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FastUUID.java
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FastUUID.java
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/*
* The MIT License (MIT)
*
* Copyright (c) 2018 Jon Chambers
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package com.eatthepath.uuid;
import java.util.Arrays;
import java.util.UUID;
/**
* <p>A utility class for quickly and efficiently parsing {@link java.util.UUID} instances from strings and writing UUID
* instances as strings. The methods contained in this class are optimized for speed and to minimize garbage collection
* pressure. In benchmarks, {@link #parseUUID(CharSequence)} is a little more than 14 times faster than
* {@link UUID#fromString(String)}, and {@link #toString(UUID)} is a little more than six times faster than
* {@link UUID#toString()} when compared to the implementations in Java 8 and older. Under Java 9 and newer,
* {@link #parseUUID(CharSequence)} is about six times faster than the JDK implementation and {@link #toString(UUID)}
* does not offer any performance enhancements (or regressions!).</p>
*
* @author <a href="https://github.com/jchambers/">Jon Chambers</a>
*/
public class FastUUID {
private static final boolean USE_JDK_UUID_TO_STRING;
static {
int majorVersion = 0;
try {
majorVersion = Integer.parseInt(System.getProperty("java.specification.version"));
} catch (final NumberFormatException ignored) {
// This will happen for pretty much anything before Java 9, which had a version scheme like "1.8" instead of
// just "8".
}
USE_JDK_UUID_TO_STRING = majorVersion >= 9;
}
private static final int UUID_STRING_LENGTH = 36;
private static final char[] HEX_DIGITS =
new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
private static final long[] HEX_VALUES = new long[128];
static {
Arrays.fill(HEX_VALUES, -1);
HEX_VALUES['0'] = 0x0;
HEX_VALUES['1'] = 0x1;
HEX_VALUES['2'] = 0x2;
HEX_VALUES['3'] = 0x3;
HEX_VALUES['4'] = 0x4;
HEX_VALUES['5'] = 0x5;
HEX_VALUES['6'] = 0x6;
HEX_VALUES['7'] = 0x7;
HEX_VALUES['8'] = 0x8;
HEX_VALUES['9'] = 0x9;
HEX_VALUES['a'] = 0xa;
HEX_VALUES['b'] = 0xb;
HEX_VALUES['c'] = 0xc;
HEX_VALUES['d'] = 0xd;
HEX_VALUES['e'] = 0xe;
HEX_VALUES['f'] = 0xf;
HEX_VALUES['A'] = 0xa;
HEX_VALUES['B'] = 0xb;
HEX_VALUES['C'] = 0xc;
HEX_VALUES['D'] = 0xd;
HEX_VALUES['E'] = 0xe;
HEX_VALUES['F'] = 0xf;
}
private FastUUID() {
// A private constructor prevents callers from accidentally instantiating FastUUID objects
}
/**
* Parses a UUID from the given character sequence. The character sequence must represent a UUID as described in
* {@link UUID#toString()}.
*
* @param uuidSequence the character sequence from which to parse a UUID
*
* @return the UUID represented by the given character sequence
*
* @throws IllegalArgumentException if the given character sequence does not conform to the string representation as
* described in {@link UUID#toString()}
*/
public static UUID parseUUID(final CharSequence uuidSequence) {
if (uuidSequence.length() != UUID_STRING_LENGTH ||
uuidSequence.charAt(8) != '-' ||
uuidSequence.charAt(13) != '-' ||
uuidSequence.charAt(18) != '-' ||
uuidSequence.charAt(23) != '-') {
throw new IllegalArgumentException("Illegal UUID string: " + uuidSequence);
}
long mostSignificantBits = getHexValueForChar(uuidSequence.charAt(0)) << 60;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(1)) << 56;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(2)) << 52;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(3)) << 48;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(4)) << 44;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(5)) << 40;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(6)) << 36;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(7)) << 32;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(9)) << 28;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(10)) << 24;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(11)) << 20;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(12)) << 16;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(14)) << 12;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(15)) << 8;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(16)) << 4;
mostSignificantBits |= getHexValueForChar(uuidSequence.charAt(17));
long leastSignificantBits = getHexValueForChar(uuidSequence.charAt(19)) << 60;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(20)) << 56;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(21)) << 52;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(22)) << 48;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(24)) << 44;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(25)) << 40;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(26)) << 36;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(27)) << 32;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(28)) << 28;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(29)) << 24;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(30)) << 20;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(31)) << 16;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(32)) << 12;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(33)) << 8;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(34)) << 4;
leastSignificantBits |= getHexValueForChar(uuidSequence.charAt(35));
return new UUID(mostSignificantBits, leastSignificantBits);
}
/**
* Returns a string representation of the given UUID. The returned string is formatted as described in
* {@link UUID#toString()}.
