Skip to content
This repository has been archived by the owner. It is now read-only.
Permalink
Browse files
8240094: Optimize empty substring handling
Reviewed-by: redestad, igerasim, jlaskey
  • Loading branch information
stsypanov authored and cl4es committed Feb 26, 2020
1 parent 257de28 commit f729514ebddc7de19d5e73346b918fb6f415fc8f
@@ -1,5 +1,5 @@
/*
* Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1994, 2020, 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
@@ -1819,7 +1819,7 @@ public int lastIndexOf(String str, int fromIndex) {
* @param src the characters being searched.
* @param srcCoder coder handles the mapping between bytes/chars
* @param srcCount count of the source string.
* @param tgt the characters being searched for.
* @param tgtStr the characters being searched for.
* @param fromIndex the index to begin searching from.
*/
static int lastIndexOf(byte[] src, byte srcCoder, int srcCount,
@@ -1900,10 +1900,10 @@ public String substring(int beginIndex) {
public String substring(int beginIndex, int endIndex) {
int length = length();
checkBoundsBeginEnd(beginIndex, endIndex, length);
int subLen = endIndex - beginIndex;
if (beginIndex == 0 && endIndex == length) {
return this;
}
int subLen = endIndex - beginIndex;
return isLatin1() ? StringLatin1.newString(value, beginIndex, subLen)
: StringUTF16.newString(value, beginIndex, subLen);
}
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2020, 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
@@ -630,17 +630,11 @@ public static String strip(byte[] value) {

public static String stripLeading(byte[] value) {
int left = indexOfNonWhitespace(value);
if (left == value.length) {
return "";
}
return (left != 0) ? newString(value, left, value.length - left) : null;
}

public static String stripTrailing(byte[] value) {
int right = lastIndexOfNonWhitespace(value);
if (right == 0) {
return "";
}
return (right != value.length) ? newString(value, 0, right) : null;
}

@@ -764,6 +758,9 @@ public static byte[] toBytes(char c) {
}

public static String newString(byte[] val, int index, int len) {
if (len == 0) {
return "";
}
return new String(Arrays.copyOfRange(val, index, index + len),
LATIN1);
}
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2020, 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
@@ -1016,18 +1016,12 @@ public static String strip(byte[] value) {
public static String stripLeading(byte[] value) {
int length = value.length >>> 1;
int left = indexOfNonWhitespace(value);
if (left == length) {
return "";
}
return (left != 0) ? newString(value, left, length - left) : null;
}

public static String stripTrailing(byte[] value) {
int length = value.length >>> 1;
int right = lastIndexOfNonWhitespace(value);
if (right == 0) {
return "";
}
return (right != length) ? newString(value, 0, right) : null;
}

@@ -1132,6 +1126,9 @@ private static void putChars(byte[] val, int index, char[] str, int off, int end
}

public static String newString(byte[] val, int index, int len) {
if (len == 0) {
return "";
}
if (String.COMPACT_STRINGS) {
byte[] buf = compress(val, index, len);
if (buf != null) {
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2019, 2020, 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
@@ -28,6 +28,9 @@

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(value = 3)
@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@State(Scope.Benchmark)
public class StringSubstring {

@@ -42,4 +45,12 @@ public String from26toEnd0() {
public String from26toEnd1() {
return s.substring(26, s.length());
}

/**
* An empty substring should not allocate a new String
*/
@Benchmark
public String empty() {
return s.substring(17, 17);
}
}

0 comments on commit f729514

Please sign in to comment.