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8299807: newStringNoRepl should avoid copying arrays for ASCII compatible charsets

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Reviewed-by: rriggs
This commit is contained in:
Glavo 2023-03-03 15:41:03 +00:00 • committed by Roger Riggs
parent c6de66c03f
commit 7449e1c661
2 changed files with 16 additions and 5 deletions
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19
src/java.base/share/classes/java/lang/String.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1994, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1994, 2023, 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
@ -698,8 +698,13 @@ public final class String
/*
* Throws iae, instead of replacing, if malformed or unmappable.
*
* @param noShare
* {@code true} if the resulting string MUST NOT share the byte array,
* {@code false} if the byte array can be exclusively used to construct
* the string and is not modified or used for any other purpose.
*/
static String newStringUTF8NoRepl(byte[] bytes, int offset, int length) {
static String newStringUTF8NoRepl(byte[] bytes, int offset, int length, boolean noShare) {
checkBoundsOffCount(offset, length, bytes.length);
if (length == 0) {
return "";
@ -710,7 +715,11 @@ public final class String
dp = StringCoding.countPositives(bytes, offset, length);
int sl = offset + length;
if (dp == length) {
return new String(Arrays.copyOfRange(bytes, offset, offset + length), LATIN1);
if (noShare || length != bytes.length) {
return new String(Arrays.copyOfRange(bytes, offset, offset + length), LATIN1);
} else {
return new String(bytes, LATIN1);
}
}
dst = new byte[length];
System.arraycopy(bytes, offset, dst, 0, dp);
@ -778,7 +787,7 @@ public final class String
return "";
}
if (cs == UTF_8.INSTANCE) {
return newStringUTF8NoRepl(src, 0, src.length);
return newStringUTF8NoRepl(src, 0, src.length, false);
}
if (cs == ISO_8859_1.INSTANCE) {
if (COMPACT_STRINGS)
@ -800,6 +809,8 @@ public final class String
if (cd instanceof ArrayDecoder ad &&
ad.isASCIICompatible() &&
!StringCoding.hasNegatives(src, 0, src.length)) {
if (COMPACT_STRINGS)
return new String(src, LATIN1);
return new String(src, 0, src.length, ISO_8859_1.INSTANCE);
}
int en = scale(len, cd.maxCharsPerByte());