*
* @param uuid the UUID to represent as a string
*
* @return a string representation of the given UUID
*/
public static String toString(final UUID uuid) {
if (USE_JDK_UUID_TO_STRING) {
// OpenJDK 9 and newer use a fancy native approach to converting UUIDs to strings and we're better off using
// that if it's available.
return uuid.toString();
}
final long mostSignificantBits = uuid.getMostSignificantBits();
final long leastSignificantBits = uuid.getLeastSignificantBits();
final char[] uuidChars = new char[UUID_STRING_LENGTH];
uuidChars[0] = HEX_DIGITS[(int) ((mostSignificantBits & 0xf000000000000000L) >>> 60)];
uuidChars[1] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0f00000000000000L) >>> 56)];
uuidChars[2] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00f0000000000000L) >>> 52)];
uuidChars[3] = HEX_DIGITS[(int) ((mostSignificantBits & 0x000f000000000000L) >>> 48)];
uuidChars[4] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000f00000000000L) >>> 44)];
uuidChars[5] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000f0000000000L) >>> 40)];
uuidChars[6] = HEX_DIGITS[(int) ((mostSignificantBits & 0x000000f000000000L) >>> 36)];
uuidChars[7] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000000f00000000L) >>> 32)];
uuidChars[8] = '-';
uuidChars[9] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000000f0000000L) >>> 28)];
uuidChars[10] = HEX_DIGITS[(int) ((mostSignificantBits & 0x000000000f000000L) >>> 24)];
uuidChars[11] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000000000f00000L) >>> 20)];
uuidChars[12] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000000000f0000L) >>> 16)];
uuidChars[13] = '-';
uuidChars[14] = HEX_DIGITS[(int) ((mostSignificantBits & 0x000000000000f000L) >>> 12)];
uuidChars[15] = HEX_DIGITS[(int) ((mostSignificantBits & 0x0000000000000f00L) >>> 8)];
uuidChars[16] = HEX_DIGITS[(int) ((mostSignificantBits & 0x00000000000000f0L) >>> 4)];
uuidChars[17] = HEX_DIGITS[(int) (mostSignificantBits & 0x000000000000000fL)];
uuidChars[18] = '-';
uuidChars[19] = HEX_DIGITS[(int) ((leastSignificantBits & 0xf000000000000000L) >>> 60)];
uuidChars[20] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0f00000000000000L) >>> 56)];
uuidChars[21] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00f0000000000000L) >>> 52)];
uuidChars[22] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000f000000000000L) >>> 48)];
uuidChars[23] = '-';
uuidChars[24] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000f00000000000L) >>> 44)];
uuidChars[25] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000f0000000000L) >>> 40)];
uuidChars[26] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000000f000000000L) >>> 36)];
uuidChars[27] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000000f00000000L) >>> 32)];
uuidChars[28] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000000f0000000L) >>> 28)];
uuidChars[29] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000000000f000000L) >>> 24)];
uuidChars[30] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000000000f00000L) >>> 20)];
uuidChars[31] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000000000f0000L) >>> 16)];
uuidChars[32] = HEX_DIGITS[(int) ((leastSignificantBits & 0x000000000000f000L) >>> 12)];
uuidChars[33] = HEX_DIGITS[(int) ((leastSignificantBits & 0x0000000000000f00L) >>> 8)];
uuidChars[34] = HEX_DIGITS[(int) ((leastSignificantBits & 0x00000000000000f0L) >>> 4)];
uuidChars[35] = HEX_DIGITS[(int) (leastSignificantBits & 0x000000000000000fL)];
return new String(uuidChars);
}
static long getHexValueForChar(final char c) {
try {
if (HEX_VALUES[c] < 0) {
throw new IllegalArgumentException("Illegal hexadecimal digit: " + c);
}
} catch (final ArrayIndexOutOfBoundsException e) {
throw new IllegalArgumentException("Illegal hexadecimal digit: " + c);
}
return HEX_VALUES[c];
}
}