## Hash Tables

Hash Tables — associations between keys and values so that given a key the value can be found quickly

## Functions

GHashTable * | g_hash_table_new ()
GHashTable * | g_hash_table_new_full ()
guint | (*GHashFunc) ()
gboolean | (*GEqualFunc) ()
gboolean | g_hash_table_insert ()
gboolean | g_hash_table_replace ()
gboolean | g_hash_table_add ()
gboolean | g_hash_table_contains ()
guint | g_hash_table_size ()
gpointer | g_hash_table_lookup ()
gboolean | g_hash_table_lookup_extended ()
void | g_hash_table_foreach ()
gpointer | g_hash_table_find ()
void | (*GHFunc) ()
gboolean | g_hash_table_remove ()
gboolean | g_hash_table_steal ()
guint | g_hash_table_foreach_remove ()
guint | g_hash_table_foreach_steal ()
void | g_hash_table_remove_all ()
void | g_hash_table_steal_all ()
GList * | g_hash_table_get_keys ()
GList * | g_hash_table_get_values ()
gpointer * | g_hash_table_get_keys_as_array ()
gboolean | (*GHRFunc) ()
#define | g_hash_table_freeze()
#define | g_hash_table_thaw()
void | g_hash_table_destroy ()
GHashTable * | g_hash_table_ref ()
void | g_hash_table_unref ()
void | g_hash_table_iter_init ()
gboolean | g_hash_table_iter_next ()
GHashTable * | g_hash_table_iter_get_hash_table ()
void | g_hash_table_iter_replace ()
void | g_hash_table_iter_remove ()
void | g_hash_table_iter_steal ()
gboolean | g_direct_equal ()
guint | g_direct_hash ()
gboolean | g_int_equal ()
guint | g_int_hash ()
gboolean | g_int64_equal ()
guint | g_int64_hash ()
gboolean | g_double_equal ()
guint | g_double_hash ()
gboolean | g_str_equal ()
guint | g_str_hash ()

## Types and Values

| GHashTable
struct | GHashTableIter

## Includes

    #include <glib.h>

## Description

A GHashTable provides associations between keys and values which is optimized so that given a key, the associated value can be found very quickly.

Note that neither keys nor values are copied when inserted into the GHashTable, so they must exist for the lifetime of the GHashTable. This means that the use of static strings is OK, but temporary strings (i.e. those created in buffers and those returned by GTK+ widgets) should be copied with `g_strdup()` before being inserted.

If keys or values are dynamically allocated, you must be careful to ensure that they are freed when they are removed from the GHashTable, and also when they are overwritten by new insertions into the GHashTable. It is also not advisable to mix static strings and dynamically-allocated strings in a GHashTable, because it then becomes difficult to determine whether the string should be freed.

To create a GHashTable, use `g_hash_table_new()`.

To insert a key and value into a GHashTable, use `g_hash_table_insert()`.

To lookup a value corresponding to a given key, use `g_hash_table_lookup()` and `g_hash_table_lookup_extended()`.

g_hash_table_lookup_extended() can also be used to simply check if a key is present in the hash table.

To remove a key and value, use `g_hash_table_remove()`.

To call a function for each key and value pair use `g_hash_table_foreach()` or use a iterator to iterate over the key/value pairs in the hash table, see GHashTableIter.

To destroy a GHashTable use `g_hash_table_destroy()`.

A common use-case for hash tables is to store information about a set of keys, without associating any particular value with each key. GHashTable optimizes one way of doing so: If you store only key-value pairs where key == value, then GHashTable does not allocate memory to store the values, which can be a considerable space saving, if your set is large. The functions `g_hash_table_add()` and `g_hash_table_contains()` are designed to be used when using GHashTable this way.

## Functions

### g_hash_table_new ()

    GHashTable *
    g_hash_table_new (GHashFunc hash_func,
                      GEqualFunc key_equal_func);

Creates a new GHashTable with a reference count of 1.

Hash values returned by `hash_func` are used to determine where keys are stored within the GHashTable data structure. The `g_direct_hash()`, `g_int_hash()`, `g_int64_hash()`, `g_double_hash()` and `g_str_hash()` functions are provided for some common types of keys. If `hash_func` is `NULL`, `g_direct_hash()` is used.

`key_equal_func` is used when looking up keys in the GHashTable. The `g_direct_equal()`, `g_int_equal()`, `g_int64_equal()`, `g_double_equal()` and `g_str_equal()` functions are provided for the most common types of keys. If `key_equal_func` is `NULL`, keys are compared directly in a similar fashion to `g_direct_equal()`, but without the overhead of a function call.

