES & ~PROTECTED:
|
|
return cname + "/private";
|
|
case ALL_MODES:
|
|
return cname;
|
|
case TRUSTED:
|
|
return "/trusted"; // internal only; not exported
|
|
default: // Should not happen, but it's a bitfield...
|
|
cname = cname + "/" + Integer.toHexString(allowedModes);
|
|
assert(false) : cname;
|
|
return cname;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle for a static method.
|
|
* The type of the method handle will be that of the method.
|
|
* (Since static methods do not take receivers, there is no
|
|
* additional receiver argument inserted into the method handle type,
|
|
* as there would be with {@link #findVirtual findVirtual} or {@link #findSpecial findSpecial}.)
|
|
* The method and all its argument types must be accessible to the lookup object.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the method's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* <p>
|
|
* If the returned method handle is invoked, the method's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle MH_asList = publicLookup().findStatic(Arrays.class,
|
|
"asList", methodType(List.class, Object[].class));
|
|
assertEquals("[x, y]", MH_asList.invoke("x", "y").toString());
|
|
* }</pre></blockquote>
|
|
* @param refc the class from which the method is accessed
|
|
* @param name the name of the method
|
|
* @param type the type of the method
|
|
* @return the desired method handle
|
|
* @throws NoSuchMethodException if the method does not exist
|
|
* @throws IllegalAccessException if access checking fails,
|
|
* or if the method is not {@code static},
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public
|
|
MethodHandle findStatic(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
|
|
MemberName method = resolveOrFail(REF_invokeStatic, refc, name, type);
|
|
return getDirectMethod(REF_invokeStatic, refc, method, findBoundCallerClass(method));
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle for a virtual method.
|
|
* The type of the method handle will be that of the method,
|
|
* with the receiver type (usually {@code refc}) prepended.
|
|
* The method and all its argument types must be accessible to the lookup object.
|
|
* <p>
|
|
* When called, the handle will treat the first argument as a receiver
|
|
* and dispatch on the receiver's type to determine which method
|
|
* implementation to enter.
|
|
* (The dispatching action is identical with that performed by an
|
|
* {@code invokevirtual} or {@code invokeinterface} instruction.)
|
|
* <p>
|
|
* The first argument will be of type {@code refc} if the lookup
|
|
* class has full privileges to access the member. Otherwise
|
|
* the member must be {@code protected} and the first argument
|
|
* will be restricted in type to the lookup class.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the method's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* <p>
|
|
* Because of the general <a href="MethodHandles.Lookup.html#equiv">equivalence</a> between {@code invokevirtual}
|
|
* instructions and method handles produced by {@code findVirtual},
|
|
* if the class is {@code MethodHandle} and the name string is
|
|
* {@code invokeExact} or {@code invoke}, the resulting
|
|
* method handle is equivalent to one produced by
|
|
* {@link java.lang.invoke.MethodHandles#exactInvoker MethodHandles.exactInvoker} or
|
|
* {@link java.lang.invoke.MethodHandles#invoker MethodHandles.invoker}
|
|
* with the same {@code type} argument.
|
|
*
|
|
* <b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle MH_concat = publicLookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
MethodHandle MH_hashCode = publicLookup().findVirtual(Object.class,
|
|
"hashCode", methodType(int.class));
|
|
MethodHandle MH_hashCode_String = publicLookup().findVirtual(String.class,
|
|
"hashCode", methodType(int.class));
|
|
assertEquals("xy", (String) MH_concat.invokeExact("x", "y"));
|
|
assertEquals("xy".hashCode(), (int) MH_hashCode.invokeExact((Object)"xy"));
|
|
assertEquals("xy".hashCode(), (int) MH_hashCode_String.invokeExact("xy"));
|
|
// interface method:
|
|
MethodHandle MH_subSequence = publicLookup().findVirtual(CharSequence.class,
|
|
"subSequence", methodType(CharSequence.class, int.class, int.class));
|
|
assertEquals("def", MH_subSequence.invoke("abcdefghi", 3, 6).toString());
|
|
// constructor "internal method" must be accessed differently:
|
|
MethodType MT_newString = methodType(void.class); //()V for new String()
|
|
try { assertEquals("impossible", lookup()
|
|
.findVirtual(String.class, "<init>", MT_newString));
|
|
} catch (NoSuchMethodException ex) { } // OK
|
|
MethodHandle MH_newString = publicLookup()
|
|
.findConstructor(String.class, MT_newString);
|
|
assertEquals("", (String) MH_newString.invokeExact());
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param name the name of the method
|
|
* @param type the type of the method, with the receiver argument omitted
|
|
* @return the desired method handle
|
|
* @throws NoSuchMethodException if the method does not exist
|
|
* @throws IllegalAccessException if access checking fails,
|
|
* or if the method is {@code static},
|
|
* or if the method is {@code private} method of interface,
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findVirtual(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
|
|
if (refc == MethodHandle.class) {
|
|
MethodHandle mh = findVirtualForMH(name, type);
|
|
if (mh != null) return mh;
|
|
}
|
|
byte refKind = (refc.isInterface() ? REF_invokeInterface : REF_invokeVirtual);
|
|
MemberName method = resolveOrFail(refKind, refc, name, type);
|
|
return getDirectMethod(refKind, refc, method, findBoundCallerClass(method));
|
|
}
|
|
private MethodHandle findVirtualForMH(String name, MethodType type) {
|
|
// these names require special lookups because of the implicit MethodType argument
|
|
if ("invoke".equals(name))
|
|
return invoker(type);
|
|
if ("invokeExact".equals(name))
|
|
return exactInvoker(type);
|
|
if ("invokeBasic".equals(name))
|
|
return basicInvoker(type);
|
|
assert(!MemberName.isMethodHandleInvokeName(name));
|
|
return null;
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle which creates an object and initializes it, using
|
|
* the constructor of the specified type.
|
|
* The parameter types of the method handle will be those of the constructor,
|
|
* while the return type will be a reference to the constructor's class.
|
|
* The constructor and all its argument types must be accessible to the lookup object.
|
|
* <p>
|
|
* The requested type must have a return type of {@code void}.
|
|
* (This is consistent with the JVM's treatment of constructor type descriptors.)
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the constructor's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* <p>
|
|
* If the returned method handle is invoked, the constructor's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle MH_newArrayList = publicLookup().findConstructor(
|
|
ArrayList.class, methodType(void.class, Collection.class));
|
|
Collection orig = Arrays.asList("x", "y");
|
|
Collection copy = (ArrayList) MH_newArrayList.invokeExact(orig);
|
|
assert(orig != copy);
|
|
assertEquals(orig, copy);
|
|
// a variable-arity constructor:
|
|
MethodHandle MH_newProcessBuilder = publicLookup().findConstructor(
|
|
ProcessBuilder.class, methodType(void.class, String[].class));
|
|
ProcessBuilder pb = (ProcessBuilder)
|
|
MH_newProcessBuilder.invoke("x", "y", "z");
|
|
assertEquals("[x, y, z]", pb.command().toString());
|
|
* }</pre></blockquote>
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param type the type of the method, with the receiver argument omitted, and a void return type
|
|
* @return the desired method handle
|
|
* @throws NoSuchMethodException if the constructor does not exist
|
|
* @throws IllegalAccessException if access checking fails
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findConstructor(Class<?> refc, MethodType type) throws NoSuchMethodException, IllegalAccessException {
|
|
String name = "<init>";
|
|
MemberName ctor = resolveOrFail(REF_newInvokeSpecial, refc, name, type);
|
|
return getDirectConstructor(refc, ctor);
|
|
}
|
|
|
|
/**
|
|
* Looks up a class by name from the lookup context defined by this {@code Lookup} object. The static
|
|
* initializer of the class is not run.
|
|
*
|
|
* @param targetName the fully qualified name of the class to be looked up.
|
|
* @return the requested class.
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws LinkageError if the linkage fails
|
|
* @throws ClassNotFoundException if the class does not exist.
|
|
* @throws IllegalAccessException if the class is not accessible, using the allowed access
|
|
* modes.
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @since 9
|
|
*/
|
|
public Class<?> findClass(String targetName) throws ClassNotFoundException, IllegalAccessException {
|
|
Class<?> targetClass = Class.forName(targetName, false, lookupClass.getClassLoader());
|
|
return accessClass(targetClass);
|
|
}
|
|
|
|
/**
|
|
* Determines if a class can be accessed from the lookup context defined by this {@code Lookup} object. The
|
|
* static initializer of the class is not run.
|
|
*
|
|
* @param targetClass the class to be access-checked
|
|
*
|
|
* @return the class that has been access-checked
|
|
*
|
|
* @throws IllegalAccessException if the class is not accessible from the lookup class, using the allowed access
|
|
* modes.
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @since 9
|
|
*/
|
|
public Class<?> accessClass(Class<?> targetClass) throws IllegalAccessException {
|
|
if (!VerifyAccess.isClassAccessible(targetClass, lookupClass, allowedModes)) {
|
|
throw new MemberName(targetClass).makeAccessException("access violation", this);
|
|
}
|
|
checkSecurityManager(targetClass, null);
|
|
return targetClass;
|
|
}
|
|
|
|
/**
|
|
* Produces an early-bound method handle for a virtual method.
|
|
* It will bypass checks for overriding methods on the receiver,
|
|
* <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial}
|
|
* instruction from within the explicitly specified {@code specialCaller}.
|
|
* The type of the method handle will be that of the method,
|
|
* with a suitably restricted receiver type prepended.
|
|
* (The receiver type will be {@code specialCaller} or a subtype.)
|
|
* The method and all its argument types must be accessible
|
|
* to the lookup object.
|
|
* <p>
|
|
* Before method resolution,
|
|
* if the explicitly specified caller class is not identical with the
|
|
* lookup class, or if this lookup object does not have
|
|
* <a href="MethodHandles.Lookup.html#privacc">private access</a>
|
|
* privileges, the access fails.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the method's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* <p style="font-size:smaller;">
|
|
* <em>(Note: JVM internal methods named {@code "<init>"} are not visible to this API,
|
|
* even though the {@code invokespecial} instruction can refer to them
|
|
* in special circumstances. Use {@link #findConstructor findConstructor}
|
|
* to access instance initialization methods in a safe manner.)</em>
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
static class Listie extends ArrayList {
|
|
public String toString() { return "[wee Listie]"; }
|
|
static Lookup lookup() { return MethodHandles.lookup(); }
|
|
}
|
|
...
|
|
// no access to constructor via invokeSpecial:
|
|
MethodHandle MH_newListie = Listie.lookup()
|
|
.findConstructor(Listie.class, methodType(void.class));
|
|
Listie l = (Listie) MH_newListie.invokeExact();
|
|
try { assertEquals("impossible", Listie.lookup().findSpecial(
|
|
Listie.class, "<init>", methodType(void.class), Listie.class));
|
|
} catch (NoSuchMethodException ex) { } // OK
|
|
// access to super and self methods via invokeSpecial:
|
|
MethodHandle MH_super = Listie.lookup().findSpecial(
|
|
ArrayList.class, "toString" , methodType(String.class), Listie.class);
|
|
MethodHandle MH_this = Listie.lookup().findSpecial(
|
|
Listie.class, "toString" , methodType(String.class), Listie.class);
|
|
MethodHandle MH_duper = Listie.lookup().findSpecial(
|
|
Object.class, "toString" , methodType(String.class), Listie.class);
|
|
assertEquals("[]", (String) MH_super.invokeExact(l));
|
|
assertEquals(""+l, (String) MH_this.invokeExact(l));
|
|
assertEquals("[]", (String) MH_duper.invokeExact(l)); // ArrayList method
|
|
try { assertEquals("inaccessible", Listie.lookup().findSpecial(
|
|
String.class, "toString", methodType(String.class), Listie.class));
|
|
} catch (IllegalAccessException ex) { } // OK
|
|
Listie subl = new Listie() { public String toString() { return "[subclass]"; } };
|
|
assertEquals(""+l, (String) MH_this.invokeExact(subl)); // Listie method
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param name the name of the method (which must not be "<init>")
|
|
* @param type the type of the method, with the receiver argument omitted
|
|
* @param specialCaller the proposed calling class to perform the {@code invokespecial}
|
|
* @return the desired method handle
|
|
* @throws NoSuchMethodException if the method does not exist
|
|
* @throws IllegalAccessException if access checking fails,
|
|
* or if the method is {@code static},
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findSpecial(Class<?> refc, String name, MethodType type,
|
|
Class<?> specialCaller) throws NoSuchMethodException, IllegalAccessException {
|
|
checkSpecialCaller(specialCaller, refc);
|
|
Lookup specialLookup = this.in(specialCaller);
|
|
MemberName method = specialLookup.resolveOrFail(REF_invokeSpecial, refc, name, type);
|
|
return specialLookup.getDirectMethod(REF_invokeSpecial, refc, method, findBoundCallerClass(method));
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving read access to a non-static field.
|
|
* The type of the method handle will have a return type of the field's
|
|
* value type.
|
|
* The method handle's single argument will be the instance containing
|
|
* the field.
|
|
* Access checking is performed immediately on behalf of the lookup class.
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param name the field's name
|
|
* @param type the field's type
|
|
* @return a method handle which can load values from the field
|
|
* @throws NoSuchFieldException if the field does not exist
|
|
* @throws IllegalAccessException if access checking fails, or if the field is {@code static}
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
|
|
MemberName field = resolveOrFail(REF_getField, refc, name, type);
|
|
return getDirectField(REF_getField, refc, field);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving write access to a non-static field.
|
|
* The type of the method handle will have a void return type.
|
|
* The method handle will take two arguments, the instance containing
|
|
* the field, and the value to be stored.
|
|
* The second argument will be of the field's value type.
|
|
* Access checking is performed immediately on behalf of the lookup class.
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param name the field's name
|
|
* @param type the field's type
|
|
* @return a method handle which can store values into the field
|
|
* @throws NoSuchFieldException if the field does not exist
|
|
* @throws IllegalAccessException if access checking fails, or if the field is {@code static}
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
|
|
MemberName field = resolveOrFail(REF_putField, refc, name, type);
|
|
return getDirectField(REF_putField, refc, field);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving read access to a static field.
|
|
* The type of the method handle will have a return type of the field's
|
|
* value type.
|
|
* The method handle will take no arguments.
|
|
* Access checking is performed immediately on behalf of the lookup class.
|
|
* <p>
|
|
* If the returned method handle is invoked, the field's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param name the field's name
|
|
* @param type the field's type
|
|
* @return a method handle which can load values from the field
|
|
* @throws NoSuchFieldException if the field does not exist
|
|
* @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findStaticGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
|
|
MemberName field = resolveOrFail(REF_getStatic, refc, name, type);
|
|
return getDirectField(REF_getStatic, refc, field);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving write access to a static field.
|
|
* The type of the method handle will have a void return type.
|
|
* The method handle will take a single
|
|
* argument, of the field's value type, the value to be stored.
|
|
* Access checking is performed immediately on behalf of the lookup class.
|
|
* <p>
|
|
* If the returned method handle is invoked, the field's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* @param refc the class or interface from which the method is accessed
|
|
* @param name the field's name
|
|
* @param type the field's type
|
|
* @return a method handle which can store values into the field
|
|
* @throws NoSuchFieldException if the field does not exist
|
|
* @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle findStaticSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
|
|
MemberName field = resolveOrFail(REF_putStatic, refc, name, type);
|
|
return getDirectField(REF_putStatic, refc, field);
|
|
}
|
|
|
|
/**
|
|
* Produces an early-bound method handle for a non-static method.
|
|
* The receiver must have a supertype {@code defc} in which a method
|
|
* of the given name and type is accessible to the lookup class.
|
|
* The method and all its argument types must be accessible to the lookup object.
|
|
* The type of the method handle will be that of the method,
|
|
* without any insertion of an additional receiver parameter.
|
|
* The given receiver will be bound into the method handle,
|
|
* so that every call to the method handle will invoke the
|
|
* requested method on the given receiver.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the method's variable arity modifier bit ({@code 0x0080}) is set
|
|
* <em>and</em> the trailing array argument is not the only argument.
|
|
* (If the trailing array argument is the only argument,
|
|
* the given receiver value will be bound to it.)
|
|
* <p>
|
|
* This is equivalent to the following code:
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle mh0 = lookup().findVirtual(defc, name, type);
|
|
MethodHandle mh1 = mh0.bindTo(receiver);
|
|
MethodType mt1 = mh1.type();
|
|
if (mh0.isVarargsCollector())
|
|
mh1 = mh1.asVarargsCollector(mt1.parameterType(mt1.parameterCount()-1));
|
|
return mh1;
|
|
* }</pre></blockquote>
|
|
* where {@code defc} is either {@code receiver.getClass()} or a super
|
|
* type of that class, in which the requested method is accessible
|
|
* to the lookup class.
|
|
* (Note that {@code bindTo} does not preserve variable arity.)
|
|
* @param receiver the object from which the method is accessed
|
|
* @param name the name of the method
|
|
* @param type the type of the method, with the receiver argument omitted
|
|
* @return the desired method handle
|
|
* @throws NoSuchMethodException if the method does not exist
|
|
* @throws IllegalAccessException if access checking fails
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws NullPointerException if any argument is null
|
|
* @see MethodHandle#bindTo
|
|
* @see #findVirtual
|
|
*/
|
|
public MethodHandle bind(Object receiver, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
|
|
Class<? extends Object> refc = receiver.getClass(); // may get NPE
|
|
MemberName method = resolveOrFail(REF_invokeSpecial, refc, name, type);
|
|
MethodHandle mh = getDirectMethodNoRestrict(REF_invokeSpecial, refc, method, findBoundCallerClass(method));
|
|
return mh.bindArgumentL(0, receiver).setVarargs(method);
|
|
}
|
|
|
|
/**
|
|
* Makes a <a href="MethodHandleInfo.html#directmh">direct method handle</a>
|
|
* to <i>m</i>, if the lookup class has permission.
|
|
* If <i>m</i> is non-static, the receiver argument is treated as an initial argument.
|
|
* If <i>m</i> is virtual, overriding is respected on every call.
|
|
* Unlike the Core Reflection API, exceptions are <em>not</em> wrapped.
|
|
* The type of the method handle will be that of the method,
|
|
* with the receiver type prepended (but only if it is non-static).
|
|
* If the method's {@code accessible} flag is not set,
|
|
* access checking is performed immediately on behalf of the lookup class.
|
|
* If <i>m</i> is not public, do not share the resulting handle with untrusted parties.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the method's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* <p>
|
|
* If <i>m</i> is static, and
|
|
* if the returned method handle is invoked, the method's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* @param m the reflected method
|
|
* @return a method handle which can invoke the reflected method
|
|
* @throws IllegalAccessException if access checking fails
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @throws NullPointerException if the argument is null
|
|
*/
|
|
public MethodHandle unreflect(Method m) throws IllegalAccessException {
|
|
if (m.getDeclaringClass() == MethodHandle.class) {
|
|
MethodHandle mh = unreflectForMH(m);
|
|
if (mh != null) return mh;
|
|
}
|
|
MemberName method = new MemberName(m);
|
|
byte refKind = method.getReferenceKind();
|
|
if (refKind == REF_invokeSpecial)
|
|
refKind = REF_invokeVirtual;
|
|
assert(method.isMethod());
|
|
Lookup lookup = m.isAccessible() ? IMPL_LOOKUP : this;
|
|
return lookup.getDirectMethodNoSecurityManager(refKind, method.getDeclaringClass(), method, findBoundCallerClass(method));
|
|
}
|
|
private MethodHandle unreflectForMH(Method m) {
|
|
// these names require special lookups because they throw UnsupportedOperationException
|
|
if (MemberName.isMethodHandleInvokeName(m.getName()))
|
|
return MethodHandleImpl.fakeMethodHandleInvoke(new MemberName(m));
|
|
return null;
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle for a reflected method.
|
|
* It will bypass checks for overriding methods on the receiver,
|
|
* <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial}
|
|
* instruction from within the explicitly specified {@code specialCaller}.
|
|
* The type of the method handle will be that of the method,
|
|
* with a suitably restricted receiver type prepended.
|
|
* (The receiver type will be {@code specialCaller} or a subtype.)
|
|
* If the method's {@code accessible} flag is not set,
|
|
* access checking is performed immediately on behalf of the lookup class,
|
|
* as if {@code invokespecial} instruction were being linked.
