libwget-hashmap(3)

NAME
libwget-hashmap - Hashmap functions

SYNOPSIS

  Functions
wget_hashmap_iterator * wget_hashmap_iterator_alloc (wget_hashmap *h)
void wget_hashmap_iterator_free (wget_hashmap_iterator **iter)
void * wget_hashmap_iterator_next (wget_hashmap_iterator *iter, void **value)
wget_hashmap * wget_hashmap_create (int max, wget_hashmap_hash_fn *hash, wget_hashmap_compare_fn *cmp)
int wget_hashmap_put (wget_hashmap *h, const void *key, const void *value)
int wget_hashmap_contains (const wget_hashmap *h, const void *key)
int wget_hashmap_get (const wget_hashmap *h, const void *key, void **value)
int wget_hashmap_remove (wget_hashmap *h, const void *key)
int wget_hashmap_remove_nofree (wget_hashmap *h, const void *key)
void wget_hashmap_free (wget_hashmap **h)
void wget_hashmap_clear (wget_hashmap *h)
int wget_hashmap_size (const wget_hashmap *h)
int wget_hashmap_browse (const wget_hashmap *h, wget_hashmap_browse_fn *browse, void *ctx)
void wget_hashmap_setcmpfunc (wget_hashmap *h, wget_hashmap_compare_fn *cmp)
int wget_hashmap_sethashfunc (wget_hashmap *h, wget_hashmap_hash_fn *hash)
void wget_hashmap_set_key_destructor (wget_hashmap *h, wget_hashmap_key_destructor *destructor)
void wget_hashmap_set_value_destructor (wget_hashmap *h, wget_hashmap_value_destructor *destructor)
void wget_hashmap_set_load_factor (wget_hashmap *h, float factor)
void wget_hashmap_set_resize_factor (wget_hashmap *h, float factor)
typedef struct wget_hashmap_st wget_hashmap
Type of the hashmap.
typedef int wget_hashmap_compare_fn(const void *key1, const void *key2)
Type of the hashmap compare function.
typedef unsigned int wget_hashmap_hash_fn(const void *key)
Type of the hashmap hash function.
typedef int wget_hashmap_browse_fn(void *ctx, const void *key, void *value)
Type of the hashmap browse callback function.
typedef void wget_hashmap_key_destructor(void *key)
Type of the hashmap key destructor function.
typedef void wget_hashmap_value_destructor(void *value)
Type of the hashmap value destructor function.

Detailed Description

Hashmaps are key/value stores that perform at O(1) for insertion, searching and removing.

Function Documentation

  wget_hashmap_iterator * wget_hashmap_iterator_alloc (wget_hashmap * h)

Parameters
    h Hashmap

Returns
    New iterator instance for h

Creates a hashmap iterator for h.

  void wget_hashmap_iterator_free (wget_hashmap_iterator ** iter)

Parameters
    iter Hashmap iterator

Free the given iterator iter.

  void * wget_hashmap_iterator_next (wget_hashmap_iterator * iter, void ** value)

Parameters
    iter Hashmap iterator
    value Pointer to the value belonging to the returned key

Returns
    Pointer to the key or NULL if no more elements left

Returns the next key / value in the hashmap. If all key/value pairs have been iterated over the function returns NULL and value is untouched.

When iterating over a hashmap, the order of returned key/value pairs is not defined.

  wget_hashmap * wget_hashmap_create (int max, wget_hashmap_hash_fn * hash, wget_hashmap_compare_fn * cmp)

Parameters
    max Initial number of pre-allocated entries
    hash Hash function to build hashes from elements
    cmp Comparison function used to find elements

Returns
    New hashmap instance

Create a new hashmap instance with initial size max. It should be free'd after use with wget_hashmap_free().

Before the first insertion of an element, hash and cmp must be set. So if you use NULL values here, you have to call wget_hashmap_setcmpfunc() and/or wget_hashmap_hashcmpfunc() with appropriate function pointers. No doing so will result in undefined behavior (likely you'll see a segmentation fault).

  int wget_hashmap_put (wget_hashmap * h, const void * key, const void * value)

Parameters
    h Hashmap to put data into
    key Key to insert into h
    value Value to insert into h

Returns
    0 if inserted a new entry, 1 if entry existed, WGET_E_MEMORY if internal allocation failed

Insert a key/value pair into hashmap h.

key and value are not cloned, the hashmap takes 'ownership' of both.

