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8222955: Optimize String.replace(CharSequence, CharSequence) for common cases

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Reviewed-by: redestad, tvaleev
This commit is contained in:
Ivan Gerasimov 2019-05-06 18:07:55 -07:00
parent 0c6f7e5516
commit 4f02d011b0
5 changed files with 408 additions and 34 deletions
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70
src/java.base/share/classes/java/lang/StringLatin1.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2019, 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
@ -42,6 +42,14 @@ import static java.lang.String.checkOffset;
final class StringLatin1 {
/**
* The maximum size of array to allocate (unless necessary).
* Some VMs reserve some header words in an array.
* Attempts to allocate larger arrays may result in
* OutOfMemoryError: Requested array size exceeds VM limit
*/
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
public static char charAt(byte[] value, int index) {
if (index < 0 || index >= value.length) {
throw new StringIndexOutOfBoundsException(index);
@ -304,7 +312,7 @@ final class StringLatin1 {
}
if (i < len) {
if (canEncode(newChar)) {
byte buf[] = new byte[len];
byte[] buf = StringConcatHelper.newArray(len);
for (int j = 0; j < i; j++) { // TBD arraycopy?
buf[j] = value[j];
}
@ -330,6 +338,64 @@ final class StringLatin1 {
return null; // for string to return this;
}
public static String replace(byte[] value, int valLen, byte[] targ,
int targLen, byte[] repl, int replLen)
{
assert targLen > 0;
int i, j, p = 0;
if (valLen == 0 || (i = indexOf(value, valLen, targ, targLen, 0)) < 0) {
return null; // for string to return this;
}
// find and store indices of substrings to replace
int[] pos = new int[16];
pos[0] = i;
i += targLen;
while ((j = indexOf(value, valLen, targ, targLen, i)) > 0) {
if (++p == pos.length) {
int cap = p + (p >> 1);
// overflow-conscious code
if (cap - MAX_ARRAY_SIZE > 0) {
if (p == MAX_ARRAY_SIZE) {
throw new OutOfMemoryError();
}
cap = MAX_ARRAY_SIZE;
}
pos = Arrays.copyOf(pos, cap);
}
pos[p] = j;
i = j + targLen;
}
int resultLen;
try {
resultLen = Math.addExact(valLen,
Math.multiplyExact(++p, replLen - targLen));
} catch (ArithmeticException ignored) {
throw new OutOfMemoryError();
}
if (resultLen == 0) {
return "";
}
byte[] result = StringConcatHelper.newArray(resultLen);
int posFrom = 0, posTo = 0;
for (int q = 0; q < p; ++q) {
int nextPos = pos[q];
while (posFrom < nextPos) {
result[posTo++] = value[posFrom++];
}
posFrom += targLen;
for (int k = 0; k < replLen; ++k) {
result[posTo++] = repl[k];
}
}
while (posFrom < valLen) {
result[posTo++] = value[posFrom++];
}
return new String(result, LATIN1);
}
// case insensitive
public static boolean regionMatchesCI(byte[] value, int toffset,
byte[] other, int ooffset, int len) {