| #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 struct long2string *e1, |
| * const struct long2string *e2, |
| * const void *keydata, const void *userdata) |
| * { |
| * char *string = keydata; |
| * unsigned *flags = (unsigned*)userdata; |
| * |
| * if (flags & COMPARE_VALUE) |
| * return !(e1->key == e2->key) || (keydata ? |
| * strcmp(e1->value, keydata) : strcmp(e1->value, e2->value)); |
| * else |
| * return !(e1->key == e2->key); |
| * } |
| * |
| * int main(int argc, char **argv) |
| * { |
| * long key; |
| * char *value, *action; |
| * |
| * unsigned flags = ALLOW_DUPLICATE_KEYS; |
| * |
| * hashmap_init(&map, (hashmap_cmp_fn) long2string_cmp, &flags, 0); |
| * |
| * while (scanf("%s %l %s", action, key, value)) { |
| * |
| * if (!strcmp("add", action)) { |
| * struct long2string *e; |
| * e = malloc(sizeof(struct long2string) + strlen(value)); |
| * hashmap_entry_init(e, memhash(&key, sizeof(long))); |
| * e->key = key; |
| * memcpy(e->value, value, strlen(value)); |
| * hashmap_add(&map, e); |
| * } |
| * |
| * if (!strcmp("print_all_by_key", action)) { |
| * flags &= ~COMPARE_VALUE; |
| * |
| * struct long2string k; |
| * hashmap_entry_init(&k, memhash(&key, sizeof(long))); |
| * k.key = key; |
| * |
| * struct long2string *e = hashmap_get(&map, &k, NULL); |
| * if (e) { |
| * printf("first: %l %s\n", e->key, e->value); |
| * while (e = hashmap_get_next(&map, e)) |
| * printf("found more: %l %s\n", e->key, e->value); |
| * } |
| * } |
| * |
| * if (!strcmp("has_exact_match", action)) { |
| * flags |= COMPARE_VALUE; |
| * |
| * struct long2string *e; |
| * e = malloc(sizeof(struct long2string) + strlen(value)); |
| * hashmap_entry_init(e, memhash(&key, sizeof(long))); |
| * e->key = key; |
| * memcpy(e->value, value, strlen(value)); |
| * |
| * printf("%s found\n", hashmap_get(&map, e, NULL) ? "" : "not"); |
| * } |
| * |
| * if (!strcmp("has_exact_match_no_heap_alloc", action)) { |
| * flags |= COMPARE_VALUE; |
| * |
| * struct long2string e; |
| * hashmap_entry_init(e, memhash(&key, sizeof(long))); |
| * e.key = key; |
| * |
| * printf("%s found\n", hashmap_get(&map, e, value) ? "" : "not"); |
| * } |
| * |
| * if (!strcmp("end", action)) { |
| * hashmap_free(&map, 1); |
| * break; |
| * } |
| * } |
| * } |
| */ |
| |
| /* |
| * 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 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; |
| |
| /* See `hashmap_disallow_rehash`. */ |
| unsigned disallow_rehash : 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; |
| } |
| |
| /* |
| * 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); |
| |
| /* |
| * Disallow/allow rehashing of the hashmap. |
| * This is useful if the caller knows that the hashmap needs multi-threaded |
| * access. The caller is still required to guard/lock searches and inserts |
| * in a manner appropriate to their usage. This simply prevents the table |
| * from being unexpectedly re-mapped. |
| * |
| * It is up to the caller to ensure that the hashmap is initialized to a |
| * reasonable size to prevent poor performance. |
| * |
| * A call to allow rehashing does not force a rehash; that might happen |
| * with the next insert or delete. |
| */ |
| static inline void hashmap_disallow_rehash(struct hashmap *map, unsigned value) |
| { |
| map->disallow_rehash = value; |
| } |
| |
| /* |
| * 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); |
| } |
| |
| /* 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 |