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8170467: (reflect) Optimize SignatureParser's use of StringBuilders

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Reviewed-by: shade, redestad
This commit is contained in:
Max-Kanat Alexander 2016-11-29 16:27:19 +01:00 committed by Claes Redestad
parent fa87bee688
commit 4a1bb5b90a
1 changed files with 29 additions and 18 deletions
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47
jdk/src/java.base/share/classes/sun/reflect/generics/parser/SignatureParser.java
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@ -70,6 +70,11 @@ public class SignatureParser {
private static final char EOI = ':';
private static final boolean DEBUG = false;
// StringBuilder does a lot of array copies if we don't pre-size
// it when parsing a full class name. This value was determined
// empirically by measurements of real-world code.
private static final int CLASS_NAME_SB_SIZE = 48;
// private constructor - enforces use of static factory
private SignatureParser(){}
@ -251,9 +256,19 @@ public class SignatureParser {
return FormalTypeParameter.make(id, bs);
}
private String parseIdentifier(){
private String parseIdentifier() {
StringBuilder result = new StringBuilder();
while (!Character.isWhitespace(current())) {
parseIdentifierInto(result);
return result.toString();
}
// This is separate from parseIdentifier for performance reasons.
// For a caller who already has a StringBuilder, it's much faster to
// re-use the existing builder, because it results in far fewer internal
// array copies inside of StringBuilder.
private void parseIdentifierInto(StringBuilder result) {
int startIndex = index;
parseLoop: while (!Character.isWhitespace(current())) {
char c = current();
switch(c) {
case ';':
@ -263,16 +278,14 @@ public class SignatureParser {
case ':':
case '>':
case '<':
return result.toString();
default:{
result.append(c);
break parseLoop;
default:
advance();
}
}
}
return result.toString();
result.append(input, startIndex, index - startIndex);
}
/**
* FieldTypeSignature:
* ClassTypeSignature
@ -325,19 +338,17 @@ public class SignatureParser {
// Parse both any optional leading PackageSpecifier as well as
// the following SimpleClassTypeSignature.
String id = parseIdentifier();
StringBuilder idBuild = new StringBuilder(CLASS_NAME_SB_SIZE);
parseIdentifierInto(idBuild);
if (current() == '/') { // package name
StringBuilder idBuild = new StringBuilder(id);
while(current() == '/') {
advance();
idBuild.append(".");
idBuild.append(parseIdentifier());
}
id = idBuild.toString();
while (current() == '/') { // package name
advance();
idBuild.append('.');
parseIdentifierInto(idBuild);
}
String id = idBuild.toString();
switch (current()) {
case ';':
return SimpleClassTypeSignature.make(id, false, new TypeArgument[0]); // all done!