#### Parameters

hash_func | a function to create a hash value from a key |
key_equal_func | a function to check two keys for equality |

#### Returns

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()` with a reference count of 1 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.

Since version 2.42 it is permissible for destroy notify functions to recursively remove further items from the hash table. This is only permissible if the application still holds a reference to the hash table. This means that you may need to ensure that the hash table is empty by calling g_hash_table_remove_all before releasing the last reference using `g_hash_table_unref()`.

#### Parameters

hash_func | a function to create a hash value from a key |
key_equal_func | a function to check two keys for equality |
key_destroy_func | a function to free the memory allocated for the key used when removing the entry from the GHashTable, or `NULL` if you don't want to supply such a function. | [allow-none]
value_destroy_func | a function to free the memory allocated for the value used when removing the entry from the GHashTable, or `NULL` if you don't want to supply such a function. | [allow-none]

#### Returns

a new 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.

g_direct_hash() is also the appropriate hash function for keys of the form `GINT_TO_POINTER (n)` (or similar macros).

<!-- FIXME: Need more here. --> A good hash functions should produce hash values that are 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.

Note that the hash functions provided by GLib have these qualities, but are not particularly robust against manufactured keys that cause hash collisions. Therefore, you should consider choosing a more secure hash function when using a GHashTable with keys that originate in untrusted data (such as HTTP requests). Using `g_str_hash()` in that situation might make your application vulerable to Algorithmic Complexity Attacks.

The key to choosing a good hash is unpredictability. Even cryptographic hashes are very easy to find collisions for when the remainder is taken modulo a somewhat predictable prime number. There must be an element of randomness that an attacker is unable to guess.

#### Parameters

key | a key |

#### Returns

the hash value corresponding to the key

### 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.

#### Parameters

a | a value |
b | a value to compare with |

#### Returns

`TRUE` if `a` = `b` ; `FALSE` otherwise

### g_hash_table_insert ()

    gboolean
    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.

#### Parameters

hash_table | a GHashTable |
key | a key to insert |
value | the value to associate with the key |

#### Returns

`TRUE` if the key did not exist yet

### g_hash_table_replace ()

    gboolean
    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.

#### Parameters

hash_table | a GHashTable |
key | a key to insert |
value | the value to associate with the key |

#### Returns

`TRUE` if the key did not exist yet

### g_hash_table_add ()

    gboolean
    g_hash_table_add (GHashTable *hash_table,
                      gpointer key);

This is a convenience function for using a GHashTable as a set. It is equivalent to calling `g_hash_table_replace()` with `key` as both the key and the value.

When a hash table only ever contains keys that have themselves as the corresponding value it is able to be stored more efficiently. See the discussion in the section description.

#### Parameters

hash_table | a GHashTable |
key | a key to insert |

#### Returns

`TRUE` if the key did not exist yet

Since: 2.32

### g_hash_table_contains ()

    gboolean
    g_hash_table_contains (GHashTable *hash_table,
                           gconstpointer key);

Checks if `key` is in `hash_table` .

#### Parameters

hash_table | a GHashTable |
key | a key to check |

#### Returns

`TRUE` if `key` is in `hash_table` , `FALSE` otherwise.

Since: 2.32

### g_hash_table_size ()

    guint
    g_hash_table_size (GHashTable *hash_table);

Returns the number of elements contained in the GHashTable.

#### Parameters

hash_table | a GHashTable |

#### Returns

the number of key/value pairs 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()`.

#### Parameters

hash_table | a GHashTable |
key | the key to look up |

#### Returns

the associated value, or `NULL` if the key is not found.

[allow-none]

### 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()`.

You can actually pass `NULL` for `lookup_key` to test whether the `NULL` key exists, provided the hash and equal functions of `hash_table` are `NULL`-safe.

#### Parameters

hash_table | a GHashTable |
lookup_key | the key to look up |
orig_key | return location for the original key, or `NULL`. | [allow-none]
value | return location for the value associated with the key, or `NULL`. | [allow-none]

#### Returns

`TRUE` if the key was found in the GHashTable

### 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_foreach_remove()`.

See `g_hash_table_find()` for performance caveats for linear order searches in contrast to `g_hash_table_lookup()`.

#### Parameters

hash_table | a GHashTable |
func | the function to call for each key/value pair |
user_data | user data to pass to the function |

### 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).

Note, that hash tables are really only optimized for forward lookups, i.e. `g_hash_table_lookup()`. So code that frequently issues `g_hash_table_find()` or `g_hash_table_foreach()` (e.g. in the order of once per every entry in a hash table) should probably be reworked to use additional or different data structures for reverse lookups (keep in mind that an O(n) find/foreach operation issued for all n values in a hash table ends up needing O(n*n) operations).

