GHashTable

typedef struct _GHashTable GHashTable;

The GHashTable struct is an opaque data structure to represent a Hash Table. It should only be accessed via the following functions.

g_hash_table_new ()

GHashTable* g_hash_table_new                (GHashFunc hash_func,
                                             GEqualFunc key_equal_func);

Creates a new GHashTable.

g_hash_table_new_full ()

GHashTable* g_hash_table_new_full           (GHashFunc hash_func,
                                             GEqualFunc key_equal_func,
                                             GDestroyNotify key_destroy_func,
                                             GDestroyNotify value_destroy_func);

Creates a new GHashTable like g_hash_table_new() and allows to specify functions to free the memory allocated for the key and value that get called when removing the entry from the GHashTable.

GHashFunc ()

guint       (*GHashFunc)                    (gconstpointer key);

Specifies the type of the hash function which is passed to g_hash_table_new() when a GHashTable is created.

The function is passed a key and should return a guint hash value. The functions g_direct_hash(), g_int_hash() and g_str_hash() provide hash functions which can be used when the key is a gpointer, gint, and gchar* respectively.

FIXME: Need more here. The hash values should be evenly distributed over a fairly large range? The modulus is taken with the hash table size (a prime number) to find the 'bucket' to place each key into. The function should also be very fast, since it is called for each key lookup.

GEqualFunc ()

gboolean    (*GEqualFunc)                   (gconstpointer a,
                                             gconstpointer b);

Specifies the type of a function used to test two values for equality. The function should return TRUE if both values are equal and FALSE otherwise.

g_hash_table_insert ()

void        g_hash_table_insert             (GHashTable *hash_table,
                                             gpointer key,
                                             gpointer value);

Inserts a new key and value into a GHashTable.

If the key already exists in the GHashTable its current value is replaced with the new value. If you supplied a value_destroy_func when creating the GHashTable, the old value is freed using that function. If you supplied a key_destroy_func when creating the GHashTable, the passed key is freed using that function.

g_hash_table_replace ()

void        g_hash_table_replace            (GHashTable *hash_table,
                                             gpointer key,
                                             gpointer value);

Inserts a new key and value into a GHashTable similar to g_hash_table_insert(). The difference is that if the key already exists in the GHashTable, it gets replaced by the new key. If you supplied a value_destroy_func when creating the GHashTable, the old value is freed using that function. If you supplied a key_destroy_func when creating the GHashTable, the old key is freed using that function.

g_hash_table_size ()

guint       g_hash_table_size               (GHashTable *hash_table);

Returns the number of elements contained in the GHashTable.

g_hash_table_lookup ()

gpointer    g_hash_table_lookup             (GHashTable *hash_table,
                                             gconstpointer key);

Looks up a key in a GHashTable. Note that this function cannot distinguish between a key that is not present and one which is present and has the value NULL. If you need this distinction, use g_hash_table_lookup_extended().

g_hash_table_lookup_extended ()

gboolean    g_hash_table_lookup_extended    (GHashTable *hash_table,
                                             gconstpointer lookup_key,
                                             gpointer *orig_key,
                                             gpointer *value);

Looks up a key in the GHashTable, returning the original key and the associated value and a gboolean which is TRUE if the key was found. This is useful if you need to free the memory allocated for the original key, for example before calling g_hash_table_remove().

g_hash_table_foreach ()

void        g_hash_table_foreach            (GHashTable *hash_table,
                                             GHFunc func,
                                             gpointer user_data);

Calls the given function for each of the key/value pairs in the GHashTable. The function is passed the key and value of each pair, and the given user_data parameter. The hash table may not be modified while iterating over it (you can't add/remove items). To remove all items matching a predicate, use g_hash_table_remove().

g_hash_table_find ()

gpointer    g_hash_table_find               (GHashTable *hash_table,
                                             GHRFunc predicate,
                                             gpointer user_data);

Calls the given function for key/value pairs in the GHashTable until predicate returns TRUE. The function is passed the key and value of each pair, and the given user_data parameter. The hash table may not be modified while iterating over it (you can't add/remove items).

