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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177#ifndef _LINUX_JHASH_H#define _LINUX_JHASH_H
/* jhash.h: Jenkins hash support. * * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net) * * https://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@netfilter.org) * * 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.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 arbitrary 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((u32 *)k); b += get_unaligned((u32 *)(k + 4)); c += get_unaligned((u32 *)(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; fallthrough; case 11: c += (u32)k[10]<<16; fallthrough; case 10: c += (u32)k[9]<<8; fallthrough; case 9: c += k[8]; fallthrough; case 8: b += (u32)k[7]<<24; fallthrough; case 7: b += (u32)k[6]<<16; fallthrough; case 6: b += (u32)k[5]<<8; fallthrough; case 5: b += k[4]; fallthrough; case 4: a += (u32)k[3]<<24; fallthrough; case 3: a += (u32)k[2]<<16; fallthrough; case 2: a += (u32)k[1]<<8; fallthrough; case 1: a += k[0]; __jhash_final(a, b, c); break; case 0: /* Nothing left to add */ break; }
return c;}
/* 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 arbitrary 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]; fallthrough; case 2: b += k[1]; fallthrough; case 1: a += k[0]; __jhash_final(a, b, c); break; case 0: /* Nothing left to add */ break; }
return c;}
/* __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;}
static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval){ return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2));}
static inline u32 jhash_2words(u32 a, u32 b, u32 initval){ return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));}
static inline u32 jhash_1word(u32 a, u32 initval){ return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2));}
#endif /* _LINUX_JHASH_H */