projects / lttng-ust.git / blame
| Commit | Line | Data |
|---|---|---|
| bf956ec0 | 1 | /* |
| c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| bf956ec0 MD |
3 | * |
| 4 | * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
| 5 | * | |
| c0c0989a | 6 | * LTTng hash table helpers. |
| bf956ec0 MD |
7 | */ |
| 8 | ||
| c0c0989a MJ |
9 | #ifndef _LTTNG_HASH_HELPER_H |
| 10 | #define _LTTNG_HASH_HELPER_H | |
| 11 | ||
| bf956ec0 | 12 | #include <assert.h> |
| b4051ad8 | 13 | #include <stddef.h> |
| bf956ec0 MD |
14 | #include <stdint.h> |
| 15 | #include <urcu/compiler.h> | |
| 16 | ||
| 17 | /* | |
| 18 | * Hash function | |
| 19 | * Source: http://burtleburtle.net/bob/c/lookup3.c | |
| 20 | * Originally Public Domain | |
| 21 | */ | |
| 22 | ||
| 23 | #define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k)))) | |
| 24 | ||
| 25 | #define mix(a, b, c) \ | |
| 26 | do { \ | |
| 27 | a -= c; a ^= rot(c, 4); c += b; \ | |
| 28 | b -= a; b ^= rot(a, 6); a += c; \ | |
| 29 | c -= b; c ^= rot(b, 8); b += a; \ | |
| 30 | a -= c; a ^= rot(c, 16); c += b; \ | |
| 31 | b -= a; b ^= rot(a, 19); a += c; \ | |
| 32 | c -= b; c ^= rot(b, 4); b += a; \ | |
| 33 | } while (0) | |
| 34 | ||
| 35 | #define final(a, b, c) \ | |
| 36 | { \ | |
| 37 | c ^= b; c -= rot(b, 14); \ | |
| 38 | a ^= c; a -= rot(c, 11); \ | |
| 39 | b ^= a; b -= rot(a, 25); \ | |
| 40 | c ^= b; c -= rot(b, 16); \ | |
| 41 | a ^= c; a -= rot(c, 4);\ | |
| 42 | b ^= a; b -= rot(a, 14); \ | |
| 43 | c ^= b; c -= rot(b, 24); \ | |
| 44 | } | |
| 45 | ||
| 46 | static inline __attribute__((unused)) | |
| 47 | uint32_t lttng_hash_u32( | |
| 48 | const uint32_t *k, /* the key, an array of uint32_t values */ | |
| 49 | size_t length, /* the length of the key, in uint32_ts */ | |
| 50 | uint32_t initval) /* the previous hash, or an arbitrary value */ | |
| 51 | { | |
| 52 | uint32_t a, b, c; | |
| 53 | ||
| 54 | /* Set up the internal state */ | |
| 55 | a = b = c = 0xdeadbeef + (((uint32_t) length) << 2) + initval; | |
| 56 | ||
| 57 | /*----------------------------------------- handle most of the key */ | |
| 58 | while (length > 3) { | |
| 59 | a += k[0]; | |
| 60 | b += k[1]; | |
| 61 | c += k[2]; | |
| 62 | mix(a, b, c); | |
| 63 | length -= 3; | |
| 64 | k += 3; | |
| 65 | } | |
| 66 | ||
| 67 | /*----------------------------------- handle the last 3 uint32_t's */ | |
| 68 | switch (length) { /* all the case statements fall through */ | |
| 69 | case 3: c += k[2]; | |
| 70 | case 2: b += k[1]; | |
| 71 | case 1: a += k[0]; | |
| 72 | final(a, b, c); | |
| 73 | case 0: /* case 0: nothing left to add */ | |
| 74 | break; | |
| 75 | } | |
| 76 | /*---------------------------------------------- report the result */ | |
| 77 | return c; | |
| 78 | } | |
| 79 | ||
| 80 | static inline | |
| 81 | void lttng_hashword2( | |
| 82 | const uint32_t *k, /* the key, an array of uint32_t values */ | |
| 83 | size_t length, /* the length of the key, in uint32_ts */ | |
| 84 | uint32_t *pc, /* IN: seed OUT: primary hash value */ | |
| 85 | uint32_t *pb) /* IN: more seed OUT: secondary hash value */ | |
| 86 | { | |
| 87 | uint32_t a, b, c; | |
| 88 | ||
| 89 | /* Set up the internal state */ | |
| 90 | a = b = c = 0xdeadbeef + ((uint32_t) (length << 2)) + *pc; | |
| 91 | c += *pb; | |
| 92 | ||
| 93 | /*----------------------------------------- handle most of the key */ | |
| 94 | while (length > 3) { | |
| 95 | a += k[0]; | |
| 96 | b += k[1]; | |
| 97 | c += k[2]; | |
| 98 | mix(a, b, c); | |
| 99 | length -= 3; | |
| 100 | k += 3; | |
| 101 | } | |
| 102 | ||
| 103 | /*----------------------------------- handle the last 3 uint32_t's */ | |
| 104 | switch (length) { /* all the case statements fall through */ | |
| 105 | case 3: c += k[2]; | |
| 106 | case 2: b += k[1]; | |
| 107 | case 1: a += k[0]; | |
| 108 | final(a, b, c); | |
| 109 | case 0: /* case 0: nothing left to add */ | |
| 110 | break; | |
| 111 | } | |
| 112 | /*---------------------------------------------- report the result */ | |
| 113 | *pc = c; | |
| 114 | *pb = b; | |
| 115 | } | |
| 116 | ||
| 117 | #if (CAA_BITS_PER_LONG == 32) | |
| 118 | static inline | |
| 119 | unsigned long lttng_hash_mix(const void *_key, size_t length, unsigned long seed) | |
| 120 | { | |
| 121 | unsigned int key = (unsigned int) _key; | |
| 122 | ||
| 123 | assert(length == sizeof(unsigned int)); | |
| 124 | return lttng_hash_u32(&key, 1, seed); | |
| 125 | } | |
| 126 | #else | |
| 127 | static inline | |
| 128 | unsigned long lttng_hash_mix(const void *_key, size_t length, unsigned long seed) | |
| 129 | { | |
| 130 | union { | |
| 131 | uint64_t v64; | |
| 132 | uint32_t v32[2]; | |
| 133 | } v; | |
| 134 | union { | |
| 135 | uint64_t v64; | |
| 136 | uint32_t v32[2]; | |
| 137 | } key; | |
| 138 | ||
| 139 | assert(length == sizeof(unsigned long)); | |
| 140 | v.v64 = (uint64_t) seed; | |
| 141 | key.v64 = (uint64_t) _key; | |
| 142 | lttng_hashword2(key.v32, 2, &v.v32[0], &v.v32[1]); | |
| 143 | return v.v64; | |
| 144 | } | |
| 145 | #endif | |
| 146 | ||
| 147 | #endif /* _LTTNG_HASH_HELPER_H */ |