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1 | #ifndef HASHMAP_H |
2 | #define HASHMAP_H | |
3 | ||
d40abc8e JK |
4 | #include "hash.h" |
5 | ||
6a364ced KB |
6 | /* |
7 | * Generic implementation of hash-based key-value mappings. | |
1ecbf31d SB |
8 | * |
9 | * An example that maps long to a string: | |
10 | * For the sake of the example this allows to lookup exact values, too | |
11 | * (i.e. it is operated as a set, the value is part of the key) | |
12 | * ------------------------------------- | |
13 | * | |
14 | * struct hashmap map; | |
15 | * struct long2string { | |
16 | * struct hashmap_entry ent; // must be the first member! | |
17 | * long key; | |
18 | * char value[FLEX_ARRAY]; // be careful with allocating on stack! | |
19 | * }; | |
20 | * | |
21 | * #define COMPARE_VALUE 1 | |
22 | * | |
826c778f JS |
23 | * static int long2string_cmp(const void *hashmap_cmp_fn_data, |
24 | * const struct long2string *e1, | |
1ecbf31d | 25 | * const struct long2string *e2, |
826c778f | 26 | * const void *keydata) |
1ecbf31d | 27 | * { |
826c778f JS |
28 | * const char *string = keydata; |
29 | * unsigned flags = *(unsigned *)hashmap_cmp_fn_data; | |
1ecbf31d SB |
30 | * |
31 | * if (flags & COMPARE_VALUE) | |
826c778f JS |
32 | * return e1->key != e2->key || |
33 | * strcmp(e1->value, string ? string : e2->value); | |
1ecbf31d | 34 | * else |
826c778f | 35 | * return e1->key != e2->key; |
1ecbf31d SB |
36 | * } |
37 | * | |
38 | * int main(int argc, char **argv) | |
39 | * { | |
40 | * long key; | |
826c778f JS |
41 | * char value[255], action[32]; |
42 | * unsigned flags = 0; | |
1ecbf31d SB |
43 | * |
44 | * hashmap_init(&map, (hashmap_cmp_fn) long2string_cmp, &flags, 0); | |
45 | * | |
826c778f | 46 | * while (scanf("%s %ld %s", action, &key, value)) { |
1ecbf31d SB |
47 | * |
48 | * if (!strcmp("add", action)) { | |
49 | * struct long2string *e; | |
826c778f | 50 | * FLEX_ALLOC_STR(e, value, value); |
1ecbf31d SB |
51 | * hashmap_entry_init(e, memhash(&key, sizeof(long))); |
52 | * e->key = key; | |
1ecbf31d SB |
53 | * hashmap_add(&map, e); |
54 | * } | |
55 | * | |
56 | * if (!strcmp("print_all_by_key", action)) { | |
826c778f | 57 | * struct long2string k, *e; |
1ecbf31d SB |
58 | * hashmap_entry_init(&k, memhash(&key, sizeof(long))); |
59 | * k.key = key; | |
60 | * | |
826c778f JS |
61 | * flags &= ~COMPARE_VALUE; |
62 | * e = hashmap_get(&map, &k, NULL); | |
1ecbf31d | 63 | * if (e) { |
826c778f JS |
64 | * printf("first: %ld %s\n", e->key, e->value); |
65 | * while ((e = hashmap_get_next(&map, e))) | |
66 | * printf("found more: %ld %s\n", e->key, e->value); | |
1ecbf31d SB |
67 | * } |
68 | * } | |
69 | * | |
70 | * if (!strcmp("has_exact_match", action)) { | |
1ecbf31d | 71 | * struct long2string *e; |
826c778f | 72 | * FLEX_ALLOC_STR(e, value, value); |
1ecbf31d SB |
73 | * hashmap_entry_init(e, memhash(&key, sizeof(long))); |
74 | * e->key = key; | |
1ecbf31d | 75 | * |
826c778f JS |
76 | * flags |= COMPARE_VALUE; |
77 | * printf("%sfound\n", hashmap_get(&map, e, NULL) ? "" : "not "); | |
78 | * free(e); | |
1ecbf31d SB |
79 | * } |
80 | * | |
81 | * if (!strcmp("has_exact_match_no_heap_alloc", action)) { | |
826c778f JS |
82 | * struct long2string k; |
83 | * hashmap_entry_init(&k, memhash(&key, sizeof(long))); | |
84 | * k.key = key; | |
1ecbf31d | 85 | * |
826c778f JS |
86 | * flags |= COMPARE_VALUE; |
87 | * printf("%sfound\n", hashmap_get(&map, &k, value) ? "" : "not "); | |
1ecbf31d SB |
88 | * } |
89 | * | |
90 | * if (!strcmp("end", action)) { | |
91 | * hashmap_free(&map, 1); | |
92 | * break; | |
93 | * } | |
94 | * } | |
826c778f JS |
95 | * |
96 | * return 0; | |
1ecbf31d | 97 | * } |
6a364ced KB |
98 | */ |
99 | ||
1ecbf31d SB |
100 | /* |
101 | * Ready-to-use hash functions for strings, using the FNV-1 algorithm (see | |
