freshlybakedca.ke
Git fork
1/*
2 * Generic implementation of hash-based key value mappings.
3 */
4#include "git-compat-util.h"
5#include "hashmap.h"
6
7#define FNV32_BASE ((unsigned int) 0x811c9dc5)
8#define FNV32_PRIME ((unsigned int) 0x01000193)
9
10unsigned 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
18unsigned 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
29unsigned 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
40unsigned 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
53/*
54 * Incorporate another chunk of data into a memihash
55 * computation.
56 */
57unsigned 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
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
76static void alloc_table(struct hashmap *map, unsigned int size)
77{
78 map->tablesize = size;
79 CALLOC_ARRAY(map->table, size);
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
94static inline int entry_equals(const struct hashmap *map,
95 const struct hashmap_entry *e1,
96 const struct hashmap_entry *e2,
97 const void *keydata)
98{
99 return (e1 == e2) ||
100 (e1->hash == e2->hash &&
101 !map->cmpfn(map->cmpfn_data, e1, e2, keydata));
102}
103
104static inline unsigned int bucket(const struct hashmap *map,
105 const struct hashmap_entry *key)
106{
107 return key->hash & (map->tablesize - 1);
108}
109
110int hashmap_bucket(const struct hashmap *map, unsigned int hash)
111{
112 return hash & (map->tablesize - 1);
113}
114
115static void rehash(struct hashmap *map, unsigned int newsize)
116{
117 /* map->table MUST NOT be NULL when this function is called */
118 unsigned int i, oldsize = map->tablesize;
119 struct hashmap_entry **oldtable = map->table;
120
121 alloc_table(map, newsize);
122 for (i = 0; i < oldsize; i++) {
123 struct hashmap_entry *e = oldtable[i];
124 while (e) {
125 struct hashmap_entry *next = e->next;
126 unsigned int b = bucket(map, e);
127 e->next = map->table[b];
128 map->table[b] = e;
129 e = next;
130 }
131 }
132 free(oldtable);
133}
134
135static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
136 const struct hashmap_entry *key, const void *keydata)
137{
138 /* map->table MUST NOT be NULL when this function is called */
139 struct hashmap_entry **e = &map->table[bucket(map, key)];
140 while (*e && !entry_equals(map, *e, key, keydata))
141 e = &(*e)->next;
142 return e;
143}
144
145static int always_equal(const void *cmp_data UNUSED,
146 const struct hashmap_entry *entry1 UNUSED,
147 const struct hashmap_entry *entry2 UNUSED,
148 const void *keydata UNUSED)
149{
150 return 0;
151}
152
153void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
154 const void *cmpfn_data, size_t initial_size)
155{
156 unsigned int size = HASHMAP_INITIAL_SIZE;
157
158 memset(map, 0, sizeof(*map));
159
160 map->cmpfn = equals_function ? equals_function : always_equal;
161 map->cmpfn_data = cmpfn_data;
162
163 /* calculate initial table size and allocate the table */
164 initial_size = (unsigned int) ((uint64_t) initial_size * 100
165 / HASHMAP_LOAD_FACTOR);
166 while (initial_size > size)
167 size <<= HASHMAP_RESIZE_BITS;
168 alloc_table(map, size);
169
170 /*
171 * Keep track of the number of items in the map and
172 * allow the map to automatically grow as necessary.
