io.split.client.utils.MurmurHash3 Maven / Gradle / Ivy
package io.split.client.utils;
/**
* The MurmurHash3 algorithm was created by Austin Appleby and placed in the public domain.
* This java port was authored by Yonik Seeley and also placed into the public domain.
* The author hereby disclaims copyright to this source code.
*
* This produces exactly the same hash values as the final C++
* version of MurmurHash3 and is thus suitable for producing the same hash values across
* platforms.
*
* The 32 bit x86 version of this hash should be the fastest variant for relatively short keys like ids.
* murmurhash3_x64_128 is a good choice for longer strings or if you need more than 32 bits of hash.
*
* Note - The x86 and x64 versions do _not_ produce the same results, as the
* algorithms are optimized for their respective platforms.
*
* See http://github.com/yonik/java_util for future updates to this file.
*/
public final class MurmurHash3 {
/**
* 128 bits of state
*/
public static final class LongPair {
public long val1;
public long val2;
}
public static final int fmix32(int h) {
h ^= h >>> 16;
h *= 0x85ebca6b;
h ^= h >>> 13;
h *= 0xc2b2ae35;
h ^= h >>> 16;
return h;
}
public static final long fmix64(long k) {
k ^= k >>> 33;
k *= 0xff51afd7ed558ccdL;
k ^= k >>> 33;
k *= 0xc4ceb9fe1a85ec53L;
k ^= k >>> 33;
return k;
}
/**
* Gets a long from a byte buffer in little endian byte order.
*/
public static final long getLongLittleEndian(byte[] buf, int offset) {
return ((long) buf[offset + 7] << 56) // no mask needed
| ((buf[offset + 6] & 0xffL) << 48)
| ((buf[offset + 5] & 0xffL) << 40)
| ((buf[offset + 4] & 0xffL) << 32)
| ((buf[offset + 3] & 0xffL) << 24)
| ((buf[offset + 2] & 0xffL) << 16)
| ((buf[offset + 1] & 0xffL) << 8)
| ((buf[offset] & 0xffL)); // no shift needed
}
/**
* Returns the MurmurHash3_x86_32 hash of the UTF-8 bytes of the String without actually encoding
* the string to a temporary buffer. This is more than 2x faster than hashing the result
* of String.getBytes().
*/
public static long murmurhash3_x86_32(CharSequence data, int offset, int len, int seed) {
final int c1 = 0xcc9e2d51;
final int c2 = 0x1b873593;
int h1 = seed;
int pos = offset;
int end = offset + len;
int k1 = 0;
int k2 = 0;
int shift = 0;
int bits = 0;
int nBytes = 0; // length in UTF8 bytes
while (pos < end) {
int code = data.charAt(pos++);
if (code < 0x80) {
k2 = code;
bits = 8;
} else if (code < 0x800) {
k2 = (0xC0 | (code >> 6))
| ((0x80 | (code & 0x3F)) << 8);
bits = 16;
} else if (code < 0xD800 || code > 0xDFFF || pos >= end) {
// we check for pos>=end to encode an unpaired surrogate as 3 bytes.
k2 = (0xE0 | (code >> 12))
| ((0x80 | ((code >> 6) & 0x3F)) << 8)
| ((0x80 | (code & 0x3F)) << 16);
bits = 24;
} else {
// surrogate pair
// int utf32 = pos < end ? (int) data.charAt(pos++) : 0;
int utf32 = (int) data.charAt(pos++);
utf32 = ((code - 0xD7C0) << 10) + (utf32 & 0x3FF);
k2 = (0xff & (0xF0 | (utf32 >> 18)))
| ((0x80 | ((utf32 >> 12) & 0x3F))) << 8
| ((0x80 | ((utf32 >> 6) & 0x3F))) << 16
| (0x80 | (utf32 & 0x3F)) << 24;
bits = 32;
}
k1 |= k2 << shift;
// int used_bits = 32 - shift; // how many bits of k2 were used in k1.
