hashmap.c - jrn/git - Git at Google

 /*
  * Generic implementation of hash-based key value mappings.
  */
 #include "cache.h"
 #include "hashmap.h"

 #define FNV32_BASE ((unsigned int) 0x811c9dc5)
 #define FNV32_PRIME ((unsigned int) 0x01000193)

 unsigned int strhash(const char *str)
 {
 	unsigned int c, hash = FNV32_BASE;
 	while ((c = (unsigned char) *str++))
 		hash = (hash * FNV32_PRIME) ^ c;
 	return hash;
 }

 unsigned int strihash(const char *str)
 {
 	unsigned int c, hash = FNV32_BASE;
 	while ((c = (unsigned char) *str++)) {
 		if (c >= 'a' && c <= 'z')
 			c -= 'a' - 'A';
 		hash = (hash * FNV32_PRIME) ^ c;
 	}
 	return hash;
 }

 unsigned int memhash(const void *buf, size_t len)
 {
 	unsigned int hash = FNV32_BASE;
 	unsigned char *ucbuf = (unsigned char *) buf;
 	while (len--) {
 		unsigned int c = *ucbuf++;
 		hash = (hash * FNV32_PRIME) ^ c;
 	}
 	return hash;
 }

 unsigned int memihash(const void *buf, size_t len)
 {
 	unsigned int hash = FNV32_BASE;
 	unsigned char *ucbuf = (unsigned char *) buf;
 	while (len--) {
 		unsigned int c = *ucbuf++;
 		if (c >= 'a' && c <= 'z')
 			c -= 'a' - 'A';
 		hash = (hash * FNV32_PRIME) ^ c;
 	}
 	return hash;
 }

 /*
  * Incoporate another chunk of data into a memihash
  * computation.
  */
 unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
 {
 	unsigned int hash = hash_seed;
 	unsigned char *ucbuf = (unsigned char *) buf;
 	while (len--) {
 		unsigned int c = *ucbuf++;
 		if (c >= 'a' && c <= 'z')
 			c -= 'a' - 'A';
 		hash = (hash * FNV32_PRIME) ^ c;
 	}
 	return hash;
 }

 #define HASHMAP_INITIAL_SIZE 64
 /* grow / shrink by 2^2 */
 #define HASHMAP_RESIZE_BITS 2
 /* load factor in percent */
 #define HASHMAP_LOAD_FACTOR 80

 static void alloc_table(struct hashmap *map, unsigned int size)
 {
 	map->tablesize = size;
 	map->table = xcalloc(size, sizeof(struct hashmap_entry *));

 	/* calculate resize thresholds for new size */
 	map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
 	if (size <= HASHMAP_INITIAL_SIZE)
 		map->shrink_at = 0;
 	else
 		/*
 		 * The shrink-threshold must be slightly smaller than
 		 * (grow-threshold / resize-factor) to prevent erratic resizing,
 		 * thus we divide by (resize-factor + 1).
 		 */
 		map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
 }

 static inline int entry_equals(const struct hashmap *map,
 		const struct hashmap_entry *e1, const struct hashmap_entry *e2,
 		const void *keydata)
 {
 	return (e1 == e2) ||
 	       (e1->hash == e2->hash &&
 		!map->cmpfn(map->cmpfn_data, e1, e2, keydata));
 }

 static inline unsigned int bucket(const struct hashmap *map,
 		const struct hashmap_entry *key)
 {
 	return key->hash & (map->tablesize - 1);
 }

 int hashmap_bucket(const struct hashmap *map, unsigned int hash)
 {
 	return hash & (map->tablesize - 1);
 }

 static void rehash(struct hashmap *map, unsigned int newsize)
 {
 	unsigned int i, oldsize = map->tablesize;
 	struct hashmap_entry **oldtable = map->table;

 	alloc_table(map, newsize);
 	for (i = 0; i < oldsize; i++) {
 		struct hashmap_entry *e = oldtable[i];
 		while (e) {
 			struct hashmap_entry *next = e->next;
 			unsigned int b = bucket(map, e);
 			e->next = map->table[b];
 			map->table[b] = e;
 			e = next;
 		}
 	}
 	free(oldtable);
 }

 static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
 		const struct hashmap_entry *key, const void *keydata)
 {
 	struct hashmap_entry **e = &map->table[bucket(map, key)];
 	while (*e && !entry_equals(map, *e, key, keydata))
 		e = &(*e)->next;
 	return e;
 }

 static int always_equal(const void *unused_cmp_data,
 			const void *unused1,
 			const void *unused2,
 			const void *unused_keydata)
 {
 	return 0;
 }

 void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
 		const void *cmpfn_data, size_t initial_size)
 {
 	unsigned int size = HASHMAP_INITIAL_SIZE;

 	memset(map, 0, sizeof(*map));

 	map->cmpfn = equals_function ? equals_function : always_equal;
 	map->cmpfn_data = cmpfn_data;