#### Parameters

hash_table | a GHashTable |
predicate | function to test the key/value pairs for a certain property |
user_data | user data to pass to the function |

#### Returns

The value of the first key/value pair is returned, for which `predicate` evaluates to `TRUE`. If no pair with the requested property is found, `NULL` is returned.

[allow-none]

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()`.

#### Parameters

key | a key |
value | the value corresponding to the key |
user_data | user data 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.

#### Parameters

hash_table | a GHashTable |
key | the key to remove |

#### Returns

`TRUE` if the key was found and removed from the GHashTable

### 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.

#### Parameters

hash_table | a GHashTable |
key | the key to remove |

#### Returns

`TRUE` if the key was found and removed from the GHashTable

### 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.

See GHashTableIter for an alternative way to loop over the key/value pairs in the hash table.

#### Parameters

hash_table | a GHashTable |
func | the function to call for each key/value pair |
user_data | user data to pass to the function |

#### Returns

the number of key/value pairs removed

### 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.

See GHashTableIter for an alternative way to loop over the key/value pairs in the hash table.

#### Parameters

hash_table | a GHashTable |
func | the function to call for each key/value pair |
user_data | user data to pass to the function |

#### Returns

the number of key/value pairs removed.

### g_hash_table_remove_all ()

    void
    g_hash_table_remove_all (GHashTable *hash_table);

Removes all keys and their associated values from a GHashTable.

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

#### Parameters

hash_table | a GHashTable |

Since: 2.12

### g_hash_table_steal_all ()

    void
    g_hash_table_steal_all (GHashTable *hash_table);

Removes all keys and their associated values from a GHashTable without calling the key and value destroy functions.

#### Parameters

hash_table | a GHashTable |

Since: 2.12

### g_hash_table_get_keys ()

    GList *
    g_hash_table_get_keys (GHashTable *hash_table);

Retrieves every key inside `hash_table` . The returned data is valid until changes to the hash release those keys.

This iterates over every entry in the hash table to build its return value. To iterate over the entries in a GHashTable more efficiently, use a GHashTableIter.

#### Parameters

hash_table | a GHashTable |

#### Returns

a GList containing all the keys inside the hash table. The content of the list is owned by the hash table and should not be modified or freed. Use `g_list_free()` when done using the list.

Since: 2.14

### g_hash_table_get_values ()

    GList *
    g_hash_table_get_values (GHashTable *hash_table);

Retrieves every value inside `hash_table` . The returned data is valid until `hash_table` is modified.

This iterates over every entry in the hash table to build its return value. To iterate over the entries in a GHashTable more efficiently, use a GHashTableIter.

#### Parameters

hash_table | a GHashTable |

#### Returns

a GList containing all the values inside the hash table. The content of the list is owned by the hash table and should not be modified or freed. Use `g_list_free()` when done using the list.

Since: 2.14

### g_hash_table_get_keys_as_array ()

    gpointer *
    g_hash_table_get_keys_as_array (GHashTable *hash_table,
                                    guint *length);

Retrieves every key inside `hash_table` , as an array.

The returned array is `NULL`-terminated but may contain `NULL` as a key. Use `length` to determine the true length if it's possible that `NULL` was used as the value for a key.

Note: in the common case of a string-keyed GHashTable, the return value of this function can be conveniently cast to (const gchar **).

This iterates over every entry in the hash table to build its return value. To iterate over the entries in a GHashTable more efficiently, use a GHashTableIter.

You should always free the return result with `g_free()`. In the above-mentioned case of a string-keyed hash table, it may be appropriate to use `g_strfreev()` if you call `g_hash_table_steal_all()` first to transfer ownership of the keys.

#### Parameters

hash_table | a GHashTable |
length | the length of the returned array. | [out]

#### Returns

a `NULL`-terminated array containing each key from the table.

[array length=length][transfer container]

Since: 2.40

### 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.

#### Parameters

key | a key |
value | the value associated with the key |
user_data | user data passed to `g_hash_table_remove()` |

#### Returns

`TRUE` if the key/value pair should be removed from the GHashTable

### g_hash_table_freeze()

    #define             g_hash_table_freeze(hash_table)

`g_hash_table_freeze` is deprecated and should not be used in newly-written code.

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

#### Parameters

hash_table | a GHashTable |

### g_hash_table_thaw()

    #define             g_hash_table_thaw(hash_table)

`g_hash_table_thaw` is deprecated and should not be used in newly-written code.