|
|
* <p>
|
|
* Before method resolution,
|
|
* if the explicitly specified caller class is not identical with the
|
|
* lookup class, or if this lookup object does not have
|
|
* <a href="MethodHandles.Lookup.html#privacc">private access</a>
|
|
* privileges, the access fails.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the method's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* @param m the reflected method
|
|
* @param specialCaller the class nominally calling the method
|
|
* @return a method handle which can invoke the reflected method
|
|
* @throws IllegalAccessException if access checking fails,
|
|
* or if the method is {@code static},
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @throws NullPointerException if any argument is null
|
|
*/
|
|
public MethodHandle unreflectSpecial(Method m, Class<?> specialCaller) throws IllegalAccessException {
|
|
checkSpecialCaller(specialCaller, null);
|
|
Lookup specialLookup = this.in(specialCaller);
|
|
MemberName method = new MemberName(m, true);
|
|
assert(method.isMethod());
|
|
// ignore m.isAccessible: this is a new kind of access
|
|
return specialLookup.getDirectMethodNoSecurityManager(REF_invokeSpecial, method.getDeclaringClass(), method, findBoundCallerClass(method));
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle for a reflected constructor.
|
|
* The type of the method handle will be that of the constructor,
|
|
* with the return type changed to the declaring class.
|
|
* The method handle will perform a {@code newInstance} operation,
|
|
* creating a new instance of the constructor's class on the
|
|
* arguments passed to the method handle.
|
|
* <p>
|
|
* If the constructor's {@code accessible} flag is not set,
|
|
* access checking is performed immediately on behalf of the lookup class.
|
|
* <p>
|
|
* The returned method handle will have
|
|
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
|
|
* the constructor's variable arity modifier bit ({@code 0x0080}) is set.
|
|
* <p>
|
|
* If the returned method handle is invoked, the constructor's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* @param c the reflected constructor
|
|
* @return a method handle which can invoke the reflected constructor
|
|
* @throws IllegalAccessException if access checking fails
|
|
* or if the method's variable arity modifier bit
|
|
* is set and {@code asVarargsCollector} fails
|
|
* @throws NullPointerException if the argument is null
|
|
*/
|
|
public MethodHandle unreflectConstructor(Constructor<?> c) throws IllegalAccessException {
|
|
MemberName ctor = new MemberName(c);
|
|
assert(ctor.isConstructor());
|
|
Lookup lookup = c.isAccessible() ? IMPL_LOOKUP : this;
|
|
return lookup.getDirectConstructorNoSecurityManager(ctor.getDeclaringClass(), ctor);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving read access to a reflected field.
|
|
* The type of the method handle will have a return type of the field's
|
|
* value type.
|
|
* If the field is static, the method handle will take no arguments.
|
|
* Otherwise, its single argument will be the instance containing
|
|
* the field.
|
|
* If the field's {@code accessible} flag is not set,
|
|
* access checking is performed immediately on behalf of the lookup class.
|
|
* <p>
|
|
* If the field is static, and
|
|
* if the returned method handle is invoked, the field's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* @param f the reflected field
|
|
* @return a method handle which can load values from the reflected field
|
|
* @throws IllegalAccessException if access checking fails
|
|
* @throws NullPointerException if the argument is null
|
|
*/
|
|
public MethodHandle unreflectGetter(Field f) throws IllegalAccessException {
|
|
return unreflectField(f, false);
|
|
}
|
|
private MethodHandle unreflectField(Field f, boolean isSetter) throws IllegalAccessException {
|
|
MemberName field = new MemberName(f, isSetter);
|
|
assert(isSetter
|
|
? MethodHandleNatives.refKindIsSetter(field.getReferenceKind())
|
|
: MethodHandleNatives.refKindIsGetter(field.getReferenceKind()));
|
|
Lookup lookup = f.isAccessible() ? IMPL_LOOKUP : this;
|
|
return lookup.getDirectFieldNoSecurityManager(field.getReferenceKind(), f.getDeclaringClass(), field);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving write access to a reflected field.
|
|
* The type of the method handle will have a void return type.
|
|
* If the field is static, the method handle will take a single
|
|
* argument, of the field's value type, the value to be stored.
|
|
* Otherwise, the two arguments will be the instance containing
|
|
* the field, and the value to be stored.
|
|
* If the field's {@code accessible} flag is not set,
|
|
* access checking is performed immediately on behalf of the lookup class.
|
|
* <p>
|
|
* If the field is static, and
|
|
* if the returned method handle is invoked, the field's class will
|
|
* be initialized, if it has not already been initialized.
|
|
* @param f the reflected field
|
|
* @return a method handle which can store values into the reflected field
|
|
* @throws IllegalAccessException if access checking fails
|
|
* @throws NullPointerException if the argument is null
|
|
*/
|
|
public MethodHandle unreflectSetter(Field f) throws IllegalAccessException {
|
|
return unreflectField(f, true);
|
|
}
|
|
|
|
/**
|
|
* Cracks a <a href="MethodHandleInfo.html#directmh">direct method handle</a>
|
|
* created by this lookup object or a similar one.
|
|
* Security and access checks are performed to ensure that this lookup object
|
|
* is capable of reproducing the target method handle.
|
|
* This means that the cracking may fail if target is a direct method handle
|
|
* but was created by an unrelated lookup object.
|
|
* This can happen if the method handle is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>
|
|
* and was created by a lookup object for a different class.
|
|
* @param target a direct method handle to crack into symbolic reference components
|
|
* @return a symbolic reference which can be used to reconstruct this method handle from this lookup object
|
|
* @exception SecurityException if a security manager is present and it
|
|
* <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
|
|
* @throws IllegalArgumentException if the target is not a direct method handle or if access checking fails
|
|
* @exception NullPointerException if the target is {@code null}
|
|
* @see MethodHandleInfo
|
|
* @since 1.8
|
|
*/
|
|
public MethodHandleInfo revealDirect(MethodHandle target) {
|
|
MemberName member = target.internalMemberName();
|
|
if (member == null || (!member.isResolved() && !member.isMethodHandleInvoke()))
|
|
throw newIllegalArgumentException("not a direct method handle");
|
|
Class<?> defc = member.getDeclaringClass();
|
|
byte refKind = member.getReferenceKind();
|
|
assert(MethodHandleNatives.refKindIsValid(refKind));
|
|
if (refKind == REF_invokeSpecial && !target.isInvokeSpecial())
|
|
// Devirtualized method invocation is usually formally virtual.
|
|
// To avoid creating extra MemberName objects for this common case,
|
|
// we encode this extra degree of freedom using MH.isInvokeSpecial.
|
|
refKind = REF_invokeVirtual;
|
|
if (refKind == REF_invokeVirtual && defc.isInterface())
|
|
// Symbolic reference is through interface but resolves to Object method (toString, etc.)
|
|
refKind = REF_invokeInterface;
|
|
// Check SM permissions and member access before cracking.
|
|
try {
|
|
checkAccess(refKind, defc, member);
|
|
checkSecurityManager(defc, member);
|
|
} catch (IllegalAccessException ex) {
|
|
throw new IllegalArgumentException(ex);
|
|
}
|
|
if (allowedModes != TRUSTED && member.isCallerSensitive()) {
|
|
Class<?> callerClass = target.internalCallerClass();
|
|
if (!hasPrivateAccess() || callerClass != lookupClass())
|
|
throw new IllegalArgumentException("method handle is caller sensitive: "+callerClass);
|
|
}
|
|
// Produce the handle to the results.
|
|
return new InfoFromMemberName(this, member, refKind);
|
|
}
|
|
|
|
/// Helper methods, all package-private.
|
|
|
|
MemberName resolveOrFail(byte refKind, Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
|
|
checkSymbolicClass(refc); // do this before attempting to resolve
|
|
Objects.requireNonNull(name);
|
|
Objects.requireNonNull(type);
|
|
return IMPL_NAMES.resolveOrFail(refKind, new MemberName(refc, name, type, refKind), lookupClassOrNull(),
|
|
NoSuchFieldException.class);
|
|
}
|
|
|
|
MemberName resolveOrFail(byte refKind, Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
|
|
checkSymbolicClass(refc); // do this before attempting to resolve
|
|
Objects.requireNonNull(name);
|
|
Objects.requireNonNull(type);
|
|
checkMethodName(refKind, name); // NPE check on name
|
|
return IMPL_NAMES.resolveOrFail(refKind, new MemberName(refc, name, type, refKind), lookupClassOrNull(),
|
|
NoSuchMethodException.class);
|
|
}
|
|
|
|
MemberName resolveOrFail(byte refKind, MemberName member) throws ReflectiveOperationException {
|
|
checkSymbolicClass(member.getDeclaringClass()); // do this before attempting to resolve
|
|
Objects.requireNonNull(member.getName());
|
|
Objects.requireNonNull(member.getType());
|
|
return IMPL_NAMES.resolveOrFail(refKind, member, lookupClassOrNull(),
|
|
ReflectiveOperationException.class);
|
|
}
|
|
|
|
void checkSymbolicClass(Class<?> refc) throws IllegalAccessException {
|
|
Objects.requireNonNull(refc);
|
|
Class<?> caller = lookupClassOrNull();
|
|
if (caller != null && !VerifyAccess.isClassAccessible(refc, caller, allowedModes))
|
|
throw new MemberName(refc).makeAccessException("symbolic reference class is not public", this);
|
|
}
|
|
|
|
/** Check name for an illegal leading "<" character. */
|
|
void checkMethodName(byte refKind, String name) throws NoSuchMethodException {
|
|
if (name.startsWith("<") && refKind != REF_newInvokeSpecial)
|
|
throw new NoSuchMethodException("illegal method name: "+name);
|
|
}
|
|
|
|
|
|
/**
|
|
* Find my trustable caller class if m is a caller sensitive method.
|
|
* If this lookup object has private access, then the caller class is the lookupClass.
|
|
* Otherwise, if m is caller-sensitive, throw IllegalAccessException.
|
|
*/
|
|
Class<?> findBoundCallerClass(MemberName m) throws IllegalAccessException {
|
|
Class<?> callerClass = null;
|
|
if (MethodHandleNatives.isCallerSensitive(m)) {
|
|
// Only lookups with private access are allowed to resolve caller-sensitive methods
|
|
if (hasPrivateAccess()) {
|
|
callerClass = lookupClass;
|
|
} else {
|
|
throw new IllegalAccessException("Attempt to lookup caller-sensitive method using restricted lookup object");
|
|
}
|
|
}
|
|
return callerClass;
|
|
}
|
|
|
|
private boolean hasPrivateAccess() {
|
|
return (allowedModes & PRIVATE) != 0;
|
|
}
|
|
|
|
/**
|
|
* Perform necessary <a href="MethodHandles.Lookup.html#secmgr">access checks</a>.
|
|
* Determines a trustable caller class to compare with refc, the symbolic reference class.
|
|
* If this lookup object has private access, then the caller class is the lookupClass.
|
|
*/
|
|
void checkSecurityManager(Class<?> refc, MemberName m) {
|
|
SecurityManager smgr = System.getSecurityManager();
|
|
if (smgr == null) return;
|
|
if (allowedModes == TRUSTED) return;
|
|
|
|
// Step 1:
|
|
boolean fullPowerLookup = hasPrivateAccess();
|
|
if (!fullPowerLookup ||
|
|
!VerifyAccess.classLoaderIsAncestor(lookupClass, refc)) {
|
|
ReflectUtil.checkPackageAccess(refc);
|
|
}
|
|
|
|
if (m == null) { // findClass or accessClass
|
|
// Step 2b:
|
|
if (!fullPowerLookup) {
|
|
smgr.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
|
|
}
|
|
return;
|
|
}
|
|
|
|
// Step 2a:
|
|
if (m.isPublic()) return;
|
|
if (!fullPowerLookup) {
|
|
smgr.checkPermission(SecurityConstants.CHECK_MEMBER_ACCESS_PERMISSION);
|
|
}
|
|
|
|
// Step 3:
|
|
Class<?> defc = m.getDeclaringClass();
|
|
if (!fullPowerLookup && defc != refc) {
|
|
ReflectUtil.checkPackageAccess(defc);
|
|
}
|
|
}
|
|
|
|
void checkMethod(byte refKind, Class<?> refc, MemberName m) throws IllegalAccessException {
|
|
boolean wantStatic = (refKind == REF_invokeStatic);
|
|
String message;
|
|
if (m.isConstructor())
|
|
message = "expected a method, not a constructor";
|
|
else if (!m.isMethod())
|
|
message = "expected a method";
|
|
else if (wantStatic != m.isStatic())
|
|
message = wantStatic ? "expected a static method" : "expected a non-static method";
|
|
else
|
|
{ checkAccess(refKind, refc, m); return; }
|
|
throw m.makeAccessException(message, this);
|
|
}
|
|
|
|
void checkField(byte refKind, Class<?> refc, MemberName m) throws IllegalAccessException {
|
|
boolean wantStatic = !MethodHandleNatives.refKindHasReceiver(refKind);
|
|
String message;
|
|
if (wantStatic != m.isStatic())
|
|
message = wantStatic ? "expected a static field" : "expected a non-static field";
|
|
else
|
|
{ checkAccess(refKind, refc, m); return; }
|
|
throw m.makeAccessException(message, this);
|
|
}
|
|
|
|
/** Check public/protected/private bits on the symbolic reference class and its member. */
|
|
void checkAccess(byte refKind, Class<?> refc, MemberName m) throws IllegalAccessException {
|
|
assert(m.referenceKindIsConsistentWith(refKind) &&
|
|
MethodHandleNatives.refKindIsValid(refKind) &&
|
|
(MethodHandleNatives.refKindIsField(refKind) == m.isField()));
|
|
int allowedModes = this.allowedModes;
|
|
if (allowedModes == TRUSTED) return;
|
|
int mods = m.getModifiers();
|
|
if (Modifier.isProtected(mods) &&
|
|
refKind == REF_invokeVirtual &&
|
|
m.getDeclaringClass() == Object.class &&
|
|
m.getName().equals("clone") &&
|
|
refc.isArray()) {
|
|
// The JVM does this hack also.
|
|
// (See ClassVerifier::verify_invoke_instructions
|
|
// and LinkResolver::check_method_accessability.)
|
|
// Because the JVM does not allow separate methods on array types,
|
|
// there is no separate method for int[].clone.
|
|
// All arrays simply inherit Object.clone.
|
|
// But for access checking logic, we make Object.clone
|
|
// (normally protected) appear to be public.
|
|
// Later on, when the DirectMethodHandle is created,
|
|
// its leading argument will be restricted to the
|
|
// requested array type.
|
|
// N.B. The return type is not adjusted, because
|
|
// that is *not* the bytecode behavior.
|
|
mods ^= Modifier.PROTECTED | Modifier.PUBLIC;
|
|
}
|
|
if (Modifier.isProtected(mods) && refKind == REF_newInvokeSpecial) {
|
|
// cannot "new" a protected ctor in a different package
|
|
mods ^= Modifier.PROTECTED;
|
|
}
|
|
if (Modifier.isFinal(mods) &&
|
|
MethodHandleNatives.refKindIsSetter(refKind))
|
|
throw m.makeAccessException("unexpected set of a final field", this);
|
|
if (Modifier.isPublic(mods) && Modifier.isPublic(refc.getModifiers()) && allowedModes != 0)
|
|
return; // common case
|
|
int requestedModes = fixmods(mods); // adjust 0 => PACKAGE
|
|
if ((requestedModes & allowedModes) != 0) {
|
|
if (VerifyAccess.isMemberAccessible(refc, m.getDeclaringClass(),
|
|
mods, lookupClass(), allowedModes))
|
|
return;
|
|
} else {
|
|
// Protected members can also be checked as if they were package-private.
|
|
if ((requestedModes & PROTECTED) != 0 && (allowedModes & PACKAGE) != 0
|
|
&& VerifyAccess.isSamePackage(m.getDeclaringClass(), lookupClass()))
|
|
return;
|
|
}
|
|
throw m.makeAccessException(accessFailedMessage(refc, m), this);
|
|
}
|
|
|
|
String accessFailedMessage(Class<?> refc, MemberName m) {
|
|
Class<?> defc = m.getDeclaringClass();
|
|
int mods = m.getModifiers();
|
|
// check the class first:
|
|
boolean classOK = (Modifier.isPublic(defc.getModifiers()) &&
|
|
(defc == refc ||
|
|
Modifier.isPublic(refc.getModifiers())));
|
|
if (!classOK && (allowedModes & PACKAGE) != 0) {
|
|
classOK = (VerifyAccess.isClassAccessible(defc, lookupClass(), ALL_MODES) &&
|
|
(defc == refc ||
|
|
VerifyAccess.isClassAccessible(refc, lookupClass(), ALL_MODES)));
|
|
}
|
|
if (!classOK)
|
|
return "class is not public";
|
|
if (Modifier.isPublic(mods))
|
|
return "access to public member failed"; // (how?)
|
|
if (Modifier.isPrivate(mods))
|
|
return "member is private";
|
|
if (Modifier.isProtected(mods))
|
|
return "member is protected";
|
|
return "member is private to package";
|
|
}
|
|
|
|
private static final boolean ALLOW_NESTMATE_ACCESS = false;
|
|
|
|
private void checkSpecialCaller(Class<?> specialCaller, Class<?> refc) throws IllegalAccessException {
|
|
int allowedModes = this.allowedModes;
|
|
if (allowedModes == TRUSTED) return;
|
|
if (!hasPrivateAccess()
|
|
|| (specialCaller != lookupClass()
|
|
// ensure non-abstract methods in superinterfaces can be special-invoked
|
|
&& !(refc != null && refc.isInterface() && refc.isAssignableFrom(specialCaller))
|
|
&& !(ALLOW_NESTMATE_ACCESS &&
|
|
VerifyAccess.isSamePackageMember(specialCaller, lookupClass()))))
|
|
throw new MemberName(specialCaller).
|
|
makeAccessException("no private access for invokespecial", this);
|
|
}
|
|
|
|
private boolean restrictProtectedReceiver(MemberName method) {
|
|
// The accessing class only has the right to use a protected member
|
|
// on itself or a subclass. Enforce that restriction, from JVMS 5.4.4, etc.
|
|
if (!method.isProtected() || method.isStatic()
|
|
|| allowedModes == TRUSTED
|
|
|| method.getDeclaringClass() == lookupClass()
|
|
|| VerifyAccess.isSamePackage(method.getDeclaringClass(), lookupClass())
|
|
|| (ALLOW_NESTMATE_ACCESS &&
|
|
VerifyAccess.isSamePackageMember(method.getDeclaringClass(), lookupClass())))
|
|
return false;
|
|
return true;
|
|
}
|
|
private MethodHandle restrictReceiver(MemberName method, DirectMethodHandle mh, Class<?> caller) throws IllegalAccessException {
|
|
assert(!method.isStatic());
|
|
// receiver type of mh is too wide; narrow to caller
|
|
if (!method.getDeclaringClass().isAssignableFrom(caller)) {
|
|
throw method.makeAccessException("caller class must be a subclass below the method", caller);
|
|
}
|
|
MethodType rawType = mh.type();
|
|
if (rawType.parameterType(0) == caller) return mh;
|
|
MethodType narrowType = rawType.changeParameterType(0, caller);
|
|
assert(!mh.isVarargsCollector()); // viewAsType will lose varargs-ness
|
|
assert(mh.viewAsTypeChecks(narrowType, true));
|
|
return mh.copyWith(narrowType, mh.form);
|
|
}
|
|
|
|
/** Check access and get the requested method. */
|
|
private MethodHandle getDirectMethod(byte refKind, Class<?> refc, MemberName method, Class<?> callerClass) throws IllegalAccessException {
|
|
final boolean doRestrict = true;
|
|
final boolean checkSecurity = true;
|
|
return getDirectMethodCommon(refKind, refc, method, checkSecurity, doRestrict, callerClass);
|
|
}
|
|
/** Check access and get the requested method, eliding receiver narrowing rules. */
|
|
private MethodHandle getDirectMethodNoRestrict(byte refKind, Class<?> refc, MemberName method, Class<?> callerClass) throws IllegalAccessException {
|
|
final boolean doRestrict = false;
|
|
final boolean checkSecurity = true;
|
|
return getDirectMethodCommon(refKind, refc, method, checkSecurity, doRestrict, callerClass);
|
|
}
|
|
/** Check access and get the requested method, eliding security manager checks. */
|
|
private MethodHandle getDirectMethodNoSecurityManager(byte refKind, Class<?> refc, MemberName method, Class<?> callerClass) throws IllegalAccessException {
|
|
final boolean doRestrict = true;
|
|
final boolean checkSecurity = false; // not needed for reflection or for linking CONSTANT_MH constants
|
|
return getDirectMethodCommon(refKind, refc, method, checkSecurity, doRestrict, callerClass);
|
|
}
|
|
/** Common code for all methods; do not call directly except from immediately above. */
|
|
private MethodHandle getDirectMethodCommon(byte refKind, Class<?> refc, MemberName method,
|
|
boolean checkSecurity,
|
|
boolean doRestrict, Class<?> callerClass) throws IllegalAccessException {
|
|
checkMethod(refKind, refc, method);
|
|
// Optionally check with the security manager; this isn't needed for unreflect* calls.