102 | * http://www.isthe.com/chongo/tech/comp/fnv). | |
103 | * `strhash` and `strihash` take 0-terminated strings, while `memhash` and | |
104 | * `memihash` operate on arbitrary-length memory. | |
105 | * `strihash` and `memihash` are case insensitive versions. | |
106 | * `memihash_cont` is a variant of `memihash` that allows a computation to be | |
107 | * continued with another chunk of data. | |
108 | */ | |
55454427 DL |
109 | unsigned int strhash(const char *buf); |
110 | unsigned int strihash(const char *buf); | |
111 | unsigned int memhash(const void *buf, size_t len); | |
112 | unsigned int memihash(const void *buf, size_t len); | |
113 | unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len); | |
6a364ced | 114 | |
1ecbf31d SB |
115 | /* |
116 | * Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code | |
117 | * for use in hash tables. Cryptographic hashes are supposed to have | |
118 | * uniform distribution, so in contrast to `memhash()`, this just copies | |
119 | * the first `sizeof(int)` bytes without shuffling any bits. Note that | |
120 | * the results will be different on big-endian and little-endian | |
121 | * platforms, so they should not be stored or transferred over the net. | |
122 | */ | |
d40abc8e | 123 | static inline unsigned int oidhash(const struct object_id *oid) |
039dc71a KB |
124 | { |
125 | /* | |
d40abc8e | 126 | * Equivalent to 'return *(unsigned int *)oid->hash;', but safe on |
039dc71a KB |
127 | * platforms that don't support unaligned reads. |
128 | */ | |
129 | unsigned int hash; | |
d40abc8e | 130 | memcpy(&hash, oid->hash, sizeof(hash)); |
039dc71a KB |
131 | return hash; |
132 | } | |
133 | ||
1ecbf31d SB |
134 | /* |
135 | * struct hashmap_entry is an opaque structure representing an entry in the | |
136 | * hash table, which must be used as first member of user data structures. | |
137 | * Ideally it should be followed by an int-sized member to prevent unused | |
138 | * memory on 64-bit systems due to alignment. | |
139 | */ | |
6a364ced | 140 | struct hashmap_entry { |
1ecbf31d SB |
141 | /* |
142 | * next points to the next entry in case of collisions (i.e. if | |
143 | * multiple entries map to the same bucket) | |
144 | */ | |
6a364ced | 145 | struct hashmap_entry *next; |
1ecbf31d SB |
146 | |
147 | /* entry's hash code */ | |
6a364ced KB |
148 | unsigned int hash; |
149 | }; | |
150 | ||
1ecbf31d SB |
151 | /* |
152 | * User-supplied function to test two hashmap entries for equality. Shall | |
153 | * return 0 if the entries are equal. | |
154 | * | |
155 | * This function is always called with non-NULL `entry` and `entry_or_key` | |
156 | * parameters that have the same hash code. | |
157 | * | |
158 | * When looking up an entry, the `key` and `keydata` parameters to hashmap_get | |
159 | * and hashmap_remove are always passed as second `entry_or_key` and third | |
160 | * argument `keydata`, respectively. Otherwise, `keydata` is NULL. | |
161 | * | |
162 | * When it is too expensive to allocate a user entry (either because it is | |
163 | * large or varialbe sized, such that it is not on the stack), then the | |
164 | * relevant data to check for equality should be passed via `keydata`. | |
165 | * In this case `key` can be a stripped down version of the user key data | |
166 | * or even just a hashmap_entry having the correct hash. | |
167 | * | |
168 | * The `hashmap_cmp_fn_data` entry is the pointer given in the init function. | |
169 | */ | |
7663cdc8 SB |
170 | typedef int (*hashmap_cmp_fn)(const void *hashmap_cmp_fn_data, |
171 | const void *entry, const void *entry_or_key, | |
172 | const void *keydata); | |
6a364ced | 173 | |
1ecbf31d SB |
174 | /* |
175 | * struct hashmap is the hash table structure. Members can be used as follows, | |
