Merge branch 'cb/test-use-ere-for-alternation'
[git.git] / hashmap.c
blob09813e1a46676c1475c1ad903f1d9358bf56827e
1 /*
2 * Generic implementation of hash-based key value mappings.
3 */
4 #include "cache.h"
5 #include "hashmap.h"
7 #define FNV32_BASE ((unsigned int) 0x811c9dc5)
8 #define FNV32_PRIME ((unsigned int) 0x01000193)
10 unsigned int strhash(const char *str)
12 unsigned int c, hash = FNV32_BASE;
13 while ((c = (unsigned char) *str++))
14 hash = (hash * FNV32_PRIME) ^ c;
15 return hash;
18 unsigned int strihash(const char *str)
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;
26 return hash;
29 unsigned int memhash(const void *buf, size_t len)
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;
37 return hash;
40 unsigned int memihash(const void *buf, size_t len)
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;
50 return hash;
54 * Incorporate another chunk of data into a memihash
55 * computation.
57 unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
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;
67 return hash;
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
76 static void alloc_table(struct hashmap *map, unsigned int size)
78 map->tablesize = size;
79 map->table = xcalloc(size, sizeof(struct hashmap_entry *));
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
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).
91 map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
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)
98 return (e1 == e2) ||
99 (e1->hash == e2->hash &&
100 !map->cmpfn(map->cmpfn_data, e1, e2, keydata));
103 static inline unsigned int bucket(const struct hashmap *map,
104 const struct hashmap_entry *key)
106 return key->hash & (map->tablesize - 1);
109 int hashmap_bucket(const struct hashmap *map, unsigned int hash)
111 return hash & (map->tablesize - 1);
114 static void rehash(struct hashmap *map, unsigned int newsize)
116 unsigned int i, oldsize = map->tablesize;
117 struct hashmap_entry **oldtable = map->table;
119 alloc_table(map, newsize);
120 for (i = 0; i < oldsize; i++) {
121 struct hashmap_entry *e = oldtable[i];
122 while (e) {
123 struct hashmap_entry *next = e->next;
124 unsigned int b = bucket(map, e);
125 e->next = map->table[b];
126 map->table[b] = e;
127 e = next;
130 free(oldtable);
133 static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
134 const struct hashmap_entry *key, const void *keydata)
136 struct hashmap_entry **e = &map->table[bucket(map, key)];
137 while (*e && !entry_equals(map, *e, key, keydata))
138 e = &(*e)->next;
139 return e;
142 static int always_equal(const void *unused_cmp_data,
143 const struct hashmap_entry *unused1,
144 const struct hashmap_entry *unused2,
145 const void *unused_keydata)
147 return 0;
150 void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
151 const void *cmpfn_data, size_t initial_size)
153 unsigned int size = HASHMAP_INITIAL_SIZE;
155 memset(map, 0, sizeof(*map));
157 map->cmpfn = equals_function ? equals_function : always_equal;
158 map->cmpfn_data = cmpfn_data;
160 /* calculate initial table size and allocate the table */
161 initial_size = (unsigned int) ((uint64_t) initial_size * 100
162 / HASHMAP_LOAD_FACTOR);
163 while (initial_size > size)
164 size <<= HASHMAP_RESIZE_BITS;
165 alloc_table(map, size);
168 * Keep track of the number of items in the map and
169 * allow the map to automatically grow as necessary.
171 map->do_count_items = 1;
174 void hashmap_free_(struct hashmap *map, ssize_t entry_offset)
176 if (!map || !map->table)
177 return;
178 if (entry_offset >= 0) { /* called by hashmap_free_entries */
179 struct hashmap_iter iter;
180 struct hashmap_entry *e;
182 hashmap_iter_init(map, &iter);
183 while ((e = hashmap_iter_next(&iter)))
185 * like container_of, but using caller-calculated
186 * offset (caller being hashmap_free_entries)
188 free((char *)e - entry_offset);
190 free(map->table);
191 memset(map, 0, sizeof(*map));
194 struct hashmap_entry *hashmap_get(const struct hashmap *map,
195 const struct hashmap_entry *key,
196 const void *keydata)
198 return *find_entry_ptr(map, key, keydata);
201 struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
202 const struct hashmap_entry *entry)
204 struct hashmap_entry *e = entry->next;
205 for (; e; e = e->next)
206 if (entry_equals(map, entry, e, NULL))
207 return e;
208 return NULL;
211 void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)
213 unsigned int b = bucket(map, entry);
215 /* add entry */
216 entry->next = map->table[b];
217 map->table[b] = entry;
219 /* fix size and rehash if appropriate */
220 if (map->do_count_items) {
221 map->private_size++;
222 if (map->private_size > map->grow_at)
223 rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
227 struct hashmap_entry *hashmap_remove(struct hashmap *map,
228 const struct hashmap_entry *key,
229 const void *keydata)
231 struct hashmap_entry *old;
232 struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
233 if (!*e)
234 return NULL;
236 /* remove existing entry */
237 old = *e;
238 *e = old->next;
239 old->next = NULL;
241 /* fix size and rehash if appropriate */
242 if (map->do_count_items) {
243 map->private_size--;
244 if (map->private_size < map->shrink_at)
245 rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
248 return old;
251 struct hashmap_entry *hashmap_put(struct hashmap *map,
252 struct hashmap_entry *entry)
254 struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
255 hashmap_add(map, entry);
256 return old;
259 void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
261 iter->map = map;
262 iter->tablepos = 0;
263 iter->next = NULL;
266 struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)
268 struct hashmap_entry *current = iter->next;
269 for (;;) {
270 if (current) {
271 iter->next = current->next;
272 return current;
275 if (iter->tablepos >= iter->map->tablesize)
276 return NULL;
278 current = iter->map->table[iter->tablepos++];
282 struct pool_entry {
283 struct hashmap_entry ent;
284 size_t len;
285 unsigned char data[FLEX_ARRAY];
288 static int pool_entry_cmp(const void *unused_cmp_data,
289 const struct hashmap_entry *eptr,
290 const struct hashmap_entry *entry_or_key,
291 const void *keydata)
293 const struct pool_entry *e1, *e2;
295 e1 = container_of(eptr, const struct pool_entry, ent);
296 e2 = container_of(entry_or_key, const struct pool_entry, ent);
298 return e1->data != keydata &&
299 (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
302 const void *memintern(const void *data, size_t len)
304 static struct hashmap map;
305 struct pool_entry key, *e;
307 /* initialize string pool hashmap */
308 if (!map.tablesize)
309 hashmap_init(&map, pool_entry_cmp, NULL, 0);
311 /* lookup interned string in pool */
312 hashmap_entry_init(&key.ent, memhash(data, len));
313 key.len = len;
314 e = hashmap_get_entry(&map, &key, ent, data);
315 if (!e) {
316 /* not found: create it */
317 FLEX_ALLOC_MEM(e, data, data, len);
318 hashmap_entry_init(&e->ent, key.ent.hash);
319 e->len = len;
320 hashmap_add(&map, &e->ent);
322 return e->data;