|
|
if (checkSecurity)
|
|
checkSecurityManager(refc, method);
|
|
assert(!method.isMethodHandleInvoke());
|
|
|
|
if (refKind == REF_invokeSpecial &&
|
|
refc != lookupClass() &&
|
|
!refc.isInterface() &&
|
|
refc != lookupClass().getSuperclass() &&
|
|
refc.isAssignableFrom(lookupClass())) {
|
|
assert(!method.getName().equals("<init>")); // not this code path
|
|
// Per JVMS 6.5, desc. of invokespecial instruction:
|
|
// If the method is in a superclass of the LC,
|
|
// and if our original search was above LC.super,
|
|
// repeat the search (symbolic lookup) from LC.super
|
|
// and continue with the direct superclass of that class,
|
|
// and so forth, until a match is found or no further superclasses exist.
|
|
// FIXME: MemberName.resolve should handle this instead.
|
|
Class<?> refcAsSuper = lookupClass();
|
|
MemberName m2;
|
|
do {
|
|
refcAsSuper = refcAsSuper.getSuperclass();
|
|
m2 = new MemberName(refcAsSuper,
|
|
method.getName(),
|
|
method.getMethodType(),
|
|
REF_invokeSpecial);
|
|
m2 = IMPL_NAMES.resolveOrNull(refKind, m2, lookupClassOrNull());
|
|
} while (m2 == null && // no method is found yet
|
|
refc != refcAsSuper); // search up to refc
|
|
if (m2 == null) throw new InternalError(method.toString());
|
|
method = m2;
|
|
refc = refcAsSuper;
|
|
// redo basic checks
|
|
checkMethod(refKind, refc, method);
|
|
}
|
|
|
|
DirectMethodHandle dmh = DirectMethodHandle.make(refKind, refc, method);
|
|
MethodHandle mh = dmh;
|
|
// Optionally narrow the receiver argument to refc using restrictReceiver.
|
|
if (doRestrict &&
|
|
(refKind == REF_invokeSpecial ||
|
|
(MethodHandleNatives.refKindHasReceiver(refKind) &&
|
|
restrictProtectedReceiver(method)))) {
|
|
mh = restrictReceiver(method, dmh, lookupClass());
|
|
}
|
|
mh = maybeBindCaller(method, mh, callerClass);
|
|
mh = mh.setVarargs(method);
|
|
return mh;
|
|
}
|
|
private MethodHandle maybeBindCaller(MemberName method, MethodHandle mh,
|
|
Class<?> callerClass)
|
|
throws IllegalAccessException {
|
|
if (allowedModes == TRUSTED || !MethodHandleNatives.isCallerSensitive(method))
|
|
return mh;
|
|
Class<?> hostClass = lookupClass;
|
|
if (!hasPrivateAccess()) // caller must have private access
|
|
hostClass = callerClass; // callerClass came from a security manager style stack walk
|
|
MethodHandle cbmh = MethodHandleImpl.bindCaller(mh, hostClass);
|
|
// Note: caller will apply varargs after this step happens.
|
|
return cbmh;
|
|
}
|
|
/** Check access and get the requested field. */
|
|
private MethodHandle getDirectField(byte refKind, Class<?> refc, MemberName field) throws IllegalAccessException {
|
|
final boolean checkSecurity = true;
|
|
return getDirectFieldCommon(refKind, refc, field, checkSecurity);
|
|
}
|
|
/** Check access and get the requested field, eliding security manager checks. */
|
|
private MethodHandle getDirectFieldNoSecurityManager(byte refKind, Class<?> refc, MemberName field) throws IllegalAccessException {
|
|
final boolean checkSecurity = false; // not needed for reflection or for linking CONSTANT_MH constants
|
|
return getDirectFieldCommon(refKind, refc, field, checkSecurity);
|
|
}
|
|
/** Common code for all fields; do not call directly except from immediately above. */
|
|
private MethodHandle getDirectFieldCommon(byte refKind, Class<?> refc, MemberName field,
|
|
boolean checkSecurity) throws IllegalAccessException {
|
|
checkField(refKind, refc, field);
|
|
// Optionally check with the security manager; this isn't needed for unreflect* calls.
|
|
if (checkSecurity)
|
|
checkSecurityManager(refc, field);
|
|
DirectMethodHandle dmh = DirectMethodHandle.make(refc, field);
|
|
boolean doRestrict = (MethodHandleNatives.refKindHasReceiver(refKind) &&
|
|
restrictProtectedReceiver(field));
|
|
if (doRestrict)
|
|
return restrictReceiver(field, dmh, lookupClass());
|
|
return dmh;
|
|
}
|
|
/** Check access and get the requested constructor. */
|
|
private MethodHandle getDirectConstructor(Class<?> refc, MemberName ctor) throws IllegalAccessException {
|
|
final boolean checkSecurity = true;
|
|
return getDirectConstructorCommon(refc, ctor, checkSecurity);
|
|
}
|
|
/** Check access and get the requested constructor, eliding security manager checks. */
|
|
private MethodHandle getDirectConstructorNoSecurityManager(Class<?> refc, MemberName ctor) throws IllegalAccessException {
|
|
final boolean checkSecurity = false; // not needed for reflection or for linking CONSTANT_MH constants
|
|
return getDirectConstructorCommon(refc, ctor, checkSecurity);
|
|
}
|
|
/** Common code for all constructors; do not call directly except from immediately above. */
|
|
private MethodHandle getDirectConstructorCommon(Class<?> refc, MemberName ctor,
|
|
boolean checkSecurity) throws IllegalAccessException {
|
|
assert(ctor.isConstructor());
|
|
checkAccess(REF_newInvokeSpecial, refc, ctor);
|
|
// Optionally check with the security manager; this isn't needed for unreflect* calls.
|
|
if (checkSecurity)
|
|
checkSecurityManager(refc, ctor);
|
|
assert(!MethodHandleNatives.isCallerSensitive(ctor)); // maybeBindCaller not relevant here
|
|
return DirectMethodHandle.make(ctor).setVarargs(ctor);
|
|
}
|
|
|
|
/** Hook called from the JVM (via MethodHandleNatives) to link MH constants:
|
|
*/
|
|
/*non-public*/
|
|
MethodHandle linkMethodHandleConstant(byte refKind, Class<?> defc, String name, Object type) throws ReflectiveOperationException {
|
|
if (!(type instanceof Class || type instanceof MethodType))
|
|
throw new InternalError("unresolved MemberName");
|
|
MemberName member = new MemberName(refKind, defc, name, type);
|
|
MethodHandle mh = LOOKASIDE_TABLE.get(member);
|
|
if (mh != null) {
|
|
checkSymbolicClass(defc);
|
|
return mh;
|
|
}
|
|
// Treat MethodHandle.invoke and invokeExact specially.
|
|
if (defc == MethodHandle.class && refKind == REF_invokeVirtual) {
|
|
mh = findVirtualForMH(member.getName(), member.getMethodType());
|
|
if (mh != null) {
|
|
return mh;
|
|
}
|
|
}
|
|
MemberName resolved = resolveOrFail(refKind, member);
|
|
mh = getDirectMethodForConstant(refKind, defc, resolved);
|
|
if (mh instanceof DirectMethodHandle
|
|
&& canBeCached(refKind, defc, resolved)) {
|
|
MemberName key = mh.internalMemberName();
|
|
if (key != null) {
|
|
key = key.asNormalOriginal();
|
|
}
|
|
if (member.equals(key)) { // better safe than sorry
|
|
LOOKASIDE_TABLE.put(key, (DirectMethodHandle) mh);
|
|
}
|
|
}
|
|
return mh;
|
|
}
|
|
private
|
|
boolean canBeCached(byte refKind, Class<?> defc, MemberName member) {
|
|
if (refKind == REF_invokeSpecial) {
|
|
return false;
|
|
}
|
|
if (!Modifier.isPublic(defc.getModifiers()) ||
|
|
!Modifier.isPublic(member.getDeclaringClass().getModifiers()) ||
|
|
!member.isPublic() ||
|
|
member.isCallerSensitive()) {
|
|
return false;
|
|
}
|
|
ClassLoader loader = defc.getClassLoader();
|
|
if (!jdk.internal.misc.VM.isSystemDomainLoader(loader)) {
|
|
ClassLoader sysl = ClassLoader.getSystemClassLoader();
|
|
boolean found = false;
|
|
while (sysl != null) {
|
|
if (loader == sysl) { found = true; break; }
|
|
sysl = sysl.getParent();
|
|
}
|
|
if (!found) {
|
|
return false;
|
|
}
|
|
}
|
|
try {
|
|
MemberName resolved2 = publicLookup().resolveOrFail(refKind,
|
|
new MemberName(refKind, defc, member.getName(), member.getType()));
|
|
checkSecurityManager(defc, resolved2);
|
|
} catch (ReflectiveOperationException | SecurityException ex) {
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
private
|
|
MethodHandle getDirectMethodForConstant(byte refKind, Class<?> defc, MemberName member)
|
|
throws ReflectiveOperationException {
|
|
if (MethodHandleNatives.refKindIsField(refKind)) {
|
|
return getDirectFieldNoSecurityManager(refKind, defc, member);
|
|
} else if (MethodHandleNatives.refKindIsMethod(refKind)) {
|
|
return getDirectMethodNoSecurityManager(refKind, defc, member, lookupClass);
|
|
} else if (refKind == REF_newInvokeSpecial) {
|
|
return getDirectConstructorNoSecurityManager(defc, member);
|
|
}
|
|
// oops
|
|
throw newIllegalArgumentException("bad MethodHandle constant #"+member);
|
|
}
|
|
|
|
static ConcurrentHashMap<MemberName, DirectMethodHandle> LOOKASIDE_TABLE = new ConcurrentHashMap<>();
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving read access to elements of an array.
|
|
* The type of the method handle will have a return type of the array's
|
|
* element type. Its first argument will be the array type,
|
|
* and the second will be {@code int}.
|
|
* @param arrayClass an array type
|
|
* @return a method handle which can load values from the given array type
|
|
* @throws NullPointerException if the argument is null
|
|
* @throws IllegalArgumentException if arrayClass is not an array type
|
|
*/
|
|
public static
|
|
MethodHandle arrayElementGetter(Class<?> arrayClass) throws IllegalArgumentException {
|
|
return MethodHandleImpl.makeArrayElementAccessor(arrayClass, false);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle giving write access to elements of an array.
|
|
* The type of the method handle will have a void return type.
|
|
* Its last argument will be the array's element type.
|
|
* The first and second arguments will be the array type and int.
|
|
* @param arrayClass the class of an array
|
|
* @return a method handle which can store values into the array type
|
|
* @throws NullPointerException if the argument is null
|
|
* @throws IllegalArgumentException if arrayClass is not an array type
|
|
*/
|
|
public static
|
|
MethodHandle arrayElementSetter(Class<?> arrayClass) throws IllegalArgumentException {
|
|
return MethodHandleImpl.makeArrayElementAccessor(arrayClass, true);
|
|
}
|
|
|
|
/// method handle invocation (reflective style)
|
|
|
|
/**
|
|
* Produces a method handle which will invoke any method handle of the
|
|
* given {@code type}, with a given number of trailing arguments replaced by
|
|
* a single trailing {@code Object[]} array.
|
|
* The resulting invoker will be a method handle with the following
|
|
* arguments:
|
|
* <ul>
|
|
* <li>a single {@code MethodHandle} target
|
|
* <li>zero or more leading values (counted by {@code leadingArgCount})
|
|
* <li>an {@code Object[]} array containing trailing arguments
|
|
* </ul>
|
|
* <p>
|
|
* The invoker will invoke its target like a call to {@link MethodHandle#invoke invoke} with
|
|
* the indicated {@code type}.
|
|
* That is, if the target is exactly of the given {@code type}, it will behave
|
|
* like {@code invokeExact}; otherwise it behave as if {@link MethodHandle#asType asType}
|
|
* is used to convert the target to the required {@code type}.
|
|
* <p>
|
|
* The type of the returned invoker will not be the given {@code type}, but rather
|
|
* will have all parameters except the first {@code leadingArgCount}
|
|
* replaced by a single array of type {@code Object[]}, which will be
|
|
* the final parameter.
|
|
* <p>
|
|
* Before invoking its target, the invoker will spread the final array, apply
|
|
* reference casts as necessary, and unbox and widen primitive arguments.
|
|
* If, when the invoker is called, the supplied array argument does
|
|
* not have the correct number of elements, the invoker will throw
|
|
* an {@link IllegalArgumentException} instead of invoking the target.
|
|
* <p>
|
|
* This method is equivalent to the following code (though it may be more efficient):
|
|
* <blockquote><pre>{@code
|
|
MethodHandle invoker = MethodHandles.invoker(type);
|
|
int spreadArgCount = type.parameterCount() - leadingArgCount;
|
|
invoker = invoker.asSpreader(Object[].class, spreadArgCount);
|
|
return invoker;
|
|
* }</pre></blockquote>
|
|
* This method throws no reflective or security exceptions.
|
|
* @param type the desired target type
|
|
* @param leadingArgCount number of fixed arguments, to be passed unchanged to the target
|
|
* @return a method handle suitable for invoking any method handle of the given type
|
|
* @throws NullPointerException if {@code type} is null
|
|
* @throws IllegalArgumentException if {@code leadingArgCount} is not in
|
|
* the range from 0 to {@code type.parameterCount()} inclusive,
|
|
* or if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
*/
|
|
public static
|
|
MethodHandle spreadInvoker(MethodType type, int leadingArgCount) {
|
|
if (leadingArgCount < 0 || leadingArgCount > type.parameterCount())
|
|
throw newIllegalArgumentException("bad argument count", leadingArgCount);
|
|
type = type.asSpreaderType(Object[].class, leadingArgCount, type.parameterCount() - leadingArgCount);
|
|
return type.invokers().spreadInvoker(leadingArgCount);
|
|
}
|
|
|
|
/**
|
|
* Produces a special <em>invoker method handle</em> which can be used to
|
|
* invoke any method handle of the given type, as if by {@link MethodHandle#invokeExact invokeExact}.
|
|
* The resulting invoker will have a type which is
|
|
* exactly equal to the desired type, except that it will accept
|
|
* an additional leading argument of type {@code MethodHandle}.
|
|
* <p>
|
|
* This method is equivalent to the following code (though it may be more efficient):
|
|
* {@code publicLookup().findVirtual(MethodHandle.class, "invokeExact", type)}
|
|
*
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* Invoker method handles can be useful when working with variable method handles
|
|
* of unknown types.
|
|
* For example, to emulate an {@code invokeExact} call to a variable method
|
|
* handle {@code M}, extract its type {@code T},
|
|
* look up the invoker method {@code X} for {@code T},
|
|
* and call the invoker method, as {@code X.invoke(T, A...)}.
|
|
* (It would not work to call {@code X.invokeExact}, since the type {@code T}
|
|
* is unknown.)
|
|
* If spreading, collecting, or other argument transformations are required,
|
|
* they can be applied once to the invoker {@code X} and reused on many {@code M}
|
|
* method handle values, as long as they are compatible with the type of {@code X}.
|
|
* <p style="font-size:smaller;">
|
|
* <em>(Note: The invoker method is not available via the Core Reflection API.
|
|
* An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
|
|
* on the declared {@code invokeExact} or {@code invoke} method will raise an
|
|
* {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)</em>
|
|
* <p>
|
|
* This method throws no reflective or security exceptions.
|
|
* @param type the desired target type
|
|
* @return a method handle suitable for invoking any method handle of the given type
|
|
* @throws IllegalArgumentException if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
*/
|
|
public static
|
|
MethodHandle exactInvoker(MethodType type) {
|
|
return type.invokers().exactInvoker();
|
|
}
|
|
|
|
/**
|
|
* Produces a special <em>invoker method handle</em> which can be used to
|
|
* invoke any method handle compatible with the given type, as if by {@link MethodHandle#invoke invoke}.
|
|
* The resulting invoker will have a type which is
|
|
* exactly equal to the desired type, except that it will accept
|
|
* an additional leading argument of type {@code MethodHandle}.
|
|
* <p>
|
|
* Before invoking its target, if the target differs from the expected type,
|
|
* the invoker will apply reference casts as
|
|
* necessary and box, unbox, or widen primitive values, as if by {@link MethodHandle#asType asType}.
|
|
* Similarly, the return value will be converted as necessary.
|
|
* If the target is a {@linkplain MethodHandle#asVarargsCollector variable arity method handle},
|
|
* the required arity conversion will be made, again as if by {@link MethodHandle#asType asType}.
|
|
* <p>
|
|
* This method is equivalent to the following code (though it may be more efficient):
|
|
* {@code publicLookup().findVirtual(MethodHandle.class, "invoke", type)}
|
|
* <p style="font-size:smaller;">
|
|
* <em>Discussion:</em>
|
|
* A {@linkplain MethodType#genericMethodType general method type} is one which
|
|
* mentions only {@code Object} arguments and return values.
|
|
* An invoker for such a type is capable of calling any method handle
|
|
* of the same arity as the general type.
|
|
* <p style="font-size:smaller;">
|
|
* <em>(Note: The invoker method is not available via the Core Reflection API.
|
|
* An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
|
|
* on the declared {@code invokeExact} or {@code invoke} method will raise an
|
|
* {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)</em>
|
|
* <p>
|
|
* This method throws no reflective or security exceptions.
|
|
* @param type the desired target type
|
|
* @return a method handle suitable for invoking any method handle convertible to the given type
|
|
* @throws IllegalArgumentException if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
*/
|
|
public static
|
|
MethodHandle invoker(MethodType type) {
|
|
return type.invokers().genericInvoker();
|
|
}
|
|
|
|
static /*non-public*/
|
|
MethodHandle basicInvoker(MethodType type) {
|
|
return type.invokers().basicInvoker();
|
|
}
|
|
|
|
/// method handle modification (creation from other method handles)
|
|
|
|
/**
|
|
* Produces a method handle which adapts the type of the
|
|
* given method handle to a new type by pairwise argument and return type conversion.
|
|
* The original type and new type must have the same number of arguments.
|
|
* The resulting method handle is guaranteed to report a type
|
|
* which is equal to the desired new type.
|
|
* <p>
|
|
* If the original type and new type are equal, returns target.
|
|
* <p>
|
|
* The same conversions are allowed as for {@link MethodHandle#asType MethodHandle.asType},
|
|
* and some additional conversions are also applied if those conversions fail.
|
|
* Given types <em>T0</em>, <em>T1</em>, one of the following conversions is applied
|
|
* if possible, before or instead of any conversions done by {@code asType}:
|
|
* <ul>
|
|
* <li>If <em>T0</em> and <em>T1</em> are references, and <em>T1</em> is an interface type,
|
|
* then the value of type <em>T0</em> is passed as a <em>T1</em> without a cast.
|
|
* (This treatment of interfaces follows the usage of the bytecode verifier.)
|
|
* <li>If <em>T0</em> is boolean and <em>T1</em> is another primitive,
|
|
* the boolean is converted to a byte value, 1 for true, 0 for false.
|
|
* (This treatment follows the usage of the bytecode verifier.)
|
|
* <li>If <em>T1</em> is boolean and <em>T0</em> is another primitive,
|
|
* <em>T0</em> is converted to byte via Java casting conversion (JLS 5.5),
|
|
* and the low order bit of the result is tested, as if by {@code (x & 1) != 0}.
|
|
* <li>If <em>T0</em> and <em>T1</em> are primitives other than boolean,
|
|
* then a Java casting conversion (JLS 5.5) is applied.
|
|
* (Specifically, <em>T0</em> will convert to <em>T1</em> by
|
|
* widening and/or narrowing.)
|
|
* <li>If <em>T0</em> is a reference and <em>T1</em> a primitive, an unboxing
|
|
* conversion will be applied at runtime, possibly followed
|
|
* by a Java casting conversion (JLS 5.5) on the primitive value,
|
|
* possibly followed by a conversion from byte to boolean by testing
|
|
* the low-order bit.
|
|
* <li>If <em>T0</em> is a reference and <em>T1</em> a primitive,
|
|
* and if the reference is null at runtime, a zero value is introduced.
|
|
* </ul>
|
|
* @param target the method handle to invoke after arguments are retyped
|
|
* @param newType the expected type of the new method handle
|
|
* @return a method handle which delegates to the target after performing
|
|
* any necessary argument conversions, and arranges for any
|
|
* necessary return value conversions
|
|
* @throws NullPointerException if either argument is null
|
|
* @throws WrongMethodTypeException if the conversion cannot be made
|
|
* @see MethodHandle#asType
|
|
*/
|
|
public static
|
|
MethodHandle explicitCastArguments(MethodHandle target, MethodType newType) {
|
|
explicitCastArgumentsChecks(target, newType);
|
|
// use the asTypeCache when possible:
|
|
MethodType oldType = target.type();
|
|
if (oldType == newType) return target;
|
|
if (oldType.explicitCastEquivalentToAsType(newType)) {
|
|
return target.asFixedArity().asType(newType);
|
|
}
|
|
return MethodHandleImpl.makePairwiseConvert(target, newType, false);
|
|
}
|
|
|
|
private static void explicitCastArgumentsChecks(MethodHandle target, MethodType newType) {
|
|
if (target.type().parameterCount() != newType.parameterCount()) {
|
|
throw new WrongMethodTypeException("cannot explicitly cast " + target + " to " + newType);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle which adapts the calling sequence of the
|
|
* given method handle to a new type, by reordering the arguments.
|
|
* The resulting method handle is guaranteed to report a type
|
|
* which is equal to the desired new type.
|
|
* <p>
|
|
* The given array controls the reordering.
|
|
* Call {@code #I} the number of incoming parameters (the value
|
|
* {@code newType.parameterCount()}, and call {@code #O} the number
|
|
* of outgoing parameters (the value {@code target.type().parameterCount()}).
|
|
* Then the length of the reordering array must be {@code #O},
|
|
* and each element must be a non-negative number less than {@code #I}.
|
|
* For every {@code N} less than {@code #O}, the {@code N}-th
|
|
* outgoing argument will be taken from the {@code I}-th incoming
|
|
* argument, where {@code I} is {@code reorder[N]}.
|
|
* <p>
|
|
* No argument or return value conversions are applied.
|
|
* The type of each incoming argument, as determined by {@code newType},
|
|
* must be identical to the type of the corresponding outgoing parameter
|
|
* or parameters in the target method handle.
|
|
* The return type of {@code newType} must be identical to the return
|
|
* type of the original target.
|
|
* <p>
|
|
* The reordering array need not specify an actual permutation.
|
|
* An incoming argument will be duplicated if its index appears
|
|
* more than once in the array, and an incoming argument will be dropped
|
|
* if its index does not appear in the array.
|
|
* As in the case of {@link #dropArguments(MethodHandle,int,List) dropArguments},
|
|
* incoming arguments which are not mentioned in the reordering array
|
|
* may be of any type, as determined only by {@code newType}.
