mirror of
https://github.com/ClickHouse/ClickHouse.git
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421 lines
9.1 KiB
C++
421 lines
9.1 KiB
C++
// MurmurHash2 was written by Austin Appleby, and is placed in the public
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// domain. The author hereby disclaims copyright to this source code.
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// Note - This code makes a few assumptions about how your machine behaves -
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// 1. We can read a 4-byte value from any address without crashing
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// 2. sizeof(int) == 4
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// And it has a few limitations -
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// 1. It will not work incrementally.
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// 2. It will not produce the same results on little-endian and big-endian
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// machines.
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#include "murmurhash2.h"
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// Platform-specific functions and macros
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// Microsoft Visual Studio
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#if defined(_MSC_VER)
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#define BIG_CONSTANT(x) (x)
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// Other compilers
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#else // defined(_MSC_VER)
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#define BIG_CONSTANT(x) (x##LLU)
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#endif // !defined(_MSC_VER)
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uint32_t MurmurHash2(const void * key, int len, uint32_t seed)
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{
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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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const uint32_t m = 0x5bd1e995;
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const int r = 24;
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// Initialize the hash to a 'random' value
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uint32_t h = seed ^ len;
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// Mix 4 bytes at a time into the hash
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const unsigned char * data = reinterpret_cast<const unsigned char *>(key);
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while (len >= 4)
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{
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uint32_t k = *reinterpret_cast<const uint32_t *>(data);
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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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data += 4;
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len -= 4;
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}
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// Handle the last few bytes of the input array
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switch (len)
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{
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case 3: h ^= data[2] << 16;
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case 2: h ^= data[1] << 8;
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case 1: h ^= data[0];
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h *= m;
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};
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// Do a few final mixes of the hash to ensure the last few
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// bytes are well-incorporated.
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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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// MurmurHash2, 64-bit versions, by Austin Appleby
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// The same caveats as 32-bit MurmurHash2 apply here - beware of alignment
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// and endian-ness issues if used across multiple platforms.
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// 64-bit hash for 64-bit platforms
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uint64_t MurmurHash64A(const void * key, int len, uint64_t seed)
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{
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const uint64_t m = BIG_CONSTANT(0xc6a4a7935bd1e995);
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const int r = 47;
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uint64_t h = seed ^ (len * m);
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const uint64_t * data = reinterpret_cast<const uint64_t *>(key);
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const uint64_t * end = data + (len/8);
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while (data != end)
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{
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uint64_t k = *data++;
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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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const unsigned char * data2 = reinterpret_cast<const unsigned char *>(data);
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switch (len & 7)
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{
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case 7: h ^= static_cast<uint64_t>(data2[6]) << 48;
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case 6: h ^= static_cast<uint64_t>(data2[5]) << 40;
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case 5: h ^= static_cast<uint64_t>(data2[4]) << 32;
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case 4: h ^= static_cast<uint64_t>(data2[3]) << 24;
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case 3: h ^= static_cast<uint64_t>(data2[2]) << 16;
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case 2: h ^= static_cast<uint64_t>(data2[1]) << 8;
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case 1: h ^= static_cast<uint64_t>(data2[0]);
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h *= m;
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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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// 64-bit hash for 32-bit platforms
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uint64_t MurmurHash64B(const void * key, int len, uint64_t seed)
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{
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const uint32_t m = 0x5bd1e995;
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const int r = 24;
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uint32_t h1 = static_cast<uint32_t>(seed) ^ len;
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uint32_t h2 = static_cast<uint32_t>(seed >> 32);
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const uint32_t * data = reinterpret_cast<const uint32_t *>(key);
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while (len >= 8)
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{
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uint32_t k1 = *data++;
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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len -= 4;
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uint32_t k2 = *data++;
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k2 *= m; k2 ^= k2 >> r; k2 *= m;
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h2 *= m; h2 ^= k2;
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len -= 4;
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}
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if (len >= 4)
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{
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uint32_t k1 = *data++;
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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len -= 4;
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}
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switch (len)
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{
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case 3: h2 ^= reinterpret_cast<const unsigned char *>(data)[2] << 16;
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case 2: h2 ^= reinterpret_cast<const unsigned char *>(data)[1] << 8;
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case 1: h2 ^= reinterpret_cast<const unsigned char *>(data)[0];
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h2 *= m;
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};
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h1 ^= h2 >> 18; h1 *= m;
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h2 ^= h1 >> 22; h2 *= m;
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h1 ^= h2 >> 17; h1 *= m;
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h2 ^= h1 >> 19; h2 *= m;
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uint64_t h = h1;
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h = (h << 32) | h2;
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return h;
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}
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// MurmurHash2A, by Austin Appleby
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// This is a variant of MurmurHash2 modified to use the Merkle-Damgard
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// construction. Bulk speed should be identical to Murmur2, small-key speed
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// will be 10%-20% slower due to the added overhead at the end of the hash.
