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/*
* 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.
*
* 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
* All rights reserved.
*/
/** \file string/STR_HashedString.h
* \ingroup string
*
* Copyright (C) 2001 NaN Technologies B.V.
* This file was formerly known as: GEN_StdString.cpp.
* \date November, 14, 2001
*/
#ifndef __STR_HASHEDSTRING_H__
#define __STR_HASHEDSTRING_H__
#include "STR_String.h"
/* copied from 'BLI_compiler_attrs.h' */
/* Use to suppress '-Wimplicit-fallthrough' (in place of 'break'). */
#if defined(__GNUC__) && (__GNUC__ >= 7) /* gcc7.0+ only */
#define ATTR_FALLTHROUGH __attribute__((fallthrough))
#else
#define ATTR_FALLTHROUGH ((void)0)
#endif
// 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); ATTR_FALLTHROUGH;
case 10: c += ((dword)p_in[9] << 16); ATTR_FALLTHROUGH;
case 9: c += ((dword)p_in[8] << 8); ATTR_FALLTHROUGH; /* the first byte of c is reserved for the length */
case 8: b += ((dword)p_in[7] << 24); ATTR_FALLTHROUGH;
case 7: b += ((dword)p_in[6] << 16); ATTR_FALLTHROUGH;
case 6: b += ((dword)p_in[5] << 8); ATTR_FALLTHROUGH;
case 5: b += p_in[4]; ATTR_FALLTHROUGH;
case 4: a += ((dword)p_in[3] << 24); ATTR_FALLTHROUGH;
case 3: a += ((dword)p_in[2] << 16); ATTR_FALLTHROUGH;
case 2: a += ((dword)p_in[1] << 8); ATTR_FALLTHROUGH;
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_HASHEDSTRING_H__
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