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/**
* $Id$
* ***** BEGIN GPL/BL DUAL LICENSE BLOCK *****
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version. The Blender
* Foundation also sells licenses for use in proprietary software under
* the Blender License. See http://www.blender.org/BL/ for information
* about this.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
* All rights reserved.
*
* The Original Code is: all of this file.
*
* Contributor(s): none yet.
*
* ***** END GPL/BL DUAL LICENSE BLOCK *****
*/
/**
* $Id$
* Copyright (C) 2001 NaN Technologies B.V.
* This file was formerly known as: GEN_StdString.cpp.
* @date November, 14, 2001
*/
#ifndef __STR_HASHSTRING
#define __STR_HASHSTRING
#include "STR_String.h"
// Hash Mix utility function, by Bob Jenkins - Mix 3 32-bit values reversibly
//
// - If gHashMix() is run forward or backward, at least 32 bits in a,b,c have at
// least 1/4 probability of changing.
//
// - If gHashMix() is run forward, every bit of c will change between 1/3 and
// 2/3 of the time.
//
static inline void STR_gHashMix(dword& a, dword& b, dword& c)
{
a -= b; a -= c; a ^= (c>>13);
b -= c; b -= a; b ^= (a<<8);
c -= a; c -= b; c ^= (b>>13);
a -= b; a -= c; a ^= (c>>12);
b -= c; b -= a; b ^= (a<<16);
c -= a; c -= b; c ^= (b>>5);
a -= b; a -= c; a ^= (c>>3);
b -= c; b -= a; b ^= (a<<10);
c -= a; c -= b; c ^= (b>>15);
}
//
// Fast Hashable<int32> functionality
// http://www.concentric.net/~Ttwang/tech/inthash.htm
//
static inline dword STR_gHash(dword inDWord)
{
dword key = inDWord;
key += ~(key << 16);
key ^= (key >> 5);
key += (key << 3);
key ^= (key >> 13);
key += ~(key << 9);
key ^= (key >> 17);
return key;
}
enum { GOLDEN_RATIO = 0x9e3779b9 }; // arbitrary value to initialize hash funtion, well not so arbitrary
// as this value is taken from the pigs library (Orange Games/Lost Boys)
static dword STR_gHash(const void* in, int len, dword init_val)
{
unsigned int length = len;
dword a = (dword)GOLDEN_RATIO;
dword b = (dword)GOLDEN_RATIO;
dword c = init_val; // the previous hash value
byte *p_in = (byte *)in;
// Do the largest part of the key
while (length >= 12)
{
a += (p_in[0] + ((dword)p_in[1]<<8) + ((dword)p_in[2] <<16) + ((dword)p_in[3] <<24));
b += (p_in[4] + ((dword)p_in[5]<<8) + ((dword)p_in[6] <<16) + ((dword)p_in[7] <<24));
c += (p_in[8] + ((dword)p_in[9]<<8) + ((dword)p_in[10]<<16) + ((dword)p_in[11]<<24));
STR_gHashMix(a, b, c);
p_in += 12; length -= 12;
}
// Handle the last 11 bytes
c += len;
switch(length) {
case 11: c+=((dword)p_in[10]<<24);
case 10: c+=((dword)p_in[9]<<16);
case 9 : c+=((dword)p_in[8]<<8); // the first byte of c is reserved for the length
case 8 : b+=((dword)p_in[7]<<24);
case 7 : b+=((dword)p_in[6]<<16);
case 6 : b+=((dword)p_in[5]<<8);
case 5 : b+=p_in[4];
case 4 : a+=((dword)p_in[3]<<24);
case 3 : a+=((dword)p_in[2]<<16);
case 2 : a+=((dword)p_in[1]<<8);
case 1 : a+=p_in[0];
}
STR_gHashMix(a, b, c);
return c;
}
class STR_HashedString : public STR_String
{
public:
STR_HashedString() : STR_String(),m_Hashed(false) {}
STR_HashedString(const char* str) : STR_String(str),m_Hashed(false) {}
STR_HashedString(const STR_String& str) : STR_String(str),m_Hashed(false) {}
inline dword hash(dword init=0) const
{
if (!m_Hashed)
{
const char* str = *this;
int length = this->Length();
m_CachedHash = STR_gHash(str,length,init);
m_Hashed=true;
}
return m_CachedHash;
}
private:
mutable bool m_Hashed;
mutable dword m_CachedHash;
};
#endif //__STR_HASHSTRING
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