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6a364ced KB |
1 | /* |
2 | * Generic implementation of hash-based key value mappings. | |
3 | */ | |
4 | #include "cache.h" | |
5 | #include "hashmap.h" | |
6 | ||
7 | #define FNV32_BASE ((unsigned int) 0x811c9dc5) | |
8 | #define FNV32_PRIME ((unsigned int) 0x01000193) | |
9 | ||
10 | unsigned int strhash(const char *str) | |
11 | { | |
12 | unsigned int c, hash = FNV32_BASE; | |
13 | while ((c = (unsigned char) *str++)) | |
14 | hash = (hash * FNV32_PRIME) ^ c; | |
15 | return hash; | |
16 | } | |
17 | ||
18 | unsigned int strihash(const char *str) | |
19 | { | |
20 | unsigned int c, hash = FNV32_BASE; | |
21 | while ((c = (unsigned char) *str++)) { | |
22 | if (c >= 'a' && c <= 'z') | |
23 | c -= 'a' - 'A'; | |
24 | hash = (hash * FNV32_PRIME) ^ c; | |
25 | } | |
26 | return hash; | |
27 | } | |
28 | ||
29 | unsigned int memhash(const void *buf, size_t len) | |
30 | { | |
31 | unsigned int hash = FNV32_BASE; | |
32 | unsigned char *ucbuf = (unsigned char *) buf; | |
33 | while (len--) { | |
34 | unsigned int c = *ucbuf++; | |
35 | hash = (hash * FNV32_PRIME) ^ c; | |
36 | } | |
37 | return hash; | |
38 | } | |
39 | ||
40 | unsigned int memihash(const void *buf, size_t len) | |
41 | { | |
42 | unsigned int hash = FNV32_BASE; | |
43 | unsigned char *ucbuf = (unsigned char *) buf; | |
44 | while (len--) { | |
45 | unsigned int c = *ucbuf++; | |
46 | if (c >= 'a' && c <= 'z') | |
47 | c -= 'a' - 'A'; | |
48 | hash = (hash * FNV32_PRIME) ^ c; | |
49 | } | |
50 | return hash; | |
51 | } | |
52 | ||
f75619bd JH |
53 | /* |
54 | * Incoporate another chunk of data into a memihash | |
55 | * computation. | |
56 | */ | |
57 | unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len) | |
58 | { | |
59 | unsigned int hash = hash_seed; | |
60 | unsigned char *ucbuf = (unsigned char *) buf; | |
61 | while (len--) { | |
62 | unsigned int c = *ucbuf++; | |
63 | if (c >= 'a' && c <= 'z') | |
64 | c -= 'a' - 'A'; | |
65 | hash = (hash * FNV32_PRIME) ^ c; | |
66 | } | |
67 | return hash; | |
68 | } | |
69 | ||
6a364ced KB |
70 | #define HASHMAP_INITIAL_SIZE 64 |
71 | /* grow / shrink by 2^2 */ | |
72 | #define HASHMAP_RESIZE_BITS 2 | |
73 | /* load factor in percent */ | |
74 | #define HASHMAP_LOAD_FACTOR 80 | |
75 | ||
76 | static void alloc_table(struct hashmap *map, unsigned int size) | |
77 | { | |
78 | map->tablesize = size; | |
79 | map->table = xcalloc(size, sizeof(struct hashmap_entry *)); | |
80 | ||
81 | /* calculate resize thresholds for new size */ | |
82 | map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100); | |
83 | if (size <= HASHMAP_INITIAL_SIZE) | |
84 | map->shrink_at = 0; | |
85 | else | |
86 | /* | |
87 | * The shrink-threshold must be slightly smaller than | |
88 | * (grow-threshold / resize-factor) to prevent erratic resizing, | |
89 | * thus we divide by (resize-factor + 1). | |
90 | */ | |
91 | map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1); | |
92 | } | |
93 | ||
94 | static inline int entry_equals(const struct hashmap *map, | |
95 | const struct hashmap_entry *e1, const struct hashmap_entry *e2, | |
96 | const void *keydata) | |
