438 lines
15 KiB
Java
438 lines
15 KiB
Java
/*
|
|
* Copyright (c) 2000, 2024, 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.nio;
|
|
|
|
import java.io.FileDescriptor;
|
|
import java.io.UncheckedIOException;
|
|
import java.lang.foreign.MemorySegment;
|
|
import java.lang.ref.Reference;
|
|
import java.util.Objects;
|
|
|
|
import jdk.internal.access.foreign.UnmapperProxy;
|
|
import jdk.internal.misc.ScopedMemoryAccess;
|
|
import jdk.internal.misc.Unsafe;
|
|
|
|
|
|
/**
|
|
* A direct byte buffer whose content is a memory-mapped region of a file.
|
|
*
|
|
* <p> Mapped byte buffers are created via the {@link
|
|
* java.nio.channels.FileChannel#map FileChannel.map} method. This class
|
|
* extends the {@link ByteBuffer} class with operations that are specific to
|
|
* memory-mapped file regions.
|
|
*
|
|
* <p> A mapped byte buffer and the file mapping that it represents remain
|
|
* valid until the buffer itself is garbage-collected.
|
|
*
|
|
* <p> The content of a mapped byte buffer can change at any time, for example
|
|
* if the content of the corresponding region of the mapped file is changed by
|
|
* this program or another. Whether or not such changes occur, and when they
|
|
* occur, is operating-system dependent and therefore unspecified.
|
|
*
|
|
* <a id="inaccess"></a><p> All or part of a mapped byte buffer may become
|
|
* inaccessible at any time, for example if the mapped file is truncated. An
|
|
* attempt to access an inaccessible region of a mapped byte buffer will not
|
|
* change the buffer's content and will cause an unspecified exception to be
|
|
* thrown either at the time of the access or at some later time. It is
|
|
* therefore strongly recommended that appropriate precautions be taken to
|
|
* avoid the manipulation of a mapped file by this program, or by a
|
|
* concurrently running program, except to read or write the file's content.
|
|
*
|
|
* <p> Mapped byte buffers otherwise behave no differently than ordinary direct
|
|
* byte buffers. </p>
|
|
*
|
|
*
|
|
* @author Mark Reinhold
|
|
* @author JSR-51 Expert Group
|
|
* @since 1.4
|
|
*/
|
|
|
|
public abstract sealed class MappedByteBuffer
|
|
extends ByteBuffer
|
|
permits DirectByteBuffer
|
|
{
|
|
|
|
// This is a little bit backwards: By rights MappedByteBuffer should be a
|
|
// subclass of DirectByteBuffer, but to keep the spec clear and simple, and
|
|
// for optimization purposes, it's easier to do it the other way around.
|
|
// This works because DirectByteBuffer is a package-private class.
|
|
|
|
// For mapped buffers, a FileDescriptor that may be used for mapping
|
|
// operations if valid; null if the buffer is not mapped.
|
|
private final FileDescriptor fd;
|
|
|
|
// A flag true if this buffer is mapped against non-volatile
|
|
// memory using one of the extended FileChannel.MapMode modes,
|
|
// MapMode.READ_ONLY_SYNC or MapMode.READ_WRITE_SYNC and false if
|
|
// it is mapped using any of the other modes. This flag only
|
|
// determines the behavior of force operations.
|
|
private final boolean isSync;
|
|
|
|
static final ScopedMemoryAccess SCOPED_MEMORY_ACCESS = ScopedMemoryAccess.getScopedMemoryAccess();
|
|
|
|
// This should only be invoked by the DirectByteBuffer constructors
|
|
//
|
|
MappedByteBuffer(int mark, int pos, int lim, int cap, // package-private
|
|
FileDescriptor fd, boolean isSync, MemorySegment segment) {
|
|
super(mark, pos, lim, cap, segment);
|
|
this.fd = fd;
|
|
this.isSync = isSync;
|
|
}
|
|
|
|
MappedByteBuffer(int mark, int pos, int lim, int cap, // package-private
|
|
boolean isSync, MemorySegment segment) {
|
|
super(mark, pos, lim, cap, segment);
|
|
this.fd = null;
|
|
this.isSync = isSync;
|
|
}
|
|
|
|
MappedByteBuffer(int mark, int pos, int lim, int cap, MemorySegment segment) { // package-private
|
|
super(mark, pos, lim, cap, segment);
|
|
this.fd = null;
|
|
this.isSync = false;
|
|
}
|
|
|
|
UnmapperProxy unmapper() {
|
|
return fd == null
|
|
? null
|
|
: new UnmapperProxy() {
|
|
|
|
// Ensure safe publication as MappedByteBuffer.this.address is not final
|
|
private final long addr = address;
|
|
|
|
@Override
|
|
public long address() {
|
|
return addr;
|
|
}
|
|
|
|
@Override
|
|
public FileDescriptor fileDescriptor() {
|
|
return fd;
|
|
}
|
|
|
|
@Override
|
|
public boolean isSync() {
|
|
return isSync;
|
|
}
|
|
|
|
@Override
|
|
public void unmap() {
|
|
Unsafe.getUnsafe().invokeCleaner(MappedByteBuffer.this);
|
|
}
|
|
};
|
|
}
|
|
|
|
/**
|
|
* Tells whether this buffer was mapped against a non-volatile
|
|
* memory device by passing one of the sync map modes {@link
|
|
* jdk.nio.mapmode.ExtendedMapMode#READ_ONLY_SYNC
|
|
* ExtendedMapModeMapMode#READ_ONLY_SYNC} or {@link
|
|
* jdk.nio.mapmode.ExtendedMapMode#READ_ONLY_SYNC
|
|
* ExtendedMapMode#READ_WRITE_SYNC} in the call to {@link
|
|
* java.nio.channels.FileChannel#map FileChannel.map} or was
|
|
* mapped by passing one of the other map modes.