 	/* calculate initial table size and allocate the table */
 	initial_size = (unsigned int) ((uint64_t) initial_size * 100
 			/ HASHMAP_LOAD_FACTOR);
 	while (initial_size > size)
 		size <<= HASHMAP_RESIZE_BITS;
 	alloc_table(map, size);

 	/*
 	 * Keep track of the number of items in the map and
 	 * allow the map to automatically grow as necessary.
 	 */
 	map->do_count_items = 1;
 }

 void hashmap_free(struct hashmap *map, int free_entries)
 {
 	if (!map || !map->table)
 		return;
 	if (free_entries) {
 		struct hashmap_iter iter;
 		struct hashmap_entry *e;
 		hashmap_iter_init(map, &iter);
 		while ((e = hashmap_iter_next(&iter)))
 			free(e);
 	}
 	free(map->table);
 	memset(map, 0, sizeof(*map));
 }

 void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)
 {
 	return *find_entry_ptr(map, key, keydata);
 }

 void *hashmap_get_next(const struct hashmap *map, const void *entry)
 {
 	struct hashmap_entry *e = ((struct hashmap_entry *) entry)->next;
 	for (; e; e = e->next)
 		if (entry_equals(map, entry, e, NULL))
 			return e;
 	return NULL;
 }

 void hashmap_add(struct hashmap *map, void *entry)
 {
 	unsigned int b = bucket(map, entry);

 	/* add entry */
 	((struct hashmap_entry *) entry)->next = map->table[b];
 	map->table[b] = entry;

 	/* fix size and rehash if appropriate */
 	if (map->do_count_items) {
 		map->private_size++;
 		if (map->private_size > map->grow_at)
 			rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
 	}
 }

 void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)
 {
 	struct hashmap_entry *old;
 	struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
 	if (!*e)
 		return NULL;

 	/* remove existing entry */
 	old = *e;
 	*e = old->next;
 	old->next = NULL;

 	/* fix size and rehash if appropriate */
 	if (map->do_count_items) {
 		map->private_size--;
 		if (map->private_size < map->shrink_at)
 			rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
 	}

 	return old;
 }

 void *hashmap_put(struct hashmap *map, void *entry)
 {
 	struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
 	hashmap_add(map, entry);
 	return old;
 }

 void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
 {
 	iter->map = map;
 	iter->tablepos = 0;
 	iter->next = NULL;
 }

 void *hashmap_iter_next(struct hashmap_iter *iter)
 {
 	struct hashmap_entry *current = iter->next;
 	for (;;) {
 		if (current) {
 			iter->next = current->next;
 			return current;
 		}

 		if (iter->tablepos >= iter->map->tablesize)
 			return NULL;

 		current = iter->map->table[iter->tablepos++];
 	}
 }

 struct pool_entry {
 	struct hashmap_entry ent;
 	size_t len;
 	unsigned char data[FLEX_ARRAY];
 };

 static int pool_entry_cmp(const void *unused_cmp_data,
 			  const struct pool_entry *e1,
 			  const struct pool_entry *e2,
 			  const unsigned char *keydata)
 {
 	return e1->data != keydata &&
 	       (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
 }

 const void *memintern(const void *data, size_t len)
 {
 	static struct hashmap map;
 	struct pool_entry key, *e;

 	/* initialize string pool hashmap */
 	if (!map.tablesize)
 		hashmap_init(&map, (hashmap_cmp_fn) pool_entry_cmp, NULL, 0);

 	/* lookup interned string in pool */
 	hashmap_entry_init(&key, memhash(data, len));
 	key.len = len;
 	e = hashmap_get(&map, &key, data);
 	if (!e) {
 		/* not found: create it */
 		FLEX_ALLOC_MEM(e, data, data, len);
 		hashmap_entry_init(e, key.ent.hash);
 		e->len = len;
 		hashmap_add(&map, e);
 	}
 	return e->data;
 }
	/*
	* Generic implementation of hash-based key value mappings.
	*/
	#include "cache.h"
	#include "hashmap.h"