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodType intfn1 = methodType(int.class, int.class);
|
|
MethodType intfn2 = methodType(int.class, int.class, int.class);
|
|
MethodHandle sub = ... (int x, int y) -> (x-y) ...;
|
|
assert(sub.type().equals(intfn2));
|
|
MethodHandle sub1 = permuteArguments(sub, intfn2, 0, 1);
|
|
MethodHandle rsub = permuteArguments(sub, intfn2, 1, 0);
|
|
assert((int)rsub.invokeExact(1, 100) == 99);
|
|
MethodHandle add = ... (int x, int y) -> (x+y) ...;
|
|
assert(add.type().equals(intfn2));
|
|
MethodHandle twice = permuteArguments(add, intfn1, 0, 0);
|
|
assert(twice.type().equals(intfn1));
|
|
assert((int)twice.invokeExact(21) == 42);
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
* @param target the method handle to invoke after arguments are reordered
|
|
* @param newType the expected type of the new method handle
|
|
* @param reorder an index array which controls the reordering
|
|
* @return a method handle which delegates to the target after it
|
|
* drops unused arguments and moves and/or duplicates the other arguments
|
|
* @throws NullPointerException if any argument is null
|
|
* @throws IllegalArgumentException if the index array length is not equal to
|
|
* the arity of the target, or if any index array element
|
|
* not a valid index for a parameter of {@code newType},
|
|
* or if two corresponding parameter types in
|
|
* {@code target.type()} and {@code newType} are not identical,
|
|
*/
|
|
public static
|
|
MethodHandle permuteArguments(MethodHandle target, MethodType newType, int... reorder) {
|
|
reorder = reorder.clone(); // get a private copy
|
|
MethodType oldType = target.type();
|
|
permuteArgumentChecks(reorder, newType, oldType);
|
|
// first detect dropped arguments and handle them separately
|
|
int[] originalReorder = reorder;
|
|
BoundMethodHandle result = target.rebind();
|
|
LambdaForm form = result.form;
|
|
int newArity = newType.parameterCount();
|
|
// Normalize the reordering into a real permutation,
|
|
// by removing duplicates and adding dropped elements.
|
|
// This somewhat improves lambda form caching, as well
|
|
// as simplifying the transform by breaking it up into steps.
|
|
for (int ddIdx; (ddIdx = findFirstDupOrDrop(reorder, newArity)) != 0; ) {
|
|
if (ddIdx > 0) {
|
|
// We found a duplicated entry at reorder[ddIdx].
|
|
// Example: (x,y,z)->asList(x,y,z)
|
|
// permuted by [1*,0,1] => (a0,a1)=>asList(a1,a0,a1)
|
|
// permuted by [0,1,0*] => (a0,a1)=>asList(a0,a1,a0)
|
|
// The starred element corresponds to the argument
|
|
// deleted by the dupArgumentForm transform.
|
|
int srcPos = ddIdx, dstPos = srcPos, dupVal = reorder[srcPos];
|
|
boolean killFirst = false;
|
|
for (int val; (val = reorder[--dstPos]) != dupVal; ) {
|
|
// Set killFirst if the dup is larger than an intervening position.
|
|
// This will remove at least one inversion from the permutation.
|
|
if (dupVal > val) killFirst = true;
|
|
}
|
|
if (!killFirst) {
|
|
srcPos = dstPos;
|
|
dstPos = ddIdx;
|
|
}
|
|
form = form.editor().dupArgumentForm(1 + srcPos, 1 + dstPos);
|
|
assert (reorder[srcPos] == reorder[dstPos]);
|
|
oldType = oldType.dropParameterTypes(dstPos, dstPos + 1);
|
|
// contract the reordering by removing the element at dstPos
|
|
int tailPos = dstPos + 1;
|
|
System.arraycopy(reorder, tailPos, reorder, dstPos, reorder.length - tailPos);
|
|
reorder = Arrays.copyOf(reorder, reorder.length - 1);
|
|
} else {
|
|
int dropVal = ~ddIdx, insPos = 0;
|
|
while (insPos < reorder.length && reorder[insPos] < dropVal) {
|
|
// Find first element of reorder larger than dropVal.
|
|
// This is where we will insert the dropVal.
|
|
insPos += 1;
|
|
}
|
|
Class<?> ptype = newType.parameterType(dropVal);
|
|
form = form.editor().addArgumentForm(1 + insPos, BasicType.basicType(ptype));
|
|
oldType = oldType.insertParameterTypes(insPos, ptype);
|
|
// expand the reordering by inserting an element at insPos
|
|
int tailPos = insPos + 1;
|
|
reorder = Arrays.copyOf(reorder, reorder.length + 1);
|
|
System.arraycopy(reorder, insPos, reorder, tailPos, reorder.length - tailPos);
|
|
reorder[insPos] = dropVal;
|
|
}
|
|
assert (permuteArgumentChecks(reorder, newType, oldType));
|
|
}
|
|
assert (reorder.length == newArity); // a perfect permutation
|
|
// Note: This may cache too many distinct LFs. Consider backing off to varargs code.
|
|
form = form.editor().permuteArgumentsForm(1, reorder);
|
|
if (newType == result.type() && form == result.internalForm())
|
|
return result;
|
|
return result.copyWith(newType, form);
|
|
}
|
|
|
|
/**
|
|
* Return an indication of any duplicate or omission in reorder.
|
|
* If the reorder contains a duplicate entry, return the index of the second occurrence.
|
|
* Otherwise, return ~(n), for the first n in [0..newArity-1] that is not present in reorder.
|
|
* Otherwise, return zero.
|
|
* If an element not in [0..newArity-1] is encountered, return reorder.length.
|
|
*/
|
|
private static int findFirstDupOrDrop(int[] reorder, int newArity) {
|
|
final int BIT_LIMIT = 63; // max number of bits in bit mask
|
|
if (newArity < BIT_LIMIT) {
|
|
long mask = 0;
|
|
for (int i = 0; i < reorder.length; i++) {
|
|
int arg = reorder[i];
|
|
if (arg >= newArity) {
|
|
return reorder.length;
|
|
}
|
|
long bit = 1L << arg;
|
|
if ((mask & bit) != 0) {
|
|
return i; // >0 indicates a dup
|
|
}
|
|
mask |= bit;
|
|
}
|
|
if (mask == (1L << newArity) - 1) {
|
|
assert(Long.numberOfTrailingZeros(Long.lowestOneBit(~mask)) == newArity);
|
|
return 0;
|
|
}
|
|
// find first zero
|
|
long zeroBit = Long.lowestOneBit(~mask);
|
|
int zeroPos = Long.numberOfTrailingZeros(zeroBit);
|
|
assert(zeroPos <= newArity);
|
|
if (zeroPos == newArity) {
|
|
return 0;
|
|
}
|
|
return ~zeroPos;
|
|
} else {
|
|
// same algorithm, different bit set
|
|
BitSet mask = new BitSet(newArity);
|
|
for (int i = 0; i < reorder.length; i++) {
|
|
int arg = reorder[i];
|
|
if (arg >= newArity) {
|
|
return reorder.length;
|
|
}
|
|
if (mask.get(arg)) {
|
|
return i; // >0 indicates a dup
|
|
}
|
|
mask.set(arg);
|
|
}
|
|
int zeroPos = mask.nextClearBit(0);
|
|
assert(zeroPos <= newArity);
|
|
if (zeroPos == newArity) {
|
|
return 0;
|
|
}
|
|
return ~zeroPos;
|
|
}
|
|
}
|
|
|
|
private static boolean permuteArgumentChecks(int[] reorder, MethodType newType, MethodType oldType) {
|
|
if (newType.returnType() != oldType.returnType())
|
|
throw newIllegalArgumentException("return types do not match",
|
|
oldType, newType);
|
|
if (reorder.length == oldType.parameterCount()) {
|
|
int limit = newType.parameterCount();
|
|
boolean bad = false;
|
|
for (int j = 0; j < reorder.length; j++) {
|
|
int i = reorder[j];
|
|
if (i < 0 || i >= limit) {
|
|
bad = true; break;
|
|
}
|
|
Class<?> src = newType.parameterType(i);
|
|
Class<?> dst = oldType.parameterType(j);
|
|
if (src != dst)
|
|
throw newIllegalArgumentException("parameter types do not match after reorder",
|
|
oldType, newType);
|
|
}
|
|
if (!bad) return true;
|
|
}
|
|
throw newIllegalArgumentException("bad reorder array: "+Arrays.toString(reorder));
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle of the requested return type which returns the given
|
|
* constant value every time it is invoked.
|
|
* <p>
|
|
* Before the method handle is returned, the passed-in value is converted to the requested type.
|
|
* If the requested type is primitive, widening primitive conversions are attempted,
|
|
* else reference conversions are attempted.
|
|
* <p>The returned method handle is equivalent to {@code identity(type).bindTo(value)}.
|
|
* @param type the return type of the desired method handle
|
|
* @param value the value to return
|
|
* @return a method handle of the given return type and no arguments, which always returns the given value
|
|
* @throws NullPointerException if the {@code type} argument is null
|
|
* @throws ClassCastException if the value cannot be converted to the required return type
|
|
* @throws IllegalArgumentException if the given type is {@code void.class}
|
|
*/
|
|
public static
|
|
MethodHandle constant(Class<?> type, Object value) {
|
|
if (type.isPrimitive()) {
|
|
if (type == void.class)
|
|
throw newIllegalArgumentException("void type");
|
|
Wrapper w = Wrapper.forPrimitiveType(type);
|
|
value = w.convert(value, type);
|
|
if (w.zero().equals(value))
|
|
return zero(w, type);
|
|
return insertArguments(identity(type), 0, value);
|
|
} else {
|
|
if (value == null)
|
|
return zero(Wrapper.OBJECT, type);
|
|
return identity(type).bindTo(value);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle which returns its sole argument when invoked.
|
|
* @param type the type of the sole parameter and return value of the desired method handle
|
|
* @return a unary method handle which accepts and returns the given type
|
|
* @throws NullPointerException if the argument is null
|
|
* @throws IllegalArgumentException if the given type is {@code void.class}
|
|
*/
|
|
public static
|
|
MethodHandle identity(Class<?> type) {
|
|
Wrapper btw = (type.isPrimitive() ? Wrapper.forPrimitiveType(type) : Wrapper.OBJECT);
|
|
int pos = btw.ordinal();
|
|
MethodHandle ident = IDENTITY_MHS[pos];
|
|
if (ident == null) {
|
|
ident = setCachedMethodHandle(IDENTITY_MHS, pos, makeIdentity(btw.primitiveType()));
|
|
}
|
|
if (ident.type().returnType() == type)
|
|
return ident;
|
|
// something like identity(Foo.class); do not bother to intern these
|
|
assert(btw == Wrapper.OBJECT);
|
|
return makeIdentity(type);
|
|
}
|
|
private static final MethodHandle[] IDENTITY_MHS = new MethodHandle[Wrapper.values().length];
|
|
private static MethodHandle makeIdentity(Class<?> ptype) {
|
|
MethodType mtype = MethodType.methodType(ptype, ptype);
|
|
LambdaForm lform = LambdaForm.identityForm(BasicType.basicType(ptype));
|
|
return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.IDENTITY);
|
|
}
|
|
|
|
private static MethodHandle zero(Wrapper btw, Class<?> rtype) {
|
|
int pos = btw.ordinal();
|
|
MethodHandle zero = ZERO_MHS[pos];
|
|
if (zero == null) {
|
|
zero = setCachedMethodHandle(ZERO_MHS, pos, makeZero(btw.primitiveType()));
|
|
}
|
|
if (zero.type().returnType() == rtype)
|
|
return zero;
|
|
assert(btw == Wrapper.OBJECT);
|
|
return makeZero(rtype);
|
|
}
|
|
private static final MethodHandle[] ZERO_MHS = new MethodHandle[Wrapper.values().length];
|
|
private static MethodHandle makeZero(Class<?> rtype) {
|
|
MethodType mtype = MethodType.methodType(rtype);
|
|
LambdaForm lform = LambdaForm.zeroForm(BasicType.basicType(rtype));
|
|
return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.ZERO);
|
|
}
|
|
|
|
private static synchronized MethodHandle setCachedMethodHandle(MethodHandle[] cache, int pos, MethodHandle value) {
|
|
// Simulate a CAS, to avoid racy duplication of results.
|
|
MethodHandle prev = cache[pos];
|
|
if (prev != null) return prev;
|
|
return cache[pos] = value;
|
|
}
|
|
|
|
/**
|
|
* Provides a target method handle with one or more <em>bound arguments</em>
|
|
* in advance of the method handle's invocation.
|
|
* The formal parameters to the target corresponding to the bound
|
|
* arguments are called <em>bound parameters</em>.
|
|
* Returns a new method handle which saves away the bound arguments.
|
|
* When it is invoked, it receives arguments for any non-bound parameters,
|
|
* binds the saved arguments to their corresponding parameters,
|
|
* and calls the original target.
|
|
* <p>
|
|
* The type of the new method handle will drop the types for the bound
|
|
* parameters from the original target type, since the new method handle
|
|
* will no longer require those arguments to be supplied by its callers.
|
|
* <p>
|
|
* Each given argument object must match the corresponding bound parameter type.
|
|
* If a bound parameter type is a primitive, the argument object
|
|
* must be a wrapper, and will be unboxed to produce the primitive value.
|
|
* <p>
|
|
* The {@code pos} argument selects which parameters are to be bound.
|
|
* It may range between zero and <i>N-L</i> (inclusively),
|
|
* where <i>N</i> is the arity of the target method handle
|
|
* and <i>L</i> is the length of the values array.
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
* @param target the method handle to invoke after the argument is inserted
|
|
* @param pos where to insert the argument (zero for the first)
|
|
* @param values the series of arguments to insert
|
|
* @return a method handle which inserts an additional argument,
|
|
* before calling the original method handle
|
|
* @throws NullPointerException if the target or the {@code values} array is null
|
|
* @see MethodHandle#bindTo
|
|
*/
|
|
public static
|
|
MethodHandle insertArguments(MethodHandle target, int pos, Object... values) {
|
|
int insCount = values.length;
|
|
Class<?>[] ptypes = insertArgumentsChecks(target, insCount, pos);
|
|
if (insCount == 0) return target;
|
|
BoundMethodHandle result = target.rebind();
|
|
for (int i = 0; i < insCount; i++) {
|
|
Object value = values[i];
|
|
Class<?> ptype = ptypes[pos+i];
|
|
if (ptype.isPrimitive()) {
|
|
result = insertArgumentPrimitive(result, pos, ptype, value);
|
|
} else {
|
|
value = ptype.cast(value); // throw CCE if needed
|
|
result = result.bindArgumentL(pos, value);
|
|
}
|
|
}
|
|
return result;
|
|
}
|
|
|
|
private static BoundMethodHandle insertArgumentPrimitive(BoundMethodHandle result, int pos,
|
|
Class<?> ptype, Object value) {
|
|
Wrapper w = Wrapper.forPrimitiveType(ptype);
|
|
// perform unboxing and/or primitive conversion
|
|
value = w.convert(value, ptype);
|
|
switch (w) {
|
|
case INT: return result.bindArgumentI(pos, (int)value);
|
|
case LONG: return result.bindArgumentJ(pos, (long)value);
|
|
case FLOAT: return result.bindArgumentF(pos, (float)value);
|
|
case DOUBLE: return result.bindArgumentD(pos, (double)value);
|
|
default: return result.bindArgumentI(pos, ValueConversions.widenSubword(value));
|
|
}
|
|
}
|
|
|
|
private static Class<?>[] insertArgumentsChecks(MethodHandle target, int insCount, int pos) throws RuntimeException {
|
|
MethodType oldType = target.type();
|
|
int outargs = oldType.parameterCount();
|
|
int inargs = outargs - insCount;
|
|
if (inargs < 0)
|
|
throw newIllegalArgumentException("too many values to insert");
|
|
if (pos < 0 || pos > inargs)
|
|
throw newIllegalArgumentException("no argument type to append");
|
|
return oldType.ptypes();
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle which will discard some dummy arguments
|
|
* before calling some other specified <i>target</i> method handle.
|
|
* The type of the new method handle will be the same as the target's type,
|
|
* except it will also include the dummy argument types,
|
|
* at some given position.
|
|
* <p>
|
|
* The {@code pos} argument may range between zero and <i>N</i>,
|
|
* where <i>N</i> is the arity of the target.
|
|
* If {@code pos} is zero, the dummy arguments will precede
|
|
* the target's real arguments; if {@code pos} is <i>N</i>
|
|
* they will come after.
|
|
* <p>
|
|
* <b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle cat = lookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
assertEquals("xy", (String) cat.invokeExact("x", "y"));
|
|
MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
|
|
MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
|
|
assertEquals(bigType, d0.type());
|
|
assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* This method is also equivalent to the following code:
|
|
* <blockquote><pre>
|
|
* {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))}
|
|
* </pre></blockquote>
|
|
* @param target the method handle to invoke after the arguments are dropped
|
|
* @param valueTypes the type(s) of the argument(s) to drop
|
|
* @param pos position of first argument to drop (zero for the leftmost)
|
|
* @return a method handle which drops arguments of the given types,
|
|
* before calling the original method handle
|
|
* @throws NullPointerException if the target is null,
|
|
* or if the {@code valueTypes} list or any of its elements is null
|
|
* @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
|
|
* or if {@code pos} is negative or greater than the arity of the target,
|
|
* or if the new method handle's type would have too many parameters
|
|
*/
|
|
public static
|
|
MethodHandle dropArguments(MethodHandle target, int pos, List<Class<?>> valueTypes) {
|
|
MethodType oldType = target.type(); // get NPE
|
|
int dropped = dropArgumentChecks(oldType, pos, valueTypes);
|
|
MethodType newType = oldType.insertParameterTypes(pos, valueTypes);
|
|
if (dropped == 0) return target;
|
|
BoundMethodHandle result = target.rebind();
|
|
LambdaForm lform = result.form;
|
|
int insertFormArg = 1 + pos;
|
|
for (Class<?> ptype : valueTypes) {
|
|
lform = lform.editor().addArgumentForm(insertFormArg++, BasicType.basicType(ptype));
|
|
}
|
|
result = result.copyWith(newType, lform);
|
|
return result;
|
|
}
|
|
|
|
private static int dropArgumentChecks(MethodType oldType, int pos, List<Class<?>> valueTypes) {
|
|
int dropped = valueTypes.size();
|
|
MethodType.checkSlotCount(dropped);
|
|
int outargs = oldType.parameterCount();
|
|
int inargs = outargs + dropped;
|
|
if (pos < 0 || pos > outargs)
|
|
throw newIllegalArgumentException("no argument type to remove"
|
|
+ Arrays.asList(oldType, pos, valueTypes, inargs, outargs)
|
|
);
|
|
return dropped;
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle which will discard some dummy arguments
|
|
* before calling some other specified <i>target</i> method handle.
