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back port from openjdk, optimization for integer/long toString
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90
src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
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| /* | ||
| * Copyright (c) 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 | ||
| * under the terms of the GNU General Public License version 2 only, as | ||
| * published by the Free Software Foundation. Oracle designates this | ||
| * particular file as subject to the "Classpath" exception as provided | ||
| * by Oracle in the LICENSE file that accompanied this code. | ||
| * | ||
| * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| * version 2 for more details (a copy is included in the LICENSE file that | ||
| * accompanied this code). | ||
| * | ||
| * You should have received a copy of the GNU General Public License version | ||
| * 2 along with this work; if not, write to the Free Software Foundation, | ||
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| * | ||
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| * or visit www.oracle.com if you need additional information or have any | ||
| * questions. | ||
| */ | ||
|
|
||
| package jdk.internal.util; | ||
|
|
||
| import jdk.internal.misc.Unsafe; | ||
| import jdk.internal.vm.annotation.Stable; | ||
|
|
||
| /** | ||
| * Digits class for decimal digits. | ||
| * | ||
| */ | ||
| public final class DecimalDigits { | ||
| private static Unsafe UNSAFE = Unsafe.getUnsafe(); | ||
|
|
||
| /** | ||
| * Each element of the array represents the packaging of two ascii characters based on little endian:<p> | ||
| * <pre> | ||
| * 00 -> '0' | ('0' << 8) -> 0x3030 | ||
| * 01 -> '1' | ('0' << 8) -> 0x3130 | ||
| * 02 -> '2' | ('0' << 8) -> 0x3230 | ||
| * | ||
| * ... | ||
| * | ||
| * 10 -> '0' | ('1' << 8) -> 0x3031 | ||
| * 11 -> '1' | ('1' << 8) -> 0x3131 | ||
| * 12 -> '2' | ('1' << 8) -> 0x3231 | ||
| * | ||
| * ... | ||
| * | ||
| * 97 -> '7' | ('9' << 8) -> 0x3739 | ||
| * 98 -> '8' | ('9' << 8) -> 0x3839 | ||
| * 99 -> '9' | ('9' << 8) -> 0x3939 | ||
| * </pre> | ||
| */ | ||
| @Stable | ||
| private static final short[] DIGITS; | ||
|
|
||
| static { | ||
| short[] digits = new short[10 * 10]; | ||
|
|
||
| for (int i = 0; i < 10; i++) { | ||
| short hi = (short) (i + '0'); | ||
| for (int j = 0; j < 10; j++) { | ||
| short lo = (short) ((j + '0') << 8); | ||
| digits[i * 10 + j] = (short) (hi | lo); | ||
| } | ||
| } | ||
| DIGITS = digits; | ||
| } | ||
|
|
||
| /** | ||
| * For values from 0 to 99 return a short encoding a pair of ASCII-encoded digit characters in little-endian | ||
| * @param i value to convert | ||
| * @return a short encoding a pair of ASCII-encoded digit characters | ||
| */ | ||
| public static short digitPair(int i) { | ||
| return DIGITS[i]; | ||
| } | ||
|
|
||
| public static void putPair(byte[] buf, int charPos, int value) { | ||
| UNSAFE.putShortUnaligned( | ||
| buf, | ||
| Unsafe.ARRAY_BYTE_BASE_OFFSET + charPos, | ||
| DIGITS[value], | ||
| false); | ||
| } | ||
| } |