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/*
SuperCollider real time audio synthesis system
Copyright (c) 2002 James McCartney. All rights reserved.
http://www.audiosynth.com
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef _Hash_
#define _Hash_
#include "SC_Types.h"
#include "SC_Endian.h"
// These hash functions are among the best there are in terms of both speed and quality.
// A good hash function makes a lot of difference.
// I have not used Bob Jenkins own hash function because the keys I use are relatively short.
// hash function for a string
inline int32 Hash(const char *inKey)
{
// the one-at-a-time hash.
// a very good hash function. ref: a web page by Bob Jenkins.
// http://www.burtleburtle.net/bob/hash/doobs.html
int32 hash = 0;
while (*inKey) {
hash += *inKey++;
hash += hash << 10;
hash ^= hash >> 6;
}
hash += hash << 3;
hash ^= hash >> 11;
hash += hash << 15;
return hash;
}
// hash function for a string that also returns the length
inline int32 Hash(const char *inKey, int32 *outLength)
{
// the one-at-a-time hash.
// a very good hash function. ref: a web page by Bob Jenkins.
const char *origKey = inKey;
int32 hash = 0;
while (*inKey) {
hash += *inKey++;
hash += hash << 10;
hash ^= hash >> 6;
}
hash += hash << 3;
hash ^= hash >> 11;
hash += hash << 15;
*outLength = inKey - origKey;
return hash;
}
// hash function for an array of char
inline int32 Hash(const char *inKey, int32 inLength)
{
// the one-at-a-time hash.
// a very good hash function. ref: a web page by Bob Jenkins.
int32 hash = 0;
for (int i=0; i<inLength; ++i) {
hash += *inKey++;
hash += hash << 10;
hash ^= hash >> 6;
}
hash += hash << 3;
hash ^= hash >> 11;
hash += hash << 15;
return hash;
}
// hash function for integers
inline int32 Hash(int32 inKey)
{
// Thomas Wang's integer hash.
// http://www.concentric.net/~Ttwang/tech/inthash.htm
// a faster hash for integers. also very good.
uint32 hash = (uint32)inKey;
hash += ~(hash << 15);
hash ^= hash >> 10;
hash += hash << 3;
hash ^= hash >> 6;
hash += ~(hash << 11);
hash ^= hash >> 16;
return (int32)hash;
}
inline int64 Hash64(int64 inKey)
{
// Thomas Wang's 64 bit integer hash.
uint64 hash = (uint64)inKey;
hash += ~(hash << 32);
hash ^= (hash >> 22);
hash += ~(hash << 13);
hash ^= (hash >> 8);
hash += (hash << 3);
hash ^= (hash >> 15);
hash += ~(hash << 27);
hash ^= (hash >> 31);
return (int64)hash;
}
inline int32 Hash(const int32 *inKey, int32 inLength)
{
// one-at-a-time hashing of a string of int32's.
// uses Thomas Wang's integer hash for the combining step.
int32 hash = 0;
for (int i=0; i<inLength; ++i) {
hash = Hash(hash + *inKey++);
}
return hash;
}
#ifndef _LASTCHAR_
#define _LASTCHAR_
#if BYTE_ORDER == LITTLE_ENDIAN
const int32 kLASTCHAR = 0xFF000000;
#else
const int32 kLASTCHAR = 0x000000FF;
#endif
#endif
inline int32 Hash(const int32 *inKey)
{
// hashing of a string of int32's.
// uses Thomas Wang's integer hash for the combining step.
int32 hash = 0;
int32 c;
do {
c = *inKey++;
hash = Hash(hash + c);
} while (c & kLASTCHAR);
return hash;
}
#endif
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