173 */
174 map->do_count_items = 1;
175}
176
177static void free_individual_entries(struct hashmap *map, ssize_t entry_offset)
178{
179 struct hashmap_iter iter;
180 struct hashmap_entry *e;
181
182 hashmap_iter_init(map, &iter);
183 while ((e = hashmap_iter_next(&iter)))
184 /*
185 * like container_of, but using caller-calculated
186 * offset (caller being hashmap_clear_and_free)
187 */
188 free((char *)e - entry_offset);
189}
190
191void hashmap_partial_clear_(struct hashmap *map, ssize_t entry_offset)
192{
193 if (!map || !map->table)
194 return;
195 if (entry_offset >= 0) /* called by hashmap_clear_entries */
196 free_individual_entries(map, entry_offset);
197 memset(map->table, 0, map->tablesize * sizeof(struct hashmap_entry *));
198 map->shrink_at = 0;
199 map->private_size = 0;
200}
201
202void hashmap_clear_(struct hashmap *map, ssize_t entry_offset)
203{
204 if (!map || !map->table)
205 return;
206 if (entry_offset >= 0) /* called by hashmap_clear_and_free */
207 free_individual_entries(map, entry_offset);
208 FREE_AND_NULL(map->table);
209 map->tablesize = 0;
210 map->private_size = 0;
211}
212
213struct hashmap_entry *hashmap_get(const struct hashmap *map,
214 const struct hashmap_entry *key,
215 const void *keydata)
216{
217 if (!map->table)
218 return NULL;
219 return *find_entry_ptr(map, key, keydata);
220}
221
222struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
223 const struct hashmap_entry *entry)
224{
225 struct hashmap_entry *e = entry->next;
226 for (; e; e = e->next)
227 if (entry_equals(map, entry, e, NULL))
228 return e;
229 return NULL;
230}
231
232void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)
233{
234 unsigned int b;
235
236 if (!map->table)
237 alloc_table(map, HASHMAP_INITIAL_SIZE);
238
239 b = bucket(map, entry);
240 /* add entry */
241 entry->next = map->table[b];
242 map->table[b] = entry;
243
244 /* fix size and rehash if appropriate */
245 if (map->do_count_items) {
246 map->private_size++;
247 if (map->private_size > map->grow_at)
248 rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
249 }
250}
251
252struct hashmap_entry *hashmap_remove(struct hashmap *map,
253 const struct hashmap_entry *key,
254 const void *keydata)
255{
256 struct hashmap_entry *old;
257 struct hashmap_entry **e;
258
259 if (!map->table)
260 return NULL;
261 e = find_entry_ptr(map, key, keydata);
262 if (!*e)
263 return NULL;
264
265 /* remove existing entry */
266 old = *e;
267 *e = old->next;
268 old->next = NULL;
269
270 /* fix size and rehash if appropriate */
271 if (map->do_count_items) {
272 map->private_size--;
273 if (map->private_size < map->shrink_at)
274 rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
275 }
276
277 return old;
278}
279
280struct hashmap_entry *hashmap_put(struct hashmap *map,
281 struct hashmap_entry *entry)
282{
283 struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
284 hashmap_add(map, entry);
285 return old;
286}
287
288void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
289{
290 iter->map = map;
291 iter->tablepos = 0;
292 iter->next = NULL;
293}
294
295struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)
296{
297 struct hashmap_entry *current = iter->next;
298 for (;;) {
299 if (current) {
300 iter->next = current->next;
301 return current;
302 }
303
304 if (iter->tablepos >= iter->map->tablesize)
305 return NULL;
306
307 current = iter->map->table[iter->tablepos++];
308 }
309}
310
311struct pool_entry {
312 struct hashmap_entry ent;
313 size_t len;
314 unsigned char data[FLEX_ARRAY];
315};
316
317static int pool_entry_cmp(const void *cmp_data UNUSED,
318 const struct hashmap_entry *eptr,
319 const struct hashmap_entry *entry_or_key,
320 const void *keydata)
321{
322 const struct pool_entry *e1, *e2;
323
324 e1 = container_of(eptr, const struct pool_entry, ent);
325 e2 = container_of(entry_or_key, const struct pool_entry, ent);
326
327 return e1->data != keydata &&
328 (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
329}
330
331const void *memintern(const void *data, size_t len)
332{
333 static struct hashmap map;
334 struct pool_entry key, *e;
335
336 /* initialize string pool hashmap */
337 if (!map.tablesize)
338 hashmap_init(&map, pool_entry_cmp, NULL, 0);
339
340 /* lookup interned string in pool */
341 hashmap_entry_init(&key.ent, memhash(data, len));
342 key.len = len;
343 e = hashmap_get_entry(&map, &key, ent, data);
344 if (!e) {
345 /* not found: create it */
346 FLEX_ALLOC_MEM(e, data, data, len);
347 hashmap_entry_init(&e->ent, key.ent.hash);
348 e->len = len;
349 hashmap_add(&map, &e->ent);
350 }
351 return e->data;
352}