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8006627: UUID to/from String performance should be improved by reducing object allocations

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Co-authored-by: Steven Schlansker <stevenschlansker@gmail.com>
Reviewed-by: mduigou, plevart
This commit is contained in:
Claes Redestad 2014-07-21 23:07:40 +02:00
parent 744f8147ae
commit 23f341125f
2 changed files with 60 additions and 24 deletions
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61
jdk/src/share/classes/java/util/UUID.java
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@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -27,6 +27,9 @@ package java.util;
import java.security.*; import java.security.*;
import sun.misc.JavaLangAccess;
import sun.misc.SharedSecrets;
/** /**
* A class that represents an immutable universally unique identifier (UUID). * A class that represents an immutable universally unique identifier (UUID).
* A UUID represents a 128-bit value. * A UUID represents a 128-bit value.
@ -88,6 +91,8 @@ public final class UUID implements java.io.Serializable, Comparable<UUID> {
*/ */
private final long leastSigBits; private final long leastSigBits;
private static final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();
/* /*
* The random number generator used by this class to create random * The random number generator used by this class to create random
* based UUIDs. In a holder class to defer initialization until needed. * based UUIDs. In a holder class to defer initialization until needed.
@ -189,21 +194,35 @@ public final class UUID implements java.io.Serializable, Comparable<UUID> {
* *
*/ */
public static UUID fromString(String name) { public static UUID fromString(String name) {
String[] components = name.split("-"); if (name.length() > 36) {
if (components.length != 5) throw new IllegalArgumentException("UUID string too large");
}
int dash1 = name.indexOf('-', 0);
int dash2 = name.indexOf('-', dash1 + 1);
int dash3 = name.indexOf('-', dash2 + 1);
int dash4 = name.indexOf('-', dash3 + 1);
int dash5 = name.indexOf('-', dash4 + 1);
// For any valid input, dash1 through dash4 will be positive and dash5
// negative, but it's enough to check dash4 and dash5:
// - if dash1 is -1, dash4 will be -1
// - if dash1 is positive but dash2 is -1, dash4 will be -1
// - if dash1 and dash2 is positive, dash3 will be -1, dash4 will be
// positive, but so will dash5
if (dash4 < 0 || dash5 >= 0) {
throw new IllegalArgumentException("Invalid UUID string: " + name); throw new IllegalArgumentException("Invalid UUID string: " + name);
for (int i=0; i<5; i++) }
components[i] = "0x"+components[i];
long mostSigBits = Long.decode(components[0]).longValue(); long mostSigBits = Long.parseLong(name, 16, 0, dash1) & 0xffffffffL;
mostSigBits <<= 16; mostSigBits <<= 16;
mostSigBits |= Long.decode(components[1]).longValue(); mostSigBits |= Long.parseLong(name, 16, dash1 + 1, dash2) & 0xffffL;
mostSigBits <<= 16; mostSigBits <<= 16;
mostSigBits |= Long.decode(components[2]).longValue(); mostSigBits |= Long.parseLong(name, 16, dash2 + 1, dash3) & 0xffffL;
long leastSigBits = Long.decode(components[3]).longValue(); long leastSigBits = Long.parseLong(name, 16, dash3 + 1, dash4) & 0xffffL;
leastSigBits <<= 48; leastSigBits <<= 48;
leastSigBits |= Long.decode(components[4]).longValue(); leastSigBits |= Long.parseLong(name, 16, dash4 + 1) & 0xffffffffffffL;
return new UUID(mostSigBits, leastSigBits); return new UUID(mostSigBits, leastSigBits);
} }
@ -373,17 +392,17 @@ public final class UUID implements java.io.Serializable, Comparable<UUID> {
* @return A string representation of this {@code UUID} * @return A string representation of this {@code UUID}
*/ */
public String toString() { public String toString() {
return (digits(mostSigBits >> 32, 8) + "-" + char[] chars = new char[36];
digits(mostSigBits >> 16, 4) + "-" + jla.formatUnsignedLong(mostSigBits >> 32, 4, chars, 0, 8);
digits(mostSigBits, 4) + "-" + chars[8] = '-';
digits(leastSigBits >> 48, 4) + "-" + jla.formatUnsignedLong(mostSigBits >> 16, 4, chars, 9, 4);
digits(leastSigBits, 12)); chars[13] = '-';
} jla.formatUnsignedLong(mostSigBits, 4, chars, 14, 4);
chars[18] = '-';
/** Returns val represented by the specified number of hex digits. */ jla.formatUnsignedLong(leastSigBits >> 48, 4, chars, 19, 4);
private static String digits(long val, int digits) { chars[23] = '-';
long hi = 1L << (digits * 4); jla.formatUnsignedLong(leastSigBits, 4, chars, 24, 12);
return Long.toHexString(hi | (val & (hi - 1))).substring(1); return jla.newStringUnsafe(chars);
} }
/** /**

17
jdk/test/java/util/UUID/UUIDTest.java
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@ -96,6 +96,23 @@ public class UUIDTest {
if (!u1.equals(u2)) if (!u1.equals(u2))
throw new Exception("UUID -> string -> UUID failed"); throw new Exception("UUID -> string -> UUID failed");
} }
testFromStringError("-0");
testFromStringError("x");
testFromStringError("----");
testFromStringError("-0-0-0-0");
testFromStringError("0-0-0-0-");
testFromStringError("0-0-0-0-0-");
testFromStringError("0-0-0-0-x");
}
private static void testFromStringError(String str) {
try {
UUID test = UUID.fromString(str);
throw new RuntimeException("Should have thrown IAE");
} catch (IllegalArgumentException iae) {
// pass
}
} }
private static void versionTest() throws Exception { private static void versionTest() throws Exception {