6 #include "compiler/compiler.h"
8 /* Fast hashing routine for a long.
9 (C) 2002 William Lee Irwin III, IBM */
12 * Although a random odd number will do, it turns out that the golden
13 * ratio phi = (sqrt(5)-1)/2, or its negative, has particularly nice
16 * These are the negative, (1 - phi) = (phi^2) = (3 - sqrt(5))/2.
17 * (See Knuth vol 3, section 6.4, exercise 9.)
19 #define GOLDEN_RATIO_32 0x61C88647
20 #define GOLDEN_RATIO_64 0x61C8864680B583EBull
22 static inline unsigned long __hash_long(uint64_t val)
26 #if BITS_PER_LONG == 64
27 hash *= GOLDEN_RATIO_64;
29 /* Sigh, gcc can't optimise this alone like it does for 32 bits. */
48 static inline unsigned long hash_long(unsigned long val, unsigned int bits)
50 /* High bits are more random, so use them. */
51 return __hash_long(val) >> (BITS_PER_LONG - bits);
54 static inline uint64_t __hash_u64(uint64_t val)
56 return val * GOLDEN_RATIO_64;
59 static inline unsigned long hash_ptr(void *ptr, unsigned int bits)
61 return hash_long((uintptr_t)ptr, bits);
68 #define JHASH_INITVAL GOLDEN_RATIO_32
70 static inline uint32_t rol32(uint32_t word, uint32_t shift)
72 return (word << shift) | (word >> (32 - shift));
75 /* __jhash_mix -- mix 3 32-bit values reversibly. */
76 #define __jhash_mix(a, b, c) \
78 a -= c; a ^= rol32(c, 4); c += b; \
79 b -= a; b ^= rol32(a, 6); a += c; \
80 c -= b; c ^= rol32(b, 8); b += a; \
81 a -= c; a ^= rol32(c, 16); c += b; \
82 b -= a; b ^= rol32(a, 19); a += c; \
83 c -= b; c ^= rol32(b, 4); b += a; \
86 /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
87 #define __jhash_final(a, b, c) \
89 c ^= b; c -= rol32(b, 14); \
90 a ^= c; a -= rol32(c, 11); \
91 b ^= a; b -= rol32(a, 25); \
92 c ^= b; c -= rol32(b, 16); \
93 a ^= c; a -= rol32(c, 4); \
94 b ^= a; b -= rol32(a, 14); \
95 c ^= b; c -= rol32(b, 24); \
98 static inline uint32_t jhash(const void *key, uint32_t length, uint32_t initval)
100 const uint8_t *k = key;
103 /* Set up the internal state */
104 a = b = c = JHASH_INITVAL + length + initval;
106 /* All but the last block: affect some 32 bits of (a,b,c) */
107 while (length > 12) {
111 __jhash_mix(a, b, c);
116 /* Last block: affect all 32 bits of (c) */
117 /* All the case statements fall through */
119 case 12: c += (uint32_t) k[11] << 24; fio_fallthrough;
120 case 11: c += (uint32_t) k[10] << 16; fio_fallthrough;
121 case 10: c += (uint32_t) k[9] << 8; fio_fallthrough;
122 case 9: c += k[8]; fio_fallthrough;
123 case 8: b += (uint32_t) k[7] << 24; fio_fallthrough;
124 case 7: b += (uint32_t) k[6] << 16; fio_fallthrough;
125 case 6: b += (uint32_t) k[5] << 8; fio_fallthrough;
126 case 5: b += k[4]; fio_fallthrough;
127 case 4: a += (uint32_t) k[3] << 24; fio_fallthrough;
128 case 3: a += (uint32_t) k[2] << 16; fio_fallthrough;
129 case 2: a += (uint32_t) k[1] << 8; fio_fallthrough;
131 __jhash_final(a, b, c);
133 case 0: /* Nothing left to add */
140 #endif /* _LINUX_HASH_H */