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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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
*
* http://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 org.apache.commons.codec.digest;
import static java.lang.Integer.rotateLeft;
import java.util.zip.Checksum;
/**
* Implementation of the xxhash32 hash algorithm.
*
* Copied from Commons Compress 1.14
* https://git-wip-us.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
* NotThreadSafe
* @see xxHash
* @since 1.11
*/
public class XXHash32 implements Checksum {
private static final int BUF_SIZE = 16;
private static final int ROTATE_BITS = 13;
private static final int PRIME1 = (int) 2654435761l;
private static final int PRIME2 = (int) 2246822519l;
private static final int PRIME3 = (int) 3266489917l;
private static final int PRIME4 = 668265263;
private static final int PRIME5 = 374761393;
private final byte[] oneByte = new byte[1];
private final int[] state = new int[4];
// Note: the code used to use ByteBuffer but the manual method is 50% faster
// See: http://git-wip-us.apache.org/repos/asf/commons-compress/diff/2f56fb5c
private final byte[] buffer = new byte[BUF_SIZE];
private final int seed;
private int totalLen;
private int pos;
/**
* Creates an XXHash32 instance with a seed of 0.
*/
public XXHash32() {
this(0);
}
/**
* Creates an XXHash32 instance.
* @param seed the seed to use
*/
public XXHash32(final int seed) {
this.seed = seed;
initializeState();
}
@Override
public void reset() {
initializeState();
totalLen = 0;
pos = 0;
}
@Override
public void update(final int b) {
oneByte[0] = (byte) (b & 0xff);
update(oneByte, 0, 1);
}
@Override
public void update(final byte[] b, int off, final int len) {
if (len <= 0) {
return;
}
totalLen += len;
final int end = off + len;
if (pos + len < BUF_SIZE) {
System.arraycopy(b, off, buffer, pos, len);
pos += len;
return;
}
if (pos > 0) {
final int size = BUF_SIZE - pos;
System.arraycopy(b, off, buffer, pos, size);
process(buffer, 0);
off += size;
}
final int limit = end - BUF_SIZE;
while (off <= limit) {
process(b, off);
off += BUF_SIZE;
}
if (off < end) {
pos = end - off;
System.arraycopy(b, off, buffer, 0, pos);
}
}
@Override
public long getValue() {
int hash;
if (totalLen > BUF_SIZE) {
hash =
rotateLeft(state[0], 1) +
rotateLeft(state[1], 7) +
rotateLeft(state[2], 12) +
rotateLeft(state[3], 18);
} else {
hash = state[2] + PRIME5;
}
hash += totalLen;
int idx = 0;
final int limit = pos - 4;
for (; idx <= limit; idx += 4) {
hash = rotateLeft(hash + getInt(buffer, idx) * PRIME3, 17) * PRIME4;
}
while (idx < pos) {
hash = rotateLeft(hash + (buffer[idx++] & 0xff) * PRIME5, 11) * PRIME1;
}
hash ^= hash >>> 15;
hash *= PRIME2;
hash ^= hash >>> 13;
hash *= PRIME3;
hash ^= hash >>> 16;
return hash & 0xffffffffl;
}
private static int getInt(final byte[] buffer, final int idx) {
return (int) (fromLittleEndian(buffer, idx, 4) & 0xffffffffl);
}
private void initializeState() {
state[0] = seed + PRIME1 + PRIME2;
state[1] = seed + PRIME2;
state[2] = seed;
state[3] = seed - PRIME1;
}
private void process(final byte[] b, final int offset) {
// local shadows for performance
int s0 = state[0];
int s1 = state[1];
int s2 = state[2];
int s3 = state[3];
s0 = rotateLeft(s0 + getInt(b, offset) * PRIME2, ROTATE_BITS) * PRIME1;
s1 = rotateLeft(s1 + getInt(b, offset + 4) * PRIME2, ROTATE_BITS) * PRIME1;
s2 = rotateLeft(s2 + getInt(b, offset + 8) * PRIME2, ROTATE_BITS) * PRIME1;
s3 = rotateLeft(s3 + getInt(b, offset + 12) * PRIME2, ROTATE_BITS) * PRIME1;
state[0] = s0;
state[1] = s1;
state[2] = s2;
state[3] = s3;
pos = 0;
}
/**
* Reads the given byte array as a little endian long.
* @param bytes the byte array to convert
* @param off the offset into the array that starts the value
* @param length the number of bytes representing the value
* @return the number read
* @throws IllegalArgumentException if len is bigger than eight
*/
private static long fromLittleEndian(final byte[] bytes, final int off, final int length) {
if (length > 8) {
throw new IllegalArgumentException("can't read more than eight bytes into a long value");
}
long l = 0;
for (int i = 0; i < length; i++) {
l |= (bytes[off + i] & 0xffl) << (8 * i);
}
return l;
}
}