|
|
* The type of the new method handle will be the same as the target's type,
|
|
* except it will also include the dummy argument types,
|
|
* at some given position.
|
|
* <p>
|
|
* The {@code pos} argument may range between zero and <i>N</i>,
|
|
* where <i>N</i> is the arity of the target.
|
|
* If {@code pos} is zero, the dummy arguments will precede
|
|
* the target's real arguments; if {@code pos} is <i>N</i>
|
|
* they will come after.
|
|
* <p>
|
|
* <b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle cat = lookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
assertEquals("xy", (String) cat.invokeExact("x", "y"));
|
|
MethodHandle d0 = dropArguments(cat, 0, String.class);
|
|
assertEquals("yz", (String) d0.invokeExact("x", "y", "z"));
|
|
MethodHandle d1 = dropArguments(cat, 1, String.class);
|
|
assertEquals("xz", (String) d1.invokeExact("x", "y", "z"));
|
|
MethodHandle d2 = dropArguments(cat, 2, String.class);
|
|
assertEquals("xy", (String) d2.invokeExact("x", "y", "z"));
|
|
MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class);
|
|
assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z"));
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* This method is also equivalent to the following code:
|
|
* <blockquote><pre>
|
|
* {@link #dropArguments(MethodHandle,int,List) dropArguments}{@code (target, pos, Arrays.asList(valueTypes))}
|
|
* </pre></blockquote>
|
|
* @param target the method handle to invoke after the arguments are dropped
|
|
* @param valueTypes the type(s) of the argument(s) to drop
|
|
* @param pos position of first argument to drop (zero for the leftmost)
|
|
* @return a method handle which drops arguments of the given types,
|
|
* before calling the original method handle
|
|
* @throws NullPointerException if the target is null,
|
|
* or if the {@code valueTypes} array or any of its elements is null
|
|
* @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
|
|
* or if {@code pos} is negative or greater than the arity of the target,
|
|
* or if the new method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
*/
|
|
public static
|
|
MethodHandle dropArguments(MethodHandle target, int pos, Class<?>... valueTypes) {
|
|
return dropArguments(target, pos, Arrays.asList(valueTypes));
|
|
}
|
|
|
|
/**
|
|
* Adapts a target method handle by pre-processing
|
|
* one or more of its arguments, each with its own unary filter function,
|
|
* and then calling the target with each pre-processed argument
|
|
* replaced by the result of its corresponding filter function.
|
|
* <p>
|
|
* The pre-processing is performed by one or more method handles,
|
|
* specified in the elements of the {@code filters} array.
|
|
* The first element of the filter array corresponds to the {@code pos}
|
|
* argument of the target, and so on in sequence.
|
|
* <p>
|
|
* Null arguments in the array are treated as identity functions,
|
|
* and the corresponding arguments left unchanged.
|
|
* (If there are no non-null elements in the array, the original target is returned.)
|
|
* Each filter is applied to the corresponding argument of the adapter.
|
|
* <p>
|
|
* If a filter {@code F} applies to the {@code N}th argument of
|
|
* the target, then {@code F} must be a method handle which
|
|
* takes exactly one argument. The type of {@code F}'s sole argument
|
|
* replaces the corresponding argument type of the target
|
|
* in the resulting adapted method handle.
|
|
* The return type of {@code F} must be identical to the corresponding
|
|
* parameter type of the target.
|
|
* <p>
|
|
* It is an error if there are elements of {@code filters}
|
|
* (null or not)
|
|
* which do not correspond to argument positions in the target.
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle cat = lookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
MethodHandle upcase = lookup().findVirtual(String.class,
|
|
"toUpperCase", methodType(String.class));
|
|
assertEquals("xy", (String) cat.invokeExact("x", "y"));
|
|
MethodHandle f0 = filterArguments(cat, 0, upcase);
|
|
assertEquals("Xy", (String) f0.invokeExact("x", "y")); // Xy
|
|
MethodHandle f1 = filterArguments(cat, 1, upcase);
|
|
assertEquals("xY", (String) f1.invokeExact("x", "y")); // xY
|
|
MethodHandle f2 = filterArguments(cat, 0, upcase, upcase);
|
|
assertEquals("XY", (String) f2.invokeExact("x", "y")); // XY
|
|
* }</pre></blockquote>
|
|
* <p>Here is pseudocode for the resulting adapter. In the code, {@code T}
|
|
* denotes the return type of both the {@code target} and resulting adapter.
|
|
* {@code P}/{@code p} and {@code B}/{@code b} represent the types and values
|
|
* of the parameters and arguments that precede and follow the filter position
|
|
* {@code pos}, respectively. {@code A[i]}/{@code a[i]} stand for the types and
|
|
* values of the filtered parameters and arguments; they also represent the
|
|
* return types of the {@code filter[i]} handles. The latter accept arguments
|
|
* {@code v[i]} of type {@code V[i]}, which also appear in the signature of
|
|
* the resulting adapter.
|
|
* <blockquote><pre>{@code
|
|
* T target(P... p, A[i]... a[i], B... b);
|
|
* A[i] filter[i](V[i]);
|
|
* T adapter(P... p, V[i]... v[i], B... b) {
|
|
* return target(p..., filter[i](v[i])..., b...);
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
*
|
|
* @param target the method handle to invoke after arguments are filtered
|
|
* @param pos the position of the first argument to filter
|
|
* @param filters method handles to call initially on filtered arguments
|
|
* @return method handle which incorporates the specified argument filtering logic
|
|
* @throws NullPointerException if the target is null
|
|
* or if the {@code filters} array is null
|
|
* @throws IllegalArgumentException if a non-null element of {@code filters}
|
|
* does not match a corresponding argument type of target as described above,
|
|
* or if the {@code pos+filters.length} is greater than {@code target.type().parameterCount()},
|
|
* or if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
*/
|
|
public static
|
|
MethodHandle filterArguments(MethodHandle target, int pos, MethodHandle... filters) {
|
|
filterArgumentsCheckArity(target, pos, filters);
|
|
MethodHandle adapter = target;
|
|
int curPos = pos-1; // pre-incremented
|
|
for (MethodHandle filter : filters) {
|
|
curPos += 1;
|
|
if (filter == null) continue; // ignore null elements of filters
|
|
adapter = filterArgument(adapter, curPos, filter);
|
|
}
|
|
return adapter;
|
|
}
|
|
|
|
/*non-public*/ static
|
|
MethodHandle filterArgument(MethodHandle target, int pos, MethodHandle filter) {
|
|
filterArgumentChecks(target, pos, filter);
|
|
MethodType targetType = target.type();
|
|
MethodType filterType = filter.type();
|
|
BoundMethodHandle result = target.rebind();
|
|
Class<?> newParamType = filterType.parameterType(0);
|
|
LambdaForm lform = result.editor().filterArgumentForm(1 + pos, BasicType.basicType(newParamType));
|
|
MethodType newType = targetType.changeParameterType(pos, newParamType);
|
|
result = result.copyWithExtendL(newType, lform, filter);
|
|
return result;
|
|
}
|
|
|
|
private static void filterArgumentsCheckArity(MethodHandle target, int pos, MethodHandle[] filters) {
|
|
MethodType targetType = target.type();
|
|
int maxPos = targetType.parameterCount();
|
|
if (pos + filters.length > maxPos)
|
|
throw newIllegalArgumentException("too many filters");
|
|
}
|
|
|
|
private static void filterArgumentChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
|
|
MethodType targetType = target.type();
|
|
MethodType filterType = filter.type();
|
|
if (filterType.parameterCount() != 1
|
|
|| filterType.returnType() != targetType.parameterType(pos))
|
|
throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
|
|
}
|
|
|
|
/**
|
|
* Adapts a target method handle by pre-processing
|
|
* a sub-sequence of its arguments with a filter (another method handle).
|
|
* The pre-processed arguments are replaced by the result (if any) of the
|
|
* filter function.
|
|
* The target is then called on the modified (usually shortened) argument list.
|
|
* <p>
|
|
* If the filter returns a value, the target must accept that value as
|
|
* its argument in position {@code pos}, preceded and/or followed by
|
|
* any arguments not passed to the filter.
|
|
* If the filter returns void, the target must accept all arguments
|
|
* not passed to the filter.
|
|
* No arguments are reordered, and a result returned from the filter
|
|
* replaces (in order) the whole subsequence of arguments originally
|
|
* passed to the adapter.
|
|
* <p>
|
|
* The argument types (if any) of the filter
|
|
* replace zero or one argument types of the target, at position {@code pos},
|
|
* in the resulting adapted method handle.
|
|
* The return type of the filter (if any) must be identical to the
|
|
* argument type of the target at position {@code pos}, and that target argument
|
|
* is supplied by the return value of the filter.
|
|
* <p>
|
|
* In all cases, {@code pos} must be greater than or equal to zero, and
|
|
* {@code pos} must also be less than or equal to the target's arity.
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle deepToString = publicLookup()
|
|
.findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
|
|
|
|
MethodHandle ts1 = deepToString.asCollector(String[].class, 1);
|
|
assertEquals("[strange]", (String) ts1.invokeExact("strange"));
|
|
|
|
MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
|
|
assertEquals("[up, down]", (String) ts2.invokeExact("up", "down"));
|
|
|
|
MethodHandle ts3 = deepToString.asCollector(String[].class, 3);
|
|
MethodHandle ts3_ts2 = collectArguments(ts3, 1, ts2);
|
|
assertEquals("[top, [up, down], strange]",
|
|
(String) ts3_ts2.invokeExact("top", "up", "down", "strange"));
|
|
|
|
MethodHandle ts3_ts2_ts1 = collectArguments(ts3_ts2, 3, ts1);
|
|
assertEquals("[top, [up, down], [strange]]",
|
|
(String) ts3_ts2_ts1.invokeExact("top", "up", "down", "strange"));
|
|
|
|
MethodHandle ts3_ts2_ts3 = collectArguments(ts3_ts2, 1, ts3);
|
|
assertEquals("[top, [[up, down, strange], charm], bottom]",
|
|
(String) ts3_ts2_ts3.invokeExact("top", "up", "down", "strange", "charm", "bottom"));
|
|
* }</pre></blockquote>
|
|
* <p>Here is pseudocode for the resulting adapter. In the code, {@code T}
|
|
* represents the return type of the {@code target} and resulting adapter.
|
|
* {@code V}/{@code v} stand for the return type and value of the
|
|
* {@code filter}, which are also found in the signature and arguments of
|
|
* the {@code target}, respectively, unless {@code V} is {@code void}.
|
|
* {@code A}/{@code a} and {@code C}/{@code c} represent the parameter types
|
|
* and values preceding and following the collection position, {@code pos},
|
|
* in the {@code target}'s signature. They also turn up in the resulting
|
|
* adapter's signature and arguments, where they surround
|
|
* {@code B}/{@code b}, which represent the parameter types and arguments
|
|
* to the {@code filter} (if any).
|
|
* <blockquote><pre>{@code
|
|
* T target(A...,V,C...);
|
|
* V filter(B...);
|
|
* T adapter(A... a,B... b,C... c) {
|
|
* V v = filter(b...);
|
|
* return target(a...,v,c...);
|
|
* }
|
|
* // and if the filter has no arguments:
|
|
* T target2(A...,V,C...);
|
|
* V filter2();
|
|
* T adapter2(A... a,C... c) {
|
|
* V v = filter2();
|
|
* return target2(a...,v,c...);
|
|
* }
|
|
* // and if the filter has a void return:
|
|
* T target3(A...,C...);
|
|
* void filter3(B...);
|
|
* T adapter3(A... a,B... b,C... c) {
|
|
* filter3(b...);
|
|
* return target3(a...,c...);
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* A collection adapter {@code collectArguments(mh, 0, coll)} is equivalent to
|
|
* one which first "folds" the affected arguments, and then drops them, in separate
|
|
* steps as follows:
|
|
* <blockquote><pre>{@code
|
|
* mh = MethodHandles.dropArguments(mh, 1, coll.type().parameterList()); //step 2
|
|
* mh = MethodHandles.foldArguments(mh, coll); //step 1
|
|
* }</pre></blockquote>
|
|
* If the target method handle consumes no arguments besides than the result
|
|
* (if any) of the filter {@code coll}, then {@code collectArguments(mh, 0, coll)}
|
|
* is equivalent to {@code filterReturnValue(coll, mh)}.
|
|
* If the filter method handle {@code coll} consumes one argument and produces
|
|
* a non-void result, then {@code collectArguments(mh, N, coll)}
|
|
* is equivalent to {@code filterArguments(mh, N, coll)}.
|
|
* Other equivalences are possible but would require argument permutation.
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
*
|
|
* @param target the method handle to invoke after filtering the subsequence of arguments
|
|
* @param pos the position of the first adapter argument to pass to the filter,
|
|
* and/or the target argument which receives the result of the filter
|
|
* @param filter method handle to call on the subsequence of arguments
|
|
* @return method handle which incorporates the specified argument subsequence filtering logic
|
|
* @throws NullPointerException if either argument is null
|
|
* @throws IllegalArgumentException if the return type of {@code filter}
|
|
* is non-void and is not the same as the {@code pos} argument of the target,
|
|
* or if {@code pos} is not between 0 and the target's arity, inclusive,
|
|
* or if the resulting method handle's type would have
|
|
* <a href="MethodHandle.html#maxarity">too many parameters</a>
|
|
* @see MethodHandles#foldArguments
|
|
* @see MethodHandles#filterArguments
|
|
* @see MethodHandles#filterReturnValue
|
|
*/
|
|
public static
|
|
MethodHandle collectArguments(MethodHandle target, int pos, MethodHandle filter) {
|
|
MethodType newType = collectArgumentsChecks(target, pos, filter);
|
|
MethodType collectorType = filter.type();
|
|
BoundMethodHandle result = target.rebind();
|
|
LambdaForm lform;
|
|
if (collectorType.returnType().isArray() && filter.intrinsicName() == Intrinsic.NEW_ARRAY) {
|
|
lform = result.editor().collectArgumentArrayForm(1 + pos, filter);
|
|
if (lform != null) {
|
|
return result.copyWith(newType, lform);
|
|
}
|
|
}
|
|
lform = result.editor().collectArgumentsForm(1 + pos, collectorType.basicType());
|
|
return result.copyWithExtendL(newType, lform, filter);
|
|
}
|
|
|
|
private static MethodType collectArgumentsChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
|
|
MethodType targetType = target.type();
|
|
MethodType filterType = filter.type();
|
|
Class<?> rtype = filterType.returnType();
|
|
List<Class<?>> filterArgs = filterType.parameterList();
|
|
if (rtype == void.class) {
|
|
return targetType.insertParameterTypes(pos, filterArgs);
|
|
}
|
|
if (rtype != targetType.parameterType(pos)) {
|
|
throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
|
|
}
|
|
return targetType.dropParameterTypes(pos, pos+1).insertParameterTypes(pos, filterArgs);
|
|
}
|
|
|
|
/**
|
|
* Adapts a target method handle by post-processing
|
|
* its return value (if any) with a filter (another method handle).
|
|
* The result of the filter is returned from the adapter.
|
|
* <p>
|
|
* If the target returns a value, the filter must accept that value as
|
|
* its only argument.
|
|
* If the target returns void, the filter must accept no arguments.
|
|
* <p>
|
|
* The return type of the filter
|
|
* replaces the return type of the target
|
|
* in the resulting adapted method handle.
|
|
* The argument type of the filter (if any) must be identical to the
|
|
* return type of the target.
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle cat = lookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
MethodHandle length = lookup().findVirtual(String.class,
|
|
"length", methodType(int.class));
|
|
System.out.println((String) cat.invokeExact("x", "y")); // xy
|
|
MethodHandle f0 = filterReturnValue(cat, length);
|
|
System.out.println((int) f0.invokeExact("x", "y")); // 2
|
|
* }</pre></blockquote>
|
|
* <p>Here is pseudocode for the resulting adapter. In the code,
|
|
* {@code T}/{@code t} represent the result type and value of the
|
|
* {@code target}; {@code V}, the result type of the {@code filter}; and
|
|
* {@code A}/{@code a}, the types and values of the parameters and arguments
|
|
* of the {@code target} as well as the resulting adapter.
|
|
* <blockquote><pre>{@code
|
|
* T target(A...);
|
|
* V filter(T);
|
|
* V adapter(A... a) {
|
|
* T t = target(a...);
|
|
* return filter(t);
|
|
* }
|
|
* // and if the target has a void return:
|
|
* void target2(A...);
|
|
* V filter2();
|
|
* V adapter2(A... a) {
|
|
* target2(a...);
|
|
* return filter2();
|
|
* }
|
|
* // and if the filter has a void return:
|
|
* T target3(A...);
|
|
* void filter3(V);
|
|
* void adapter3(A... a) {
|
|
* T t = target3(a...);
|
|
* filter3(t);
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
* @param target the method handle to invoke before filtering the return value
|
|
* @param filter method handle to call on the return value
|
|
* @return method handle which incorporates the specified return value filtering logic
|
|
* @throws NullPointerException if either argument is null
|
|
* @throws IllegalArgumentException if the argument list of {@code filter}
|
|
* does not match the return type of target as described above
|
|
*/
|
|
public static
|
|
MethodHandle filterReturnValue(MethodHandle target, MethodHandle filter) {
|
|
MethodType targetType = target.type();
|
|
MethodType filterType = filter.type();
|
|
filterReturnValueChecks(targetType, filterType);
|
|
BoundMethodHandle result = target.rebind();
|
|
BasicType rtype = BasicType.basicType(filterType.returnType());
|
|
LambdaForm lform = result.editor().filterReturnForm(rtype, false);
|
|
MethodType newType = targetType.changeReturnType(filterType.returnType());
|
|
result = result.copyWithExtendL(newType, lform, filter);
|
|
return result;
|
|
}
|
|
|
|
private static void filterReturnValueChecks(MethodType targetType, MethodType filterType) throws RuntimeException {
|
|
Class<?> rtype = targetType.returnType();
|
|
int filterValues = filterType.parameterCount();
|
|
if (filterValues == 0
|
|
? (rtype != void.class)
|
|
: (rtype != filterType.parameterType(0)))
|
|
throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
|
|
}
|
|
|
|
/**
|
|
* Adapts a target method handle by pre-processing
|
|
* some of its arguments, and then calling the target with
|
|
* the result of the pre-processing, inserted into the original
|
|
* sequence of arguments.
|
|
* <p>
|
|
* The pre-processing is performed by {@code combiner}, a second method handle.
|
|
* Of the arguments passed to the adapter, the first {@code N} arguments
|
|
* are copied to the combiner, which is then called.
|
|
* (Here, {@code N} is defined as the parameter count of the combiner.)
|
|
* After this, control passes to the target, with any result
|
|
* from the combiner inserted before the original {@code N} incoming
|
|
* arguments.
|
|
* <p>
|
|
* If the combiner returns a value, the first parameter type of the target
|
|
* must be identical with the return type of the combiner, and the next
|
|
* {@code N} parameter types of the target must exactly match the parameters
|
|
* of the combiner.
|
|
* <p>
|
|
* If the combiner has a void return, no result will be inserted,
|
|
* and the first {@code N} parameter types of the target
|
|
* must exactly match the parameters of the combiner.
|
|
* <p>
|
|
* The resulting adapter is the same type as the target, except that the
|
|
* first parameter type is dropped,
|
|
* if it corresponds to the result of the combiner.
|
|
* <p>
|
|
* (Note that {@link #dropArguments(MethodHandle,int,List) dropArguments} can be used to remove any arguments
|
|
* that either the combiner or the target does not wish to receive.
|
|
* If some of the incoming arguments are destined only for the combiner,
|
|
* consider using {@link MethodHandle#asCollector asCollector} instead, since those
|
|
* arguments will not need to be live on the stack on entry to the
|
|
* target.)
|
|
* <p><b>Example:</b>
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
|
|
"println", methodType(void.class, String.class))
|
|
.bindTo(System.out);
|
|
MethodHandle cat = lookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
|
|
MethodHandle catTrace = foldArguments(cat, trace);
|
|
// also prints "boo":
|
|
assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
|
|
* }</pre></blockquote>
|
|
* <p>Here is pseudocode for the resulting adapter. In the code, {@code T}
|
|
* represents the result type of the {@code target} and resulting adapter.
|
|
* {@code V}/{@code v} represent the type and value of the parameter and argument
|
|
* of {@code target} that precedes the folding position; {@code V} also is
|
|
* the result type of the {@code combiner}. {@code A}/{@code a} denote the
|
|
* types and values of the {@code N} parameters and arguments at the folding
|
|
* position. {@code B}/{@code b} represent the types and values of the
|
|
* {@code target} parameters and arguments that follow the folded parameters
|
|
* and arguments.