176 | * but should not be modified directly. | |
177 | */ | |
6a364ced KB |
178 | struct hashmap { |
179 | struct hashmap_entry **table; | |
1ecbf31d SB |
180 | |
181 | /* Stores the comparison function specified in `hashmap_init()`. */ | |
6a364ced | 182 | hashmap_cmp_fn cmpfn; |
7663cdc8 | 183 | const void *cmpfn_data; |
6a364ced | 184 | |
1ecbf31d | 185 | /* total number of entries (0 means the hashmap is empty) */ |
8b604d19 | 186 | unsigned int private_size; /* use hashmap_get_size() */ |
1ecbf31d SB |
187 | |
188 | /* | |
189 | * tablesize is the allocated size of the hash table. A non-0 value | |
190 | * indicates that the hashmap is initialized. It may also be useful | |
191 | * for statistical purposes (i.e. `size / tablesize` is the current | |
192 | * load factor). | |
193 | */ | |
194 | unsigned int tablesize; | |
195 | ||
196 | unsigned int grow_at; | |
197 | unsigned int shrink_at; | |
198 | ||
8b604d19 | 199 | unsigned int do_count_items : 1; |
6a364ced KB |
200 | }; |
201 | ||
202 | /* hashmap functions */ | |
203 | ||
1ecbf31d SB |
204 | /* |
205 | * Initializes a hashmap structure. | |
206 | * | |
207 | * `map` is the hashmap to initialize. | |
208 | * | |
209 | * The `equals_function` can be specified to compare two entries for equality. | |
210 | * If NULL, entries are considered equal if their hash codes are equal. | |
211 | * | |
212 | * The `equals_function_data` parameter can be used to provide additional data | |
213 | * (a callback cookie) that will be passed to `equals_function` each time it | |
214 | * is called. This allows a single `equals_function` to implement multiple | |
215 | * comparison functions. | |
216 | * | |
217 | * If the total number of entries is known in advance, the `initial_size` | |
218 | * parameter may be used to preallocate a sufficiently large table and thus | |
219 | * prevent expensive resizing. If 0, the table is dynamically resized. | |
220 | */ | |
55454427 | 221 | void hashmap_init(struct hashmap *map, |
7663cdc8 SB |
222 | hashmap_cmp_fn equals_function, |
223 | const void *equals_function_data, | |
224 | size_t initial_size); | |
1ecbf31d SB |
225 | |
226 | /* | |
227 | * Frees a hashmap structure and allocated memory. | |
228 | * | |
229 | * If `free_entries` is true, each hashmap_entry in the map is freed as well | |
230 | * using stdlibs free(). | |
231 | */ | |
55454427 | 232 | void hashmap_free(struct hashmap *map, int free_entries); |
6a364ced KB |
233 | |
234 | /* hashmap_entry functions */ | |
235 | ||
1ecbf31d SB |
236 | /* |
237 | * Initializes a hashmap_entry structure. | |
238 | * | |
239 | * `entry` points to the entry to initialize. | |
240 | * `hash` is the hash code of the entry. | |
241 | * | |
242 | * The hashmap_entry structure does not hold references to external resources, | |
243 | * and it is safe to just discard it once you are done with it (i.e. if | |
244 | * your structure was allocated with xmalloc(), you can just free(3) it, | |
245 | * and if it is on stack, you can just let it go out of scope). | |
246 | */ | |
b6aad994 | 247 | static inline void hashmap_entry_init(void *entry, unsigned int hash) |
6a364ced KB |
248 | { |
249 | struct hashmap_entry *e = entry; | |
250 | e->hash = hash; | |
251 | e->next = NULL; | |
252 | } | |
1ecbf31d | 253 | |
8b604d19 JH |
254 | /* |
255 | * Return the number of items in the map. | |
256 | */ | |
257 | static inline unsigned int hashmap_get_size(struct hashmap *map) | |
258 | { | |
259 | if (map->do_count_items) | |
260 | return map->private_size; | |
261 | ||
262 | BUG("hashmap_get_size: size not set"); | |
263 | return 0; | |
264 | } | |
265 | ||
1ecbf31d SB |
266 | /* |
267 | * Returns the hashmap entry for the specified key, or NULL if not found. | |
268 | * | |
