SWARUtil.java — netty Source File

Source Code

/*
 * Copyright 2024 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at:
 *
 * https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package io.netty.util.internal;


/**
 * Utility class for SWAR (SIMD within a register) operations.
 */
public final class SWARUtil {

    /**
     * Compiles given byte into a long pattern suitable for SWAR operations.
     */
    public static long compilePattern(byte byteToFind) {
        return (byteToFind & 0xFFL) * 0x101010101010101L;
    }

    /**
     * Applies a compiled pattern to given word.
     * Returns a word where each byte that matches the pattern has the highest bit set.
     *
     * @param word    the word to apply the pattern to
     * @param pattern the pattern to apply
     * @return a word where each byte that matches the pattern has the highest bit set
     */
    public static long applyPattern(final long word, final long pattern) {
        long input = word ^ pattern;
        long tmp = (input & 0x7F7F7F7F7F7F7F7FL) + 0x7F7F7F7F7F7F7F7FL;
        return ~(tmp | input | 0x7F7F7F7F7F7F7F7FL);
    }

    /**
     * Returns the index of the first occurrence of byte that specificied in the pattern.
     * If no pattern is found, returns 8.
     *
     * @param word     the return value of {@link #applyPattern(long, long)}
     * @param isBigEndian if true, if given word is big endian
     *                 if false, if given word is little endian
     * @return the index of the first occurrence of the specified pattern in the specified word.
     * If no pattern is found, returns 8.
     */
    public static int getIndex(final long word, final boolean isBigEndian) {
        final int zeros = isBigEndian? Long.numberOfLeadingZeros(word) : Long.numberOfTrailingZeros(word);
        return zeros >>> 3;
    }

    /**
     * Returns a word where each ASCII uppercase byte has the highest bit set.
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