|
|
*
|
|
* @return true if the file was mapped using one of the sync map
|
|
* modes, otherwise false.
|
|
*/
|
|
final boolean isSync() { // package-private
|
|
return isSync;
|
|
}
|
|
|
|
/**
|
|
* Returns the {@code FileDescriptor} associated with this
|
|
* {@code MappedByteBuffer}.
|
|
*
|
|
* @return the buffer's file descriptor; may be {@code null}
|
|
*/
|
|
final FileDescriptor fileDescriptor() { // package-private
|
|
return fd;
|
|
}
|
|
|
|
/**
|
|
* Tells whether or not this buffer's content is resident in physical
|
|
* memory.
|
|
*
|
|
* <p> A return value of {@code true} implies that it is highly likely
|
|
* that all of the data in this buffer is resident in physical memory and
|
|
* may therefore be accessed without incurring any virtual-memory page
|
|
* faults or I/O operations. A return value of {@code false} does not
|
|
* necessarily imply that the buffer's content is not resident in physical
|
|
* memory.
|
|
*
|
|
* <p> The returned value is a hint, rather than a guarantee, because the
|
|
* underlying operating system may have paged out some of the buffer's data
|
|
* by the time that an invocation of this method returns. </p>
|
|
*
|
|
* @return {@code true} if it is likely that this buffer's content
|
|
* is resident in physical memory
|
|
*/
|
|
public final boolean isLoaded() {
|
|
if (fd == null) {
|
|
return true;
|
|
}
|
|
return SCOPED_MEMORY_ACCESS.isLoaded(session(), address, isSync, capacity());
|
|
}
|
|
|
|
/**
|
|
* Loads this buffer's content into physical memory.
|
|
*
|
|
* <p> This method makes a best effort to ensure that, when it returns,
|
|
* this buffer's content is resident in physical memory. Invoking this
|
|
* method may cause some number of page faults and I/O operations to
|
|
* occur. </p>
|
|
*
|
|
* @return This buffer
|
|
*/
|
|
public final MappedByteBuffer load() {
|
|
if (fd == null) {
|
|
return this;
|
|
}
|
|
try {
|
|
SCOPED_MEMORY_ACCESS.load(session(), address, isSync, capacity());
|
|
} finally {
|
|
Reference.reachabilityFence(this);
|
|
}
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* Forces any changes made to this buffer's content to be written to the
|
|
* storage device containing the mapped file. The region starts at index
|
|
* zero in this buffer and is {@code capacity()} bytes. An invocation of
|
|
* this method behaves in exactly the same way as the invocation
|
|
* {@link force(int,int) force(0,capacity())}.
|
|
*
|
|
* <p> If the file mapped into this buffer resides on a local storage
|
|
* device then when this method returns it is guaranteed that all changes
|
|
* made to the buffer since it was created, or since this method was last
|
|
* invoked, will have been written to that device.
|
|
*
|
|
* <p> If the file does not reside on a local device then no such guarantee
|
|
* is made.
