clone: initialize atexit cleanup handler earlier
[git.git] / hashmap.c
blobd1b8056d8d53c35d62599999026766a4342eb764
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;
53 #define HASHMAP_INITIAL_SIZE 64
54 /* grow / shrink by 2^2 */
55 #define HASHMAP_RESIZE_BITS 2
56 /* load factor in percent */
57 #define HASHMAP_LOAD_FACTOR 80
59 static void alloc_table(struct hashmap *map, unsigned int size)
61 map->tablesize = size;
62 map->table = xcalloc(size, sizeof(struct hashmap_entry *));
64 /* calculate resize thresholds for new size */
65 map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
66 if (size <= HASHMAP_INITIAL_SIZE)
67 map->shrink_at = 0;
68 else
70 * The shrink-threshold must be slightly smaller than
71 * (grow-threshold / resize-factor) to prevent erratic resizing,
72 * thus we divide by (resize-factor + 1).
74 map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
77 static inline int entry_equals(const struct hashmap *map,
78 const struct hashmap_entry *e1, const struct hashmap_entry *e2,
79 const void *keydata)
81 return (e1 == e2) || (e1->hash == e2->hash && !map->cmpfn(e1, e2, keydata));
84 static inline unsigned int bucket(const struct hashmap *map,
85 const struct hashmap_entry *key)
87 return key->hash & (map->tablesize - 1);
90 static void rehash(struct hashmap *map, unsigned int newsize)
92 unsigned int i, oldsize = map->tablesize;
93 struct hashmap_entry **oldtable = map->table;
95 alloc_table(map, newsize);
96 for (i = 0; i < oldsize; i++) {
97 struct hashmap_entry *e = oldtable[i];
98 while (e) {
99 struct hashmap_entry *next = e->next;
100 unsigned int b = bucket(map, e);
101 e->next = map->table[b];
102 map->table[b] = e;
103 e = next;
106 free(oldtable);
109 static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
110 const struct hashmap_entry *key, const void *keydata)
112 struct hashmap_entry **e = &map->table[bucket(map, key)];
113 while (*e && !entry_equals(map, *e, key, keydata))
114 e = &(*e)->next;
115 return e;
118 static int always_equal(const void *unused1, const void *unused2, const void *unused3)
120 return 0;
123 void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
124 size_t initial_size)
126 unsigned int size = HASHMAP_INITIAL_SIZE;
127 map->size = 0;
128 map->cmpfn = equals_function ? equals_function : always_equal;
130 /* calculate initial table size and allocate the table */
131 initial_size = (unsigned int) ((uint64_t) initial_size * 100
132 / HASHMAP_LOAD_FACTOR);
133 while (initial_size > size)
134 size <<= HASHMAP_RESIZE_BITS;
135 alloc_table(map, size);
138 void hashmap_free(struct hashmap *map, int free_entries)
140 if (!map || !map->table)
141 return;
142 if (free_entries) {
143 struct hashmap_iter iter;
144 struct hashmap_entry *e;
145 hashmap_iter_init(map, &iter);
146 while ((e = hashmap_iter_next(&iter)))
147 free(e);
149 free(map->table);
150 memset(map, 0, sizeof(*map));
153 void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)
155 return *find_entry_ptr(map, key, keydata);
158 void *hashmap_get_next(const struct hashmap *map, const void *entry)
160 struct hashmap_entry *e = ((struct hashmap_entry *) entry)->next;
161 for (; e; e = e->next)
162 if (entry_equals(map, entry, e, NULL))
163 return e;
164 return NULL;
167 void hashmap_add(struct hashmap *map, void *entry)
169 unsigned int b = bucket(map, entry);
171 /* add entry */
172 ((struct hashmap_entry *) entry)->next = map->table[b];
173 map->table[b] = entry;
175 /* fix size and rehash if appropriate */
176 map->size++;
177 if (map->size > map->grow_at)
178 rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
181 void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)
183 struct hashmap_entry *old;
184 struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
185 if (!*e)
186 return NULL;
188 /* remove existing entry */
189 old = *e;
190 *e = old->next;
191 old->next = NULL;
193 /* fix size and rehash if appropriate */
194 map->size--;
195 if (map->size < map->shrink_at)
196 rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
197 return old;
200 void *hashmap_put(struct hashmap *map, void *entry)
202 struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
203 hashmap_add(map, entry);
204 return old;
207 void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
209 iter->map = map;
210 iter->tablepos = 0;
211 iter->next = NULL;
214 void *hashmap_iter_next(struct hashmap_iter *iter)
216 struct hashmap_entry *current = iter->next;
217 for (;;) {
218 if (current) {
219 iter->next = current->next;
220 return current;
223 if (iter->tablepos >= iter->map->tablesize)
224 return NULL;
226 current = iter->map->table[iter->tablepos++];