Source code
Description: source: package: org.apache.commons.codec.digest, class: XXHash32

    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      https://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.codec.digest;
    019
    020import static java.lang.Integer.rotateLeft;
    021
    022import java.util.zip.Checksum;
    023
    024/**
    025 * Implements the xxHash32 hash algorithm.
    026 *
    027 * <p>
    028 * Copied from Commons Compress 1.14 <a href=
    029 * "https://gitbox.apache.org/repos/asf?p=commons-compress.git;a=blob;f=src/main/java/org/apache/commons/compress/compressors/lz4/XXHash32.java;h=a406ffc197449be594d46f0d2712b2d4786a1e68;hb=HEAD">https://gitbox.apache.org/repos/asf?p=commons-compress.git;a=blob;f=src/main/java/org/apache/commons/compress/compressors/lz4/XXHash32.java;h=a406ffc197449be594d46f0d2712b2d4786a1e68;hb=HEAD</a>
    030 * </p>
    031 * <p>
    032 * NotThreadSafe
    033 * </p>
    034 *
    035 * @see <a href="https://cyan4973.github.io/xxHash/">xxHash</a>
    036 * @since 1.11
    037 */
    038public class XXHash32 implements Checksum {
    039
    040    private static final int BUF_SIZE = 16;
    041    private static final int ROTATE_BITS = 13;
    042
    043    private static final int PRIME1 = (int) 2654435761L;
    044    private static final int PRIME2 = (int) 2246822519L;
    045    private static final int PRIME3 = (int) 3266489917L;
    046    private static final int PRIME4 =  668265263;
    047    private static final int PRIME5 =  374761393;
    048
    049    /**
    050     * Gets the little-endian int from 4 bytes starting at the specified index.
    051     *
    052     * @param buffer The data.
    053     * @param idx The index.
    054     * @return The little-endian int.
    055     */
    056    private static int getInt(final byte[] buffer, final int idx) {
    057        return buffer[idx    ] & 0xff |
    058               (buffer[idx + 1] & 0xff) <<  8 |
    059               (buffer[idx + 2] & 0xff) << 16 |
    060               (buffer[idx + 3] & 0xff) << 24;
    061    }
    062    private final byte[] oneByte = new byte[1];
    063    private final int[] state = new int[4];
    064    // Note: The code used to use ByteBuffer but the manual method is 50% faster
    065    // See: https://gitbox.apache.org/repos/asf/commons-compress/diff/2f56fb5c
    066    private final byte[] buffer = new byte[BUF_SIZE];
    067
    068    private final int seed;
    069    private int totalLen;
    070
    071    private int pos;
    072
    073    /** Sets to true when the state array has been updated since the last reset. */
    074    private boolean stateUpdated;
    075
    076    /**
    077     * Creates an XXHash32 instance with a seed of 0.
    078     */
    079    public XXHash32() {
    080        this(0);
    081    }
    082
    083    /**
    084     * Creates an XXHash32 instance.
    085     *
    086     * @param seed The seed to use.
    087     */
    088    public XXHash32(final int seed) {
    089        this.seed = seed;
    090        initializeState();
    091    }
    092
    093    @Override
    094    public long getValue() {
    095        int hash;
    096        if (stateUpdated) {
    097            // Hash with the state
    098            hash =
    099                rotateLeft(state[0],  1) +
    100                rotateLeft(state[1],  7) +
    101                rotateLeft(state[2], 12) +
    102                rotateLeft(state[3], 18);
    103        } else {
    104            // Hash using the original seed from position 2
    105            hash = state[2] + PRIME5;
    106        }
    107        hash += totalLen;
    108        int idx = 0;
    109        final int limit = pos - 4;
    110        for (; idx <= limit; idx += 4) {
    111            hash = rotateLeft(hash + getInt(buffer, idx) * PRIME3, 17) * PRIME4;
    112        }
    113        while (idx < pos) {
    114            hash = rotateLeft(hash + (buffer[idx++] & 0xff) * PRIME5, 11) * PRIME1;
    115        }
    116        hash ^= hash >>> 15;
    117        hash *= PRIME2;
    118        hash ^= hash >>> 13;
    119        hash *= PRIME3;
    120        hash ^= hash >>> 16;
    121        return hash & 0xffffffffL;
    122    }
    123
    124    private void initializeState() {
    125        state[0] = seed + PRIME1 + PRIME2;
    126        state[1] = seed + PRIME2;
    127        state[2] = seed;
    128        state[3] = seed - PRIME1;
    129    }
    130
    131    private void process(final byte[] b, final int offset) {
    132        // local shadows for performance
    133        int s0 = state[0];
    134        int s1 = state[1];
    135        int s2 = state[2];
    136        int s3 = state[3];
    137        s0 = rotateLeft(s0 + getInt(b, offset) * PRIME2, ROTATE_BITS) * PRIME1;
    138        s1 = rotateLeft(s1 + getInt(b, offset + 4) * PRIME2, ROTATE_BITS) * PRIME1;
    139        s2 = rotateLeft(s2 + getInt(b, offset + 8) * PRIME2, ROTATE_BITS) * PRIME1;
    140        s3 = rotateLeft(s3 + getInt(b, offset + 12) * PRIME2, ROTATE_BITS) * PRIME1;
    141        state[0] = s0;
    142        state[1] = s1;
    143        state[2] = s2;
    144        state[3] = s3;
    145        stateUpdated = true;
    146    }
    147
    148    @Override
    149    public void reset() {
    150        initializeState();
    151        totalLen = 0;
    152        pos = 0;
    153        stateUpdated = false;
    154    }
    155
    156    @Override
    157    public void update(final byte[] b, int off, final int len) {
    158        if (len <= 0) {
    159            return;
    160        }
    161        totalLen += len;
    162        final int end = off + len;
    163        // Check if the unprocessed bytes and new bytes can fill a block of 16.
    164        // Make this overflow safe in the event that len is Integer.MAX_VALUE.
    165        // Equivalent to: (pos + len < BUF_SIZE)
    166        if (pos + len - BUF_SIZE < 0) {
    167            System.arraycopy(b, off, buffer, pos, len);
    168            pos += len;
    169            return;
    170        }
    171        // Process left-over bytes with new bytes
    172        if (pos > 0) {
    173            final int size = BUF_SIZE - pos;
    174            System.arraycopy(b, off, buffer, pos, size);
    175            process(buffer, 0);
    176            off += size;
    177        }
    178        final int limit = end - BUF_SIZE;
    179        while (off <= limit) {
    180            process(b, off);
    181            off += BUF_SIZE;
    182        }
    183        // Handle left-over bytes
    184        if (off < end) {
    185            pos = end - off;
    186            System.arraycopy(b, off, buffer, 0, pos);
    187        } else {
    188            pos = 0;
    189        }
    190    }
    191
    192    @Override
    193    public void update(final int b) {
    194        oneByte[0] = (byte) (b & 0xff);
    195        update(oneByte, 0, 1);
    196    }
    197}