#ifndef HASHMAP_H #define HASHMAP_H /* * Generic implementation of hash-based key-value mappings. * * An example that maps long to a string: * For the sake of the example this allows to lookup exact values, too * (i.e. it is operated as a set, the value is part of the key) * ------------------------------------- * * struct hashmap map; * struct long2string { * struct hashmap_entry ent; // must be the first member! * long key; * char value[FLEX_ARRAY]; // be careful with allocating on stack! * }; * * #define COMPARE_VALUE 1 * * static int long2string_cmp(const void *hashmap_cmp_fn_data, * const struct long2string *e1, * const struct long2string *e2, * const void *keydata) * { * const char *string = keydata; * unsigned flags = *(unsigned *)hashmap_cmp_fn_data; * * if (flags & COMPARE_VALUE) * return e1->key != e2->key || * strcmp(e1->value, string ? string : e2->value); * else * return e1->key != e2->key; * } * * int main(int argc, char **argv) * { * long key; * char value[255], action[32]; * unsigned flags = 0; * * hashmap_init(&map, (hashmap_cmp_fn) long2string_cmp, &flags, 0); * * while (scanf("%s %ld %s", action, &key, value)) { * * if (!strcmp("add", action)) { * struct long2string *e; * FLEX_ALLOC_STR(e, value, value); * hashmap_entry_init(e, memhash(&key, sizeof(long))); * e->key = key; * hashmap_add(&map, e); * } * * if (!strcmp("print_all_by_key", action)) { * struct long2string k, *e; * hashmap_entry_init(&k, memhash(&key, sizeof(long))); * k.key = key; * * flags &= ~COMPARE_VALUE; * e = hashmap_get(&map, &k, NULL); * if (e) { * printf("first: %ld %s\n", e->key, e->value); * while ((e = hashmap_get_next(&map, e))) * printf("found more: %ld %s\n", e->key, e->value); * } * } * * if (!strcmp("has_exact_match", action)) { * struct long2string *e; * FLEX_ALLOC_STR(e, value, value); * hashmap_entry_init(e, memhash(&key, sizeof(long))); * e->key = key; * * flags |= COMPARE_VALUE; * printf("%sfound\n", hashmap_get(&map, e, NULL) ? "" : "not "); * free(e); * } * * if (!strcmp("has_exact_match_no_heap_alloc", action)) { * struct long2string k; * hashmap_entry_init(&k, memhash(&key, sizeof(long))); * k.key = key; * * flags |= COMPARE_VALUE; * printf("%sfound\n", hashmap_get(&map, &k, value) ? "" : "not "); * } * * if (!strcmp("end", action)) { * hashmap_free(&map, 1); * break; * } * } * * return 0; * } */ /* * Ready-to-use hash functions for strings, using the FNV-1 algorithm (see * http://www.isthe.com/chongo/tech/comp/fnv). * `strhash` and `strihash` take 0-terminated strings, while `memhash` and * `memihash` operate on arbitrary-length memory. * `strihash` and `memihash` are case insensitive versions. * `memihash_cont` is a variant of `memihash` that allows a computation to be * continued with another chunk of data. */ extern unsigned int strhash(const char *buf); extern unsigned int strihash(const char *buf); extern unsigned int memhash(const void *buf, size_t len); extern unsigned int memihash(const void *buf, size_t len); extern 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 sha1hash(const unsigned char *sha1) { /* * Equivalent to 'return *(unsigned int *)sha1;', but safe on * platforms that don't support unaligned reads. */ unsigned int hash; memcpy(&hash, sha1, sizeof(hash)); return hash; } /* * struct hashmap_entry is an opaque structure representing an entry in the * hash table, which must be used as first member of user data structures. * Ideally it should be followed by an int-sized member to prevent unused * memory on 64-bit systems due to alignment. */ struct hashmap_entry { /* * next points to the next entry in case of collisions (i.e. if * multiple entries map to the same bucket) */ struct hashmap_entry *next; /* entry's hash code */ unsigned int hash; }; /* * User-supplied function to test two hashmap entries for equality. Shall * return 0 if the entries are equal. * * This function is always called with non-NULL `entry` and `entry_or_key` * parameters that have the same hash code. * * When looking up an entry, the `key` and `keydata` parameters to hashmap_get * and hashmap_remove are always passed as second `entry_or_key` and third * 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 * 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. * * The `hashmap_cmp_fn_data` entry is the pointer given in the init function. */ typedef int (*hashmap_cmp_fn)(const void *hashmap_cmp_fn_data, const void *entry, const void *entry_or_key, const void *keydata); /* * struct hashmap is the hash table structure. Members can be used as follows, * but should not be modified directly. */ struct hashmap { struct hashmap_entry **table; /* Stores the comparison function specified in `hashmap_init()`. */ hashmap_cmp_fn cmpfn; const void *cmpfn_data; /* total number of entries (0 means the hashmap is empty) */ unsigned int private_size; /* use hashmap_get_size() */ /* * tablesize is the allocated size of the hash table. A non-0 value * indicates that the hashmap is initialized. It may also be useful * for statistical purposes (i.e. `size / tablesize` is the current * load factor). */ unsigned int tablesize; unsigned int grow_at; unsigned int shrink_at; unsigned int do_count_items : 1; }; /* hashmap functions */ /* * Initializes a hashmap structure. * * `map` is the hashmap to initialize. * * The `equals_function` can be specified to compare two entries for equality. * If NULL, entries are considered equal if their hash codes are equal. * * The `equals_function_data` parameter can be used to provide additional data * (a callback cookie) that will be passed to `equals_function` each time it * is called. This allows a single `equals_function` to implement multiple * comparison functions. * * If the total number of entries is known in advance, the `initial_size` * parameter may be used to preallocate a sufficiently large table and thus * prevent expensive resizing. If 0, the table is dynamically resized. */ extern void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function, const void *equals_function_data, size_t initial_size); /* * Frees a hashmap structure and allocated memory. * * If `free_entries` is true, each hashmap_entry in the map is freed as well * using stdlibs free(). */ extern void hashmap_free(struct hashmap *map, int free_entries); /* hashmap_entry functions */ /* * Initializes a hashmap_entry structure. * * `entry` points to the entry to initialize. * `hash` is the hash code of the entry. * * The hashmap_entry structure does not hold references to external resources, * and it is safe to just discard it once you are done with it (i.e. if * your structure was allocated with xmalloc(), you can just free(3) it, * and if it is on stack, you can just let it go out of scope). */ static inline void hashmap_entry_init(void *entry, unsigned int hash) { struct hashmap_entry *e = entry; e->hash = hash; e->next = NULL; } /* * Return the number of items in the map. */ static inline unsigned int hashmap_get_size(struct hashmap *map) { if (map->do_count_items) return map->private_size; BUG("hashmap_get_size: size not set"); return 0; } /* * Returns the hashmap entry for the specified key, or NULL if not found. * * `map` is the hashmap structure. * * `key` is a user data structure that starts with hashmap_entry that has at * least been initialized with the proper hash code (via `hashmap_entry_init`). * * `keydata` is a data structure that holds just enough information to check * for equality to a given entry. * * If the key data is variable-sized (e.g. a FLEX_ARRAY string) or quite large, * it is undesirable to create a full-fledged entry structure on the heap and * copy all the key data into the structure. * * In this case, the `keydata` parameter can be used to pass * variable-sized key data directly to the comparison function, and the `key` * parameter can be a stripped-down, fixed size entry structure allocated on the * stack. * * If an entry with matching hash code is found, `key` and `keydata` are passed * to `hashmap_cmp_fn` to decide whether the entry matches the key. */ extern void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata); /* * Returns the hashmap entry for the specified hash code and key data, * or NULL if not found. * * `map` is the hashmap structure. * `hash` is the hash code of the entry to look up. * * If an entry with matching hash code is found, `keydata` is passed to * `hashmap_cmp_fn` to decide whether the entry matches the key. The * `entry_or_key` parameter of `hashmap_cmp_fn` points to a hashmap_entry * structure that should not be used in the comparison. */ static inline void *hashmap_get_from_hash(const struct hashmap *map, unsigned int hash, const void *keydata) { struct hashmap_entry key; hashmap_entry_init(&key, hash); return hashmap_get(map, &key, keydata); } /* * Returns the next equal hashmap entry, or NULL if not found. This can be * used to iterate over duplicate entries (see `hashmap_add`). * * `map` is the hashmap structure. * `entry` is the hashmap_entry to start the search from, obtained via a previous * call to `hashmap_get` or `hashmap_get_next`. */ extern void *hashmap_get_next(const struct hashmap *map, const void *entry); /* * Adds a hashmap entry. This allows to add duplicate entries (i.e. * separate values with the same key according to hashmap_cmp_fn). * * `map` is the hashmap structure. * `entry` is the entry to add. */ extern void hashmap_add(struct hashmap *map, void *entry); /* * Adds or replaces a hashmap entry. If the hashmap contains duplicate * entries equal to the specified entry, only one of them will be replaced. * * `map` is the hashmap structure. * `entry` is the entry to add or replace. * Returns the replaced entry, or NULL if not found (i.e. the entry was added). */ extern void *hashmap_put(struct hashmap *map, void *entry); /* * Removes a hashmap entry matching the specified key. If the hashmap contains * duplicate entries equal to the specified key, only one of them will be * removed. Returns the removed entry, or NULL if not found. * * Argument explanation is the same as in `hashmap_get`. */ extern void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata); /* * Returns the `bucket` an entry is stored in. * Useful for multithreaded read access. */ int hashmap_bucket(const struct hashmap *map, unsigned int hash); /* * Used to iterate over all entries of a hashmap. Note that it is * not safe to add or remove entries to the hashmap while * iterating. */ struct hashmap_iter { struct hashmap *map; struct hashmap_entry *next; unsigned int tablepos; }; /* Initializes a `hashmap_iter` structure. */ extern void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter); /* Returns the next hashmap_entry, or NULL if there are no more entries. */ extern void *hashmap_iter_next(struct hashmap_iter *iter); /* Initializes the iterator and returns the first entry, if any. */ static inline void *hashmap_iter_first(struct hashmap *map, struct hashmap_iter *iter) { hashmap_iter_init(map, iter); return hashmap_iter_next(iter); } /* * Disable item counting and automatic rehashing when adding/removing items. * * Normally, the hashmap keeps track of the number of items in the map * and uses it to dynamically resize it. This (both the counting and * the resizing) can cause problems when the map is being used by * threaded callers (because the hashmap code does not know about the * locking strategy used by the threaded callers and therefore, does * not know how to protect the "private_size" counter). */ static inline void hashmap_disable_item_counting(struct hashmap *map) { map->do_count_items = 0; } /* * Re-enable item couting when adding/removing items. * If counting is currently disabled, it will force count them. * It WILL NOT automatically rehash them. */ static inline void hashmap_enable_item_counting(struct hashmap *map) { unsigned int n = 0; struct hashmap_iter iter; if (map->do_count_items) return; hashmap_iter_init(map, &iter); while (hashmap_iter_next(&iter)) n++; map->do_count_items = 1; map->private_size = n; } /* String interning */ /* * Returns the unique, interned version of the specified string or data, * similar to the `String.intern` API in Java and .NET, respectively. * Interned strings remain valid for the entire lifetime of the process. * * Can be used as `[x]strdup()` or `xmemdupz` replacement, except that interned * strings / data must not be modified or freed. * * Interned strings are best used for short strings with high probability of * duplicates. * * Uses a hashmap to store the pool of interned strings. */ extern const void *memintern(const void *data, size_t len); static inline const char *strintern(const char *string) { return memintern(string, strlen(string)); } #endif