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// This variant fixes a minor issue where null keys were more likely to
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// collide with each other than expected, and also makes the function
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// more amenable to incremental implementations.
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#define mmix(h,k) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
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uint32_t MurmurHash2A(const void * key, int len, uint32_t seed)
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{
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const uint32_t m = 0x5bd1e995;
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const int r = 24;
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uint32_t l = len;
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const unsigned char * data = reinterpret_cast<const unsigned char *>(key);
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uint32_t h = seed;
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while (len >= 4)
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{
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uint32_t k = *reinterpret_cast<const uint32_t *>(data);
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mmix(h,k);
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data += 4;
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len -= 4;
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}
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uint32_t t = 0;
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switch (len)
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{
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case 3: t ^= data[2] << 16;
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case 2: t ^= data[1] << 8;
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case 1: t ^= data[0];
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};
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mmix(h,t);
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mmix(h,l);
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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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// MurmurHashNeutral2, by Austin Appleby
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// Same as MurmurHash2, but endian- and alignment-neutral.
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// Half the speed though, alas.
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uint32_t MurmurHashNeutral2(const void * key, int len, uint32_t seed)
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{
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const uint32_t m = 0x5bd1e995;
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const int r = 24;
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uint32_t h = seed ^ len;
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const unsigned char * data = reinterpret_cast<const unsigned char *>(key);
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while (len >= 4)
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{
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uint32_t k;
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k = data[0];
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k |= data[1] << 8;
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k |= data[2] << 16;
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k |= data[3] << 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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data += 4;
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len -= 4;
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}
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switch (len)
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{
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case 3: h ^= data[2] << 16;
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case 2: h ^= data[1] << 8;
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case 1: h ^= data[0];
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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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//-----------------------------------------------------------------------------
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// MurmurHashAligned2, by Austin Appleby
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// Same algorithm as MurmurHash2, but only does aligned reads - should be safer
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// on certain platforms.
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// Performance will be lower than MurmurHash2
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#define MIX(h,k,m) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
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uint32_t MurmurHashAligned2(const void * key, int len, uint32_t seed)
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{
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const uint32_t m = 0x5bd1e995;
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const int r = 24;
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const unsigned char * data = reinterpret_cast<const unsigned char *>(key);
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uint32_t h = seed ^ len;
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int align = reinterpret_cast<uint64_t>(data) & 3;
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if (align && (len >= 4))
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{
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// Pre-load the temp registers
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uint32_t t = 0, d = 0;
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switch (align)
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{
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case 1: t |= data[2] << 16;
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case 2: t |= data[1] << 8;
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case 3: t |= data[0];
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}
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t <<= (8 * align);
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data += 4-align;
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len -= 4-align;
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int sl = 8 * (4-align);
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int sr = 8 * align;
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// Mix
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while (len >= 4)
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{
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d = *(reinterpret_cast<const uint32_t *>(data));
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t = (t >> sr) | (d << sl);
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uint32_t k = t;
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MIX(h,k,m);
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t = d;
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data += 4;
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len -= 4;
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}
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// Handle leftover data in temp registers
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d = 0;
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if (len >= align)
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{
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switch (align)
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{
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case 3: d |= data[2] << 16;
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case 2: d |= data[1] << 8;
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case 1: d |= data[0];
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}
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uint32_t k = (t >> sr) | (d << sl);
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MIX(h,k,m);
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data += align;
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len -= align;
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//----------
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// Handle tail bytes
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switch (len)
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{
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case 3: h ^= data[2] << 16;
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case 2: h ^= data[1] << 8;
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case 1: h ^= data[0];
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h *= m;
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};
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}
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else
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{
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switch (len)
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{
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case 3: d |= data[2] << 16;
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case 2: d |= data[1] << 8;
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case 1: d |= data[0];
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case 0: h ^= (t >> sr) | (d << sl);
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h *= m;
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}
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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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else
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{
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while (len >= 4)
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{
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uint32_t k = *reinterpret_cast<const uint32_t *>(data);
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MIX(h,k,m);
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data += 4;
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len -= 4;
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}
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// Handle tail bytes
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switch (len)
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{
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case 3: h ^= data[2] << 16;
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case 2: h ^= data[1] << 8;
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case 1: h ^= data[0];
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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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} |