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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
/*
Murmurhash from http://sites.google.com/site/murmurhash/
All code is released to the public domain. For business purposes, Murmurhash
is under the MIT license.
*/
#include "murmurhash.h"
#include "port/lang.h"
#if defined(__x86_64__)
// -------------------------------------------------------------------
//
// The same caveats as 32-bit MurmurHash2 apply here - beware of alignment
// and endian-ness issues if used across multiple platforms.
//
// 64-bit hash for 64-bit platforms
#ifdef ROCKSDB_UBSAN_RUN
#if defined(__clang__)
__attribute__((__no_sanitize__("alignment")))
#elif defined(__GNUC__)
__attribute__((__no_sanitize_undefined__))
#endif
#endif
// clang-format off
uint64_t MurmurHash64A ( const void * key, int len, unsigned int seed )
{
const uint64_t m = 0xc6a4a7935bd1e995;
const int r = 47;
uint64_t h = seed ^ (len * m);
const uint64_t * data = (const uint64_t *)key;
const uint64_t * end = data + (len/8);
while(data != end)
{
uint64_t k = *data++;
k *= m;
k ^= k >> r;
k *= m;
h ^= k;
h *= m;
}
const unsigned char * data2 = (const unsigned char*)data;
switch(len & 7)
{
case 7: h ^= ((uint64_t)data2[6]) << 48; FALLTHROUGH_INTENDED;
case 6: h ^= ((uint64_t)data2[5]) << 40; FALLTHROUGH_INTENDED;
case 5: h ^= ((uint64_t)data2[4]) << 32; FALLTHROUGH_INTENDED;
case 4: h ^= ((uint64_t)data2[3]) << 24; FALLTHROUGH_INTENDED;
case 3: h ^= ((uint64_t)data2[2]) << 16; FALLTHROUGH_INTENDED;
case 2: h ^= ((uint64_t)data2[1]) << 8; FALLTHROUGH_INTENDED;
case 1: h ^= ((uint64_t)data2[0]);
h *= m;
};
h ^= h >> r;
h *= m;
h ^= h >> r;
return h;
}
// clang-format on
#elif defined(__i386__)
// -------------------------------------------------------------------
//
// Note - This code makes a few assumptions about how your machine behaves -
//
// 1. We can read a 4-byte value from any address without crashing
// 2. sizeof(int) == 4
//
// And it has a few limitations -
//
// 1. It will not work incrementally.
// 2. It will not produce the same results on little-endian and big-endian
// machines.
// clang-format off
unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed )
{
// 'm' and 'r' are mixing constants generated offline.
// They're not really 'magic', they just happen to work well.
const unsigned int m = 0x5bd1e995;
const int r = 24;
// Initialize the hash to a 'random' value
unsigned int h = seed ^ len;
// Mix 4 bytes at a time into the hash
const unsigned char * data = (const unsigned char *)key;
while(len >= 4)
{
unsigned int k = *(unsigned int *)data;
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
data += 4;
len -= 4;
}
// Handle the last few bytes of the input array
switch(len)
{
case 3: h ^= data[2] << 16; FALLTHROUGH_INTENDED;
case 2: h ^= data[1] << 8; FALLTHROUGH_INTENDED;
case 1: h ^= data[0];
h *= m;
};
// Do a few final mixes of the hash to ensure the last few
// bytes are well-incorporated.
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
// clang-format on
#else
// -------------------------------------------------------------------
//
// Same as MurmurHash2, but endian- and alignment-neutral.
// Half the speed though, alas.
// clang-format off
unsigned int MurmurHashNeutral2 ( const void * key, int len, unsigned int seed )
{
const unsigned int m = 0x5bd1e995;
const int r = 24;
unsigned int h = seed ^ len;
const unsigned char * data = (const unsigned char *)key;
while(len >= 4)
{
unsigned int k;
k = data[0];
k |= data[1] << 8;
k |= data[2] << 16;
k |= data[3] << 24;
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
data += 4;
len -= 4;
}
switch(len)
{
case 3: h ^= data[2] << 16; FALLTHROUGH_INTENDED;
case 2: h ^= data[1] << 8; FALLTHROUGH_INTENDED;
case 1: h ^= data[0];
h *= m;
};
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
// clang-format on
#endif
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