97 | { | |
98 | return (e1 == e2) || (e1->hash == e2->hash && !map->cmpfn(e1, e2, keydata)); | |
99 | } | |
100 | ||
101 | static inline unsigned int bucket(const struct hashmap *map, | |
102 | const struct hashmap_entry *key) | |
103 | { | |
104 | return key->hash & (map->tablesize - 1); | |
105 | } | |
106 | ||
0607e100 JH |
107 | int hashmap_bucket(const struct hashmap *map, unsigned int hash) |
108 | { | |
109 | return hash & (map->tablesize - 1); | |
110 | } | |
111 | ||
6a364ced KB |
112 | static void rehash(struct hashmap *map, unsigned int newsize) |
113 | { | |
114 | unsigned int i, oldsize = map->tablesize; | |
115 | struct hashmap_entry **oldtable = map->table; | |
116 | ||
0607e100 JH |
117 | if (map->disallow_rehash) |
118 | return; | |
119 | ||
6a364ced KB |
120 | alloc_table(map, newsize); |
121 | for (i = 0; i < oldsize; i++) { | |
122 | struct hashmap_entry *e = oldtable[i]; | |
123 | while (e) { | |
124 | struct hashmap_entry *next = e->next; | |
125 | unsigned int b = bucket(map, e); | |
126 | e->next = map->table[b]; | |
127 | map->table[b] = e; | |
128 | e = next; | |
129 | } | |
130 | } | |
131 | free(oldtable); | |
132 | } | |
133 | ||
134 | static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map, | |
135 | const struct hashmap_entry *key, const void *keydata) | |
136 | { | |
137 | struct hashmap_entry **e = &map->table[bucket(map, key)]; | |
138 | while (*e && !entry_equals(map, *e, key, keydata)) | |
139 | e = &(*e)->next; | |
140 | return e; | |
141 | } | |
142 | ||
143 | static int always_equal(const void *unused1, const void *unused2, const void *unused3) | |
144 | { | |
145 | return 0; | |
146 | } | |
147 | ||
148 | void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function, | |
149 | size_t initial_size) | |
150 | { | |
151 | unsigned int size = HASHMAP_INITIAL_SIZE; | |
0607e100 JH |
152 | |
153 | memset(map, 0, sizeof(*map)); | |
154 | ||
6a364ced KB |
155 | map->cmpfn = equals_function ? equals_function : always_equal; |
156 | ||
157 | /* calculate initial table size and allocate the table */ | |
158 | initial_size = (unsigned int) ((uint64_t) initial_size * 100 | |
159 | / HASHMAP_LOAD_FACTOR); | |
160 | while (initial_size > size) | |
161 | size <<= HASHMAP_RESIZE_BITS; | |
162 | alloc_table(map, size); | |
163 | } | |
164 | ||
165 | void hashmap_free(struct hashmap *map, int free_entries) | |
166 | { | |
167 | if (!map || !map->table) | |
168 | return; | |
169 | if (free_entries) { | |
170 | struct hashmap_iter iter; | |
171 | struct hashmap_entry *e; | |
172 | hashmap_iter_init(map, &iter); | |
173 | while ((e = hashmap_iter_next(&iter))) | |
174 | free(e); | |
175 | } | |
176 | free(map->table); | |
177 | memset(map, 0, sizeof(*map)); | |
178 | } | |
179 | ||
180 | void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata) | |
181 | { | |
182 | return *find_entry_ptr(map, key, keydata); | |
183 | } | |
184 | ||
185 | void *hashmap_get_next(const struct hashmap *map, const void *entry) | |
186 | { | |
187 | struct hashmap_entry *e = ((struct hashmap_entry *) entry)->next; | |
188 | for (; e; e = e->next) | |
189 | if (entry_equals(map, entry, e, NULL)) | |
