1 | #ifndef _LINUX_JHASH_H |
---|---|

2 | #define _LINUX_JHASH_H |

3 | |

4 | /* jhash.h: Jenkins hash support. |

5 | * |

6 | * Copyright (C) 2006. 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 | * lookup3.c, by Bob Jenkins, May 2006, Public Domain. |

13 | * |

14 | * These are functions for producing 32-bit hashes for hash table lookup. |

15 | * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final() |

16 | * are externally useful functions. Routines to test the hash are included |

17 | * if SELF_TEST is defined. You can use this free for any purpose. It's in |

18 | * the public domain. It has no warranty. |

19 | * |

20 | * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu) |

21 | * |

22 | * I've modified Bob's hash to be useful in the Linux kernel, and |

23 | * any bugs present are my fault. |

24 | * Jozsef |

25 | */ |

26 | #include <linux/bitops.h> |

27 | #include <linux/unaligned/packed_struct.h> |

28 | |

29 | /* Best hash sizes are of power of two */ |

30 | #define jhash_size(n) ((u32)1<<(n)) |

31 | /* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */ |

32 | #define jhash_mask(n) (jhash_size(n)-1) |

33 | |

34 | /* __jhash_mix -- mix 3 32-bit values reversibly. */ |

35 | #define __jhash_mix(a, b, c) \ |

36 | { \ |

37 | a -= c; a ^= rol32(c, 4); c += b; \ |

38 | b -= a; b ^= rol32(a, 6); a += c; \ |

39 | c -= b; c ^= rol32(b, 8); b += a; \ |

40 | a -= c; a ^= rol32(c, 16); c += b; \ |

41 | b -= a; b ^= rol32(a, 19); a += c; \ |

42 | c -= b; c ^= rol32(b, 4); b += a; \ |

43 | } |

44 | |

45 | /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */ |

46 | #define __jhash_final(a, b, c) \ |

47 | { \ |

48 | c ^= b; c -= rol32(b, 14); \ |

49 | a ^= c; a -= rol32(c, 11); \ |

50 | b ^= a; b -= rol32(a, 25); \ |

51 | c ^= b; c -= rol32(b, 16); \ |

52 | a ^= c; a -= rol32(c, 4); \ |

53 | b ^= a; b -= rol32(a, 14); \ |

54 | c ^= b; c -= rol32(b, 24); \ |

55 | } |

56 | |

57 | /* An arbitrary initial parameter */ |

58 | #define JHASH_INITVAL 0xdeadbeef |

59 | |

60 | /* jhash - hash an arbitrary key |

61 | * @k: sequence of bytes as key |

62 | * @length: the length of the key |

63 | * @initval: the previous hash, or an arbitray value |

64 | * |

65 | * The generic version, hashes an arbitrary sequence of bytes. |

66 | * No alignment or length assumptions are made about the input key. |

67 | * |

68 | * Returns the hash value of the key. The result depends on endianness. |

69 | */ |

70 | static inline u32 jhash(const void *key, u32 length, u32 initval) |

71 | { |

72 | u32 a, b, c; |

73 | const u8 *k = key; |

74 | |

75 | /* Set up the internal state */ |

76 | a = b = c = JHASH_INITVAL + length + initval; |

77 | |

78 | /* All but the last block: affect some 32 bits of (a,b,c) */ |

79 | while (length > 12) { |

80 | a += __get_unaligned_cpu32(k); |

81 | b += __get_unaligned_cpu32(k + 4); |

82 | c += __get_unaligned_cpu32(k + 8); |

83 | __jhash_mix(a, b, c); |

84 | length -= 12; |

85 | k += 12; |

86 | } |

87 | /* Last block: affect all 32 bits of (c) */ |

88 | switch (length) { |

89 | case 12: c += (u32)k[11]<<24; /* fall through */ |

90 | case 11: c += (u32)k[10]<<16; /* fall through */ |

91 | case 10: c += (u32)k[9]<<8; /* fall through */ |

92 | case 9: c += k[8]; /* fall through */ |

93 | case 8: b += (u32)k[7]<<24; /* fall through */ |

94 | case 7: b += (u32)k[6]<<16; /* fall through */ |

95 | case 6: b += (u32)k[5]<<8; /* fall through */ |

96 | case 5: b += k[4]; /* fall through */ |

97 | case 4: a += (u32)k[3]<<24; /* fall through */ |

98 | case 3: a += (u32)k[2]<<16; /* fall through */ |

99 | case 2: a += (u32)k[1]<<8; /* fall through */ |

100 | case 1: a += k[0]; |

101 | __jhash_final(a, b, c); |

102 | case 0: /* Nothing left to add */ |

103 | break; |

104 | } |

105 | |

106 | return c; |

107 | } |

108 | |

109 | /* jhash2 - hash an array of u32's |

110 | * @k: the key which must be an array of u32's |

111 | * @length: the number of u32's in the key |

112 | * @initval: the previous hash, or an arbitray value |

113 | * |

114 | * Returns the hash value of the key. |

115 | */ |

116 | static inline u32 jhash2(const u32 *k, u32 length, u32 initval) |

117 | { |

118 | u32 a, b, c; |

119 | |

120 | /* Set up the internal state */ |

121 | a = b = c = JHASH_INITVAL + (length<<2) + initval; |

122 | |

123 | /* Handle most of the key */ |

124 | while (length > 3) { |

125 | a += k[0]; |

126 | b += k[1]; |

127 | c += k[2]; |

128 | __jhash_mix(a, b, c); |

129 | length -= 3; |

130 | k += 3; |

131 | } |

132 | |

133 | /* Handle the last 3 u32's */ |

134 | switch (length) { |

135 | case 3: c += k[2]; /* fall through */ |

136 | case 2: b += k[1]; /* fall through */ |

137 | case 1: a += k[0]; |

138 | __jhash_final(a, b, c); |

139 | case 0: /* Nothing left to add */ |

140 | break; |

141 | } |

142 | |

143 | return c; |

144 | } |

145 | |

146 | |

147 | /* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */ |

148 | static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval) |

149 | { |

150 | a += initval; |

151 | b += initval; |

152 | c += initval; |

153 | |

154 | __jhash_final(a, b, c); |

155 | |

156 | return c; |

157 | } |

158 | |

159 | static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) |

160 | { |

161 | return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2)); |

162 | } |

163 | |

164 | static inline u32 jhash_2words(u32 a, u32 b, u32 initval) |

165 | { |

166 | return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2)); |

167 | } |

168 | |

169 | static inline u32 jhash_1word(u32 a, u32 initval) |

170 | { |

171 | return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2)); |

172 | } |

173 | |

174 | #endif /* _LINUX_JHASH_H */ |

175 |