cregit-Linux how code gets into the kernel

Release 4.7 include/linux/jhash.h

Directory: include/linux
#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) */ /* All the case statements fall through */ switch (length) { case 12: c += (u32)k[11]<<24; case 11: c += (u32)k[10]<<16; case 10: c += (u32)k[9]<<8; case 9: c += k[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_final(a, b, c); case 0: /* Nothing left to add */ break; } return c; }

Contributors

PersonTokensPropCommitsCommitProp
david s. millerdavid s. miller23481.82%125.00%
jozsef kadlecsikjozsef kadlecsik4816.78%125.00%
simon hormansimon horman20.70%125.00%
james morrisjames morris20.70%125.00%
Total286100.00%4100.00%

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

Contributors

PersonTokensPropCommitsCommitProp
david s. millerdavid s. miller10573.43%125.00%
jozsef kadlecsikjozsef kadlecsik3524.48%125.00%
james morrisjames morris21.40%125.00%
patrick mchardypatrick mchardy10.70%125.00%
Total143100.00%4100.00%

/* __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

PersonTokensPropCommitsCommitProp
david s. millerdavid s. miller3888.37%125.00%
alexander duyckalexander duyck36.98%125.00%
jozsef kadlecsikjozsef kadlecsik12.33%125.00%
james morrisjames morris12.33%125.00%
Total43100.00%4100.00%


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

PersonTokensPropCommitsCommitProp
alexander duyckalexander duyck39100.00%1100.00%
Total39100.00%1100.00%


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

Contributors

PersonTokensPropCommitsCommitProp
david s. millerdavid s. miller2158.33%133.33%
alexander duyckalexander duyck925.00%133.33%
james morrisjames morris616.67%133.33%
Total36100.00%3100.00%


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

Contributors

PersonTokensPropCommitsCommitProp
david s. millerdavid s. miller1751.52%133.33%
alexander duyckalexander duyck927.27%133.33%
james morrisjames morris721.21%133.33%
Total33100.00%3100.00%

#endif /* _LINUX_JHASH_H */

Overall Contributors

PersonTokensPropCommitsCommitProp
david s. millerdavid s. miller43767.65%116.67%
jozsef kadlecsikjozsef kadlecsik12719.66%116.67%
alexander duyckalexander duyck619.44%116.67%
james morrisjames morris182.79%116.67%
simon hormansimon horman20.31%116.67%
patrick mchardypatrick mchardy10.15%116.67%
Total646100.00%6100.00%
Directory: include/linux
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