Double-ended Queues

Double-ended Queues — double-ended queue data structure

Types and Values

struct GQueue
#define G_QUEUE_INIT

Includes

#include <glib.h>

Description

The GQueue structure and its associated functions provide a standard queue data structure. Internally, GQueue uses the same data structure as GList to store elements.

The data contained in each element can be either integer values, by using one of the Type Conversion Macros, or simply pointers to any type of data.

To create a new GQueue, use g_queue_new().

To initialize a statically-allocated GQueue, use G_QUEUE_INIT or g_queue_init().

To add elements, use g_queue_push_head(), g_queue_push_head_link(), g_queue_push_tail() and g_queue_push_tail_link().

To remove elements, use g_queue_pop_head() and g_queue_pop_tail().

To free the entire queue, use g_queue_free().

Functions

g_queue_new ()

GQueue *
g_queue_new (void);

Creates a new GQueue.

Returns

a newly allocated GQueue


g_queue_free ()

void
g_queue_free (GQueue *queue);

Frees the memory allocated for the GQueue. Only call this function if queue was created with g_queue_new(). If queue elements contain dynamically-allocated memory, they should be freed first.

If queue elements contain dynamically-allocated memory, you should either use g_queue_free_full() or free them manually first.

Parameters

queue

a GQueue

 

g_queue_free_full ()

void
g_queue_free_full (GQueue *queue,
                   GDestroyNotify free_func);

Convenience method, which frees all the memory used by a GQueue, and calls the specified destroy function on every element's data.

Parameters

queue

a pointer to a GQueue

 

free_func

the function to be called to free each element's data

 

Since: 2.32


g_queue_init ()

void
g_queue_init (GQueue *queue);

A statically-allocated GQueue must be initialized with this function before it can be used. Alternatively you can initialize it with G_QUEUE_INIT. It is not necessary to initialize queues created with g_queue_new().

Parameters

queue

an uninitialized GQueue

 

Since: 2.14


g_queue_clear ()

void
g_queue_clear (GQueue *queue);

Removes all the elements in queue . If queue elements contain dynamically-allocated memory, they should be freed first.

Parameters

queue

a GQueue

 

Since: 2.14


g_queue_is_empty ()

gboolean
g_queue_is_empty (GQueue *queue);

Returns TRUE if the queue is empty.

Parameters

queue

a GQueue.

 

Returns

TRUE if the queue is empty


g_queue_get_length ()

guint
g_queue_get_length (GQueue *queue);

Returns the number of items in queue .

Parameters

queue

a GQueue

 

Returns

the number of items in queue

Since: 2.4


g_queue_reverse ()

void
g_queue_reverse (GQueue *queue);

Reverses the order of the items in queue .

Parameters

queue

a GQueue

 

Since: 2.4


g_queue_copy ()

GQueue *
g_queue_copy (GQueue *queue);

Copies a queue . Note that is a shallow copy. If the elements in the queue consist of pointers to data, the pointers are copied, but the actual data is not.

Parameters

queue

a GQueue

 

Returns

a copy of queue

Since: 2.4


g_queue_foreach ()

void
g_queue_foreach (GQueue *queue,
                 GFunc func,
                 gpointer user_data);

Calls func for each element in the queue passing user_data to the function.

Parameters

queue

a GQueue

 

func

the function to call for each element's data

 

user_data

user data to pass to func

 

Since: 2.4


g_queue_find ()

GList *
g_queue_find (GQueue *queue,
              gconstpointer data);

Finds the first link in queue which contains data .

Parameters

queue

a GQueue

 

data

data to find

 

Returns

the first link in queue which contains data

Since: 2.4


g_queue_find_custom ()

GList *
g_queue_find_custom (GQueue *queue,
                     gconstpointer data,
                     GCompareFunc func);

Finds an element in a GQueue, using a supplied function to find the desired element. It iterates over the queue, calling the given function which should return 0 when the desired element is found. The function takes two gconstpointer arguments, the GQueue element's data as the first argument and the given user data as the second argument.

Parameters

queue

a GQueue

 

data

user data passed to func

 

func

a GCompareFunc to call for each element. It should return 0 when the desired element is found

 

Returns

the found link, or NULL if it wasn't found

Since: 2.4


g_queue_sort ()

void
g_queue_sort (GQueue *queue,
              GCompareDataFunc compare_func,
              gpointer user_data);

Sorts queue using compare_func .

Parameters

queue

a GQueue

 

compare_func

the GCompareDataFunc used to sort queue . This function is passed two elements of the queue and should return 0 if they are equal, a negative value if the first comes before the second, and a positive value if the second comes before the first.