	#define FNV32_BASE ((unsigned int) 0x811c9dc5)
	#define FNV32_PRIME ((unsigned int) 0x01000193)

	unsigned int strhash(const char *str)
	{
	unsigned int c, hash = FNV32_BASE;
	while ((c = (unsigned char) *str++))
	hash = (hash * FNV32_PRIME) ^ c;
	return hash;
	}

	unsigned int strihash(const char *str)
	{
	unsigned int c, hash = FNV32_BASE;
	while ((c = (unsigned char) *str++)) {
	if (c >= 'a' && c <= 'z')
	c -= 'a' - 'A';
	hash = (hash * FNV32_PRIME) ^ c;
	}
	return hash;
	}

	unsigned int memhash(const void *buf, size_t len)
	{
	unsigned int hash = FNV32_BASE;
	unsigned char ucbuf = (unsigned char ) buf;
	while (len--) {
	unsigned int c = *ucbuf++;
	hash = (hash * FNV32_PRIME) ^ c;
	}
	return hash;
	}

	unsigned int memihash(const void *buf, size_t len)
	{
	unsigned int hash = FNV32_BASE;
	unsigned char ucbuf = (unsigned char ) buf;
	while (len--) {
	unsigned int c = *ucbuf++;
	if (c >= 'a' && c <= 'z')
	c -= 'a' - 'A';
	hash = (hash * FNV32_PRIME) ^ c;
	}
	return hash;
	}

	/*
	* Incoporate another chunk of data into a memihash
	* computation.
	*/
	unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
	{
	unsigned int hash = hash_seed;
	unsigned char ucbuf = (unsigned char ) buf;
	while (len--) {
	unsigned int c = *ucbuf++;
	if (c >= 'a' && c <= 'z')
	c -= 'a' - 'A';
	hash = (hash * FNV32_PRIME) ^ c;
	}
	return hash;
	}

	#define HASHMAP_INITIAL_SIZE 64
	/* grow / shrink by 2^2 */
	#define HASHMAP_RESIZE_BITS 2
	/* load factor in percent */
	#define HASHMAP_LOAD_FACTOR 80

	static void alloc_table(struct hashmap *map, unsigned int size)
	{
	map->tablesize = size;
	map->table = xcalloc(size, sizeof(struct hashmap_entry *));

	/* calculate resize thresholds for new size */
	map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
	if (size <= HASHMAP_INITIAL_SIZE)
	map->shrink_at = 0;
	else
	/*
	* The shrink-threshold must be slightly smaller than
	* (grow-threshold / resize-factor) to prevent erratic resizing,
	* thus we divide by (resize-factor + 1).
	*/
	map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
	}

	static inline int entry_equals(const struct hashmap *map,
	const struct hashmap_entry e1, const struct hashmap_entry e2,
	const void *keydata)
	{
	return (e1 == e2) \|\|
	(e1->hash == e2->hash &&
	!map->cmpfn(map->cmpfn_data, e1, e2, keydata));
	}

	static inline unsigned int bucket(const struct hashmap *map,
	const struct hashmap_entry *key)
	{
	return key->hash & (map->tablesize - 1);
	}

	int hashmap_bucket(const struct hashmap *map, unsigned int hash)
	{
	return hash & (map->tablesize - 1);
	}

	static void rehash(struct hashmap *map, unsigned int newsize)
	{
	unsigned int i, oldsize = map->tablesize;
	struct hashmap_entry **oldtable = map->table;

	alloc_table(map, newsize);
	for (i = 0; i < oldsize; i++) {
	struct hashmap_entry *e = oldtable[i];
	while (e) {
	struct hashmap_entry *next = e->next;
	unsigned int b = bucket(map, e);
	e->next = map->table[b];
	map->table[b] = e;
	e = next;
	}
	}
	free(oldtable);
	}

	static inline struct hashmap_entry *find_entry_ptr(const struct hashmap map,
	const struct hashmap_entry key, const void keydata)
	{
	struct hashmap_entry **e = &map->table[bucket(map, key)];
	while (e && !entry_equals(map, e, key, keydata))
	e = &(*e)->next;
	return e;
	}

	static int always_equal(const void *unused_cmp_data,
	const void *unused1,
	const void *unused2,
	const void *unused_keydata)
	{
	return 0;
	}

	void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
	const void *cmpfn_data, size_t initial_size)
	{
	unsigned int size = HASHMAP_INITIAL_SIZE;

	memset(map, 0, sizeof(*map));

	map->cmpfn = equals_function ? equals_function : always_equal;
	map->cmpfn_data = cmpfn_data;

