#ifndef _JHASH_H
#define _JHASH_H
/* jhash.h: Jenkins hash support.
*
* Copyright (C) 1996 Bob Jenkins (
[email protected])
*
*
http://burtleburtle.net/bob/hash/
*
* These are the credits from Bob's sources:
*
* lookup2.c, by Bob Jenkins, December 1996, Public Domain.
* hash(), hash2(), hash3, and mix() 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 has no warranty.
*/
/* NOTE: Arguments are modified. */
#define __jhash_mix(a, b, 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); \
}
/* The golden ration: an arbitrary value */
#define JHASH_GOLDEN_RATIO 0x9e3779b9
/* The most generic version, hashes an arbitrary sequence
* of bytes. No alignment or length assumptions are made about
* the input key.
*/
static __inline u32 jhash(const void *key, u32 length, u32 initval)
{
u32 a, b, c, len;
const u8 *k = key;
len = length;
a = b = JHASH_GOLDEN_RATIO;
c = initval;
while (len >= 12) {
a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
__jhash_mix(a,b,c);
k += 12;
len -= 12;
}
c += length;
switch (len) {
case 11: c += ((u32)k[10]<<24);
case 10: c += ((u32)k[9]<<16);
case 9 : c += ((u32)k[8]<<8);
case 8 : b += ((u32)k[7]<<24);
case 7 : b += ((u32)k[6]<<16);
case 6 : b += ((u32)k[5]<<8);
case 5 : b += k[4];
case 4 : a += ((u32)k[3]<<24);
case 3 : a += ((u32)k[2]<<16);
case 2 : a += ((u32)k[1]<<8);
case 1 : a += k[0];
};
__jhash_mix(a,b,c);
return c;
}
/* A special optimized version that handles 1 or more of u32s.
* The length parameter here is the number of u32s in the key.
*/
static __inline u32 jhash2(u32 *k, u32 length, u32 initval)
{
u32 a, b, c, len;
a = b = JHASH_GOLDEN_RATIO;
c = initval;
len = length;
while (len >= 3) {
a += k[0];
b += k[1];
c += k[2];
__jhash_mix(a, b, c);
k += 3; len -= 3;
}
c += length * 4;
switch (len) {
case 2 : b += k[1];
case 1 : a += k[0];
};
__jhash_mix(a,b,c);
return c;
}
/* A special ultra-optimized versions that knows they are hashing exactly
* 3, 2 or 1 word(s).
*
* NOTE: In particular the "c += length; __jhash_mix(a,b,c);" normally
* done at the end is not done here.
*/
static __inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
{
a += JHASH_GOLDEN_RATIO;
b += JHASH_GOLDEN_RATIO;
c += initval;
__jhash_mix(a, b, c);
return c;
}
static __inline u32 jhash_2words(u32 a, u32 b, u32 initval)
{
return jhash_3words(a, b, 0, initval);
}
static __inline u32 jhash_1word(u32 a, u32 initval)
{
return jhash_3words(a, 0, 0, initval);
}
#endif /* _JHASH_H */
