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/* 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
*/
#include "zebra.h"
#include "jhash.h"
/* The golden ration: an arbitrary value */
#define JHASH_GOLDEN_RATIO 0x9e3779b9
/* 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 most generic version, hashes an arbitrary sequence
* of bytes. No alignment or length assumptions are made about
* the input key.
*/
u_int32_t
jhash (void *key, u_int32_t length, u_int32_t initval)
{
u_int32_t a, b, c, len;
u_int8_t *k = key;
len = length;
a = b = JHASH_GOLDEN_RATIO;
c = initval;
while (len >= 12)
{
a +=
(k[0] + ((u_int32_t) k[1] << 8) + ((u_int32_t) k[2] << 16) +
((u_int32_t) k[3] << 24));
b +=
(k[4] + ((u_int32_t) k[5] << 8) + ((u_int32_t) k[6] << 16) +
((u_int32_t) k[7] << 24));
c +=
(k[8] + ((u_int32_t) k[9] << 8) + ((u_int32_t) k[10] << 16) +
((u_int32_t) k[11] << 24));
__jhash_mix (a, b, c);
k += 12;
len -= 12;
}
c += length;
switch (len)
{
case 11:
c += ((u_int32_t) k[10] << 24);
case 10:
c += ((u_int32_t) k[9] << 16);
case 9:
c += ((u_int32_t) k[8] << 8);
case 8:
b += ((u_int32_t) k[7] << 24);
case 7:
b += ((u_int32_t) k[6] << 16);
case 6:
b += ((u_int32_t) k[5] << 8);
case 5:
b += k[4];
case 4:
a += ((u_int32_t) k[3] << 24);
case 3:
a += ((u_int32_t) k[2] << 16);
case 2:
a += ((u_int32_t) 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 u_int32_ts.
* The length parameter here is the number of u_int32_ts in the key.
*/
u_int32_t
jhash2 (u_int32_t * k, u_int32_t length, u_int32_t initval)
{
u_int32_t 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.
*/
u_int32_t
jhash_3words (u_int32_t a, u_int32_t b, u_int32_t c, u_int32_t initval)
{
a += JHASH_GOLDEN_RATIO;
b += JHASH_GOLDEN_RATIO;
c += initval;
__jhash_mix (a, b, c);
return c;
}
u_int32_t
jhash_2words (u_int32_t a, u_int32_t b, u_int32_t initval)
{
return jhash_3words (a, b, 0, initval);
}
u_int32_t
jhash_1word (u_int32_t a, u_int32_t initval)
{
return jhash_3words (a, 0, 0, initval);
}
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