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murmurhash 下载_MurmurHash.java

东郭瀚玥
2023-12-01

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) <<

...

...

(完整源码请下载查看)

...

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