source-engine/gcsdk/steamextra/tier1/murmurhash3.h

//======= Copyright <EFBFBD> Valve Corporation, All rights reserved. =================
//
// Public domain MurmurHash3 by Austin Appleby is a very solid general-purpose
// hash with a 32-bit output. References:
// http://code.google.com/p/smhasher/ (home of MurmurHash3)
// https://sites.google.com/site/murmurhash/avalanche
// http://www.strchr.com/hash_functions 
//
//=============================================================================

#ifndef MURMURHASH3_H
#define MURMURHASH3_H

#if defined(_WIN32)
#pragma once
#endif

uint32 MurmurHash3_32( const void *key, size_t len, uint32 seed, bool bCaselessStringVariant = false );

inline uint32 MurmurHash3String( const char *pszKey, size_t len )
{
	return MurmurHash3_32( pszKey, len, 1047 /*anything will do for a seed*/, false );
}

inline uint32 MurmurHash3StringCaseless( const char *pszKey, size_t len )
{
	return MurmurHash3_32( pszKey, len, 1047 /*anything will do for a seed*/, true );
}

inline uint32 MurmurHash3String( const char *pszKey )
{
	return MurmurHash3String( pszKey, strlen( pszKey ) );
}

inline uint32 MurmurHash3StringCaseless( const char *pszKey )
{
	return MurmurHash3StringCaseless( pszKey, strlen( pszKey ) );
}

template <typename T>
inline uint32 MurmurHash3Item( const T &item )
{
	return MurmurHash3_32( &item, sizeof(item), 1047 );
}

inline uint32 MurmurHash3Int( uint32 h )
{
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;
	return h;
}


template <>
inline uint32 MurmurHash3Item( const uint32 &item )
{
	return MurmurHash3Int( item );
}

template <>
inline uint32 MurmurHash3Item( const int32 &item )
{
	return MurmurHash3Int( item );
}


template<typename T>
struct MurmurHash3Functor
{
	typedef uint32 TargetType;
	TargetType operator()(const T &key) const
	{
		return MurmurHash3Item( key );
	}
};

template<>
struct MurmurHash3Functor<char *>
{
	typedef uint32 TargetType;
	TargetType operator()(const char *key) const
	{
		return MurmurHash3String( key );
	}
};

template<>
struct MurmurHash3Functor<const char *>
{
	typedef uint32 TargetType;
	TargetType operator()(const char *key) const
	{
		return MurmurHash3String( key );
	}
};

#endif	// MURMURHASH3_H