190 | return e; | |
191 | return NULL; | |
192 | } | |
193 | ||
194 | void hashmap_add(struct hashmap *map, void *entry) | |
195 | { | |
196 | unsigned int b = bucket(map, entry); | |
197 | ||
198 | /* add entry */ | |
199 | ((struct hashmap_entry *) entry)->next = map->table[b]; | |
200 | map->table[b] = entry; | |
201 | ||
202 | /* fix size and rehash if appropriate */ | |
203 | map->size++; | |
204 | if (map->size > map->grow_at) | |
205 | rehash(map, map->tablesize << HASHMAP_RESIZE_BITS); | |
206 | } | |
207 | ||
208 | void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata) | |
209 | { | |
210 | struct hashmap_entry *old; | |
211 | struct hashmap_entry **e = find_entry_ptr(map, key, keydata); | |
212 | if (!*e) | |
213 | return NULL; | |
214 | ||
215 | /* remove existing entry */ | |
216 | old = *e; | |
217 | *e = old->next; | |
218 | old->next = NULL; | |
219 | ||
220 | /* fix size and rehash if appropriate */ | |
221 | map->size--; | |
222 | if (map->size < map->shrink_at) | |
223 | rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS); | |
224 | return old; | |
225 | } | |
226 | ||
227 | void *hashmap_put(struct hashmap *map, void *entry) | |
228 | { | |
229 | struct hashmap_entry *old = hashmap_remove(map, entry, NULL); | |
230 | hashmap_add(map, entry); | |
231 | return old; | |
232 | } | |
233 | ||
234 | void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter) | |
235 | { | |
236 | iter->map = map; | |
237 | iter->tablepos = 0; | |
238 | iter->next = NULL; | |
239 | } | |
240 | ||
241 | void *hashmap_iter_next(struct hashmap_iter *iter) | |
242 | { | |
243 | struct hashmap_entry *current = iter->next; | |
244 | for (;;) { | |
245 | if (current) { | |
246 | iter->next = current->next; | |
247 | return current; | |
248 | } | |
249 | ||
250 | if (iter->tablepos >= iter->map->tablesize) | |
251 | return NULL; | |
252 | ||
253 | current = iter->map->table[iter->tablepos++]; | |
254 | } | |
255 | } | |
7b64d42d KB |
256 | |
257 | struct pool_entry { | |
258 | struct hashmap_entry ent; | |
259 | size_t len; | |
260 | unsigned char data[FLEX_ARRAY]; | |
261 | }; | |
262 | ||
263 | static int pool_entry_cmp(const struct pool_entry *e1, | |
264 | const struct pool_entry *e2, | |
265 | const unsigned char *keydata) | |
266 | { | |
267 | return e1->data != keydata && | |
268 | (e1->len != e2->len || memcmp(e1->data, keydata, e1->len)); | |
269 | } | |
270 | ||
271 | const void *memintern(const void *data, size_t len) | |
272 | { | |
273 | static struct hashmap map; | |
274 | struct pool_entry key, *e; | |
275 | ||
276 | /* initialize string pool hashmap */ | |
277 | if (!map.tablesize) | |
278 | hashmap_init(&map, (hashmap_cmp_fn) pool_entry_cmp, 0); | |
279 | ||
280 | /* lookup interned string in pool */ | |
281 | hashmap_entry_init(&key, memhash(data, len)); | |
282 | key.len = len; | |
283 | e = hashmap_get(&map, &key, data); | |
284 | if (!e) { | |
285 | /* not found: create it */ | |
96ffc06f | 286 | FLEX_ALLOC_MEM(e, data, data, len); |
7b64d42d KB |
287 | hashmap_entry_init(e, key.ent.hash); |
288 | e->len = len; | |
7b64d42d KB |
289 | hashmap_add(&map, e); |
290 | } | |
291 | return e->data; | |
292 | } |