diff options
Diffstat (limited to 'hashmap.h')
| -rw-r--r-- | hashmap.h | 125 |
1 files changed, 78 insertions, 47 deletions
@@ -1,8 +1,6 @@ #ifndef HASHMAP_H #define HASHMAP_H -#include "hash.h" - /* * Generic implementation of hash-based key-value mappings. * @@ -59,7 +57,7 @@ * * if (!strcmp("print_all_by_key", action)) { * struct long2string k, *e; - * hashmap_entry_init(&k->ent, memhash(&key, sizeof(long))); + * hashmap_entry_init(&k.ent, memhash(&key, sizeof(long))); * k.key = key; * * flags &= ~COMPARE_VALUE; @@ -87,16 +85,16 @@ * * if (!strcmp("has_exact_match_no_heap_alloc", action)) { * struct long2string k; - * hashmap_entry_init(&k->ent, memhash(&key, sizeof(long))); + * hashmap_entry_init(&k.ent, memhash(&key, sizeof(long))); * k.key = key; * * flags |= COMPARE_VALUE; * printf("%sfound\n", - * hashmap_get(&map, &k->ent, value) ? "" : "not "); + * hashmap_get(&map, &k.ent, value) ? "" : "not "); * } * * if (!strcmp("end", action)) { - * hashmap_free_entries(&map, struct long2string, ent); + * hashmap_clear_and_free(&map, struct long2string, ent); * break; * } * } @@ -121,25 +119,6 @@ unsigned int memihash(const void *buf, size_t len); unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len); /* - * Converts a cryptographic hash (e.g. SHA-1) into an int-sized hash code - * for use in hash tables. Cryptographic hashes are supposed to have - * uniform distribution, so in contrast to `memhash()`, this just copies - * the first `sizeof(int)` bytes without shuffling any bits. Note that - * the results will be different on big-endian and little-endian - * platforms, so they should not be stored or transferred over the net. - */ -static inline unsigned int oidhash(const struct object_id *oid) -{ - /* - * Equivalent to 'return *(unsigned int *)oid->hash;', but safe on - * platforms that don't support unaligned reads. - */ - unsigned int hash; - memcpy(&hash, oid->hash, sizeof(hash)); - return hash; -} - -/* * struct hashmap_entry is an opaque structure representing an entry in the * hash table. * Ideally it should be followed by an int-sized member to prevent unused @@ -168,7 +147,7 @@ struct hashmap_entry { * argument `keydata`, respectively. Otherwise, `keydata` is NULL. * * When it is too expensive to allocate a user entry (either because it is - * large or varialbe sized, such that it is not on the stack), then the + * large or variable sized, such that it is not on the stack), then the * relevant data to check for equality should be passed via `keydata`. * In this case `key` can be a stripped down version of the user key data * or even just a hashmap_entry having the correct hash. @@ -210,6 +189,9 @@ struct hashmap { /* hashmap functions */ +#define HASHMAP_INIT(fn, data) { .cmpfn = fn, .cmpfn_data = data, \ + .do_count_items = 1 } + /* * Initializes a hashmap structure. * @@ -228,24 +210,72 @@ struct hashmap { * prevent expensive resizing. If 0, the table is dynamically resized. */ void hashmap_init(struct hashmap *map, - hashmap_cmp_fn equals_function, - const void *equals_function_data, - size_t initial_size); + hashmap_cmp_fn equals_function, + const void *equals_function_data, + size_t initial_size); + +/* internal functions for clearing or freeing hashmap */ +void hashmap_partial_clear_(struct hashmap *map, ssize_t offset); +void hashmap_clear_(struct hashmap *map, ssize_t offset); + +/* + * Frees a hashmap structure and allocated memory for the table, but does not + * free the entries nor anything they point to. + * + * Usage note: + * + * Many callers will need to iterate over all entries and free the data each + * entry points to; in such a case, they can free the entry itself while at it. + * Thus, you might see: + * + * hashmap_for_each_entry(map, hashmap_iter, e, hashmap_entry_name) { + * free(e->somefield); + * free(e); + * } + * hashmap_clear(map); + * + * instead of + * + * hashmap_for_each_entry(map, hashmap_iter, e, hashmap_entry_name) { + * free(e->somefield); + * } + * hashmap_clear_and_free(map, struct my_entry_struct, hashmap_entry_name); + * + * to avoid the implicit extra loop over the entries. However, if there are + * no special fields in your entry that need to be freed beyond the entry + * itself, it is probably simpler to avoid the explicit loop and just call + * hashmap_clear_and_free(). + */ +#define hashmap_clear(map) hashmap_clear_(map, -1) -/* internal function for freeing hashmap */ -void