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/*
* lookup3.h
*
* These routines were originally written by Bob Jenkins. The original file
* http://burtleburtle.net/bob/c/lookup3.c (10th Aug 2013) contained these
* credits:
*
* ---
* lookup3.c, by Bob Jenkins, May 2006, Public Domain.
*
* These are functions for producing 32-bit hashes for hash table lookup.
* hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
* are externally useful functions. Routines to test the hash are included
* if SELF_TEST is defined. You can use this free for any purpose. It's in
* the public domain. It has no warranty.
* ---
*
* This file is a (rigorously) modified version for Gambas.
*
* Copyright (C) 2013 Tobias Boege <tobias@gambas-buch.de>
*
* 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, 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.
*/
#ifndef __LOOKUP3_H
#define __LOOKUP3_H
#include <stdint.h>
#define lookup3_size(n) ((uint32_t) 1 << (n))
#define lookup3_mask(n) (lookup3_size(n) - 1)
#define lookup3_rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
/* lookup3_mix -- mix 3 32-bit values reversibly. */
#define lookup3_mix(a, b, c) \
{ \
a -= c; a ^= lookup3_rot(c, 4); c += b; \
b -= a; b ^= lookup3_rot(a, 6); a += c; \
c -= b; c ^= lookup3_rot(b, 8); b += a; \
a -= c; a ^= lookup3_rot(c, 16); c += b; \
b -= a; b ^= lookup3_rot(a, 19); a += c; \
c -= b; c ^= lookup3_rot(b, 4); b += a; \
}
/* lookup3_final -- final mixing of 3 32-bit values (a,b,c) into c */
#define lookup3_final(a,b,c) \
{ \
c ^= b; c -= lookup3_rot(b, 14); \
a ^= c; a -= lookup3_rot(c, 11); \
b ^= a; b -= lookup3_rot(a, 25); \
c ^= b; c -= lookup3_rot(b, 16); \
a ^= c; a -= lookup3_rot(c, 4); \
b ^= a; b -= lookup3_rot(a, 14); \
c ^= b; c -= lookup3_rot(b, 24); \
}
/*
* __lookup3_64() -- Hashes an array of 32 bit values into a 64 bit value
* @k : the key, an array of uint32_t values
* @length: the length of the key, in uint32_ts
* @pc : seed #1
* @pb : seed #2
*
* If 'pb' is zero then the result will be valid a 32 bit value.
*/
static inline uint64_t __lookup3_64(const uint32_t *k, size_t length,
uint32_t pc, uint32_t pb)
{
uint32_t a, b, c;
/* Set up the internal state */
a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + pc;
c += pb;
/* Handle most of the key */
while (length > 3) {
a += k[0];
b += k[1];
c += k[2];
lookup3_mix(a, b, c);
length -= 3;
k += 3;
}
/* Handle the last 3 uint32_t's */
switch(length) { /* All the case statements fall through */
case 3:
c += k[2];
case 2:
b += k[1];
case 1:
a += k[0];
lookup3_final(a, b, c);
case 0: /* case 0: nothing left to add */
break;
}
/* Report the result. Mirror the 32 bit version if 'pb' was zero. */
return c + pb ? ((uint64_t) b) << 32 : 0;
}
/*
* Arbitrary string hash wrappers. They pad the string with '\0' to a 32
* bits boundary. So two (key,length) pairs ("a",1) and ("a\0",2) would
* give identical hashes. Beware!
*/
static inline uint32_t lookup3_32(const char *k, size_t length,
uint32_t initval)
{
size_t len = (length + 31) / 32;
uint32_t key[len];
bzero(key, len * sizeof(key[0]));
memcpy(key, k, length);
return __lookup3_64(key, len, initval, 0);
}
static inline uint64_t lookup3_64(const char *k, size_t length,
uint32_t pc, uint32_t pb)
{
size_t len = (length + 31) / 32;
uint32_t key[len];
bzero(key, len * sizeof(key[0]));
memcpy(key, k, length);
return __lookup3_64(key, len, pc, pb);
}
#endif /* __LOOKUP3_H */
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