uap-cpp/MurmurHash2.cpp at master · aitech-lab/uap-cpp · GitHub

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//-----------------------------------------------------------------------------

// MurmurHash2 was written by Austin Appleby, and is placed in the public

// domain. The author hereby disclaims copyright to this source code.

// 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.

#include "MurmurHash2.h"

//-----------------------------------------------------------------------------

// Platform-specific functions and macros

// Microsoft Visual Studio

#if defined(_MSC_VER)

#define BIG_CONSTANT(x) (x)

// Other compilers

#else // defined(_MSC_VER)

#define BIG_CONSTANT(x) (x##LLU)

#endif // !defined(_MSC_VER)

//-----------------------------------------------------------------------------

// objsize: 0-0x166: 358

uint32_t MurmurHash2 ( const void * key, int len, uint32_t seed )

{

// 'm' and 'r' are mixing constants generated offline.

// They're not really 'magic', they just happen to work well.

const uint32_t m = 0x5bd1e995;

const int r = 24;

// Initialize the hash to a 'random' value

uint32_t h = seed ^ len;

// Mix 4 bytes at a time into the hash

const unsigned char * data = (const unsigned char *)key;

while(len >= 4)

{

uint32_t k = *(uint32_t*)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;

case 2: h ^= data[1] << 8;

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;

}

//-----------------------------------------------------------------------------

// MurmurHash2, 64-bit versions, by Austin Appleby

// 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

// objsize: 0x170-0x321: 433

uint64_t MurmurHash64A ( const void * key, int len, uint64_t seed )

{

const uint64_t m = BIG_CONSTANT(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;

case 6: h ^= uint64_t(data2[5]) << 40;

case 5: h ^= uint64_t(data2[4]) << 32;

case 4: h ^= uint64_t(data2[3]) << 24;

case 3: h ^= uint64_t(data2[2]) << 16;

case 2: h ^= uint64_t(data2[1]) << 8;

case 1: h ^= uint64_t(data2[0]);

h *= m;

};

h ^= h >> r;

h *= m;

h ^= h >> r;

return h;

}

// 64-bit hash for 32-bit platforms

// objsize: 0x340-0x4fc: 444

uint64_t MurmurHash64B ( const void * key, int len, uint64_t seed )

{

const uint32_t m = 0x5bd1e995;

const int r = 24;

uint32_t h1 = uint32_t(seed) ^ len;

uint32_t h2 = uint32_t(seed >> 32);

const uint32_t * data = (const uint32_t *)key;

while(len >= 8)

{

uint32_t k1 = *data++;

k1 *= m; k1 ^= k1 >> r; k1 *= m;

h1 *= m; h1 ^= k1;

len -= 4;

uint32_t k2 = *data++;

k2 *= m; k2 ^= k2 >> r; k2 *= m;

h2 *= m; h2 ^= k2;

len -= 4;

}

if(len >= 4)

{

uint32_t k1 = *data++;

k1 *= m; k1 ^= k1 >> r; k1 *= m;

h1 *= m; h1 ^= k1;

len -= 4;

}

switch(len)

{

case 3: h2 ^= ((unsigned char*)data)[2] << 16;

case 2: h2 ^= ((unsigned char*)data)[1] << 8;

case 1: h2 ^= ((unsigned char*)data)[0];

h2 *= m;

};

h1 ^= h2 >> 18; h1 *= m;

h2 ^= h1 >> 22; h2 *= m;

h1 ^= h2 >> 17; h1 *= m;

h2 ^= h1 >> 19; h2 *= m;

uint64_t h = h1;

h = (h << 32) | h2;

return h;

}

//-----------------------------------------------------------------------------

// MurmurHash2A, by Austin Appleby

// This is a variant of MurmurHash2 modified to use the Merkle-Damgard

// construction. Bulk speed should be identical to Murmur2, small-key speed

// will be 10%-20% slower due to the added overhead at the end of the hash.

// This variant fixes a minor issue where null keys were more likely to

// collide with each other than expected, and also makes the function

// more amenable to incremental implementations.

#define mmix(h,k) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }

// objsize: 0x500-0x697: 407

uint32_t MurmurHash2A ( const void * key, int len, uint32_t seed )

{

const uint32_t m = 0x5bd1e995;

const int r = 24;

uint32_t l = len;

const unsigned char * data = (const unsigned char *)key;

uint32_t h = seed;

while(len >= 4)

{

uint32_t k = *(uint32_t*)data;

mmix(h,k);

data += 4;

len -= 4;

}

uint32_t t = 0;

switch(len)

{

case 3: t ^= data[2] << 16;

case 2: t ^= data[1] << 8;

case 1: t ^= data[0];

};

mmix(h,t);

mmix(h,l);

h ^= h >> 13;

h *= m;

h ^= h >> 15;

return h;

}

//-----------------------------------------------------------------------------

// CMurmurHash2A, by Austin Appleby

// This is a sample implementation of MurmurHash2A designed to work

// incrementally.

