package org.videolan.vlc;
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/** Murmur hash 2.0.
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*
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* The murmur hash is a relative fast hash function from
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* http://murmurhash.googlepages.com/ for platforms with efficient
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* multiplication.
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*
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* This is a re-implementation of the original C code plus some
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* additional features.
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*
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* Public domain.
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*
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* @author Viliam Holub
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* @version 1.0.2
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*
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*/
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public final class MurmurHash {
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/** Generates 32 bit hash from byte array of the given length and
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* seed.
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*
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* @param data byte array to hash
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* @param length length of the array to hash
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* @param seed initial seed value
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* @return 32 bit hash of the given array
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*/
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public static int hash32(final byte[] data, int length, int seed) {
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// 'm' and 'r' are mixing constants generated offline.
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// They're not really 'magic', they just happen to work well.
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final int m = 0x5bd1e995;
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final int r = 24;
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// Initialize the hash to a random value
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int h = seed ^ length;
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int length4 = length / 4;
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for (int i = 0; i < length4; i++) {
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final int i4 = i * 4;
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int k = (data[i4 + 0] & 0xff) + ((data[i4 + 1] & 0xff) << 8)
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+ ((data[i4 + 2] & 0xff) << 16) + ((data[i4 + 3] & 0xff) << 24);
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k *= m;
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k ^= k >>> r;
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k *= m;
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h *= m;
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h ^= k;
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}
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// Handle the last few bytes of the input array
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switch (length % 4) {
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case 3:
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h ^= (data[(length & ~3) + 2] & 0xff) << 16;
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case 2:
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h ^= (data[(length & ~3) + 1] & 0xff) << 8;
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case 1:
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h ^= (data[length & ~3] & 0xff);
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h *= m;
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}
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h ^= h >>> 13;
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h *= m;
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h ^= h >>> 15;
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return h;
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}
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/** Generates 32 bit hash from byte array with default seed value.
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*
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* @param data byte array to hash
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* @param length length of the array to hash
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* @return 32 bit hash of the given array
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*/
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public static int hash32(final byte[] data, int length) {
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return hash32(data, length, 0x9747b28c);
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}
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/** Generates 32 bit hash from a string.
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*
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* @param text string to hash
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* @return 32 bit hash of the given string
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*/
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public static int hash32(final String text) {
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final byte[] bytes = text.getBytes();
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return hash32(bytes, bytes.length);
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}
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/** Generates 32 bit hash from a substring.
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*
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* @param text string to hash
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* @param from starting index
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* @param length length of the substring to hash
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* @return 32 bit hash of the given string
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*/
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public static int hash32(final String text, int from, int length) {
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return hash32(text.substring(from, from + length));
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}
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/** Generates 64 bit hash from byte array of the given length and seed.
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*
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* @param data byte array to hash
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* @param length length of the array to hash
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* @param seed initial seed value
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* @return 64 bit hash of the given array
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*/
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public static long hash64(final byte[] data, int length, int seed) {
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final long m = 0xc6a4a7935bd1e995L;
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final int r = 47;
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long h = (seed & 0xffffffffl) ^ (length * m);
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int length8 = length / 8;
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for (int i = 0; i < length8; i++) {
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final int i8 = i * 8;
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long k = ((long) data[i8 + 0] & 0xff) + (((long) data[i8 + 1] & 0xff) << 8)
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+ (((long) data[i8 + 2] & 0xff) << 16) + (((long) data[i8 + 3] & 0xff) << 24)
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+ (((long) data[i8 + 4] & 0xff) << 32) + (((long) data[i8 + 5] & 0xff) << 40)
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+ (((long) data[i8 + 6] & 0xff) << 48) + (((long) data[i8 + 7] & 0xff) << 56);
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k *= m;
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k ^= k >>> r;
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k *= m;
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h ^= k;
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h *= m;
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}
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switch (length % 8) {
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case 7:
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h ^= (long) (data[(length & ~7) + 6] & 0xff) << 48;
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case 6:
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h ^= (long) (data[(length & ~7) + 5] & 0xff) << 40;
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case 5:
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h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
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case 4:
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h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
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case 3:
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h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
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case 2:
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h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
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case 1:
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h ^= (long) (data[length & ~7] & 0xff);
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h *= m;
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}
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;
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h ^= h >>> r;
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h *= m;
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h ^= h >>> r;
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return h;
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}
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/** Generates 64 bit hash from byte array with default seed value.
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*
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* @param data byte array to hash
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* @param length length of the array to hash
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* @return 64 bit hash of the given string
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*/
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public static long hash64(final byte[] data, int length) {
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return hash64(data, length, 0xe17a1465);
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}
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/** Generates 64 bit hash from a string.
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*
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* @param text string to hash
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* @return 64 bit hash of the given string
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*/
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public static long hash64(final String text) {
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final byte[] bytes = text.getBytes();
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return hash64(bytes, bytes.length);
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}
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/** Generates 64 bit hash from a substring.
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*
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* @param text string to hash
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* @param from starting index
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* @param length length of the substring to hash
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* @return 64 bit hash of the given array
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*/
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public static long hash64(final String text, int from, int length) {
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return hash64(text.substring(from, from + length));
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}
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}
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