projects / lttng-ust.git / blame
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1 | #ifndef _LTTNG_HASH_HELPER_H |
| 2 | #define _LTTNG_HASH_HELPER_H | |
| 3 | ||
| 4 | /* | |
| 5 | * lttng-hash-helper.h | |
| 6 | * | |
| 7 | * LTTng hash table helpers. | |
| 8 | * | |
| 9 | * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
| 10 | * | |
| 11 | * This library is free software; you can redistribute it and/or | |
| 12 | * modify it under the terms of the GNU Lesser General Public | |
| 13 | * License as published by the Free Software Foundation; only | |
| 14 | * version 2.1 of the License. | |
| 15 | * | |
| 16 | * This library is distributed in the hope that it will be useful, | |
| 17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 19 | * Lesser General Public License for more details. | |
| 20 | * | |
| 21 | * You should have received a copy of the GNU Lesser General Public | |
| 22 | * License along with this library; if not, write to the Free Software | |
| 23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
| 24 | */ | |
| 25 | ||
| 26 | #include <assert.h> | |
| b4051ad8 | 27 | #include <stddef.h> |
| bf956ec0 MD |
28 | #include <stdint.h> |
| 29 | #include <urcu/compiler.h> | |
| 30 | ||
| 31 | /* | |
| 32 | * Hash function | |
| 33 | * Source: http://burtleburtle.net/bob/c/lookup3.c | |
| 34 | * Originally Public Domain | |
| 35 | */ | |
| 36 | ||
| 37 | #define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k)))) | |
| 38 | ||
| 39 | #define mix(a, b, c) \ | |
| 40 | do { \ | |
| 41 | a -= c; a ^= rot(c, 4); c += b; \ | |
| 42 | b -= a; b ^= rot(a, 6); a += c; \ | |
| 43 | c -= b; c ^= rot(b, 8); b += a; \ | |
| 44 | a -= c; a ^= rot(c, 16); c += b; \ | |
| 45 | b -= a; b ^= rot(a, 19); a += c; \ | |
| 46 | c -= b; c ^= rot(b, 4); b += a; \ | |
| 47 | } while (0) | |
| 48 | ||
| 49 | #define final(a, b, c) \ | |
| 50 | { \ | |
| 51 | c ^= b; c -= rot(b, 14); \ | |
| 52 | a ^= c; a -= rot(c, 11); \ | |
| 53 | b ^= a; b -= rot(a, 25); \ | |
| 54 | c ^= b; c -= rot(b, 16); \ | |
| 55 | a ^= c; a -= rot(c, 4);\ | |
| 56 | b ^= a; b -= rot(a, 14); \ | |
| 57 | c ^= b; c -= rot(b, 24); \ | |
| 58 | } | |
| 59 | ||
| 60 | static inline __attribute__((unused)) | |
| 61 | uint32_t lttng_hash_u32( | |
| 62 | const uint32_t *k, /* the key, an array of uint32_t values */ | |
| 63 | size_t length, /* the length of the key, in uint32_ts */ | |
| 64 | uint32_t initval) /* the previous hash, or an arbitrary value */ | |
| 65 | { | |
| 66 | uint32_t a, b, c; | |
| 67 | ||
| 68 | /* Set up the internal state */ | |
| 69 | a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval; | |
| 70 | ||
| 71 | /*----------------------------------------- handle most of the key */ | |
| 72 | while (length > 3) { | |
| 73 | a += k[0]; | |
| 74 | b += k[1]; | |
| 75 | c += k[2]; | |
| 76 | mix(a, b, c); | |
| 77 | length -= 3; | |
| 78 | k += 3; | |
| 79 | } | |
| 80 | ||
| 81 | /*----------------------------------- handle the last 3 uint32_t's */ | |
| 82 | switch (length) { /* all the case statements fall through */ | |
| 83 | case 3: c += k[2]; | |
| 84 | case 2: b += k[1]; | |
| 85 | case 1: a += k[0]; | |
| 86 | final(a, b, c); | |
| 87 | case 0: /* case 0: nothing left to add */ | |
| 88 | break; | |
| 89 | } | |
| 90 | /*---------------------------------------------- report the result */ | |
| 91 | return c; | |
| 92 | } | |
| 93 | ||
| 94 | static inline | |
| 95 | void lttng_hashword2( | |
| 96 | const uint32_t *k, /* the key, an array of uint32_t values */ | |
| 97 | size_t length, /* the length of the key, in uint32_ts */ | |
| 98 | uint32_t *pc, /* IN: seed OUT: primary hash value */ | |
| 99 | uint32_t *pb) /* IN: more seed OUT: secondary hash value */ | |
| 100 | { | |
| 101 | uint32_t a, b, c; | |
| 102 | ||
| 103 | /* Set up the internal state */ | |
| 104 | a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + *pc; | |
| 105 | c += *pb; | |
| 106 | ||
| 107 | /*----------------------------------------- handle most of the key */ | |
| 108 | while (length > 3) { | |
| 109 | a += k[0]; | |
| 110 | b += k[1]; | |
| 111 | c += k[2]; | |
| 112 | mix(a, b, c); | |
| 113 | length -= 3; | |
| 114 | k += 3; | |
| 115 | } | |
| 116 | ||
| 117 | /*----------------------------------- handle the last 3 uint32_t's */ | |
| 118 | switch (length) { /* all the case statements fall through */ | |
| 119 | case 3: c += k[2]; | |
| 120 | case 2: b += k[1]; | |
| 121 | case 1: a += k[0]; | |
| 122 | final(a, b, c); | |
| 123 | case 0: /* case 0: nothing left to add */ | |
| 124 | break; | |
| 125 | } | |
| 126 | /*---------------------------------------------- report the result */ | |
| 127 | *pc = c; | |
| 128 | *pb = b; | |
| 129 | } | |
| 130 | ||
| 131 | #if (CAA_BITS_PER_LONG == 32) | |
| 132 | static inline | |
| 133 | unsigned long lttng_hash_mix(const void *_key, size_t length, unsigned long seed) | |
| 134 | { | |
| 135 | unsigned int key = (unsigned int) _key; | |
| 136 | ||
| 137 | assert(length == sizeof(unsigned int)); | |
| 138 | return lttng_hash_u32(&key, 1, seed); | |
| 139 | } | |
| 140 | #else | |
| 141 | static inline | |
| 142 | unsigned long lttng_hash_mix(const void *_key, size_t length, unsigned long seed) | |
| 143 | { | |
| 144 | union { | |
| 145 | uint64_t v64; | |
| 146 | uint32_t v32[2]; | |
| 147 | } v; | |
| 148 | union { | |
| 149 | uint64_t v64; | |
| 150 | uint32_t v32[2]; | |
| 151 | } key; | |
| 152 | ||
| 153 | assert(length == sizeof(unsigned long)); | |
| 154 | v.v64 = (uint64_t) seed; | |
| 155 | key.v64 = (uint64_t) _key; | |
| 156 | lttng_hashword2(key.v32, 2, &v.v32[0], &v.v32[1]); | |
| 157 | return v.v64; | |
| 158 | } | |
| 159 | #endif | |
| 160 | ||
| 161 | #endif /* _LTTNG_HASH_HELPER_H */ |