|
|
* <blockquote><pre>{@code
|
|
* // there are N arguments in A...
|
|
* T target(V, A[N]..., B...);
|
|
* V combiner(A...);
|
|
* T adapter(A... a, B... b) {
|
|
* V v = combiner(a...);
|
|
* return target(v, a..., b...);
|
|
* }
|
|
* // and if the combiner has a void return:
|
|
* T target2(A[N]..., B...);
|
|
* void combiner2(A...);
|
|
* T adapter2(A... a, B... b) {
|
|
* combiner2(a...);
|
|
* return target2(a..., b...);
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
* @param target the method handle to invoke after arguments are combined
|
|
* @param combiner method handle to call initially on the incoming arguments
|
|
* @return method handle which incorporates the specified argument folding logic
|
|
* @throws NullPointerException if either argument is null
|
|
* @throws IllegalArgumentException if {@code combiner}'s return type
|
|
* is non-void and not the same as the first argument type of
|
|
* the target, or if the initial {@code N} argument types
|
|
* of the target
|
|
* (skipping one matching the {@code combiner}'s return type)
|
|
* are not identical with the argument types of {@code combiner}
|
|
*/
|
|
public static
|
|
MethodHandle foldArguments(MethodHandle target, MethodHandle combiner) {
|
|
return foldArguments(target, 0, combiner);
|
|
}
|
|
|
|
private static Class<?> foldArgumentChecks(int foldPos, MethodType targetType, MethodType combinerType) {
|
|
int foldArgs = combinerType.parameterCount();
|
|
Class<?> rtype = combinerType.returnType();
|
|
int foldVals = rtype == void.class ? 0 : 1;
|
|
int afterInsertPos = foldPos + foldVals;
|
|
boolean ok = (targetType.parameterCount() >= afterInsertPos + foldArgs);
|
|
if (ok && !(combinerType.parameterList()
|
|
.equals(targetType.parameterList().subList(afterInsertPos,
|
|
afterInsertPos + foldArgs))))
|
|
ok = false;
|
|
if (ok && foldVals != 0 && combinerType.returnType() != targetType.parameterType(foldPos))
|
|
ok = false;
|
|
if (!ok)
|
|
throw misMatchedTypes("target and combiner types", targetType, combinerType);
|
|
return rtype;
|
|
}
|
|
|
|
/**
|
|
* Makes a method handle which adapts a target method handle,
|
|
* by guarding it with a test, a boolean-valued method handle.
|
|
* If the guard fails, a fallback handle is called instead.
|
|
* All three method handles must have the same corresponding
|
|
* argument and return types, except that the return type
|
|
* of the test must be boolean, and the test is allowed
|
|
* to have fewer arguments than the other two method handles.
|
|
* <p>
|
|
* Here is pseudocode for the resulting adapter. In the code, {@code T}
|
|
* represents the uniform result type of the three involved handles;
|
|
* {@code A}/{@code a}, the types and values of the {@code target}
|
|
* parameters and arguments that are consumed by the {@code test}; and
|
|
* {@code B}/{@code b}, those types and values of the {@code target}
|
|
* parameters and arguments that are not consumed by the {@code test}.
|
|
* <blockquote><pre>{@code
|
|
* boolean test(A...);
|
|
* T target(A...,B...);
|
|
* T fallback(A...,B...);
|
|
* T adapter(A... a,B... b) {
|
|
* if (test(a...))
|
|
* return target(a..., b...);
|
|
* else
|
|
* return fallback(a..., b...);
|
|
* }
|
|
* }</pre></blockquote>
|
|
* Note that the test arguments ({@code a...} in the pseudocode) cannot
|
|
* be modified by execution of the test, and so are passed unchanged
|
|
* from the caller to the target or fallback as appropriate.
|
|
* @param test method handle used for test, must return boolean
|
|
* @param target method handle to call if test passes
|
|
* @param fallback method handle to call if test fails
|
|
* @return method handle which incorporates the specified if/then/else logic
|
|
* @throws NullPointerException if any argument is null
|
|
* @throws IllegalArgumentException if {@code test} does not return boolean,
|
|
* or if all three method types do not match (with the return
|
|
* type of {@code test} changed to match that of the target).
|
|
*/
|
|
public static
|
|
MethodHandle guardWithTest(MethodHandle test,
|
|
MethodHandle target,
|
|
MethodHandle fallback) {
|
|
MethodType gtype = test.type();
|
|
MethodType ttype = target.type();
|
|
MethodType ftype = fallback.type();
|
|
if (!ttype.equals(ftype))
|
|
throw misMatchedTypes("target and fallback types", ttype, ftype);
|
|
if (gtype.returnType() != boolean.class)
|
|
throw newIllegalArgumentException("guard type is not a predicate "+gtype);
|
|
List<Class<?>> targs = ttype.parameterList();
|
|
List<Class<?>> gargs = gtype.parameterList();
|
|
if (!targs.equals(gargs)) {
|
|
int gpc = gargs.size(), tpc = targs.size();
|
|
if (gpc >= tpc || !targs.subList(0, gpc).equals(gargs))
|
|
throw misMatchedTypes("target and test types", ttype, gtype);
|
|
test = dropArguments(test, gpc, targs.subList(gpc, tpc));
|
|
gtype = test.type();
|
|
}
|
|
return MethodHandleImpl.makeGuardWithTest(test, target, fallback);
|
|
}
|
|
|
|
static <T> RuntimeException misMatchedTypes(String what, T t1, T t2) {
|
|
return newIllegalArgumentException(what + " must match: " + t1 + " != " + t2);
|
|
}
|
|
|
|
/**
|
|
* Makes a method handle which adapts a target method handle,
|
|
* by running it inside an exception handler.
|
|
* If the target returns normally, the adapter returns that value.
|
|
* If an exception matching the specified type is thrown, the fallback
|
|
* handle is called instead on the exception, plus the original arguments.
|
|
* <p>
|
|
* The target and handler must have the same corresponding
|
|
* argument and return types, except that handler may omit trailing arguments
|
|
* (similarly to the predicate in {@link #guardWithTest guardWithTest}).
|
|
* Also, the handler must have an extra leading parameter of {@code exType} or a supertype.
|
|
* <p>
|
|
* Here is pseudocode for the resulting adapter. In the code, {@code T}
|
|
* represents the return type of the {@code target} and {@code handler},
|
|
* and correspondingly that of the resulting adapter; {@code A}/{@code a},
|
|
* the types and values of arguments to the resulting handle consumed by
|
|
* {@code handler}; and {@code B}/{@code b}, those of arguments to the
|
|
* resulting handle discarded by {@code handler}.
|
|
* <blockquote><pre>{@code
|
|
* T target(A..., B...);
|
|
* T handler(ExType, A...);
|
|
* T adapter(A... a, B... b) {
|
|
* try {
|
|
* return target(a..., b...);
|
|
* } catch (ExType ex) {
|
|
* return handler(ex, a...);
|
|
* }
|
|
* }
|
|
* }</pre></blockquote>
|
|
* Note that the saved arguments ({@code a...} in the pseudocode) cannot
|
|
* be modified by execution of the target, and so are passed unchanged
|
|
* from the caller to the handler, if the handler is invoked.
|
|
* <p>
|
|
* The target and handler must return the same type, even if the handler
|
|
* always throws. (This might happen, for instance, because the handler
|
|
* is simulating a {@code finally} clause).
|
|
* To create such a throwing handler, compose the handler creation logic
|
|
* with {@link #throwException throwException},
|
|
* in order to create a method handle of the correct return type.
|
|
* @param target method handle to call
|
|
* @param exType the type of exception which the handler will catch
|
|
* @param handler method handle to call if a matching exception is thrown
|
|
* @return method handle which incorporates the specified try/catch logic
|
|
* @throws NullPointerException if any argument is null
|
|
* @throws IllegalArgumentException if {@code handler} does not accept
|
|
* the given exception type, or if the method handle types do
|
|
* not match in their return types and their
|
|
* corresponding parameters
|
|
* @see MethodHandles#tryFinally(MethodHandle, MethodHandle)
|
|
*/
|
|
public static
|
|
MethodHandle catchException(MethodHandle target,
|
|
Class<? extends Throwable> exType,
|
|
MethodHandle handler) {
|
|
MethodType ttype = target.type();
|
|
MethodType htype = handler.type();
|
|
if (!Throwable.class.isAssignableFrom(exType))
|
|
throw new ClassCastException(exType.getName());
|
|
if (htype.parameterCount() < 1 ||
|
|
!htype.parameterType(0).isAssignableFrom(exType))
|
|
throw newIllegalArgumentException("handler does not accept exception type "+exType);
|
|
if (htype.returnType() != ttype.returnType())
|
|
throw misMatchedTypes("target and handler return types", ttype, htype);
|
|
List<Class<?>> targs = ttype.parameterList();
|
|
List<Class<?>> hargs = htype.parameterList();
|
|
hargs = hargs.subList(1, hargs.size()); // omit leading parameter from handler
|
|
if (!targs.equals(hargs)) {
|
|
int hpc = hargs.size(), tpc = targs.size();
|
|
if (hpc >= tpc || !targs.subList(0, hpc).equals(hargs))
|
|
throw misMatchedTypes("target and handler types", ttype, htype);
|
|
handler = dropArguments(handler, 1+hpc, targs.subList(hpc, tpc));
|
|
htype = handler.type();
|
|
}
|
|
return MethodHandleImpl.makeGuardWithCatch(target, exType, handler);
|
|
}
|
|
|
|
/**
|
|
* Produces a method handle which will throw exceptions of the given {@code exType}.
|
|
* The method handle will accept a single argument of {@code exType},
|
|
* and immediately throw it as an exception.
|
|
* The method type will nominally specify a return of {@code returnType}.
|
|
* The return type may be anything convenient: It doesn't matter to the
|
|
* method handle's behavior, since it will never return normally.
|
|
* @param returnType the return type of the desired method handle
|
|
* @param exType the parameter type of the desired method handle
|
|
* @return method handle which can throw the given exceptions
|
|
* @throws NullPointerException if either argument is null
|
|
*/
|
|
public static
|
|
MethodHandle throwException(Class<?> returnType, Class<? extends Throwable> exType) {
|
|
if (!Throwable.class.isAssignableFrom(exType))
|
|
throw new ClassCastException(exType.getName());
|
|
return MethodHandleImpl.throwException(MethodType.methodType(returnType, exType));
|
|
}
|
|
|
|
/**
|
|
* Constructs a method handle representing a loop with several loop variables that are updated and checked upon each
|
|
* iteration. Upon termination of the loop due to one of the predicates, a corresponding finalizer is run and
|
|
* delivers the loop's result, which is the return value of the resulting handle.
|
|
* <p>
|
|
* Intuitively, every loop is formed by one or more "clauses", each specifying a local iteration value and/or a loop
|
|
* exit. Each iteration of the loop executes each clause in order. A clause can optionally update its iteration
|
|
* variable; it can also optionally perform a test and conditional loop exit. In order to express this logic in
|
|
* terms of method handles, each clause will determine four actions:<ul>
|
|
* <li>Before the loop executes, the initialization of an iteration variable or loop invariant local.
|
|
* <li>When a clause executes, an update step for the iteration variable.
|
|
* <li>When a clause executes, a predicate execution to test for loop exit.
|
|
* <li>If a clause causes a loop exit, a finalizer execution to compute the loop's return value.
|
|
* </ul>
|
|
* <p>
|
|
* Some of these clause parts may be omitted according to certain rules, and useful default behavior is provided in
|
|
* this case. See below for a detailed description.
|
|
* <p>
|
|
* Each clause function, with the exception of clause initializers, is able to observe the entire loop state,
|
|
* because it will be passed <em>all</em> current iteration variable values, as well as all incoming loop
|
|
* parameters. Most clause functions will not need all of this information, but they will be formally connected as
|
|
* if by {@link #dropArguments}.
|
|
* <p>
|
|
* Given a set of clauses, there is a number of checks and adjustments performed to connect all the parts of the
|
|
* loop. They are spelled out in detail in the steps below. In these steps, every occurrence of the word "must"
|
|
* corresponds to a place where {@link IllegalArgumentException} may be thrown if the required constraint is not met
|
|
* by the inputs to the loop combinator. The term "effectively identical", applied to parameter type lists, means
|
|
* that they must be identical, or else one list must be a proper prefix of the other.
|
|
* <p>
|
|
* <em>Step 0: Determine clause structure.</em><ol type="a">
|
|
* <li>The clause array (of type {@code MethodHandle[][]} must be non-{@code null} and contain at least one element.
|
|
* <li>The clause array may not contain {@code null}s or sub-arrays longer than four elements.
|
|
* <li>Clauses shorter than four elements are treated as if they were padded by {@code null} elements to length
|
|
* four. Padding takes place by appending elements to the array.
|
|
* <li>Clauses with all {@code null}s are disregarded.
|
|
* <li>Each clause is treated as a four-tuple of functions, called "init", "step", "pred", and "fini".
|
|
* </ol>
|
|
* <p>
|
|
* <em>Step 1A: Determine iteration variables.</em><ol type="a">
|
|
* <li>Examine init and step function return types, pairwise, to determine each clause's iteration variable type.
|
|
* <li>If both functions are omitted, use {@code void}; else if one is omitted, use the other's return type; else
|
|
* use the common return type (they must be identical).
|
|
* <li>Form the list of return types (in clause order), omitting all occurrences of {@code void}.
|
|
* <li>This list of types is called the "common prefix".
|
|
* </ol>
|
|
* <p>
|
|
* <em>Step 1B: Determine loop parameters.</em><ul>
|
|
* <li><b>If at least one init function is given,</b><ol type="a">
|
|
* <li>Examine init function parameter lists.
|
|
* <li>Omitted init functions are deemed to have {@code null} parameter lists.
|
|
* <li>All init function parameter lists must be effectively identical.
|
|
* <li>The longest parameter list (which is necessarily unique) is called the "common suffix".
|
|
* </ol>
|
|
* <li><b>If no init function is given,</b><ol type="a">
|
|
* <li>Examine the suffixes of the step, pred, and fini parameter lists, after removing the "common prefix".
|
|
* <li>The longest of these suffixes is taken as the "common suffix".
|
|
* </ol></ul>
|
|
* <p>
|
|
* <em>Step 1C: Determine loop return type.</em><ol type="a">
|
|
* <li>Examine fini function return types, disregarding omitted fini functions.
|
|
* <li>If there are no fini functions, use {@code void} as the loop return type.
|
|
* <li>Otherwise, use the common return type of the fini functions; they must all be identical.
|
|
* </ol>
|
|
* <p>
|
|
* <em>Step 1D: Check other types.</em><ol type="a">
|
|
* <li>There must be at least one non-omitted pred function.
|
|
* <li>Every non-omitted pred function must have a {@code boolean} return type.
|
|
* </ol>
|
|
* <p>
|
|
* <em>Step 2: Determine parameter lists.</em><ol type="a">
|
|
* <li>The parameter list for the resulting loop handle will be the "common suffix".
|
|
* <li>The parameter list for init functions will be adjusted to the "common suffix". (Note that their parameter
|
|
* lists are already effectively identical to the common suffix.)
|
|
* <li>The parameter list for non-init (step, pred, and fini) functions will be adjusted to the common prefix
|
|
* followed by the common suffix, called the "common parameter sequence".
|
|
* <li>Every non-init, non-omitted function parameter list must be effectively identical to the common parameter
|
|
* sequence.
|
|
* </ol>
|
|
* <p>
|
|
* <em>Step 3: Fill in omitted functions.</em><ol type="a">
|
|
* <li>If an init function is omitted, use a {@linkplain #constant constant function} of the appropriate
|
|
* {@code null}/zero/{@code false}/{@code void} type. (For this purpose, a constant {@code void} is simply a
|
|
* function which does nothing and returns {@code void}; it can be obtained from another constant function by
|
|
* {@linkplain MethodHandle#asType type conversion}.)
|
|
* <li>If a step function is omitted, use an {@linkplain #identity identity function} of the clause's iteration
|
|
* variable type; insert dropped argument parameters before the identity function parameter for the non-{@code void}
|
|
* iteration variables of preceding clauses. (This will turn the loop variable into a local loop invariant.)
|
|
* <li>If a pred function is omitted, the corresponding fini function must also be omitted.
|
|
* <li>If a pred function is omitted, use a constant {@code true} function. (This will keep the loop going, as far
|
|
* as this clause is concerned.)
|
|
* <li>If a fini function is omitted, use a constant {@code null}/zero/{@code false}/{@code void} function of the
|
|
* loop return type.
|
|
* </ol>
|
|
* <p>
|
|
* <em>Step 4: Fill in missing parameter types.</em><ol type="a">
|
|
* <li>At this point, every init function parameter list is effectively identical to the common suffix, but some
|
|
* lists may be shorter. For every init function with a short parameter list, pad out the end of the list by
|
|
* {@linkplain #dropArguments dropping arguments}.
|
|
* <li>At this point, every non-init function parameter list is effectively identical to the common parameter
|
|
* sequence, but some lists may be shorter. For every non-init function with a short parameter list, pad out the end
|
|
* of the list by {@linkplain #dropArguments dropping arguments}.
|
|
* </ol>
|
|
* <p>
|
|
* <em>Final observations.</em><ol type="a">
|
|
* <li>After these steps, all clauses have been adjusted by supplying omitted functions and arguments.
|
|
* <li>All init functions have a common parameter type list, which the final loop handle will also have.
|
|
* <li>All fini functions have a common return type, which the final loop handle will also have.
|
|
* <li>All non-init functions have a common parameter type list, which is the common parameter sequence, of
|
|
* (non-{@code void}) iteration variables followed by loop parameters.
|
|
* <li>Each pair of init and step functions agrees in their return types.
|
|
* <li>Each non-init function will be able to observe the current values of all iteration variables, by means of the
|
|
* common prefix.
|
|
* </ol>
|
|
* <p>
|
|
* <em>Loop execution.</em><ol type="a">
|
|
* <li>When the loop is called, the loop input values are saved in locals, to be passed (as the common suffix) to
|
|
* every clause function. These locals are loop invariant.
|
|
* <li>Each init function is executed in clause order (passing the common suffix) and the non-{@code void} values
|
|
* are saved (as the common prefix) into locals. These locals are loop varying (unless their steps are identity
|
|
* functions, as noted above).
|
|
* <li>All function executions (except init functions) will be passed the common parameter sequence, consisting of
|
|
* the non-{@code void} iteration values (in clause order) and then the loop inputs (in argument order).
|
|
* <li>The step and pred functions are then executed, in clause order (step before pred), until a pred function
|
|
* returns {@code false}.
|
|
* <li>The non-{@code void} result from a step function call is used to update the corresponding loop variable. The
|
|
* updated value is immediately visible to all subsequent function calls.
|
|
* <li>If a pred function returns {@code false}, the corresponding fini function is called, and the resulting value
|
|
* is returned from the loop as a whole.
|
|
* </ol>
|
|
* <p>
|
|
* Here is pseudocode for the resulting loop handle. In the code, {@code V}/{@code v} represent the types / values
|
|
* of loop variables; {@code A}/{@code a}, those of arguments passed to the resulting loop; and {@code R}, the
|
|
* result types of finalizers as well as of the resulting loop.
|
|
* <blockquote><pre>{@code
|
|
* V... init...(A...);
|
|
* boolean pred...(V..., A...);
|
|
* V... step...(V..., A...);
|
|
* R fini...(V..., A...);
|
|
* R loop(A... a) {
|
|
* V... v... = init...(a...);
|
|
* for (;;) {
|
|
* for ((v, p, s, f) in (v..., pred..., step..., fini...)) {
|
|
* v = s(v..., a...);
|
|
* if (!p(v..., a...)) {
|
|
* return f(v..., a...);
|
|
* }
|
|
* }
|
|
* }
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
* // iterative implementation of the factorial function as a loop handle
|
|
* static int one(int k) { return 1; }
|
|
* static int inc(int i, int acc, int k) { return i + 1; }
|
|
* static int mult(int i, int acc, int k) { return i * acc; }
|
|
* static boolean pred(int i, int acc, int k) { return i < k; }
|
|
* static int fin(int i, int acc, int k) { return acc; }
|
|
* // assume MH_one, MH_inc, MH_mult, MH_pred, and MH_fin are handles to the above methods
|
|
* // null initializer for counter, should initialize to 0
|
|
* MethodHandle[] counterClause = new MethodHandle[]{null, MH_inc};
|
|
* MethodHandle[] accumulatorClause = new MethodHandle[]{MH_one, MH_mult, MH_pred, MH_fin};
|
|
* MethodHandle loop = MethodHandles.loop(counterClause, accumulatorClause);
|
|
* assertEquals(120, loop.invoke(5));
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param clauses an array of arrays (4-tuples) of {@link MethodHandle}s adhering to the rules described above.
|
|
*
|
|
* @return a method handle embodying the looping behavior as defined by the arguments.
