117 lines
3.3 KiB
C++
117 lines
3.3 KiB
C++
//========= Copyright 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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