269 | * `map` is the hashmap structure. | |
270 | * | |
271 | * `key` is a user data structure that starts with hashmap_entry that has at | |
272 | * least been initialized with the proper hash code (via `hashmap_entry_init`). | |
273 | * | |
274 | * `keydata` is a data structure that holds just enough information to check | |
275 | * for equality to a given entry. | |
276 | * | |
277 | * If the key data is variable-sized (e.g. a FLEX_ARRAY string) or quite large, | |
278 | * it is undesirable to create a full-fledged entry structure on the heap and | |
279 | * copy all the key data into the structure. | |
280 | * | |
281 | * In this case, the `keydata` parameter can be used to pass | |
282 | * variable-sized key data directly to the comparison function, and the `key` | |
283 | * parameter can be a stripped-down, fixed size entry structure allocated on the | |
284 | * stack. | |
285 | * | |
286 | * If an entry with matching hash code is found, `key` and `keydata` are passed | |
287 | * to `hashmap_cmp_fn` to decide whether the entry matches the key. | |
288 | */ | |
55454427 | 289 | void *hashmap_get(const struct hashmap *map, const void *key, |
1ecbf31d | 290 | const void *keydata); |
6a364ced | 291 | |
1ecbf31d SB |
292 | /* |
293 | * Returns the hashmap entry for the specified hash code and key data, | |
294 | * or NULL if not found. | |
295 | * | |
296 | * `map` is the hashmap structure. | |
297 | * `hash` is the hash code of the entry to look up. | |
298 | * | |
299 | * If an entry with matching hash code is found, `keydata` is passed to | |
300 | * `hashmap_cmp_fn` to decide whether the entry matches the key. The | |
301 | * `entry_or_key` parameter of `hashmap_cmp_fn` points to a hashmap_entry | |
302 | * structure that should not be used in the comparison. | |
303 | */ | |
ab73a9d1 | 304 | static inline void *hashmap_get_from_hash(const struct hashmap *map, |
1ecbf31d SB |
305 | unsigned int hash, |
306 | const void *keydata) | |
ab73a9d1 KB |
307 | { |
308 | struct hashmap_entry key; | |
309 | hashmap_entry_init(&key, hash); | |
310 | return hashmap_get(map, &key, keydata); | |
311 | } | |
312 | ||
1ecbf31d SB |
313 | /* |
314 | * Returns the next equal hashmap entry, or NULL if not found. This can be | |
315 | * used to iterate over duplicate entries (see `hashmap_add`). | |
316 | * | |
317 | * `map` is the hashmap structure. | |
318 | * `entry` is the hashmap_entry to start the search from, obtained via a previous | |
319 | * call to `hashmap_get` or `hashmap_get_next`. | |
320 | */ | |
55454427 | 321 | void *hashmap_get_next(const struct hashmap *map, const void *entry); |
1ecbf31d SB |
322 | |
323 | /* | |
324 | * Adds a hashmap entry. This allows to add duplicate entries (i.e. | |
325 | * separate values with the same key according to hashmap_cmp_fn). | |
326 | * | |
327 | * `map` is the hashmap structure. | |
328 | * `entry` is the entry to add. | |
329 | */ | |
55454427 | 330 | void hashmap_add(struct hashmap *map, void *entry); |
1ecbf31d SB |
331 | |
332 | /* | |
333 | * Adds or replaces a hashmap entry. If the hashmap contains duplicate | |
334 | * entries equal to the specified entry, only one of them will be replaced. | |
335 | * | |
336 | * `map` is the hashmap structure. | |
337 | * `entry` is the entry to add or replace. | |
338 | * Returns the replaced entry, or NULL if not found (i.e. the entry was added). | |
339 | */ | |
55454427 | 340 | void *hashmap_put(struct hashmap *map, void *entry); |
1ecbf31d SB |
341 | |
342 | /* | |
343 | * Removes a hashmap entry matching the specified key. If the hashmap contains | |
344 | * duplicate entries equal to the specified key, only one of them will be | |
345 | * removed. Returns the removed entry, or NULL if not found. | |
346 | * | |
347 | * Argument explanation is the same as in `hashmap_get`. | |