|
|
*
|
|
* @throws IllegalArgumentException in case any of the constraints described above is violated.
|
|
*
|
|
* @see MethodHandles#whileLoop(MethodHandle, MethodHandle, MethodHandle)
|
|
* @see MethodHandles#doWhileLoop(MethodHandle, MethodHandle, MethodHandle)
|
|
* @see MethodHandles#countedLoop(MethodHandle, MethodHandle, MethodHandle)
|
|
* @see MethodHandles#iteratedLoop(MethodHandle, MethodHandle, MethodHandle)
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle loop(MethodHandle[]... clauses) {
|
|
// Step 0: determine clause structure.
|
|
checkLoop0(clauses);
|
|
|
|
List<MethodHandle> init = new ArrayList<>();
|
|
List<MethodHandle> step = new ArrayList<>();
|
|
List<MethodHandle> pred = new ArrayList<>();
|
|
List<MethodHandle> fini = new ArrayList<>();
|
|
|
|
Stream.of(clauses).filter(c -> Stream.of(c).anyMatch(Objects::nonNull)).forEach(clause -> {
|
|
init.add(clause[0]); // all clauses have at least length 1
|
|
step.add(clause.length <= 1 ? null : clause[1]);
|
|
pred.add(clause.length <= 2 ? null : clause[2]);
|
|
fini.add(clause.length <= 3 ? null : clause[3]);
|
|
});
|
|
|
|
assert Stream.of(init, step, pred, fini).map(List::size).distinct().count() == 1;
|
|
final int nclauses = init.size();
|
|
|
|
// Step 1A: determine iteration variables.
|
|
final List<Class<?>> iterationVariableTypes = new ArrayList<>();
|
|
for (int i = 0; i < nclauses; ++i) {
|
|
MethodHandle in = init.get(i);
|
|
MethodHandle st = step.get(i);
|
|
if (in == null && st == null) {
|
|
iterationVariableTypes.add(void.class);
|
|
} else if (in != null && st != null) {
|
|
checkLoop1a(i, in, st);
|
|
iterationVariableTypes.add(in.type().returnType());
|
|
} else {
|
|
iterationVariableTypes.add(in == null ? st.type().returnType() : in.type().returnType());
|
|
}
|
|
}
|
|
final List<Class<?>> commonPrefix = iterationVariableTypes.stream().filter(t -> t != void.class).
|
|
collect(Collectors.toList());
|
|
|
|
// Step 1B: determine loop parameters.
|
|
final List<Class<?>> commonSuffix = buildCommonSuffix(init, step, pred, fini, commonPrefix.size());
|
|
checkLoop1b(init, commonSuffix);
|
|
|
|
// Step 1C: determine loop return type.
|
|
// Step 1D: check other types.
|
|
final Class<?> loopReturnType = fini.stream().filter(Objects::nonNull).map(MethodHandle::type).
|
|
map(MethodType::returnType).findFirst().orElse(void.class);
|
|
checkLoop1cd(pred, fini, loopReturnType);
|
|
|
|
// Step 2: determine parameter lists.
|
|
final List<Class<?>> commonParameterSequence = new ArrayList<>(commonPrefix);
|
|
commonParameterSequence.addAll(commonSuffix);
|
|
checkLoop2(step, pred, fini, commonParameterSequence);
|
|
|
|
// Step 3: fill in omitted functions.
|
|
for (int i = 0; i < nclauses; ++i) {
|
|
Class<?> t = iterationVariableTypes.get(i);
|
|
if (init.get(i) == null) {
|
|
init.set(i, zeroHandle(t));
|
|
}
|
|
if (step.get(i) == null) {
|
|
step.set(i, dropArguments(t == void.class ? zeroHandle(t) : identity(t), 0, commonPrefix.subList(0, i)));
|
|
}
|
|
if (pred.get(i) == null) {
|
|
pred.set(i, constant(boolean.class, true));
|
|
}
|
|
if (fini.get(i) == null) {
|
|
fini.set(i, zeroHandle(t));
|
|
}
|
|
}
|
|
|
|
// Step 4: fill in missing parameter types.
|
|
List<MethodHandle> finit = fillParameterTypes(init, commonSuffix);
|
|
List<MethodHandle> fstep = fillParameterTypes(step, commonParameterSequence);
|
|
List<MethodHandle> fpred = fillParameterTypes(pred, commonParameterSequence);
|
|
List<MethodHandle> ffini = fillParameterTypes(fini, commonParameterSequence);
|
|
|
|
assert finit.stream().map(MethodHandle::type).map(MethodType::parameterList).
|
|
allMatch(pl -> pl.equals(commonSuffix));
|
|
assert Stream.of(fstep, fpred, ffini).flatMap(List::stream).map(MethodHandle::type).map(MethodType::parameterList).
|
|
allMatch(pl -> pl.equals(commonParameterSequence));
|
|
|
|
return MethodHandleImpl.makeLoop(loopReturnType, commonSuffix, commonPrefix, finit, fstep, fpred, ffini);
|
|
}
|
|
|
|
private static List<MethodHandle> fillParameterTypes(List<MethodHandle> hs, final List<Class<?>> targetParams) {
|
|
return hs.stream().map(h -> {
|
|
int pc = h.type().parameterCount();
|
|
int tpsize = targetParams.size();
|
|
return pc < tpsize ? dropArguments(h, pc, targetParams.subList(pc, tpsize)) : h;
|
|
}).collect(Collectors.toList());
|
|
}
|
|
|
|
/**
|
|
* Constructs a {@code while} loop from an initializer, a body, and a predicate. This is a convenience wrapper for
|
|
* the {@linkplain #loop(MethodHandle[][]) generic loop combinator}.
|
|
* <p>
|
|
* The loop handle's result type is the same as the sole loop variable's, i.e., the result type of {@code init}.
|
|
* The parameter type list of {@code init} also determines that of the resulting handle. The {@code pred} handle
|
|
* must have an additional leading parameter of the same type as {@code init}'s result, and so must the {@code
|
|
* body}. These constraints follow directly from those described for the {@linkplain MethodHandles#loop(MethodHandle[][])
|
|
* generic loop combinator}.
|
|
* <p>
|
|
* Here is pseudocode for the resulting loop handle. In the code, {@code V}/{@code v} represent the type / value of
|
|
* the sole loop variable as well as the result type of the loop; and {@code A}/{@code a}, that of the argument
|
|
* passed to the loop.
|
|
* <blockquote><pre>{@code
|
|
* V init(A);
|
|
* boolean pred(V, A);
|
|
* V body(V, A);
|
|
* V whileLoop(A a) {
|
|
* V v = init(a);
|
|
* while (pred(v, a)) {
|
|
* v = body(v, a);
|
|
* }
|
|
* return v;
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
* // implement the zip function for lists as a loop handle
|
|
* static List<String> initZip(Iterator<String> a, Iterator<String> b) { return new ArrayList<>(); }
|
|
* static boolean zipPred(List<String> zip, Iterator<String> a, Iterator<String> b) { return a.hasNext() && b.hasNext(); }
|
|
* static List<String> zipStep(List<String> zip, Iterator<String> a, Iterator<String> b) {
|
|
* zip.add(a.next());
|
|
* zip.add(b.next());
|
|
* return zip;
|
|
* }
|
|
* // assume MH_initZip, MH_zipPred, and MH_zipStep are handles to the above methods
|
|
* MethodHandle loop = MethodHandles.whileLoop(MH_initZip, MH_zipPred, MH_zipStep);
|
|
* List<String> a = Arrays.asList("a", "b", "c", "d");
|
|
* List<String> b = Arrays.asList("e", "f", "g", "h");
|
|
* List<String> zipped = Arrays.asList("a", "e", "b", "f", "c", "g", "d", "h");
|
|
* assertEquals(zipped, (List<String>) loop.invoke(a.iterator(), b.iterator()));
|
|
* }</pre></blockquote>
|
|
*
|
|
* <p>
|
|
* @implSpec The implementation of this method is equivalent to:
|
|
* <blockquote><pre>{@code
|
|
* MethodHandle whileLoop(MethodHandle init, MethodHandle pred, MethodHandle body) {
|
|
* MethodHandle[]
|
|
* checkExit = {null, null, pred, identity(init.type().returnType())},
|
|
* varBody = {init, body};
|
|
* return loop(checkExit, varBody);
|
|
* }
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param init initializer: it should provide the initial value of the loop variable. This controls the loop's
|
|
* result type. Passing {@code null} or a {@code void} init function will make the loop's result type
|
|
* {@code void}.
|
|
* @param pred condition for the loop, which may not be {@code null}.
|
|
* @param body body of the loop, which may not be {@code null}.
|
|
*
|
|
* @return the value of the loop variable as the loop terminates.
|
|
* @throws IllegalArgumentException if any argument has a type inconsistent with the loop structure
|
|
*
|
|
* @see MethodHandles#loop(MethodHandle[][])
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle whileLoop(MethodHandle init, MethodHandle pred, MethodHandle body) {
|
|
MethodHandle fin = init == null ? zeroHandle(void.class) : identity(init.type().returnType());
|
|
MethodHandle[] checkExit = {null, null, pred, fin};
|
|
MethodHandle[] varBody = {init, body};
|
|
return loop(checkExit, varBody);
|
|
}
|
|
|
|
/**
|
|
* Constructs a {@code do-while} loop from an initializer, a body, and a predicate. This is a convenience wrapper
|
|
* for the {@linkplain MethodHandles#loop(MethodHandle[][]) generic loop combinator}.
|
|
* <p>
|
|
* The loop handle's result type is the same as the sole loop variable's, i.e., the result type of {@code init}.
|
|
* The parameter type list of {@code init} also determines that of the resulting handle. The {@code pred} handle
|
|
* must have an additional leading parameter of the same type as {@code init}'s result, and so must the {@code
|
|
* body}. These constraints follow directly from those described for the {@linkplain MethodHandles#loop(MethodHandle[][])
|
|
* generic loop combinator}.
|
|
* <p>
|
|
* Here is pseudocode for the resulting loop handle. In the code, {@code V}/{@code v} represent the type / value of
|
|
* the sole loop variable as well as the result type of the loop; and {@code A}/{@code a}, that of the argument
|
|
* passed to the loop.
|
|
* <blockquote><pre>{@code
|
|
* V init(A);
|
|
* boolean pred(V, A);
|
|
* V body(V, A);
|
|
* V doWhileLoop(A a) {
|
|
* V v = init(a);
|
|
* do {
|
|
* v = body(v, a);
|
|
* } while (pred(v, a));
|
|
* return v;
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
* // int i = 0; while (i < limit) { ++i; } return i; => limit
|
|
* static int zero(int limit) { return 0; }
|
|
* static int step(int i, int limit) { return i + 1; }
|
|
* static boolean pred(int i, int limit) { return i < limit; }
|
|
* // assume MH_zero, MH_step, and MH_pred are handles to the above methods
|
|
* MethodHandle loop = MethodHandles.doWhileLoop(MH_zero, MH_step, MH_pred);
|
|
* assertEquals(23, loop.invoke(23));
|
|
* }</pre></blockquote>
|
|
*
|
|
* <p>
|
|
* @implSpec The implementation of this method is equivalent to:
|
|
* <blockquote><pre>{@code
|
|
* MethodHandle doWhileLoop(MethodHandle init, MethodHandle body, MethodHandle pred) {
|
|
* MethodHandle[] clause = { init, body, pred, identity(init.type().returnType()) };
|
|
* return loop(clause);
|
|
* }
|
|
* }</pre></blockquote>
|
|
*
|
|
*
|
|
* @param init initializer: it should provide the initial value of the loop variable. This controls the loop's
|
|
* result type. Passing {@code null} or a {@code void} init function will make the loop's result type
|
|
* {@code void}.
|
|
* @param pred condition for the loop, which may not be {@code null}.
|
|
* @param body body of the loop, which may not be {@code null}.
|
|
*
|
|
* @return the value of the loop variable as the loop terminates.
|
|
* @throws IllegalArgumentException if any argument has a type inconsistent with the loop structure
|
|
*
|
|
* @see MethodHandles#loop(MethodHandle[][])
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle doWhileLoop(MethodHandle init, MethodHandle body, MethodHandle pred) {
|
|
MethodHandle fin = init == null ? zeroHandle(void.class) : identity(init.type().returnType());
|
|
MethodHandle[] clause = {init, body, pred, fin};
|
|
return loop(clause);
|
|
}
|
|
|
|
/**
|
|
* Constructs a loop that runs a given number of iterations. The loop counter is an {@code int} initialized from the
|
|
* {@code iterations} handle evaluation result. The counter is passed to the {@code body} function, so that must
|
|
* accept an initial {@code int} argument. The result of the loop execution is the final value of the additional
|
|
* local state. This is a convenience wrapper for the {@linkplain MethodHandles#loop(MethodHandle[][]) generic loop
|
|
* combinator}.
|
|
* <p>
|
|
* The result type and parameter type list of {@code init} determine those of the resulting handle. The {@code
|
|
* iterations} handle must accept the same parameter types as {@code init} but return an {@code int}. The {@code
|
|
* body} handle must accept the same parameter types as well, preceded by an {@code int} parameter for the counter,
|
|
* and a parameter of the same type as {@code init}'s result. These constraints follow directly from those described
|
|
* for the {@linkplain MethodHandles#loop(MethodHandle[][]) generic loop combinator}.
|
|
* <p>
|
|
* Here is pseudocode for the resulting loop handle. In the code, {@code V}/{@code v} represent the type / value of
|
|
* the sole loop variable as well as the result type of the loop; and {@code A}/{@code a}, that of the argument
|
|
* passed to the loop.
|
|
* <blockquote><pre>{@code
|
|
* int iterations(A);
|
|
* V init(A);
|
|
* V body(int, V, A);
|
|
* V countedLoop(A a) {
|
|
* int end = iterations(a);
|
|
* V v = init(a);
|
|
* for (int i = 0; i < end; ++i) {
|
|
* v = body(i, v, a);
|
|
* }
|
|
* return v;
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
* // String s = "Lambdaman!"; for (int i = 0; i < 13; ++i) { s = "na " + s; } return s;
|
|
* // => a variation on a well known theme
|
|
* static String start(String arg) { return arg; }
|
|
* static String step(int counter, String v, String arg) { return "na " + v; }
|
|
* // assume MH_start and MH_step are handles to the two methods above
|
|
* MethodHandle fit13 = MethodHandles.constant(int.class, 13);
|
|
* MethodHandle loop = MethodHandles.countedLoop(fit13, MH_start, MH_step);
|
|
* assertEquals("na na na na na na na na na na na na na Lambdaman!", loop.invoke("Lambdaman!"));
|
|
* }</pre></blockquote>
|
|
*
|
|
* <p>
|
|
* @implSpec The implementation of this method is equivalent to:
|
|
* <blockquote><pre>{@code
|
|
* MethodHandle countedLoop(MethodHandle iterations, MethodHandle init, MethodHandle body) {
|
|
* return countedLoop(null, iterations, init, body); // null => constant zero
|
|
* }
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param iterations a handle to return the number of iterations this loop should run.
|
|
* @param init initializer for additional loop state. This determines the loop's result type.
|
|
* Passing {@code null} or a {@code void} init function will make the loop's result type
|
|
* {@code void}.
|
|
* @param body the body of the loop, which must not be {@code null}.
|
|
* It must accept an initial {@code int} parameter (for the counter), and then any
|
|
* additional loop-local variable plus loop parameters.
|
|
*
|
|
* @return a method handle representing the loop.
|
|
* @throws IllegalArgumentException if any argument has a type inconsistent with the loop structure
|
|
*
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle countedLoop(MethodHandle iterations, MethodHandle init, MethodHandle body) {
|
|
return countedLoop(null, iterations, init, body);
|
|
}
|
|
|
|
/**
|
|
* Constructs a loop that counts over a range of numbers. The loop counter is an {@code int} that will be
|
|
* initialized to the {@code int} value returned from the evaluation of the {@code start} handle and run to the
|
|
* value returned from {@code end} (exclusively) with a step width of 1. The counter value is passed to the {@code
|
|
* body} function in each iteration; it has to accept an initial {@code int} parameter
|
|
* for that. The result of the loop execution is the final value of the additional local state
|
|
* obtained by running {@code init}.
|
|
* This is a
|
|
* convenience wrapper for the {@linkplain MethodHandles#loop(MethodHandle[][]) generic loop combinator}.
|
|
* <p>
|
|
* The constraints for the {@code init} and {@code body} handles are the same as for {@link
|
|
* #countedLoop(MethodHandle, MethodHandle, MethodHandle)}. Additionally, the {@code start} and {@code end} handles
|
|
* must return an {@code int} and accept the same parameters as {@code init}.
|
|
* <p>
|
|
* Here is pseudocode for the resulting loop handle. In the code, {@code V}/{@code v} represent the type / value of
|
|
* the sole loop variable as well as the result type of the loop; and {@code A}/{@code a}, that of the argument
|
|
* passed to the loop.
|
|
* <blockquote><pre>{@code
|
|
* int start(A);
|
|
* int end(A);
|
|
* V init(A);
|
|
* V body(int, V, A);
|
|
* V countedLoop(A a) {
|
|
* int s = start(a);
|
|
* int e = end(a);
|
|
* V v = init(a);
|
|
* for (int i = s; i < e; ++i) {
|
|
* v = body(i, v, a);
|
|
* }
|
|
* return v;
|
|
* }
|
|
* }</pre></blockquote>
|
|
*
|
|
* <p>
|
|
* @implSpec The implementation of this method is equivalent to:
|
|
* <blockquote><pre>{@code
|
|
* MethodHandle countedLoop(MethodHandle start, MethodHandle end, MethodHandle init, MethodHandle body) {
|
|
* MethodHandle returnVar = dropArguments(identity(init.type().returnType()), 0, int.class, int.class);
|
|
* // assume MH_increment and MH_lessThan are handles to x+1 and x<y of type int
|
|
* MethodHandle[]
|
|
* indexVar = {start, MH_increment}, // i = start; i = i+1
|
|
* loopLimit = {end, null, MH_lessThan, returnVar }, // i<end
|
|
* bodyClause = {init, dropArguments(body, 1, int.class)}; // v = body(i, v);
|
|
* return loop(indexVar, loopLimit, bodyClause);
|
|
* }
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param start a handle to return the start value of the loop counter.
|
|
* If it is {@code null}, a constant zero is assumed.
|
|
* @param end a non-{@code null} handle to return the end value of the loop counter (the loop will run to {@code end-1}).
|
|
* @param init initializer for additional loop state. This determines the loop's result type.
|
|
* Passing {@code null} or a {@code void} init function will make the loop's result type
|
|
* {@code void}.
|
|
* @param body the body of the loop, which must not be {@code null}.
|
|
* It must accept an initial {@code int} parameter (for the counter), and then any
|
|
* additional loop-local variable plus loop parameters.
|
|
*
|
|
* @return a method handle representing the loop.
|
|
* @throws IllegalArgumentException if any argument has a type inconsistent with the loop structure
|
|
*
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle countedLoop(MethodHandle start, MethodHandle end, MethodHandle init, MethodHandle body) {
|
|
MethodHandle returnVar = dropArguments(init == null ? zeroHandle(void.class) : identity(init.type().returnType()),
|
|
0, int.class, int.class);
|
|
MethodHandle[] indexVar = {start, MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_countedLoopStep)};
|
|
MethodHandle[] loopLimit = {end, null, MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_countedLoopPred), returnVar};
|
|
MethodHandle[] bodyClause = {init, dropArguments(body, 1, int.class)};
|
|
return loop(indexVar, loopLimit, bodyClause);
|
|
}
|
|
|
|
/**
|
|
* Constructs a loop that ranges over the elements produced by an {@code Iterator<T>}.
|
|
* The iterator will be produced by the evaluation of the {@code iterator} handle.
|
|
* If this handle is passed as {@code null} the method {@link Iterable#iterator} will be used instead,
|
|
* and will be applied to a leading argument of the loop handle.
|
|
* Each value produced by the iterator is passed to the {@code body}, which must accept an initial {@code T} parameter.
|
|
* The result of the loop execution is the final value of the additional local state
|
|
* obtained by running {@code init}.
|
|
* <p>
|
|
* This is a convenience wrapper for the
|
|
* {@linkplain MethodHandles#loop(MethodHandle[][]) generic loop combinator}, and the constraints imposed on the {@code body}
|
|
* handle follow directly from those described for the latter.
|
|
* <p>
|
|
* Here is pseudocode for the resulting loop handle. In the code, {@code V}/{@code v} represent the type / value of
|
|
* the loop variable as well as the result type of the loop; {@code T}/{@code t}, that of the elements of the
|
|
* structure the loop iterates over, and {@code A}/{@code a}, that of the argument passed to the loop.