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

#### Parameters

hash_table | a GHashTable |

### g_hash_table_destroy ()

    void
    g_hash_table_destroy (GHashTable *hash_table);

Destroys all keys and values in the GHashTable and decrements its reference count by 1. If keys and/or values are dynamically allocated, you should either free them first or create the GHashTable with destroy notifiers using `g_hash_table_new_full()`. In the latter case the destroy functions you supplied will be called on all keys and values during the destruction phase.

#### Parameters

hash_table | a GHashTable |

### g_hash_table_ref ()

    GHashTable *
    g_hash_table_ref (GHashTable *hash_table);

Atomically increments the reference count of `hash_table` by one. This function is MT-safe and may be called from any thread.

#### Parameters

hash_table | a valid GHashTable |

#### Returns

the passed in GHashTable

Since: 2.10

### g_hash_table_unref ()

    void
    g_hash_table_unref (GHashTable *hash_table);

Atomically decrements the reference count of `hash_table` by one. If the reference count drops to 0, all keys and values will be destroyed, and all memory allocated by the hash table is released. This function is MT-safe and may be called from any thread.

#### Parameters

hash_table | a valid GHashTable |

Since: 2.10

### g_hash_table_iter_init ()

    void
    g_hash_table_iter_init (GHashTableIter *iter,
                            GHashTable *hash_table);

Initializes a key/value pair iterator and associates it with `hash_table` . Modifying the hash table after calling this function invalidates the returned iterator.

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    GHashTableIter iter;
    gpointer key, value;

    g_hash_table_iter_init (&iter, hash_table);
    while (g_hash_table_iter_next (&iter, &key, &value))
      {
        // do something with key and value
      }

#### Parameters

iter | an uninitialized GHashTableIter |
hash_table | a GHashTable |

Since: 2.16

### g_hash_table_iter_next ()

    gboolean
    g_hash_table_iter_next (GHashTableIter *iter,
                            gpointer *key,
                            gpointer *value);

Advances `iter` and retrieves the key and/or value that are now pointed to as a result of this advancement. If `FALSE` is returned, `key` and `value` are not set, and the iterator becomes invalid.

#### Parameters

iter | an initialized GHashTableIter |
key | a location to store the key, or `NULL`. | [allow-none]
value | a location to store the value, or `NULL`. | [allow-none]

#### Returns

`FALSE` if the end of the GHashTable has been reached.

Since: 2.16

### g_hash_table_iter_get_hash_table ()

    GHashTable *
    g_hash_table_iter_get_hash_table (GHashTableIter *iter);

Returns the GHashTable associated with `iter` .

#### Parameters

iter | an initialized GHashTableIter |

#### Returns

the GHashTable associated with `iter` .

Since: 2.16

### g_hash_table_iter_replace ()

    void
    g_hash_table_iter_replace (GHashTableIter *iter,
                               gpointer value);

Replaces the value currently pointed to by the iterator from its associated GHashTable. Can only be called after `g_hash_table_iter_next()` returned `TRUE`.

If you supplied a `value_destroy_func` when creating the GHashTable, the old value is freed using that function.

#### Parameters

iter | an initialized GHashTableIter |
value | the value to replace with |

Since: 2.30

### g_hash_table_iter_remove ()

    void
    g_hash_table_iter_remove (GHashTableIter *iter);

Removes the key/value pair currently pointed to by the iterator from its associated GHashTable. Can only be called after `g_hash_table_iter_next()` returned `TRUE`, and cannot be called more than once for the same key/value pair.

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.

It is safe to continue iterating the GHashTable afterward:

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    while (g_hash_table_iter_next (&iter, &key, &value))
      {
        if (condition)
          g_hash_table_iter_remove (&iter);
      }

#### Parameters

iter | an initialized GHashTableIter |

Since: 2.16

### g_hash_table_iter_steal ()

    void
    g_hash_table_iter_steal (GHashTableIter *iter);

Removes the key/value pair currently pointed to by the iterator from its associated GHashTable, without calling the key and value destroy functions. Can only be called after `g_hash_table_iter_next()` returned `TRUE`, and cannot be called more than once for the same key/value pair.

#### Parameters

iter | an initialized GHashTableIter |

Since: 2.16

### g_direct_equal ()

    gboolean
    g_direct_equal (gconstpointer v1,
                    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 opaque pointers compared by pointer value as keys in a GHashTable.

This equality function is also appropriate for keys that are integers stored in pointers, such as `GINT_TO_POINTER (n)`.

