include/qemu/jhash.h

   1 /* jhash.h: Jenkins hash support.
   2   *
   3   * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
   4   *
   5   * http://burtleburtle.net/bob/hash/
   6   *
   7   * These are the credits from Bob's sources:
   8   *
   9   * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
  10   *
  11   * These are functions for producing 32-bit hashes for hash table lookup.
  12   * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
  13   * are externally useful functions.  Routines to test the hash are included
  14   * if SELF_TEST is defined.  You can use this free for any purpose. It's in
  15   * the public domain.  It has no warranty.
  16   *
  17   * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
  18   *
  19   * I've modified Bob's hash to be useful in the Linux kernel, and
  20   * any bugs present are my fault.
  21   * Jozsef
  22   */
  23
  24 #ifndef QEMU_JHASH_H__
  25 #define QEMU_JHASH_H__
  26
  27 #include "qemu/bitops.h"
  28
  29 /*
  30  * hashtable relation copy from linux kernel jhash
  31  */
  32
  33 /* __jhash_mix -- mix 3 32-bit values reversibly. */
  34 #define __jhash_mix(a, b, c)                \
  35 {                                           \
  36     a -= c;  a ^= rol32(c, 4);  c += b;     \
  37     b -= a;  b ^= rol32(a, 6);  a += c;     \
  38     c -= b;  c ^= rol32(b, 8);  b += a;     \
  39     a -= c;  a ^= rol32(c, 16); c += b;     \
  40     b -= a;  b ^= rol32(a, 19); a += c;     \
  41     c -= b;  c ^= rol32(b, 4);  b += a;     \
  42 }
  43
  44 /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
  45 #define __jhash_final(a, b, c)  \
  46 {                               \
  47     c ^= b; c -= rol32(b, 14);  \
  48     a ^= c; a -= rol32(c, 11);  \
  49     b ^= a; b -= rol32(a, 25);  \
  50     c ^= b; c -= rol32(b, 16);  \
  51     a ^= c; a -= rol32(c, 4);   \
  52     b ^= a; b -= rol32(a, 14);  \
  53     c ^= b; c -= rol32(b, 24);  \
  54 }
  55
  56 /* An arbitrary initial parameter */
  57 #define JHASH_INITVAL           0xdeadbeef
  58
  59 #endif /* QEMU_JHASH_H__ */