Release 4.16 include/linux/jhash.h

#ifndef _LINUX_JHASH_H

#define _LINUX_JHASH_H

/* jhash.h: Jenkins hash support.
 *
 * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
 *
 * http://burtleburtle.net/bob/hash/
 *
 * These are the credits from Bob's sources:
 *
 * 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.
 *
 * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
 *
 * I've modified Bob's hash to be useful in the Linux kernel, and
 * any bugs present are my fault.
 * Jozsef
 */
#include <linux/bitops.h>
#include <linux/unaligned/packed_struct.h>

/* Best hash sizes are of power of two */

#define jhash_size(n)   ((u32)1<<(n))
/* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */

#define jhash_mask(n)   (jhash_size(n)-1)

/* __jhash_mix -- mix 3 32-bit values reversibly. */

#define __jhash_mix(a, b, c)			\
{                                               \
        a -= c;  a ^= rol32(c, 4);  c += b;     \
        b -= a;  b ^= rol32(a, 6);  a += c;     \
        c -= b;  c ^= rol32(b, 8);  b += a;     \
        a -= c;  a ^= rol32(c, 16); c += b;     \
        b -= a;  b ^= rol32(a, 19); a += c;     \
        c -= b;  c ^= rol32(b, 4);  b += a;     \
}

/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */

#define __jhash_final(a, b, c)			\
{                                               \
        c ^= b; c -= rol32(b, 14);              \
        a ^= c; a -= rol32(c, 11);              \
        b ^= a; b -= rol32(a, 25);              \
        c ^= b; c -= rol32(b, 16);              \
        a ^= c; a -= rol32(c, 4);               \
        b ^= a; b -= rol32(a, 14);              \
        c ^= b; c -= rol32(b, 24);              \
}

/* An arbitrary initial parameter */

#define JHASH_INITVAL		0xdeadbeef

/* jhash - hash an arbitrary key
 * @k: sequence of bytes as key
 * @length: the length of the key
 * @initval: the previous hash, or an arbitray value
 *
 * The generic version, hashes an arbitrary sequence of bytes.
 * No alignment or length assumptions are made about the input key.
 *
 * Returns the hash value of the key. The result depends on endianness.
 */


static inline u32 jhash(const void *key, u32 length, u32 initval)
{
	u32 a, b, c;
	const u8 *k = key;

	/* Set up the internal state */
	a = b = c = JHASH_INITVAL + length + initval;

	/* All but the last block: affect some 32 bits of (a,b,c) */
	while (length > 12) {
		a += __get_unaligned_cpu32(k);
		b += __get_unaligned_cpu32(k + 4);
		c += __get_unaligned_cpu32(k + 8);
		__jhash_mix(a, b, c);
		length -= 12;
		k += 12;
	}
	/* Last block: affect all 32 bits of (c) */
	switch (length) {
	case 12: c += (u32)k[11]<<24;	/* fall through */
	case 11: c += (u32)k[10]<<16;	/* fall through */
	case 10: c += (u32)k[9]<<8;	/* fall through */
	case 9:  c += k[8];		/* fall through */
	case 8:  b += (u32)k[7]<<24;	/* fall through */
	case 7:  b += (u32)k[6]<<16;	/* fall through */
	case 6:  b += (u32)k[5]<<8;	/* fall through */
	case 5:  b += k[4];		/* fall through */
	case 4:  a += (u32)k[3]<<24;	/* fall through */
	case 3:  a += (u32)k[2]<<16;	/* fall through */
	case 2:  a += (u32)k[1]<<8;	/* fall through */
	case 1:  a += k[0];
		 __jhash_final(a, b, c);
	case 0: /* Nothing left to add */
		break;
	}

	return c;
}

Contributors
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CommitProp
David S. Miller
234
79.05%
1
20.00%
Jozsef Kadlecsik
47
15.88%
1
20.00%
Jakub Kiciński
11
3.72%
1
20.00%
James Morris
2
0.68%
1
20.00%
Simon Horman
2
0.68%
1
20.00%
Total
296
100.00%
5
100.00%

/* jhash2 - hash an array of u32's
 * @k: the key which must be an array of u32's
 * @length: the number of u32's in the key
 * @initval: the previous hash, or an arbitray value
 *
 * Returns the hash value of the key.
 */


static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
{
	u32 a, b, c;

	/* Set up the internal state */
	a = b = c = JHASH_INITVAL + (length<<2) + initval;

	/* Handle most of the key */
	while (length > 3) {
		a += k[0];
		b += k[1];
		c += k[2];
		__jhash_mix(a, b, c);
		length -= 3;
		k += 3;
	}

	/* Handle the last 3 u32's */
	switch (length) {
	case 3: c += k[2];	/* fall through */
	case 2: b += k[1];	/* fall through */
	case 1: a += k[0];
		__jhash_final(a, b, c);
	case 0:	/* Nothing left to add */
		break;
	}

	return c;
}


Contributors
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CommitProp
David S. Miller
105
72.41%
1
20.00%
Jozsef Kadlecsik
34
23.45%
1
20.00%
Jakub Kiciński
3
2.07%
1
20.00%
James Morris
2
1.38%
1
20.00%
Patrick McHardy
1
0.69%
1
20.00%
Total
145
100.00%
5
100.00%

/* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */


static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval)
{
	a += initval;
	b += initval;
	c += initval;

	__jhash_final(a, b, c);

	return c;
}

Contributors
Person
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Commits
CommitProp
David S. Miller
38
88.37%
1
25.00%
Alexander Duyck
3
6.98%
1
25.00%
James Morris
1
2.33%
1
25.00%
Jozsef Kadlecsik
1
2.33%
1
25.00%
Total
43
100.00%
4
100.00%



static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
{
	return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2));
}

Contributors
Person
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Alexander Duyck
39
100.00%
1
100.00%
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39
100.00%
1
100.00%



static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
{
	return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
}

Contributors
Person
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CommitProp
David S. Miller
21
58.33%
1
33.33%
Alexander Duyck
9
25.00%
1
33.33%
James Morris
6
16.67%
1
33.33%
Total
36
100.00%
3
100.00%



static inline u32 jhash_1word(u32 a, u32 initval)
{
	return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2));
}

Contributors
Person
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CommitProp
David S. Miller
17
51.52%
1
33.33%
Alexander Duyck
9
27.27%
1
33.33%
James Morris
7
21.21%
1
33.33%
Total
33
100.00%
3
100.00%

#endif /* _LINUX_JHASH_H */
Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
David S. Miller
437
66.41%
1
14.29%
Jozsef Kadlecsik
125
19.00%
1
14.29%
Alexander Duyck
61
9.27%
1
14.29%
James Morris
18
2.74%
1
14.29%
Jakub Kiciński
14
2.13%
1
14.29%
Simon Horman
2
0.30%
1
14.29%
Patrick McHardy
1
0.15%
1
14.29%
Total
658
100.00%
7
100.00%
Directory: include/linux

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