git

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/*
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 * Generic implementation of hash-based key value mappings.
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 */
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#include "git-compat-util.h"
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#include "hashmap.h"
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#define FNV32_BASE ((unsigned int) 0x811c9dc5)
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#define FNV32_PRIME ((unsigned int) 0x01000193)
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unsigned int strhash(const char *str)
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{
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	unsigned int c, hash = FNV32_BASE;
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	while ((c = (unsigned char) *str++))
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		hash = (hash * FNV32_PRIME) ^ c;
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	return hash;
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}
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unsigned int strihash(const char *str)
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{
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	unsigned int c, hash = FNV32_BASE;
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	while ((c = (unsigned char) *str++)) {
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		if (c >= 'a' && c <= 'z')
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			c -= 'a' - 'A';
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		hash = (hash * FNV32_PRIME) ^ c;
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	}
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	return hash;
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}
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unsigned int memhash(const void *buf, size_t len)
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{
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	unsigned int hash = FNV32_BASE;
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	unsigned char *ucbuf = (unsigned char *) buf;
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	while (len--) {
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		unsigned int c = *ucbuf++;
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		hash = (hash * FNV32_PRIME) ^ c;
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	}
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	return hash;
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}
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unsigned int memihash(const void *buf, size_t len)
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{
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	unsigned int hash = FNV32_BASE;
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	unsigned char *ucbuf = (unsigned char *) buf;
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	while (len--) {
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		unsigned int c = *ucbuf++;
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		if (c >= 'a' && c <= 'z')
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			c -= 'a' - 'A';
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		hash = (hash * FNV32_PRIME) ^ c;
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	}
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	return hash;
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}
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/*
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 * Incorporate another chunk of data into a memihash
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 * computation.
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 */
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unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)
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{
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	unsigned int hash = hash_seed;
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	unsigned char *ucbuf = (unsigned char *) buf;
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	while (len--) {
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		unsigned int c = *ucbuf++;
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		if (c >= 'a' && c <= 'z')
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			c -= 'a' - 'A';
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		hash = (hash * FNV32_PRIME) ^ c;
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	}
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	return hash;
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}
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#define HASHMAP_INITIAL_SIZE 64
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/* grow / shrink by 2^2 */
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#define HASHMAP_RESIZE_BITS 2
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/* load factor in percent */
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#define HASHMAP_LOAD_FACTOR 80
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static void alloc_table(struct hashmap *map, unsigned int size)
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{
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	map->tablesize = size;
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	CALLOC_ARRAY(map->table, size);
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	/* calculate resize thresholds for new size */
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	map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
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	if (size <= HASHMAP_INITIAL_SIZE)
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		map->shrink_at = 0;
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	else
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		/*
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		 * The shrink-threshold must be slightly smaller than
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		 * (grow-threshold / resize-factor) to prevent erratic resizing,
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		 * thus we divide by (resize-factor + 1).
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		 */
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		map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
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}
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static inline int entry_equals(const struct hashmap *map,
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			       const struct hashmap_entry *e1,
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			       const struct hashmap_entry *e2,
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			       const void *keydata)
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{
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	return (e1 == e2) ||
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	       (e1->hash == e2->hash &&
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		!map->cmpfn(map->cmpfn_data, e1, e2, keydata));
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}
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static inline unsigned int bucket(const struct hashmap *map,
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				  const struct hashmap_entry *key)
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{
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	return key->hash & (map->tablesize - 1);
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}
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int hashmap_bucket(const struct hashmap *map, unsigned int hash)
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{
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	return hash & (map->tablesize - 1);
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}
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static void rehash(struct hashmap *map, unsigned int newsize)
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{
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	/* map->table MUST NOT be NULL when this function is called */
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	unsigned int i, oldsize = map->tablesize;
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	struct hashmap_entry **oldtable = map->table;
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	alloc_table(map, newsize);
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	for (i = 0; i < oldsize; i++) {
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		struct hashmap_entry *e = oldtable[i];
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		while (e) {
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			struct hashmap_entry *next = e->next;
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			unsigned int b = bucket(map, e);
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			e->next = map->table[b];
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			map->table[b] = e;
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			e = next;
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		}
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	}
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	free(oldtable);
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}
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static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
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		const struct hashmap_entry *key, const void *keydata)
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{
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	/* map->table MUST NOT be NULL when this function is called */
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	struct hashmap_entry **e = &map->table[bucket(map, key)];
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	while (*e && !entry_equals(map, *e, key, keydata))
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		e = &(*e)->next;
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	return e;
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}
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static int always_equal(const void *cmp_data UNUSED,
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			const struct hashmap_entry *entry1 UNUSED,
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			const struct hashmap_entry *entry2 UNUSED,
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			const void *keydata UNUSED)
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{
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	return 0;
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}
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void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
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		  const void *cmpfn_data, size_t initial_size)
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{
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	unsigned int size = HASHMAP_INITIAL_SIZE;
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	memset(map, 0, sizeof(*map));
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	map->cmpfn = equals_function ? equals_function : always_equal;
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	map->cmpfn_data = cmpfn_data;
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	/* calculate initial table size and allocate the table */
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	initial_size = (unsigned int) ((uint64_t) initial_size * 100
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			/ HASHMAP_LOAD_FACTOR);
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	while (initial_size > size)
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		size <<= HASHMAP_RESIZE_BITS;
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	alloc_table(map, size);
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	/*
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	 * Keep track of the number of items in the map and
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	 * allow the map to automatically grow as necessary.
