[urcu.git] / urcu / jhash.h

#ifndef _KCOMPAT_JHASH_H
#define _KCOMPAT_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
 */

#include <stdint.h>

typedef uint8_t u8;
typedef uint32_t u32;

/* 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;
}

#endif /* _KCOMPAT_JHASH_H */
Commit	Line	Data
	1	#ifndef _KCOMPAT_JHASH_H
	2	#define _KCOMPAT_JHASH_H
	3
	4	/* jhash.h: Jenkins hash support.
	5	*
	6	* Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
	7	*
	8	* http://burtleburtle.net/bob/hash/
	9	*
	10	* These are the credits from Bob's sources:
	11	*
	12	* lookup2.c, by Bob Jenkins, December 1996, Public Domain.
	13	* hash(), hash2(), hash3, and mix() are externally useful functions.
	14	* Routines to test the hash are included if SELF_TEST is defined.
	15	* You can use this free for any purpose. It has no warranty.
	16	*
	17	* Copyright (C) 2003 David S. Miller (davem@redhat.com)
	18	*
	19	* I've modified Bob's hash to be useful in the Linux kernel, and
	20	* any bugs present are surely my fault. -DaveM
	21	*/
	22
	23	#include <stdint.h>
	24
	25	typedef uint8_t u8;
	26	typedef uint32_t u32;
	27
	28	/* NOTE: Arguments are modified. */
	29	#define __jhash_mix(a, b, c) \
	30	{ \
	31	a -= b; a -= c; a ^= (c>>13); \
	32	b -= c; b -= a; b ^= (a<<8); \
	33	c -= a; c -= b; c ^= (b>>13); \
	34	a -= b; a -= c; a ^= (c>>12); \
	35	b -= c; b -= a; b ^= (a<<16); \
	36	c -= a; c -= b; c ^= (b>>5); \
	37	a -= b; a -= c; a ^= (c>>3); \
	38	b -= c; b -= a; b ^= (a<<10); \
	39	c -= a; c -= b; c ^= (b>>15); \
	40	}
	41
	42	/* The golden ration: an arbitrary value */
	43	#define JHASH_GOLDEN_RATIO 0x9e3779b9
	44
	45	/* The most generic version, hashes an arbitrary sequence
	46	* of bytes. No alignment or length assumptions are made about
	47	* the input key.
	48	*/
	49	static inline u32 jhash(const void *key, u32 length, u32 initval)
	50	{
	51	u32 a, b, c, len;
	52	const u8 *k = key;
	53
	54	len = length;
	55	a = b = JHASH_GOLDEN_RATIO;
	56	c = initval;
	57
	58	while (len >= 12) {
	59	a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
	60	b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
	61	c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
	62
	63	__jhash_mix(a,b,c);
	64
	65	k += 12;
	66	len -= 12;
	67	}
	68
	69	c += length;
	70	switch (len) {
	71	case 11: c += ((u32)k[10]<<24);
	72	case 10: c += ((u32)k[9]<<16);
	73	case 9 : c += ((u32)k[8]<<8);
	74	case 8 : b += ((u32)k[7]<<24);
	75	case 7 : b += ((u32)k[6]<<16);
	76	case 6 : b += ((u32)k[5]<<8);
	77	case 5 : b += k[4];
	78	case 4 : a += ((u32)k[3]<<24);
	79	case 3 : a += ((u32)k[2]<<16);
	80	case 2 : a += ((u32)k[1]<<8);
	81	case 1 : a += k[0];
	82	};
	83
	84	__jhash_mix(a,b,c);
	85
	86	return c;
	87	}
	88
	89	#endif /* _KCOMPAT_JHASH_H */