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	#ifndef HASHMAP_H
	#define HASHMAP_H

	#include "hash.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;
	* 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 hashmap_entry *eptr,
	* const struct hashmap_entry *entry_or_key,
	* const void *keydata)
	* {
	* const char *string = keydata;
	* unsigned flags = (unsigned )hashmap_cmp_fn_data;
	* const struct long2string e1, e2;
	*
	* e1 = container_of(eptr, const struct long2string, ent);
	* e2 = container_of(entry_or_key, const struct long2string, ent);
	*
	* 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, 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->ent, memhash(&key, sizeof(long)));
	* e->key = key;
	* hashmap_add(&map, &e->ent);
	* }
	*
	* if (!strcmp("print_all_by_key", action)) {
	* struct long2string k, *e;
	* hashmap_entry_init(&k.ent, memhash(&key, sizeof(long)));
	* k.key = key;
	*
	* flags &= ~COMPARE_VALUE;
	* e = hashmap_get_entry(&map, &k, ent, NULL);
	* if (e) {
	* printf("first: %ld %s\n", e->key, e->value);
	* while ((e = hashmap_get_next_entry(&map, e,
	* struct long2string, ent))) {
	* 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->ent, memhash(&key, sizeof(long)));
	* e->key = key;
	*
	* flags \|= COMPARE_VALUE;
	* printf("%sfound\n",
	* hashmap_get(&map, &e->ent, NULL) ? "" : "not ");
	* free(e);
	* }
	*
	* if (!strcmp("has_exact_match_no_heap_alloc", action)) {
	* struct long2string k;
	* 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 ");
	* }
	*
	* if (!strcmp("end", action)) {
	* hashmap_clear_and_free(&map, struct long2string, ent);
	* 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.
	*/
	unsigned int strhash(const char *buf);
	unsigned int strihash(const char *buf);
	unsigned int memhash(const void *buf, size_t len);
	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
	* 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 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.
	*
	* 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 struct hashmap_entry *entry,
	const struct hashmap_entry *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 */

	#define HASHMAP_INIT(fn, data) { .cmpfn = fn, .cmpfn_data = data, \
	.do_count_items = 1 }

	/*
	* 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.
	*/
	void hashmap_init(struct hashmap *map,
	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)

	/*
	* Similar to hashmap_clear(), except that the table is no 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)

	/*
	* 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_clear_and_free(map, type, member) \
	hashmap_clear_(map, offsetof(type, member))

	/*
	* 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_partial_clear_and_free(map, type, member) \
	hashmap_partial_clear_(map, offsetof(type, member))

	/* 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(struct hashmap_entry *e,
	unsigned int hash)
	{
	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.
	*/
	struct hashmap_entry hashmap_get(const struct hashmap map,
	const struct hashmap_entry *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 struct hashmap_entry *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`.
	*/
	struct hashmap_entry hashmap_get_next(const struct hashmap map,
	const struct hashmap_entry *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.
	*/
	void hashmap_add(struct hashmap map, struct hashmap_entry 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).
	*/
	struct hashmap_entry hashmap_put(struct hashmap map,
	struct hashmap_entry *entry);

	/*
	* Adds or replaces a hashmap entry contained within @keyvar,
	* where @keyvar is a pointer to a struct containing a
	* "struct hashmap_entry" @member.
	*
	* Returns the replaced pointer which is of the same type as @keyvar,
	* or NULL if not found.
	*/
	#define hashmap_put_entry(map, keyvar, member) \
	container_of_or_null_offset(hashmap_put(map, &(keyvar)->member), \
	OFFSETOF_VAR(keyvar, member))

	/*
	* 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`.
	*/
	struct hashmap_entry hashmap_remove(struct hashmap map,
	const struct hashmap_entry *key,
	const void *keydata);

	/*
	* Removes a hashmap entry contained within @keyvar,
	* where @keyvar is a pointer to a struct containing a
	* "struct hashmap_entry" @member.
	*
	* See `hashmap_get` for an explanation of @keydata
	*
	* Returns the replaced pointer which is of the same type as @keyvar,
	* or NULL if not found.
	*/
	#define hashmap_remove_entry(map, keyvar, member, keydata) \
	container_of_or_null_offset( \
	hashmap_remove(map, &(keyvar)->member, keydata), \
	OFFSETOF_VAR(keyvar, member))

	/*
	* 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. */
	void hashmap_iter_init(struct hashmap map, struct hashmap_iter iter);

	/* Returns the next hashmap_entry, or NULL if there are no more entries. */
	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)
	{
	hashmap_iter_init(map, iter);
	return hashmap_iter_next(iter);
	}

	/*
	* returns the first entry in @map using @iter, where the entry is of
	* @type (e.g. "struct foo") and @member is the name of the
	* "struct hashmap_entry" in @type
	*/
	#define hashmap_iter_first_entry(map, iter, type, member) \
	container_of_or_null(hashmap_iter_first(map, iter), type, member)

	/* internal macro for hashmap_for_each_entry */
	#define hashmap_iter_next_entry_offset(iter, offset) \
	container_of_or_null_offset(hashmap_iter_next(iter), offset)

	/* internal macro for hashmap_for_each_entry */
	#define hashmap_iter_first_entry_offset(map, iter, offset) \
	container_of_or_null_offset(hashmap_iter_first(map, iter), offset)

	/*
	* iterate through @map using @iter, @var is a pointer to a type
	* containing a @member which is a "struct hashmap_entry"
	*/
	#define hashmap_for_each_entry(map, iter, var, member) \
	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, \
	OFFSETOF_VAR(var, member)))

	/*
	* returns a pointer of type matching @keyvar, or NULL if nothing found.
	* @keyvar is a pointer to a struct containing a
	* "struct hashmap_entry" @member.
	*/
	#define hashmap_get_entry(map, keyvar, member, keydata) \
	container_of_or_null_offset( \
	hashmap_get(map, &(keyvar)->member, keydata), \
	OFFSETOF_VAR(keyvar, member))

	#define hashmap_get_entry_from_hash(map, hash, keydata, type, member) \
	container_of_or_null(hashmap_get_from_hash(map, hash, keydata), \
	type, member)
	/*
	* returns the next equal pointer to @var, or NULL if not found.
	* @var is a pointer of any type containing "struct hashmap_entry"
	* @member is the name of the "struct hashmap_entry" field
	*/
	#define hashmap_get_next_entry(map, var, member) \
	container_of_or_null_offset(hashmap_get_next(map, &(var)->member), \
	OFFSETOF_VAR(var, member))

	/*
	* iterate @map starting from @var, where @var is a pointer of @type
	* and @member is the name of the "struct hashmap_entry" field in @type
	*/
	#define hashmap_for_each_entry_from(map, var, member) \
	for (; \
	var; \
	var = hashmap_get_next_entry(map, var, member))

	/*
	* 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 counting 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.
	*/
	const void memintern(const void data, size_t len);
	static inline const char strintern(const char string)
	{
	return memintern(string, strlen(string));
	}

	#endif

git / git

git/hashmap.h