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	 */
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	map->do_count_items = 1;
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}
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static void free_individual_entries(struct hashmap *map, ssize_t entry_offset)
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{
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	struct hashmap_iter iter;
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	struct hashmap_entry *e;
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	hashmap_iter_init(map, &iter);
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	while ((e = hashmap_iter_next(&iter)))
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		/*
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		 * like container_of, but using caller-calculated
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		 * offset (caller being hashmap_clear_and_free)
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		 */
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		free((char *)e - entry_offset);
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}
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void hashmap_partial_clear_(struct hashmap *map, ssize_t entry_offset)
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{
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	if (!map || !map->table)
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		return;
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	if (entry_offset >= 0)  /* called by hashmap_clear_entries */
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		free_individual_entries(map, entry_offset);
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	memset(map->table, 0, map->tablesize * sizeof(struct hashmap_entry *));
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	map->shrink_at = 0;
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	map->private_size = 0;
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}
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void hashmap_clear_(struct hashmap *map, ssize_t entry_offset)
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{
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	if (!map || !map->table)
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		return;
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	if (entry_offset >= 0)  /* called by hashmap_clear_and_free */
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		free_individual_entries(map, entry_offset);
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	free(map->table);
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	memset(map, 0, sizeof(*map));
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}
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struct hashmap_entry *hashmap_get(const struct hashmap *map,
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				const struct hashmap_entry *key,
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				const void *keydata)
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{
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	if (!map->table)
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		return NULL;
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	return *find_entry_ptr(map, key, keydata);
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}
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struct hashmap_entry *hashmap_get_next(const struct hashmap *map,
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				       const struct hashmap_entry *entry)
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{
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	struct hashmap_entry *e = entry->next;
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	for (; e; e = e->next)
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		if (entry_equals(map, entry, e, NULL))
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			return e;
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	return NULL;
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}
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void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)
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{
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	unsigned int b;
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	if (!map->table)
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		alloc_table(map, HASHMAP_INITIAL_SIZE);
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	b = bucket(map, entry);
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	/* add entry */
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	entry->next = map->table[b];
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	map->table[b] = entry;
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	/* fix size and rehash if appropriate */
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	if (map->do_count_items) {
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		map->private_size++;
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		if (map->private_size > map->grow_at)
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			rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
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	}
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}
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struct hashmap_entry *hashmap_remove(struct hashmap *map,
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				     const struct hashmap_entry *key,
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				     const void *keydata)
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{
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	struct hashmap_entry *old;
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	struct hashmap_entry **e;
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	if (!map->table)
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		return NULL;
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	e = find_entry_ptr(map, key, keydata);
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	if (!*e)
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		return NULL;
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	/* remove existing entry */
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	old = *e;
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	*e = old->next;
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	old->next = NULL;
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	/* fix size and rehash if appropriate */
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	if (map->do_count_items) {
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		map->private_size--;
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		if (map->private_size < map->shrink_at)
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			rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
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	}
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	return old;
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}
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struct hashmap_entry *hashmap_put(struct hashmap *map,
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				  struct hashmap_entry *entry)
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{
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	struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
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	hashmap_add(map, entry);
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	return old;
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}
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void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
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{
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	iter->map = map;
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	iter->tablepos = 0;
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	iter->next = NULL;
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}
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struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)
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{
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	struct hashmap_entry *current = iter->next;
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	for (;;) {
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		if (current) {
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			iter->next = current->next;
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			return current;
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		}
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		if (iter->tablepos >= iter->map->tablesize)
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			return NULL;
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		current = iter->map->table[iter->tablepos++];
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	}
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}
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struct pool_entry {
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	struct hashmap_entry ent;
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	size_t len;
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	unsigned char data[FLEX_ARRAY];
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};
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static int pool_entry_cmp(const void *cmp_data UNUSED,
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			  const struct hashmap_entry *eptr,
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			  const struct hashmap_entry *entry_or_key,
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			  const void *keydata)
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{
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	const struct pool_entry *e1, *e2;
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	e1 = container_of(eptr, const struct pool_entry, ent);
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	e2 = container_of(entry_or_key, const struct pool_entry, ent);
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	return e1->data != keydata &&
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	       (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
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}
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const void *memintern(const void *data, size_t len)
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{
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	static struct hashmap map;
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	struct pool_entry key, *e;
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	/* initialize string pool hashmap */
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	if (!map.tablesize)
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		hashmap_init(&map, pool_entry_cmp, NULL, 0);
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	/* lookup interned string in pool */
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	hashmap_entry_init(&key.ent, memhash(data, len));
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	key.len = len;
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	e = hashmap_get_entry(&map, &key, ent, data);
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	if (!e) {
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		/* not found: create it */
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		FLEX_ALLOC_MEM(e, data, data, len);
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		hashmap_entry_init(&e->ent, key.ent.hash);
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		e->len = len;
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		hashmap_add(&map, &e->ent);
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	}
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	return e->data;
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}
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