If key already exists and the pointer values the old and the new key differ, the old key will be destroyed by calling the key destructor function (default is free()).

To realize a hashset (just keys without values), value may be NULL.

Neither h nor key must be NULL, else the return value will always be 0.

  int wget_hashmap_contains (const wget_hashmap * h, const void * key)

Parameters
    h Hashmap
    key Key to search for

Returns
    1 if key has been found, 0 if not found

Check if key exists in h.

  int wget_hashmap_get (const wget_hashmap * h, const void * key, void ** value)

Parameters
    h Hashmap
    key Key to search for
    value Value to be returned

Returns
    1 if key has been found, 0 if not found

Get the value for a given key.

Neither h nor key must be NULL.

  int wget_hashmap_remove (wget_hashmap * h, const void * key)

Parameters
    h Hashmap
    key Key to be removed

Returns
    1 if key has been removed, 0 if not found

Remove key from hashmap h.

If key is found, the key and value destructor functions are called when removing the entry from the hashmap.

  int wget_hashmap_remove_nofree (wget_hashmap * h, const void * key)

Parameters
    h Hashmap
    key Key to be removed

Returns
    1 if key has been removed, 0 if not found

Remove key from hashmap h.

Key and value destructor functions are not called when removing the entry from the hashmap.

  void wget_hashmap_free (wget_hashmap ** h)

Parameters
    h Hashmap to be free'd

Remove all entries from hashmap h and free the hashmap instance.

Key and value destructor functions are called for each entry in the hashmap.

  void wget_hashmap_clear (wget_hashmap * h)

Parameters
    h Hashmap to be cleared

Remove all entries from hashmap h.

Key and value destructor functions are called for each entry in the hashmap.

  int wget_hashmap_size (const wget_hashmap * h)

Parameters
    h Hashmap

Returns
    Number of entries in hashmap h

Return the number of entries in the hashmap h.

  int wget_hashmap_browse (const wget_hashmap * h, wget_hashmap_browse_fn * browse, void * ctx)

Parameters
    h Hashmap
    browse Function to be called for each element of h
    ctx Context variable use as param to browse

Returns
    Return value of the last call to browse

Call function browse for each element of hashmap h or until browse returns a value not equal to zero.

browse is called with ctx and the pointer to the current element.

The return value of the last call to browse is returned or 0 if either h or browse is NULL.

  void wget_hashmap_setcmpfunc (wget_hashmap * h, wget_hashmap_compare_fn * cmp)

Parameters
    h Hashmap
    cmp Comparison function used to find keys

Set the comparison function.

  int wget_hashmap_sethashfunc (wget_hashmap * h, wget_hashmap_hash_fn * hash)

Parameters
    h Hashmap
    hash Hash function used to hash keys

Returns
    WGET_E_SUCCESS if set successfully, else WGET_E_MEMORY or WGET_E_INVALID

Set the key hash function.

The keys of all entries in the hashmap will be hashed again. This includes a memory allocation, so there is a possibility of failure.

  void wget_hashmap_set_key_destructor (wget_hashmap * h, wget_hashmap_key_destructor * destructor)

Parameters
    h Hashmap
    destructor Destructor function for keys

Set the key destructor function.

Default is free().

  void wget_hashmap_set_value_destructor (wget_hashmap * h, wget_hashmap_value_destructor * destructor)

Parameters
    h Hashmap
    destructor Destructor function for values

Set the value destructor function.

Default is free().

  void wget_hashmap_set_load_factor (wget_hashmap * h, float factor)

Parameters
    h Hashmap
    factor The load factor

Set the load factor function.

The load factor is determines when to resize the internal memory. 0.75 means 'resize if 75% or more of all slots are used'.

The resize strategy is set by wget_hashmap_set_growth_policy().

The resize (and rehashing) occurs earliest on the next insertion of a new key.

Default is 0.75.

  void wget_hashmap_set_resize_factor (wget_hashmap * h, float factor)

Parameters
    h Hashmap
    factor Hashmap growth factor

Set the factor for resizing the hashmap when it's load factor is reached.

The new size is 'factor * oldsize'. If the new size is less or equal 0, the involved put function will do nothing and the internal state of the hashmap will not change.

Default is 2.

Author

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