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116 lines
3.3 KiB
116 lines
3.3 KiB
//======= Copyright © 2005, , Valve Corporation, All rights reserved. ========= |
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// |
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// Purpose: Variant Pearson Hash general purpose hashing algorithm described |
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// by Cargill in C++ Report 1994. Generates a 16-bit result. |
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// |
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//============================================================================= |
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#ifndef GENERICHASH_H |
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#define GENERICHASH_H |
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#if defined(_WIN32) |
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#pragma once |
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#endif |
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//----------------------------------------------------------------------------- |
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unsigned FASTCALL HashString( const char *pszKey ); |
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unsigned FASTCALL HashStringCaseless( const char *pszKey ); |
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unsigned FASTCALL HashStringCaselessConventional( const char *pszKey ); |
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unsigned FASTCALL Hash4( const void *pKey ); |
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unsigned FASTCALL Hash8( const void *pKey ); |
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unsigned FASTCALL Hash12( const void *pKey ); |
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unsigned FASTCALL Hash16( const void *pKey ); |
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unsigned FASTCALL HashBlock( const void *pKey, unsigned size ); |
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unsigned FASTCALL HashInt( const int key ); |
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// hash a uint32 into a uint32 |
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FORCEINLINE uint32 HashIntAlternate( uint32 n) |
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{ |
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n = ( n + 0x7ed55d16 ) + ( n << 12 ); |
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n = ( n ^ 0xc761c23c ) ^ ( n >> 19 ); |
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n = ( n + 0x165667b1 ) + ( n << 5 ); |
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n = ( n + 0xd3a2646c ) ^ ( n << 9 ); |
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n = ( n + 0xfd7046c5 ) + ( n << 3 ); |
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n = ( n ^ 0xb55a4f09 ) ^ ( n >> 16 ); |
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return n; |
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} |
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inline unsigned HashIntConventional( const int n ) // faster but less effective |
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{ |
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// first byte |
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unsigned hash = 0xAAAAAAAA + (n & 0xFF); |
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// second byte |
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hash = ( hash << 5 ) + hash + ( (n >> 8) & 0xFF ); |
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// third byte |
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hash = ( hash << 5 ) + hash + ( (n >> 16) & 0xFF ); |
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// fourth byte |
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hash = ( hash << 5 ) + hash + ( (n >> 24) & 0xFF ); |
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return hash; |
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/* this is the old version, which would cause a load-hit-store on every |
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line on a PowerPC, and therefore took hundreds of clocks to execute! |
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byte *p = (byte *)&n; |
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unsigned hash = 0xAAAAAAAA + *p++; |
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hash = ( ( hash << 5 ) + hash ) + *p++; |
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hash = ( ( hash << 5 ) + hash ) + *p++; |
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return ( ( hash << 5 ) + hash ) + *p; |
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*/ |
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} |
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//----------------------------------------------------------------------------- |
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template <typename T> |
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inline unsigned HashItem( const T &item ) |
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{ |
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// TODO: Confirm comiler optimizes out unused paths |
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if ( sizeof(item) == 4 ) |
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return Hash4( &item ); |
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else if ( sizeof(item) == 8 ) |
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return Hash8( &item ); |
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else if ( sizeof(item) == 12 ) |
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return Hash12( &item ); |
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else if ( sizeof(item) == 16 ) |
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return Hash16( &item ); |
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else |
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return HashBlock( &item, sizeof(item) ); |
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} |
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template <> inline unsigned HashItem<int>(const int &key ) |
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{ |
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return HashInt( key ); |
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} |
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template <> inline unsigned HashItem<unsigned>(const unsigned &key ) |
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{ |
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return HashInt( (int)key ); |
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} |
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template<> inline unsigned HashItem<const char *>(const char * const &pszKey ) |
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{ |
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return HashString( pszKey ); |
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} |
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template<> inline unsigned HashItem<char *>(char * const &pszKey ) |
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{ |
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return HashString( pszKey ); |
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} |
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//----------------------------------------------------------------------------- |
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//----------------------------------------------------------------------------- |
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// Murmur hash |
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//----------------------------------------------------------------------------- |
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uint32 MurmurHash2( const void * key, int len, uint32 seed ); |
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// return murmurhash2 of a downcased string |
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uint32 MurmurHash2LowerCase( char const *pString, uint32 nSeed ); |
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uint64 MurmurHash64( const void * key, int len, uint32 seed ); |
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#endif /* !GENERICHASH_H */
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