Since 2.4

GHFunc ()

void        (*GHFunc)                       (gpointer key,
                                             gpointer value,
                                             gpointer user_data);

Specifies the type of the function passed to g_hash_table_foreach(). It is called with each key/value pair, together with the user_data parameter which is passed to g_hash_table_foreach().

g_hash_table_remove ()

gboolean    g_hash_table_remove             (GHashTable *hash_table,
                                             gconstpointer key);

Removes a key and its associated value from a GHashTable.

If the GHashTable was created using g_hash_table_new_full(), the key and value are freed using the supplied destroy functions, otherwise you have to make sure that any dynamically allocated values are freed yourself.

g_hash_table_steal ()

gboolean    g_hash_table_steal              (GHashTable *hash_table,
                                             gconstpointer key);

Removes a key and its associated value from a GHashTable without calling the key and value destroy functions.

g_hash_table_foreach_remove ()

guint       g_hash_table_foreach_remove     (GHashTable *hash_table,
                                             GHRFunc func,
                                             gpointer user_data);

Calls the given function for each key/value pair in the GHashTable. If the function returns TRUE, then the key/value pair is removed from the GHashTable. If you supplied key or value destroy functions when creating the GHashTable, they are used to free the memory allocated for the removed keys and values.

g_hash_table_foreach_steal ()

guint       g_hash_table_foreach_steal      (GHashTable *hash_table,
                                             GHRFunc func,
                                             gpointer user_data);

Calls the given function for each key/value pair in the GHashTable. If the function returns TRUE, then the key/value pair is removed from the GHashTable, but no key or value destroy functions are called.

GHRFunc ()

gboolean    (*GHRFunc)                      (gpointer key,
                                             gpointer value,
                                             gpointer user_data);

Specifies the type of the function passed to g_hash_table_foreach_remove(). It is called with each key/value pair, together with the user_data parameter passed to g_hash_table_foreach_remove(). It should return TRUE if the key/value pair should be removed from the GHashTable.

g_hash_table_freeze()

#define     g_hash_table_freeze(hash_table)

This function is deprecated and will be removed in the next major release of GLib. It does nothing.

g_hash_table_thaw()

#define     g_hash_table_thaw(hash_table)

This function is deprecated and will be removed in the next major release of GLib. It does nothing.

g_hash_table_destroy ()

void        g_hash_table_destroy            (GHashTable *hash_table);

Destroys the GHashTable. If keys and/or values are dynamically allocated, you should either free them first or create the GHashTable using g_hash_table_new_full(). In the latter case the destroy functions you supplied will be called on all keys and values before destroying the GHashTable.

g_direct_equal ()

gboolean    g_direct_equal                  (gconstpointer v,
                                             gconstpointer v2);

Compares two gpointer arguments and returns TRUE if they are equal. It can be passed to g_hash_table_new() as the key_equal_func parameter, when using pointers as keys in a GHashTable.

g_direct_hash ()

guint       g_direct_hash                   (gconstpointer v);

Converts a gpointer to a hash value. It can be passed to g_hash_table_new() as the hash_func parameter, when using pointers as keys in a GHashTable.

g_int_equal ()

gboolean    g_int_equal                     (gconstpointer v,
                                             gconstpointer v2);

Compares the two gint values being pointed to and returns TRUE if they are equal. It can be passed to g_hash_table_new() as the key_equal_func parameter, when using pointers to integers as keys in a GHashTable.

g_int_hash ()

guint       g_int_hash                      (gconstpointer v);

Converts a pointer to a gint to a hash value. It can be passed to g_hash_table_new() as the hash_func parameter, when using pointers to integers values as keys in a GHashTable.

g_str_equal ()

gboolean    g_str_equal                     (gconstpointer v,
                                             gconstpointer v2);

Compares two strings and returns TRUE if they are equal. It can be passed to g_hash_table_new() as the key_equal_func parameter, when using strings as keys in a GHashTable.

g_str_hash ()

guint       g_str_hash                      (gconstpointer v);

Converts a string to a hash value. It can be passed to g_hash_table_new() as the hash_func parameter, when using strings as keys in a GHashTable.