|
|
*
|
|
* <p> If this buffer was not mapped in read/write mode ({@link
|
|
* java.nio.channels.FileChannel.MapMode#READ_WRITE}) then
|
|
* invoking this method may have no effect. In particular, the
|
|
* method has no effect for buffers mapped in read-only or private
|
|
* mapping modes. This method may or may not have an effect for
|
|
* implementation-specific mapping modes. </p>
|
|
*
|
|
* @throws UncheckedIOException
|
|
* If an I/O error occurs writing the buffer's content to the
|
|
* storage device containing the mapped file
|
|
*
|
|
* @return This buffer
|
|
*/
|
|
public final MappedByteBuffer force() {
|
|
if (fd == null) {
|
|
return this;
|
|
}
|
|
int capacity = capacity();
|
|
if (isSync || ((address != 0) && (capacity != 0))) {
|
|
return force(0, capacity);
|
|
}
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* Forces any changes made to a region of this buffer's content to
|
|
* be written to the storage device containing the mapped
|
|
* file. The region starts at the given {@code index} in this
|
|
* buffer and is {@code length} bytes.
|
|
*
|
|
* <p> If the file mapped into this buffer resides on a local
|
|
* storage device then when this method returns it is guaranteed
|
|
* that all changes made to the selected region buffer since it
|
|
* was created, or since this method was last invoked, will have
|
|
* been written to that device. The force operation is free to
|
|
* write bytes that lie outside the specified region, for example
|
|
* to ensure that data blocks of some device-specific granularity
|
|
* are transferred in their entirety.
|
|
*
|
|
* <p> If the file does not reside on a local device then no such
|
|
* guarantee is made.
|
|
*
|
|
* <p> If this buffer was not mapped in read/write mode ({@link
|
|
* java.nio.channels.FileChannel.MapMode#READ_WRITE}) then
|
|
* invoking this method may have no effect. In particular, the
|
|
* method has no effect for buffers mapped in read-only or private
|
|
* mapping modes. This method may or may not have an effect for
|
|
* implementation-specific mapping modes. </p>
|
|
*
|
|
* @param index
|
|
* The index of the first byte in the buffer region that is
|
|
* to be written back to storage; must be non-negative
|
|
* and less than {@code capacity()}
|
|
*
|
|
* @param length
|
|
* The length of the region in bytes; must be non-negative
|
|
* and no larger than {@code capacity() - index}
|
|
*
|
|
* @throws IndexOutOfBoundsException
|
|
* if the preconditions on the index and length do not
|
|
* hold.
|
|
*
|
|
* @throws UncheckedIOException
|
|
* If an I/O error occurs writing the buffer's content to the
|
|
* storage device containing the mapped file
|
|
*
|
|
* @return This buffer
|
|
*
|
|
* @since 13
|
|
*/
|
|
public final MappedByteBuffer force(int index, int length) {
|
|
if (fd == null) {
|
|
return this;
|
|
}
|
|
int capacity = capacity();
|
|
if ((address != 0) && (capacity != 0)) {
|
|
// check inputs
|
|
Objects.checkFromIndexSize(index, length, capacity);
|
|
SCOPED_MEMORY_ACCESS.force(session(), fd, address, isSync, index, length);
|
|
}
|
|
return this;
|
|
}
|
|
|
|
// -- Covariant return type overrides
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer position(int newPosition) {
|
|
super.position(newPosition);
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer limit(int newLimit) {
|
|
super.limit(newLimit);
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer mark() {
|
|
super.mark();
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer reset() {
|
|
super.reset();
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer clear() {
|
|
super.clear();
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer flip() {
|
|
super.flip();
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @since 9
|
|
*/
|
|
@Override
|
|
public final MappedByteBuffer rewind() {
|
|
super.rewind();
|
|
return this;
|
|
}
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
*
|
|
* <p> Reading bytes into physical memory by invoking {@code load()} on the
|
|
* returned buffer, or writing bytes to the storage device by invoking
|
|
* {@code force()} on the returned buffer, will only act on the sub-range
|
|
* of this buffer that the returned buffer represents, namely
|
|
* {@code [position(),limit())}.
|
|
*
|
|
* @since 17
|
|
*/
|
|
@Override
|
|
public abstract MappedByteBuffer slice();
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
*
|
|
* <p> Reading bytes into physical memory by invoking {@code load()} on the
|
|
* returned buffer, or writing bytes to the storage device by invoking
|
|
* {@code force()} on the returned buffer, will only act on the sub-range
|
|
* of this buffer that the returned buffer represents, namely
|
|
* {@code [index,index+length)}, where {@code index} and {@code length} are
|
|
* assumed to satisfy the preconditions.
|
|
*
|
|
* @since 17
|
|
*/
|
|
@Override
|
|
public abstract MappedByteBuffer slice(int index, int length);
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
*
|
|
* @since 17
|
|
*/
|
|
@Override
|
|
public abstract MappedByteBuffer duplicate();
|
|
|
|
/**
|
|
* {@inheritDoc}
|
|
* @throws ReadOnlyBufferException {@inheritDoc}
|
|
*
|
|
* @since 17
|
|
*/
|
|
@Override
|
|
public abstract MappedByteBuffer compact();
|
|
}
|