murmurhash 下载_MurmurHash.java
package org.videolan.vlc;
/** Murmur hash 2.0.
*
* The murmur hash is a relative fast hash function from
* http://murmurhash.googlepages.com/ for platforms with efficient
* multiplication.
*
* This is a re-implementation of the original C code plus some
* additional features.
*
* Public domain.
*
* @author Viliam Holub
* @version 1.0.2
*
*/
public final class MurmurHash {
/** Generates 32 bit hash from byte array of the given length and
* seed.
*
* @param data byte array to hash
* @param length length of the array to hash
* @param seed initial seed value
* @return 32 bit hash of the given array
*/
public static int hash32(final byte[] data, int length, int seed) {
// 'm' and 'r' are mixing constants generated offline.
// They're not really 'magic', they just happen to work well.
final int m = 0x5bd1e995;
final int r = 24;
// Initialize the hash to a random value
int h = seed ^ length;
int length4 = length / 4;
for (int i = 0; i < length4; i++) {
final int i4 = i * 4;
int k = (data[i4 + 0] & 0xff) + ((data[i4 + 1] & 0xff) << 8)
+ ((data[i4 + 2] & 0xff) << 16) + ((data[i4 + 3] & 0xff) << 24);
k *= m;
k ^= k >>> r;
k *= m;
h *= m;
h ^= k;
}
// Handle the last few bytes of the input array
switch (length % 4) {
case 3:
h ^= (data[(length & ~3) + 2] & 0xff) << 16;
case 2:
h ^= (data[(length & ~3) + 1] & 0xff) << 8;
case 1:
h ^= (data[length & ~3] & 0xff);
h *= m;
}
h ^= h >>> 13;
h *= m;
h ^= h >>> 15;
return h;
}
/** Generates 32 bit hash from byte array with default seed value.
*
* @param data byte array to hash
* @param length length of the array to hash
* @return 32 bit hash of the given array
*/
public static int hash32(final byte[] data, int length) {
return hash32(data, length, 0x9747b28c);
}
/** Generates 32 bit hash from a string.
*
* @param text string to hash
* @return 32 bit hash of the given string
*/
public static int hash32(final String text) {
final byte[] bytes = text.getBytes();
return hash32(bytes, bytes.length);
}
/** Generates 32 bit hash from a substring.
*
* @param text string to hash
* @param from starting index
* @param length length of the substring to hash
* @return 32 bit hash of the given string
*/
public static int hash32(final String text, int from, int length) {
return hash32(text.substring(from, from + length));
}
/** Generates 64 bit hash from byte array of the given length and seed.
*
* @param data byte array to hash
* @param length length of the array to hash
* @param seed initial seed value
* @return 64 bit hash of the given array
*/
public static long hash64(final byte[] data, int length, int seed) {
final long m = 0xc6a4a7935bd1e995L;
final int r = 47;
long h = (seed & 0xffffffffl) ^ (length * m);
int length8 = length / 8;
for (int i = 0; i < length8; i++) {
final int i8 = i * 8;
long k = ((long) data[i8 + 0] & 0xff) + (((long) data[i8 + 1] & 0xff) << 8)
+ (((long) data[i8 + 2] & 0xff) << 16) + (((long) data[i8 + 3] & 0xff) << 24)
+ (((long) data[i8 + 4] & 0xff) << 32) + (((long) data[i8 + 5] & 0xff) << 40)
+ (((long) data[i8 + 6] & 0xff) << 48) + (((long) data[i8 + 7] & 0xff) <<
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