LCOV - code coverage report
Current view: top level - include/linux - jhash.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 2 2 100.0 %
Date: 2017-01-25 Functions: 0 0 -

          Line data    Source code
       1             : #ifndef _LINUX_JHASH_H
       2             : #define _LINUX_JHASH_H
       3             : 
       4             : /* jhash.h: Jenkins hash support.
       5             :  *
       6             :  * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
       7             :  *
       8             :  * http://burtleburtle.net/bob/hash/
       9             :  *
      10             :  * These are the credits from Bob's sources:
      11             :  *
      12             :  * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
      13             :  * hash(), hash2(), hash3, and mix() are externally useful functions.
      14             :  * Routines to test the hash are included if SELF_TEST is defined.
      15             :  * You can use this free for any purpose.  It has no warranty.
      16             :  *
      17             :  * Copyright (C) 2003 David S. Miller (davem@redhat.com)
      18             :  *
      19             :  * I've modified Bob's hash to be useful in the Linux kernel, and
      20             :  * any bugs present are surely my fault.  -DaveM
      21             :  */
      22             : 
      23             : /* NOTE: Arguments are modified. */
      24             : #define __jhash_mix(a, b, c) \
      25             : { \
      26             :   a -= b; a -= c; a ^= (c>>13); \
      27             :   b -= c; b -= a; b ^= (a<<8); \
      28             :   c -= a; c -= b; c ^= (b>>13); \
      29             :   a -= b; a -= c; a ^= (c>>12);  \
      30             :   b -= c; b -= a; b ^= (a<<16); \
      31             :   c -= a; c -= b; c ^= (b>>5); \
      32             :   a -= b; a -= c; a ^= (c>>3);  \
      33             :   b -= c; b -= a; b ^= (a<<10); \
      34             :   c -= a; c -= b; c ^= (b>>15); \
      35             : }
      36             : 
      37             : /* The golden ration: an arbitrary value */
      38             : #define JHASH_GOLDEN_RATIO      0x9e3779b9
      39             : 
      40             : /* The most generic version, hashes an arbitrary sequence
      41             :  * of bytes.  No alignment or length assumptions are made about
      42             :  * the input key.
      43             :  */
      44             : static inline u32 jhash(const void *key, u32 length, u32 initval)
      45             : {
      46             :         u32 a, b, c, len;
      47             :         const u8 *k = key;
      48             : 
      49             :         len = length;
      50             :         a = b = JHASH_GOLDEN_RATIO;
      51             :         c = initval;
      52             : 
      53             :         while (len >= 12) {
      54             :                 a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
      55             :                 b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
      56             :                 c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
      57             : 
      58             :                 __jhash_mix(a,b,c);
      59             : 
      60             :                 k += 12;
      61             :                 len -= 12;
      62             :         }
      63             : 
      64             :         c += length;
      65             :         switch (len) {
      66             :         case 11: c += ((u32)k[10]<<24);
      67             :         case 10: c += ((u32)k[9]<<16);
      68             :         case 9 : c += ((u32)k[8]<<8);
      69             :         case 8 : b += ((u32)k[7]<<24);
      70             :         case 7 : b += ((u32)k[6]<<16);
      71             :         case 6 : b += ((u32)k[5]<<8);
      72             :         case 5 : b += k[4];
      73             :         case 4 : a += ((u32)k[3]<<24);
      74             :         case 3 : a += ((u32)k[2]<<16);
      75             :         case 2 : a += ((u32)k[1]<<8);
      76             :         case 1 : a += k[0];
      77             :         };
      78             : 
      79             :         __jhash_mix(a,b,c);
      80             : 
      81             :         return c;
      82             : }
      83             : 
      84             : /* A special optimized version that handles 1 or more of u32s.
      85             :  * The length parameter here is the number of u32s in the key.
      86             :  */
      87             : static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
      88             : {
      89             :         u32 a, b, c, len;
      90             : 
      91             :         a = b = JHASH_GOLDEN_RATIO;
      92             :         c = initval;
      93             :         len = length;
      94             : 
      95             :         while (len >= 3) {
      96             :                 a += k[0];
      97             :                 b += k[1];
      98             :                 c += k[2];
      99             :                 __jhash_mix(a, b, c);
     100             :                 k += 3; len -= 3;
     101             :         }
     102             : 
     103             :         c += length * 4;
     104             : 
     105             :         switch (len) {
     106             :         case 2 : b += k[1];
     107             :         case 1 : a += k[0];
     108             :         };
     109             : 
     110             :         __jhash_mix(a,b,c);
     111             : 
     112             :         return c;
     113             : }
     114             : 
     115             : 
     116             : /* A special ultra-optimized versions that knows they are hashing exactly
     117             :  * 3, 2 or 1 word(s).
     118             :  *
     119             :  * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
     120             :  *       done at the end is not done here.
     121             :  */
     122             : static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
     123             : {
     124             :         a += JHASH_GOLDEN_RATIO;
     125             :         b += JHASH_GOLDEN_RATIO;
     126             :         c += initval;
     127             : 
     128             :         __jhash_mix(a, b, c);
     129             : 
     130             :         return c;
     131             : }
     132             : 
     133             : static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
     134             : {
     135             :         return jhash_3words(a, b, 0, initval);
     136             : }
     137             : 
     138             : static inline u32 jhash_1word(u32 a, u32 initval)
     139             : {
     140             :         return jhash_3words(a, 0, 0, initval);
     141             : }
     142           1 : 
     143             : #endif /* _LINUX_JHASH_H */

Generated by: LCOV version 1.10