	/* calculate initial table size and allocate the table */
	initial_size = (unsigned int) ((uint64_t) initial_size * 100
	/ HASHMAP_LOAD_FACTOR);
	while (initial_size > size)
	size <<= HASHMAP_RESIZE_BITS;
	alloc_table(map, size);

	/*
	* Keep track of the number of items in the map and
	* allow the map to automatically grow as necessary.
	*/
	map->do_count_items = 1;
	}

	void hashmap_free(struct hashmap *map, int free_entries)
	{
	if (!map \|\| !map->table)
	return;
	if (free_entries) {
	struct hashmap_iter iter;
	struct hashmap_entry *e;
	hashmap_iter_init(map, &iter);
	while ((e = hashmap_iter_next(&iter)))
	free(e);
	}
	free(map->table);
	memset(map, 0, sizeof(*map));
	}

	void hashmap_get(const struct hashmap map, const void key, const void keydata)
	{
	return *find_entry_ptr(map, key, keydata);
	}

	void hashmap_get_next(const struct hashmap map, const void *entry)
	{
	struct hashmap_entry e = ((struct hashmap_entry ) entry)->next;
	for (; e; e = e->next)
	if (entry_equals(map, entry, e, NULL))
	return e;
	return NULL;
	}

	void hashmap_add(struct hashmap map, void entry)
	{
	unsigned int b = bucket(map, entry);

	/* add entry */
	((struct hashmap_entry *) entry)->next = map->table[b];
	map->table[b] = entry;

	/* fix size and rehash if appropriate */
	if (map->do_count_items) {
	map->private_size++;
	if (map->private_size > map->grow_at)
	rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
	}
	}

	void hashmap_remove(struct hashmap map, const void key, const void keydata)
	{
	struct hashmap_entry *old;
	struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
	if (!*e)
	return NULL;

	/* remove existing entry */
	old = *e;
	*e = old->next;
	old->next = NULL;

	/* fix size and rehash if appropriate */
	if (map->do_count_items) {
	map->private_size--;
	if (map->private_size < map->shrink_at)
	rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
	}

	return old;
	}

	void hashmap_put(struct hashmap map, void *entry)
	{
	struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
	hashmap_add(map, entry);
	return old;
	}

	void hashmap_iter_init(struct hashmap map, struct hashmap_iter iter)
	{
	iter->map = map;
	iter->tablepos = 0;
	iter->next = NULL;
	}

	void hashmap_iter_next(struct hashmap_iter iter)
	{
	struct hashmap_entry *current = iter->next;
	for (;;) {
	if (current) {
	iter->next = current->next;
	return current;
	}

	if (iter->tablepos >= iter->map->tablesize)
	return NULL;

	current = iter->map->table[iter->tablepos++];
	}
	}

	struct pool_entry {
	struct hashmap_entry ent;
	size_t len;
	unsigned char data[FLEX_ARRAY];
	};

	static int pool_entry_cmp(const void *unused_cmp_data,
	const struct pool_entry *e1,
	const struct pool_entry *e2,
	const unsigned char *keydata)
	{
	return e1->data != keydata &&
	(e1->len != e2->len \|\| memcmp(e1->data, keydata, e1->len));
	}

	const void memintern(const void data, size_t len)
	{
	static struct hashmap map;
	struct pool_entry key, *e;

	/* initialize string pool hashmap */
	if (!map.tablesize)
	hashmap_init(&map, (hashmap_cmp_fn) pool_entry_cmp, NULL, 0);

	/* lookup interned string in pool */
	hashmap_entry_init(&key, memhash(data, len));
	key.len = len;
	e = hashmap_get(&map, &key, data);
	if (!e) {
	/* not found: create it */
	FLEX_ALLOC_MEM(e, data, data, len);
	hashmap_entry_init(e, key.ent.hash);
	e->len = len;
	hashmap_add(&map, e);
	}
	return e->data;
	}