| #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@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; |
| } |
| |
| /* 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; |
| } |
| |
| |
| /* __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 */ |