hashmap_free_(struct hashmap *map, ssize_t offset); +/* + * Similar to hashmap_clear(), except that the table is not deallocated; it + * is merely zeroed out but left the same size as before. If the hashmap + * will be reused, this avoids the overhead of deallocating and + * reallocating map->table. As with hashmap_clear(), you may need to free + * the entries yourself before calling this function. + */ +#define hashmap_partial_clear(map) hashmap_partial_clear_(map, -1) /* - * Frees a hashmap structure and allocated memory, leaves entries undisturbed + * Similar to hashmap_clear() but also frees all entries. @type is the + * struct type of the entry where @member is the hashmap_entry struct used + * to associate with @map. + * + * See usage note above hashmap_clear(). */ -#define hashmap_free(map) hashmap_free_(map, -1) +#define hashmap_clear_and_free(map, type, member) \ + hashmap_clear_(map, offsetof(type, member)) /* - * Frees @map and all entries. @type is the struct type of the entry - * where @member is the hashmap_entry struct used to associate with @map + * Similar to hashmap_partial_clear() but also frees all entries. @type is + * the struct type of the entry where @member is the hashmap_entry struct + * used to associate with @map. + * + * See usage note above hashmap_clear(). */ -#define hashmap_free_entries(map, type, member) \ - hashmap_free_(map, offsetof(type, member)); +#define hashmap_partial_clear_and_free(map, type, member) \ + hashmap_partial_clear_(map, offsetof(type, member)) /* hashmap_entry functions */ @@ -261,7 +291,7 @@ void hashmap_free_(struct hashmap *map, ssize_t offset); * and if it is on stack, you can just let it go out of scope). */ static inline void hashmap_entry_init(struct hashmap_entry *e, - unsigned int hash) + unsigned int hash) { e->hash = hash; e->next = NULL; @@ -303,8 +333,8 @@ static inline unsigned int hashmap_get_size(struct hashmap *map) * to `hashmap_cmp_fn` to decide whether the entry matches the key. */ struct hashmap_entry *hashmap_get(const struct hashmap *map, - const struct hashmap_entry *key, - const void *keydata); + const struct hashmap_entry *key, + const void *keydata); /* * Returns the hashmap entry for the specified hash code and key data, @@ -337,7 +367,7 @@ static inline struct hashmap_entry *hashmap_get_from_hash( * call to `hashmap_get` or `hashmap_get_next`. */ struct hashmap_entry *hashmap_get_next(const struct hashmap *map, - const struct hashmap_entry *entry); + const struct hashmap_entry *entry); /* * Adds a hashmap entry. This allows to add duplicate entries (i.e. @@ -357,7 +387,7 @@ void hashmap_add(struct hashmap *map, struct hashmap_entry *entry); * Returns the replaced entry, or NULL if not found (i.e. the entry was added). */ struct hashmap_entry *hashmap_put(struct hashmap *map, - struct hashmap_entry *entry); + struct hashmap_entry *entry); /* * Adds or replaces a hashmap entry contained within @keyvar, @@ -379,8 +409,8 @@ struct hashmap_entry *hashmap_put(struct hashmap *map, * Argument explanation is the same as in `hashmap_get`. */ struct hashmap_entry *hashmap_remove(struct hashmap *map, - const struct hashmap_entry *key, - const void *keydata); + const struct hashmap_entry *key, + const void *keydata); /* * Removes a hashmap entry contained within @keyvar, @@ -422,7 +452,7 @@ struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter); /* Initializes the iterator and returns the first entry, if any. */ static inline struct hashmap_entry *hashmap_iter_first(struct hashmap *map, - struct hashmap_iter *iter) + struct hashmap_iter *iter) { hashmap_iter_init(map, iter); return hashmap_iter_next(iter); @@ -449,7 +479,8 @@ static inline struct hashmap_entry *hashmap_iter_first(struct hashmap *map, * containing a @member which is a "struct hashmap_entry" */ #define hashmap_for_each_entry(map, iter, var, member) \ - for (var = hashmap_iter_first_entry_offset(map, iter, \ + for (var = NULL, /* for systems without typeof */ \ + var = hashmap_iter_first_entry_offset(map, iter, \ OFFSETOF_VAR(var, member)); \ var; \ var = hashmap_iter_next_entry_offset(iter, \ @@ -502,7 +533,7 @@ static inline void hashmap_disable_item_counting(struct hashmap *map) } /* - * Re-enable item couting when adding/removing items. + * Re-enable item counting when adding/removing items. * If counting is currently disabled, it will force count them. * It WILL NOT automatically rehash them. */ |