|
|
* <blockquote><pre>{@code
|
|
* Iterator<T> iterator(A); // defaults to Iterable::iterator
|
|
* V init(A);
|
|
* V body(T,V,A);
|
|
* V iteratedLoop(A a) {
|
|
* Iterator<T> it = iterator(a);
|
|
* V v = init(a);
|
|
* for (T t : it) {
|
|
* v = body(t, v, a);
|
|
* }
|
|
* return v;
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* The type {@code T} may be either a primitive or reference.
|
|
* Since type {@code Iterator<T>} is erased in the method handle representation to the raw type
|
|
* {@code Iterator}, the {@code iteratedLoop} combinator adjusts the leading argument type for {@code body}
|
|
* to {@code Object} as if by the {@link MethodHandle#asType asType} conversion method.
|
|
* Therefore, if an iterator of the wrong type appears as the loop is executed,
|
|
* runtime exceptions may occur as the result of dynamic conversions performed by {@code asType}.
|
|
* <p>
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
* // reverse a list
|
|
* static List<String> reverseStep(String e, List<String> r, List<String> l) {
|
|
* r.add(0, e);
|
|
* return r;
|
|
* }
|
|
* static List<String> newArrayList(List<String> l) { return new ArrayList<>(); }
|
|
* // assume MH_reverseStep, MH_newArrayList are handles to the above methods
|
|
* MethodHandle loop = MethodHandles.iteratedLoop(null, MH_newArrayList, MH_reverseStep);
|
|
* List<String> list = Arrays.asList("a", "b", "c", "d", "e");
|
|
* List<String> reversedList = Arrays.asList("e", "d", "c", "b", "a");
|
|
* assertEquals(reversedList, (List<String>) loop.invoke(list));
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* @implSpec The implementation of this method is equivalent to:
|
|
* <blockquote><pre>{@code
|
|
* MethodHandle iteratedLoop(MethodHandle iterator, MethodHandle init, MethodHandle body) {
|
|
* // assume MH_next and MH_hasNext are handles to methods of Iterator
|
|
* Class<?> itype = iterator.type().returnType();
|
|
* Class<?> ttype = body.type().parameterType(0);
|
|
* MethodHandle returnVar = dropArguments(identity(init.type().returnType()), 0, itype);
|
|
* MethodHandle nextVal = MH_next.asType(MH_next.type().changeReturnType(ttype));
|
|
* MethodHandle[]
|
|
* iterVar = {iterator, null, MH_hasNext, returnVar}, // it = iterator(); while (it.hasNext)
|
|
* bodyClause = {init, filterArgument(body, 0, nextVal)}; // v = body(t, v, a);
|
|
* return loop(iterVar, bodyClause);
|
|
* }
|
|
* }</pre></blockquote>
|
|
*
|
|
* @param iterator a handle to return the iterator to start the loop.
|
|
* Passing {@code null} will make the loop call {@link Iterable#iterator()} on the first
|
|
* incoming value.
|
|
* @param init initializer for additional loop state. This determines the loop's result type.
|
|
* Passing {@code null} or a {@code void} init function will make the loop's result type
|
|
* {@code void}.
|
|
* @param body the body of the loop, which must not be {@code null}.
|
|
* It must accept an initial {@code T} parameter (for the iterated values), and then any
|
|
* additional loop-local variable plus loop parameters.
|
|
*
|
|
* @return a method handle embodying the iteration loop functionality.
|
|
* @throws IllegalArgumentException if any argument has a type inconsistent with the loop structure
|
|
*
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle iteratedLoop(MethodHandle iterator, MethodHandle init, MethodHandle body) {
|
|
checkIteratedLoop(body);
|
|
|
|
MethodHandle initit = MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_initIterator);
|
|
MethodHandle initIterator = iterator == null ?
|
|
initit.asType(initit.type().changeParameterType(0, body.type().parameterType(init == null ? 1 : 2))) :
|
|
iterator;
|
|
Class<?> itype = initIterator.type().returnType();
|
|
Class<?> ttype = body.type().parameterType(0);
|
|
|
|
MethodHandle returnVar =
|
|
dropArguments(init == null ? zeroHandle(void.class) : identity(init.type().returnType()), 0, itype);
|
|
MethodHandle initnx = MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_iterateNext);
|
|
MethodHandle nextVal = initnx.asType(initnx.type().changeReturnType(ttype));
|
|
|
|
MethodHandle[] iterVar = {initIterator, null, MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_iteratePred), returnVar};
|
|
MethodHandle[] bodyClause = {init, filterArgument(body, 0, nextVal)};
|
|
|
|
return loop(iterVar, bodyClause);
|
|
}
|
|
|
|
/**
|
|
* Makes a method handle that adapts a {@code target} method handle by wrapping it in a {@code try-finally} block.
|
|
* Another method handle, {@code cleanup}, represents the functionality of the {@code finally} block. Any exception
|
|
* thrown during the execution of the {@code target} handle will be passed to the {@code cleanup} handle. The
|
|
* exception will be rethrown, unless {@code cleanup} handle throws an exception first. The
|
|
* value returned from the {@code cleanup} handle's execution will be the result of the execution of the
|
|
* {@code try-finally} handle.
|
|
* <p>
|
|
* The {@code cleanup} handle will be passed one or two additional leading arguments.
|
|
* The first is the exception thrown during the
|
|
* execution of the {@code target} handle, or {@code null} if no exception was thrown.
|
|
* The second is the result of the execution of the {@code target} handle, or, if it throws an exception,
|
|
* a {@code null}, zero, or {@code false} value of the required type is supplied as a placeholder.
|
|
* The second argument is not present if the {@code target} handle has a {@code void} return type.
|
|
* (Note that, except for argument type conversions, combinators represent {@code void} values in parameter lists
|
|
* by omitting the corresponding paradoxical arguments, not by inserting {@code null} or zero values.)
|
|
* <p>
|
|
* The {@code target} and {@code cleanup} handles must have the same corresponding argument and return types, except
|
|
* that the {@code cleanup} handle may omit trailing arguments. Also, the {@code cleanup} handle must have one or
|
|
* two extra leading parameters:<ul>
|
|
* <li>a {@code Throwable}, which will carry the exception thrown by the {@code target} handle (if any); and
|
|
* <li>a parameter of the same type as the return type of both {@code target} and {@code cleanup}, which will carry
|
|
* the result from the execution of the {@code target} handle.
|
|
* This parameter is not present if the {@code target} returns {@code void}.
|
|
* </ul>
|
|
* <p>
|
|
* The pseudocode for the resulting adapter looks as follows. In the code, {@code V} represents the result type of
|
|
* the {@code try/finally} construct; {@code A}/{@code a}, the types and values of arguments to the resulting
|
|
* handle consumed by the cleanup; and {@code B}/{@code b}, those of arguments to the resulting handle discarded by
|
|
* the cleanup.
|
|
* <blockquote><pre>{@code
|
|
* V target(A..., B...);
|
|
* V cleanup(Throwable, V, A...);
|
|
* V adapter(A... a, B... b) {
|
|
* V result = (zero value for V);
|
|
* Throwable throwable = null;
|
|
* try {
|
|
* result = target(a..., b...);
|
|
* } catch (Throwable t) {
|
|
* throwable = t;
|
|
* throw t;
|
|
* } finally {
|
|
* result = cleanup(throwable, result, a...);
|
|
* }
|
|
* return result;
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* Note that the saved arguments ({@code a...} in the pseudocode) cannot
|
|
* be modified by execution of the target, and so are passed unchanged
|
|
* from the caller to the cleanup, if it is invoked.
|
|
* <p>
|
|
* The target and cleanup must return the same type, even if the cleanup
|
|
* always throws.
|
|
* To create such a throwing cleanup, compose the cleanup logic
|
|
* with {@link #throwException throwException},
|
|
* in order to create a method handle of the correct return type.
|
|
* <p>
|
|
* Note that {@code tryFinally} never converts exceptions into normal returns.
|
|
* In rare cases where exceptions must be converted in that way, first wrap
|
|
* the target with {@link #catchException(MethodHandle, Class, MethodHandle)}
|
|
* to capture an outgoing exception, and then wrap with {@code tryFinally}.
|
|
*
|
|
* @param target the handle whose execution is to be wrapped in a {@code try} block.
|
|
* @param cleanup the handle that is invoked in the finally block.
|
|
*
|
|
* @return a method handle embodying the {@code try-finally} block composed of the two arguments.
|
|
* @throws NullPointerException if any argument is null
|
|
* @throws IllegalArgumentException if {@code cleanup} does not accept
|
|
* the required leading arguments, or if the method handle types do
|
|
* not match in their return types and their
|
|
* corresponding trailing parameters
|
|
*
|
|
* @see MethodHandles#catchException(MethodHandle, Class, MethodHandle)
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle tryFinally(MethodHandle target, MethodHandle cleanup) {
|
|
List<Class<?>> targetParamTypes = target.type().parameterList();
|
|
List<Class<?>> cleanupParamTypes = cleanup.type().parameterList();
|
|
Class<?> rtype = target.type().returnType();
|
|
|
|
checkTryFinally(target, cleanup);
|
|
|
|
// Match parameter lists: if the cleanup has a shorter parameter list than the target, add ignored arguments.
|
|
int tpSize = targetParamTypes.size();
|
|
int cpPrefixLength = rtype == void.class ? 1 : 2;
|
|
int cpSize = cleanupParamTypes.size();
|
|
MethodHandle aCleanup = cpSize - cpPrefixLength < tpSize ?
|
|
dropArguments(cleanup, cpSize, targetParamTypes.subList(tpSize - (cpSize - cpPrefixLength), tpSize)) :
|
|
cleanup;
|
|
|
|
MethodHandle aTarget = target.asSpreader(Object[].class, target.type().parameterCount());
|
|
aCleanup = aCleanup.asSpreader(Object[].class, tpSize);
|
|
|
|
return MethodHandleImpl.makeTryFinally(aTarget, aCleanup, rtype, targetParamTypes);
|
|
}
|
|
|
|
/**
|
|
* Adapts a target method handle by pre-processing some of its arguments, starting at a given position, and then
|
|
* calling the target with the result of the pre-processing, inserted into the original sequence of arguments just
|
|
* before the folded arguments.
|
|
* <p>
|
|
* This method is closely related to {@link #foldArguments(MethodHandle, MethodHandle)}, but allows to control the
|
|
* position in the parameter list at which folding takes place. The argument controlling this, {@code pos}, is a
|
|
* zero-based index. The aforementioned method {@link #foldArguments(MethodHandle, MethodHandle)} assumes position
|
|
* 0.
|
|
* <p>
|
|
* @apiNote Example:
|
|
* <blockquote><pre>{@code
|
|
import static java.lang.invoke.MethodHandles.*;
|
|
import static java.lang.invoke.MethodType.*;
|
|
...
|
|
MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
|
|
"println", methodType(void.class, String.class))
|
|
.bindTo(System.out);
|
|
MethodHandle cat = lookup().findVirtual(String.class,
|
|
"concat", methodType(String.class, String.class));
|
|
assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
|
|
MethodHandle catTrace = foldArguments(cat, 1, trace);
|
|
// also prints "jum":
|
|
assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
|
|
* }</pre></blockquote>
|
|
* <p>Here is pseudocode for the resulting adapter. In the code, {@code T}
|
|
* represents the result type of the {@code target} and resulting adapter.
|
|
* {@code V}/{@code v} represent the type and value of the parameter and argument
|
|
* of {@code target} that precedes the folding position; {@code V} also is
|
|
* the result type of the {@code combiner}. {@code A}/{@code a} denote the
|
|
* types and values of the {@code N} parameters and arguments at the folding
|
|
* position. {@code Z}/{@code z} and {@code B}/{@code b} represent the types
|
|
* and values of the {@code target} parameters and arguments that precede and
|
|
* follow the folded parameters and arguments starting at {@code pos},
|
|
* respectively.
|
|
* <blockquote><pre>{@code
|
|
* // there are N arguments in A...
|
|
* T target(Z..., V, A[N]..., B...);
|
|
* V combiner(A...);
|
|
* T adapter(Z... z, A... a, B... b) {
|
|
* V v = combiner(a...);
|
|
* return target(z..., v, a..., b...);
|
|
* }
|
|
* // and if the combiner has a void return:
|
|
* T target2(Z..., A[N]..., B...);
|
|
* void combiner2(A...);
|
|
* T adapter2(Z... z, A... a, B... b) {
|
|
* combiner2(a...);
|
|
* return target2(z..., a..., b...);
|
|
* }
|
|
* }</pre></blockquote>
|
|
* <p>
|
|
* <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
|
|
* variable-arity method handle}, even if the original target method handle was.
|
|
*
|
|
* @param target the method handle to invoke after arguments are combined
|
|
* @param pos the position at which to start folding and at which to insert the folding result; if this is {@code
|
|
* 0}, the effect is the same as for {@link #foldArguments(MethodHandle, MethodHandle)}.
|
|
* @param combiner method handle to call initially on the incoming arguments
|
|
* @return method handle which incorporates the specified argument folding logic
|
|
* @throws NullPointerException if either argument is null
|
|
* @throws IllegalArgumentException if {@code combiner}'s return type
|
|
* is non-void and not the same as the argument type at position {@code pos} of
|
|
* the target signature, or if the {@code N} argument types at position {@code pos}
|
|
* of the target signature
|
|
* (skipping one matching the {@code combiner}'s return type)
|
|
* are not identical with the argument types of {@code combiner}
|
|
*
|
|
* @see #foldArguments(MethodHandle, MethodHandle)
|
|
* @since 9
|
|
*/
|
|
public static MethodHandle foldArguments(MethodHandle target, int pos, MethodHandle combiner) {
|
|
MethodType targetType = target.type();
|
|
MethodType combinerType = combiner.type();
|
|
Class<?> rtype = foldArgumentChecks(pos, targetType, combinerType);
|
|
BoundMethodHandle result = target.rebind();
|
|
boolean dropResult = rtype == void.class;
|
|
LambdaForm lform = result.editor().foldArgumentsForm(1 + pos, dropResult, combinerType.basicType());
|
|
MethodType newType = targetType;
|
|
if (!dropResult) {
|
|
newType = newType.dropParameterTypes(pos, pos + 1);
|
|
}
|
|
result = result.copyWithExtendL(newType, lform, combiner);
|
|
return result;
|
|
}
|
|
|
|
/**
|
|
* Wrap creation of a proper zero handle for a given type.
|
|
*
|
|
* @param type the type.
|
|
*
|
|
* @return a zero value for the given type.
|
|
*/
|
|
static MethodHandle zeroHandle(Class<?> type) {
|
|
return type.isPrimitive() ? zero(Wrapper.forPrimitiveType(type), type) : zero(Wrapper.OBJECT, type);
|
|
}
|
|
|
|
private static void checkLoop0(MethodHandle[][] clauses) {
|
|
if (clauses == null || clauses.length == 0) {
|
|
throw newIllegalArgumentException("null or no clauses passed");
|
|
}
|
|
if (Stream.of(clauses).anyMatch(Objects::isNull)) {
|
|
throw newIllegalArgumentException("null clauses are not allowed");
|
|
}
|
|
if (Stream.of(clauses).anyMatch(c -> c.length > 4)) {
|
|
throw newIllegalArgumentException("All loop clauses must be represented as MethodHandle arrays with at most 4 elements.");
|
|
}
|
|
}
|
|
|
|
private static void checkLoop1a(int i, MethodHandle in, MethodHandle st) {
|
|
if (in.type().returnType() != st.type().returnType()) {
|
|
throw misMatchedTypes("clause " + i + ": init and step return types", in.type().returnType(),
|
|
st.type().returnType());
|
|
}
|
|
}
|
|
|
|
private static List<Class<?>> buildCommonSuffix(List<MethodHandle> init, List<MethodHandle> step, List<MethodHandle> pred, List<MethodHandle> fini, int cpSize) {
|
|
final List<Class<?>> empty = List.of();
|
|
final List<MethodHandle> nonNullInits = init.stream().filter(Objects::nonNull).collect(Collectors.toList());
|
|
if (nonNullInits.isEmpty()) {
|
|
final List<Class<?>> longest = Stream.of(step, pred, fini).flatMap(List::stream).filter(Objects::nonNull).
|
|
// take only those that can contribute to a common suffix because they are longer than the prefix
|
|
map(MethodHandle::type).filter(t -> t.parameterCount() > cpSize).map(MethodType::parameterList).
|
|
reduce((p, q) -> p.size() >= q.size() ? p : q).orElse(empty);
|
|
return longest.size() == 0 ? empty : longest.subList(cpSize, longest.size());
|
|
} else {
|
|
return nonNullInits.stream().map(MethodHandle::type).map(MethodType::parameterList).
|
|
reduce((p, q) -> p.size() >= q.size() ? p : q).get();
|
|
}
|
|
}
|
|
|
|
private static void checkLoop1b(List<MethodHandle> init, List<Class<?>> commonSuffix) {
|
|
if (init.stream().filter(Objects::nonNull).map(MethodHandle::type).map(MethodType::parameterList).
|
|
anyMatch(pl -> !pl.equals(commonSuffix.subList(0, pl.size())))) {
|
|
throw newIllegalArgumentException("found non-effectively identical init parameter type lists: " + init +
|
|
" (common suffix: " + commonSuffix + ")");
|
|
}
|
|
}
|
|
|
|
private static void checkLoop1cd(List<MethodHandle> pred, List<MethodHandle> fini, Class<?> loopReturnType) {
|
|
if (fini.stream().filter(Objects::nonNull).map(MethodHandle::type).map(MethodType::returnType).
|
|
anyMatch(t -> t != loopReturnType)) {
|
|
throw newIllegalArgumentException("found non-identical finalizer return types: " + fini + " (return type: " +
|
|
loopReturnType + ")");
|
|
}
|
|
|
|
if (!pred.stream().filter(Objects::nonNull).findFirst().isPresent()) {
|
|
throw newIllegalArgumentException("no predicate found", pred);
|
|
}
|
|
if (pred.stream().filter(Objects::nonNull).map(MethodHandle::type).map(MethodType::returnType).
|
|
anyMatch(t -> t != boolean.class)) {
|
|
throw newIllegalArgumentException("predicates must have boolean return type", pred);
|
|
}
|
|
}
|
|
|
|
private static void checkLoop2(List<MethodHandle> step, List<MethodHandle> pred, List<MethodHandle> fini, List<Class<?>> commonParameterSequence) {
|
|
final int cpSize = commonParameterSequence.size();
|
|
if (Stream.of(step, pred, fini).flatMap(List::stream).filter(Objects::nonNull).map(MethodHandle::type).
|
|
map(MethodType::parameterList).
|
|
anyMatch(pl -> pl.size() > cpSize || !pl.equals(commonParameterSequence.subList(0, pl.size())))) {
|
|
throw newIllegalArgumentException("found non-effectively identical parameter type lists:\nstep: " + step +
|
|
"\npred: " + pred + "\nfini: " + fini + " (common parameter sequence: " + commonParameterSequence + ")");
|
|
}
|
|
}
|
|
|
|
private static void checkIteratedLoop(MethodHandle body) {
|
|
if (null == body) {
|
|
throw newIllegalArgumentException("iterated loop body must not be null");
|
|
}
|
|
}
|
|
|
|
private static void checkTryFinally(MethodHandle target, MethodHandle cleanup) {
|
|
Class<?> rtype = target.type().returnType();
|
|
if (rtype != cleanup.type().returnType()) {
|
|
throw misMatchedTypes("target and return types", cleanup.type().returnType(), rtype);
|
|
}
|
|
List<Class<?>> cleanupParamTypes = cleanup.type().parameterList();
|
|
if (!Throwable.class.isAssignableFrom(cleanupParamTypes.get(0))) {
|
|
throw misMatchedTypes("cleanup first argument and Throwable", cleanup.type(), Throwable.class);
|
|
}
|
|
if (rtype != void.class && cleanupParamTypes.get(1) != rtype) {
|
|
throw misMatchedTypes("cleanup second argument and target return type", cleanup.type(), rtype);
|
|
}
|
|
// The cleanup parameter list (minus the leading Throwable and result parameters) must be a sublist of the
|
|
// target parameter list.
|
|
int cleanupArgIndex = rtype == void.class ? 1 : 2;
|
|
List<Class<?>> cleanupArgSuffix = cleanupParamTypes.subList(cleanupArgIndex, cleanupParamTypes.size());
|
|
List<Class<?>> targetParamTypes = target.type().parameterList();
|
|
if (targetParamTypes.size() < cleanupArgSuffix.size() ||
|
|
!cleanupArgSuffix.equals(targetParamTypes.subList(0, cleanupParamTypes.size() - cleanupArgIndex))) {
|
|
throw misMatchedTypes("cleanup parameters after (Throwable,result) and target parameter list prefix",
|
|
cleanup.type(), target.type());
|
|
}
|
|
}
|
|
|
|
}
|