chromium/third_party/smhasher/src/MurmurHash2.cpp

//-----------------------------------------------------------------------------
// 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 …

// Other compilers

#else	// defined(_MSC_VER)

#define BIG_CONSTANT(x) …

#endif // !defined(_MSC_VER)

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

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

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

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


// 64-bit hash for 32-bit platforms

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

//-----------------------------------------------------------------------------
// 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) …

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

//-----------------------------------------------------------------------------
// 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
{ … };

//-----------------------------------------------------------------------------
// 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 )
{ … } 

//-----------------------------------------------------------------------------
// 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) …


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

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