// int unused_bits = bits - used_bits; // (bits-(32-shift)) == bits+shift-32 == bits-newshift
shift += bits;
if (shift >= 32) {
// mix after we have a complete word
k1 *= c1;
k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15);
k1 *= c2;
h1 ^= k1;
h1 = (h1 << 13) | (h1 >>> 19); // ROTL32(h1,13);
h1 = h1 * 5 + 0xe6546b64;
shift -= 32;
// unfortunately, java won't let you shift 32 bits off, so we need to check for 0
if (shift != 0) {
k1 = k2 >>> (bits - shift); // bits used == bits - newshift
} else {
k1 = 0;
}
nBytes += 4;
}
} // inner
// handle tail
if (shift > 0) {
nBytes += shift >> 3;
k1 *= c1;
k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15);
k1 *= c2;
h1 ^= k1;
}
// finalization
h1 ^= nBytes;
// fmix(h1);
h1 ^= h1 >>> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >>> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >>> 16;
return h1 & 0xFFFFFFFFL;
}
// The following set of methods and constants are borrowed from:
// `This method is borrowed from `org.apache.commons.codec.digest.MurmurHash3`
// Constants for 128-bit variant
private static final long C1 = 0x87c37b91114253d5L;
private static final long C2 = 0x4cf5ad432745937fL;
private static final int R1 = 31;
private static final int R2 = 27;
private static final int R3 = 33;
private static final int M = 5;
private static final int N1 = 0x52dce729;
private static final int N2 = 0x38495ab5;
/**
* Gets the little-endian long from 8 bytes starting at the specified index.
*
* @param data The data
* @param index The index
* @return The little-endian long
*/
private static long getLittleEndianLong(final byte[] data, final int index) {
return (((long) data[index ] & 0xff) ) |
(((long) data[index + 1] & 0xff) << 8) |
(((long) data[index + 2] & 0xff) << 16) |
(((long) data[index + 3] & 0xff) << 24) |
(((long) data[index + 4] & 0xff) << 32) |
(((long) data[index + 5] & 0xff) << 40) |
(((long) data[index + 6] & 0xff) << 48) |
(((long) data[index + 7] & 0xff) << 56);
}
public static long[] hash128x64(final byte[] data) {
return hash128x64(data, 0, data.length, 0);
}
/**
* Generates 128-bit hash from the byte array with the given offset, length and seed.
*
*
This is an implementation of the 128-bit hash function {@code MurmurHash3_x64_128}
* from from Austin Applyby's original MurmurHash3 {@code c++} code in SMHasher.
*
* @param data The input byte array
* @param offset The first element of array
* @param length The length of array
* @param seed The initial seed value
* @return The 128-bit hash (2 longs)
*/
public static long[] hash128x64(final byte[] data, final int offset, final int length, final long seed) {
long h1 = seed;
long h2 = seed;
final int nblocks = length >> 4;
// body
for (int i = 0; i < nblocks; i++) {
final int index = offset + (i << 4);
long k1 = getLittleEndianLong(data, index);
long k2 = getLittleEndianLong(data, index + 8);
// mix functions for k1
k1 *= C1;
k1 = Long.rotateLeft(k1, R1);
k1 *= C2;
h1 ^= k1;
h1 = Long.rotateLeft(h1, R2);
h1 += h2;
h1 = h1 * M + N1;
// mix functions for k2
k2 *= C2;
k2 = Long.rotateLeft(k2, R3);
k2 *= C1;
h2 ^= k2;
h2 = Long.rotateLeft(h2, R1);
h2 += h1;
h2 = h2 * M + N2;
}
// tail
long k1 = 0;
long k2 = 0;
final int index = offset + (nblocks << 4);
switch (offset + length - index) {
case 15:
k2 ^= ((long) data[index + 14] & 0xff) << 48;
case 14:
k2 ^= ((long) data[index + 13] & 0xff) << 40;
case 13:
k2 ^= ((long) data[index + 12] & 0xff) << 32;
case 12:
k2 ^= ((long) data[index + 11] & 0xff) << 24;
case 11:
k2 ^= ((long) data[index + 10] & 0xff) << 16;
case 10:
k2 ^= ((long) data[index + 9] & 0xff) << 8;
case 9:
k2 ^= data[index + 8] & 0xff;
k2 *= C2;
k2 = Long.rotateLeft(k2, R3);
k2 *= C1;
h2 ^= k2;
case 8:
k1 ^= ((long) data[index + 7] & 0xff) << 56;
case 7:
k1 ^= ((long) data[index + 6] & 0xff) << 48;
case 6:
k1 ^= ((long) data[index + 5] & 0xff) << 40;
case 5:
k1 ^= ((long) data[index + 4] & 0xff) << 32;
case 4:
k1 ^= ((long) data[index + 3] & 0xff) << 24;
case 3:
k1 ^= ((long) data[index + 2] & 0xff) << 16;
case 2:
k1 ^= ((long) data[index + 1] & 0xff) << 8;
case 1:
k1 ^= data[index] & 0xff;
k1 *= C1;
k1 = Long.rotateLeft(k1, R1);
k1 *= C2;
h1 ^= k1;
}
// finalization
h1 ^= length;
h2 ^= length;
h1 += h2;
h2 += h1;
h1 = fmix64(h1);
h2 = fmix64(h2);
h1 += h2;
h2 += h1;
return new long[] { h1, h2 };
}
}