// Usage -

// CMurmurHash2A hasher

// hasher.Begin(seed);

// hasher.Add(data1,size1);

// hasher.Add(data2,size2);

// ...

// hasher.Add(dataN,sizeN);

// uint32_t hash = hasher.End()

class CMurmurHash2A

{

public:

void Begin ( uint32_t seed = 0 )

{

m_hash = seed;

m_tail = 0;

m_count = 0;

m_size = 0;

}

void Add ( const unsigned char * data, int len )

{

m_size += len;

MixTail(data,len);

while(len >= 4)

{

uint32_t k = *(uint32_t*)data;

mmix(m_hash,k);

data += 4;

len -= 4;

}

MixTail(data,len);

}

uint32_t End ( void )

{

mmix(m_hash,m_tail);

mmix(m_hash,m_size);

m_hash ^= m_hash >> 13;

m_hash *= m;

m_hash ^= m_hash >> 15;

return m_hash;

}

private:

static const uint32_t m = 0x5bd1e995;

static const int r = 24;

void MixTail ( const unsigned char * & data, int & len )

{

while( len && ((len<4) || m_count) )

{

m_tail |= (*data++) << (m_count * 8);

m_count++;

len--;

if(m_count == 4)

{

mmix(m_hash,m_tail);

m_tail = 0;

m_count = 0;

}

uint32_t m_hash;

uint32_t m_tail;

uint32_t m_count;

uint32_t m_size;

};

//-----------------------------------------------------------------------------

// MurmurHashNeutral2, by Austin Appleby

// Same as MurmurHash2, but endian- and alignment-neutral.

// Half the speed though, alas.

uint32_t MurmurHashNeutral2 ( const void * key, int len, uint32_t seed )

{

const uint32_t m = 0x5bd1e995;

const int r = 24;

uint32_t h = seed ^ len;

const unsigned char * data = (const unsigned char *)key;

while(len >= 4)

{

uint32_t 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;

case 2: h ^= data[1] << 8;

case 1: h ^= data[0];

h *= m;

};

h ^= h >> 13;

h *= m;

h ^= h >> 15;

return h;

}

//-----------------------------------------------------------------------------

// MurmurHashAligned2, by Austin Appleby

// Same algorithm as MurmurHash2, but only does aligned reads - should be safer

// on certain platforms.

// Performance will be lower than MurmurHash2

#define MIX(h,k,m) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }

uint32_t MurmurHashAligned2 ( const void * key, int len, uint32_t seed )

{

const uint32_t m = 0x5bd1e995;

const int r = 24;

const unsigned char * data = (const unsigned char *)key;

uint32_t h = seed ^ len;

int align = (uint64_t)data & 3;

if(align && (len >= 4))

{

// Pre-load the temp registers

uint32_t t = 0, d = 0;

switch(align)

{

case 1: t |= data[2] << 16;

case 2: t |= data[1] << 8;

case 3: t |= data[0];

}

t <<= (8 * align);

data += 4-align;

len -= 4-align;

int sl = 8 * (4-align);

int sr = 8 * align;

// Mix

while(len >= 4)

{

d = *(uint32_t *)data;

t = (t >> sr) | (d << sl);

uint32_t k = t;

MIX(h,k,m);

t = d;

data += 4;

len -= 4;

}

// Handle leftover data in temp registers

d = 0;

if(len >= align)

{

switch(align)

{

case 3: d |= data[2] << 16;

case 2: d |= data[1] << 8;

case 1: d |= data[0];

}

uint32_t k = (t >> sr) | (d << sl);

MIX(h,k,m);

data += align;

len -= align;

//----------

// Handle tail bytes

switch(len)

{

case 3: h ^= data[2] << 16;

case 2: h ^= data[1] << 8;

case 1: h ^= data[0];

h *= m;

};

}

else

{

switch(len)

{

case 3: d |= data[2] << 16;

case 2: d |= data[1] << 8;

case 1: d |= data[0];

case 0: h ^= (t >> sr) | (d << sl);

h *= m;

}

h ^= h >> 13;

h *= m;

h ^= h >> 15;

return h;

}

else

{

while(len >= 4)

{

uint32_t k = *(uint32_t *)data;

MIX(h,k,m);

data += 4;

len -= 4;

}

//----------

// Handle tail bytes

switch(len)

{

case 3: h ^= data[2] << 16;

case 2: h ^= data[1] << 8;

case 1: h ^= data[0];

h *= m;

};

h ^= h >> 13;

h *= m;

h ^= h >> 15;

return h;

}

//-----------------------------------------------------------------------------

uap-cpp/MurmurHash2.cpp at master · aitech-lab/uap-cpp · GitHub

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