#### Parameters

v1 | a key. | [allow-none]
v2 | a key to compare with `v1` . | [allow-none]

#### Returns

`TRUE` if the two keys match.

### 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 opaque pointers compared by pointer value as keys in a GHashTable.

This hash function is also appropriate for keys that are integers stored in pointers, such as `GINT_TO_POINTER (n)`.

#### Parameters

v | a gpointer key. | [allow-none]

#### Returns

a hash value corresponding to the key.

### g_int_equal ()

    gboolean
    g_int_equal (gconstpointer v1,
                 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 non-`NULL` pointers to integers as keys in a GHashTable.

Note that this function acts on pointers to gint, not on gint directly: if your hash table's keys are of the form `GINT_TO_POINTER (n)`, use `g_direct_equal()` instead.

#### Parameters

v1 | a pointer to a gint key |
v2 | a pointer to a gint key to compare with `v1` |

#### Returns

`TRUE` if the two keys match.

### 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 non-`NULL` pointers to integer values as keys in a GHashTable.

Note that this function acts on pointers to gint, not on gint directly: if your hash table's keys are of the form `GINT_TO_POINTER (n)`, use `g_direct_hash()` instead.

#### Parameters

v | a pointer to a gint key |

#### Returns

a hash value corresponding to the key.

### g_int64_equal ()

    gboolean
    g_int64_equal (gconstpointer v1,
                   gconstpointer v2);

Compares the two gint64 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 non-`NULL` pointers to 64-bit integers as keys in a GHashTable.

#### Parameters

v1 | a pointer to a gint64 key |
v2 | a pointer to a gint64 key to compare with `v1` |

#### Returns

`TRUE` if the two keys match.

Since: 2.22

### g_int64_hash ()

    guint
    g_int64_hash (gconstpointer v);

Converts a pointer to a gint64 to a hash value.

It can be passed to `g_hash_table_new()` as the `hash_func` parameter, when using non-`NULL` pointers to 64-bit integer values as keys in a GHashTable.

#### Parameters

v | a pointer to a gint64 key |

#### Returns

a hash value corresponding to the key.

Since: 2.22

### g_double_equal ()

    gboolean
    g_double_equal (gconstpointer v1,
                    gconstpointer v2);

Compares the two gdouble 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 non-`NULL` pointers to doubles as keys in a GHashTable.

#### Parameters

v1 | a pointer to a gdouble key |
v2 | a pointer to a gdouble key to compare with `v1` |

#### Returns

`TRUE` if the two keys match.

Since: 2.22

### g_double_hash ()

    guint
    g_double_hash (gconstpointer v);

Converts a pointer to a gdouble to a hash value. It can be passed to `g_hash_table_new()` as the `hash_func` parameter, It can be passed to `g_hash_table_new()` as the `hash_func` parameter, when using non-`NULL` pointers to doubles as keys in a GHashTable.

#### Parameters

v | a pointer to a gdouble key |

#### Returns

a hash value corresponding to the key.

Since: 2.22

### g_str_equal ()

    gboolean
    g_str_equal (gconstpointer v1,
                 gconstpointer v2);

Compares two strings for byte-by-byte equality and returns `TRUE` if they are equal. It can be passed to `g_hash_table_new()` as the `key_equal_func` parameter, when using non-`NULL` strings as keys in a GHashTable.

Note that this function is primarily meant as a hash table comparison function. For a general-purpose, `NULL`-safe string comparison function, see `g_strcmp0()`.

#### Parameters

v1 | a key |
v2 | a key to compare with `v1` |

#### Returns

`TRUE` if the two keys match

### g_str_hash ()

    guint
    g_str_hash (gconstpointer v);

Converts a string to a hash value.

This function implements the widely used "djb" hash apparently posted by Daniel Bernstein to comp.lang.c some time ago. The 32 bit unsigned hash value starts at 5381 and for each byte 'c' in the string, is updated: `hash = hash * 33 + c`. This function uses the signed value of each byte.

It can be passed to `g_hash_table_new()` as the `hash_func` parameter, when using non-`NULL` strings as keys in a GHashTable.

Note that this function may not be a perfect fit for all use cases. For example, it produces some hash collisions with strings as short as 2.

#### Parameters

v | a string key |

#### Returns

a hash value corresponding to the key

## Types and Values

### 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.

### struct GHashTableIter

    struct GHashTableIter {
    };

A GHashTableIter structure represents an iterator that can be used to iterate over the elements of a GHashTable. GHashTableIter structures are typically allocated on the stack and then initialized with `g_hash_table_iter_init()`.