348 | */ | |
55454427 | 349 | void *hashmap_remove(struct hashmap *map, const void *key, |
1ecbf31d SB |
350 | const void *keydata); |
351 | ||
352 | /* | |
353 | * Returns the `bucket` an entry is stored in. | |
354 | * Useful for multithreaded read access. | |
355 | */ | |
0607e100 JH |
356 | int hashmap_bucket(const struct hashmap *map, unsigned int hash); |
357 | ||
1ecbf31d SB |
358 | /* |
359 | * Used to iterate over all entries of a hashmap. Note that it is | |
360 | * not safe to add or remove entries to the hashmap while | |
361 | * iterating. | |
362 | */ | |
363 | struct hashmap_iter { | |
364 | struct hashmap *map; | |
365 | struct hashmap_entry *next; | |
366 | unsigned int tablepos; | |
367 | }; | |
6a364ced | 368 | |
1ecbf31d | 369 | /* Initializes a `hashmap_iter` structure. */ |
55454427 | 370 | void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter); |
1ecbf31d SB |
371 | |
372 | /* Returns the next hashmap_entry, or NULL if there are no more entries. */ | |
55454427 | 373 | void *hashmap_iter_next(struct hashmap_iter *iter); |
1ecbf31d SB |
374 | |
375 | /* Initializes the iterator and returns the first entry, if any. */ | |
6a364ced KB |
376 | static inline void *hashmap_iter_first(struct hashmap *map, |
377 | struct hashmap_iter *iter) | |
378 | { | |
379 | hashmap_iter_init(map, iter); | |
380 | return hashmap_iter_next(iter); | |
381 | } | |
382 | ||
8b604d19 JH |
383 | /* |
384 | * Disable item counting and automatic rehashing when adding/removing items. | |
385 | * | |
386 | * Normally, the hashmap keeps track of the number of items in the map | |
387 | * and uses it to dynamically resize it. This (both the counting and | |
388 | * the resizing) can cause problems when the map is being used by | |
389 | * threaded callers (because the hashmap code does not know about the | |
390 | * locking strategy used by the threaded callers and therefore, does | |
391 | * not know how to protect the "private_size" counter). | |
392 | */ | |
393 | static inline void hashmap_disable_item_counting(struct hashmap *map) | |
394 | { | |
395 | map->do_count_items = 0; | |
396 | } | |
397 | ||
398 | /* | |
399 | * Re-enable item couting when adding/removing items. | |
400 | * If counting is currently disabled, it will force count them. | |
401 | * It WILL NOT automatically rehash them. | |
402 | */ | |
403 | static inline void hashmap_enable_item_counting(struct hashmap *map) | |
404 | { | |
8b604d19 JH |
405 | unsigned int n = 0; |
406 | struct hashmap_iter iter; | |
407 | ||
408 | if (map->do_count_items) | |
409 | return; | |
410 | ||
411 | hashmap_iter_init(map, &iter); | |
7d68bb07 | 412 | while (hashmap_iter_next(&iter)) |
8b604d19 JH |
413 | n++; |
414 | ||
415 | map->do_count_items = 1; | |
416 | map->private_size = n; | |
417 | } | |
418 | ||
1ecbf31d | 419 | /* String interning */ |
7b64d42d | 420 | |
1ecbf31d SB |
421 | /* |
422 | * Returns the unique, interned version of the specified string or data, | |
423 | * similar to the `String.intern` API in Java and .NET, respectively. | |
424 | * Interned strings remain valid for the entire lifetime of the process. | |
425 | * | |
426 | * Can be used as `[x]strdup()` or `xmemdupz` replacement, except that interned | |
427 | * strings / data must not be modified or freed. | |
428 | * | |
429 | * Interned strings are best used for short strings with high probability of | |
430 | * duplicates. | |
431 | * | |
432 | * Uses a hashmap to store the pool of interned strings. | |
433 | */ | |
55454427 | 434 | const void *memintern(const void *data, size_t len); |
7b64d42d KB |
435 | static inline const char *strintern(const char *string) |
436 | { | |
437 | return memintern(string, strlen(string)); | |
438 | } | |
439 | ||
6a364ced | 440 | #endif |