1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
143 lines
3.2 KiB
C
143 lines
3.2 KiB
C
#ifndef _LINUX_JHASH_H
|
|
#define _LINUX_JHASH_H
|
|
|
|
/* jhash.h: Jenkins hash support.
|
|
*
|
|
* Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
|
|
*
|
|
* 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.
|
|
*
|
|
* Copyright (C) 2003 David S. Miller (davem@redhat.com)
|
|
*
|
|
* I've modified Bob's hash to be useful in the Linux kernel, and
|
|
* any bugs present are surely my fault. -DaveM
|
|
*/
|
|
|
|
/* 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 partilar 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 /* _LINUX_JHASH_H */
|