 

user_data

user data passed to compare_func

 

Since: 2.4


g_queue_push_head ()

void
g_queue_push_head (GQueue *queue,
                   gpointer data);

Adds a new element at the head of the queue.

Parameters

queue

a GQueue.

 

data

the data for the new element.

 

g_queue_push_tail ()

void
g_queue_push_tail (GQueue *queue,
                   gpointer data);

Adds a new element at the tail of the queue.

Parameters

queue

a GQueue

 

data

the data for the new element

 

g_queue_push_nth ()

void
g_queue_push_nth (GQueue *queue,
                  gpointer data,
                  gint n);

Inserts a new element into queue at the given position.

Parameters

queue

a GQueue

 

data

the data for the new element

 

n

the position to insert the new element. If n is negative or larger than the number of elements in the queue , the element is added to the end of the queue.

 

Since: 2.4


g_queue_pop_head ()

gpointer
g_queue_pop_head (GQueue *queue);

Removes the first element of the queue and returns its data.

Parameters

queue

a GQueue

 

Returns

the data of the first element in the queue, or NULL if the queue is empty


g_queue_pop_tail ()

gpointer
g_queue_pop_tail (GQueue *queue);

Removes the last element of the queue and returns its data.

Parameters

queue

a GQueue

 

Returns

the data of the last element in the queue, or NULL if the queue is empty


g_queue_pop_nth ()

gpointer
g_queue_pop_nth (GQueue *queue,
                 guint n);

Removes the n 'th element of queue and returns its data.

Parameters

queue

a GQueue

 

n

the position of the element

 

Returns

the element's data, or NULL if n is off the end of queue

Since: 2.4


g_queue_peek_head ()

gpointer
g_queue_peek_head (GQueue *queue);

Returns the first element of the queue.

Parameters

queue

a GQueue

 

Returns

the data of the first element in the queue, or NULL if the queue is empty


g_queue_peek_tail ()

gpointer
g_queue_peek_tail (GQueue *queue);

Returns the last element of the queue.

Parameters

queue

a GQueue

 

Returns

the data of the last element in the queue, or NULL if the queue is empty


g_queue_peek_nth ()

gpointer
g_queue_peek_nth (GQueue *queue,
                  guint n);

Returns the n 'th element of queue .

Parameters

queue

a GQueue

 

n

the position of the element

 

Returns

the data for the n 'th element of queue , or NULL if n is off the end of queue

Since: 2.4


g_queue_index ()

gint
g_queue_index (GQueue *queue,
               gconstpointer data);

Returns the position of the first element in queue which contains data .

Parameters

queue

a GQueue

 

data

the data to find

 

Returns

the position of the first element in queue which contains data , or -1 if no element in queue contains data

Since: 2.4


g_queue_remove ()

gboolean
g_queue_remove (GQueue *queue,
                gconstpointer data);

Removes the first element in queue that contains data .

Parameters

queue

a GQueue

 

data

the data to remove

 

Returns

TRUE if data was found and removed from queue

Since: 2.4


g_queue_remove_all ()

guint
g_queue_remove_all (GQueue *queue,
                    gconstpointer data);

Remove all elements whose data equals data from queue .

Parameters

queue

a GQueue

 

data

the data to remove

 

Returns

the number of elements removed from queue

Since: 2.4


g_queue_insert_before ()

void
g_queue_insert_before (GQueue *queue,
                       GList *sibling,
                       gpointer data);

Inserts data into queue before sibling .

sibling must be part of queue . Since GLib 2.44 a NULL sibling pushes the data at the tail of the queue.

Parameters

queue

a GQueue

 

sibling

a GList link that must be part of queue , or NULL to push at the tail of the queue.

[nullable]

data

the data to insert

 

Since: 2.4


g_queue_insert_after ()

void
g_queue_insert_after (GQueue *queue,
                      GList *sibling,
                      gpointer data);

Inserts data into queue after sibling .

sibling must be part of queue . Since GLib 2.44 a NULL sibling pushes the data at the head of the queue.

Parameters

queue

a GQueue

 

sibling

a GList link that must be part of queue , or NULL to push at the head of the queue.

[nullable]

data

the data to insert

 

Since: 2.4


g_queue_insert_sorted ()

void
g_queue_insert_sorted (GQueue *queue,
                       gpointer data,
                       GCompareDataFunc func,
                       gpointer user_data);

Inserts data into queue using func to determine the new position.

Parameters

queue

a GQueue

 

data

the data to insert

 

func

the GCompareDataFunc used to compare elements in the queue. It is called with two elements of the queue and user_data . It should return 0 if the elements are equal, a negative value if the first element comes before the second, and a positive value if the second element comes before the first.

 

user_data

user data passed to func

 

Since: 2.4


g_queue_push_head_link ()

void
g_queue_push_head_link (GQueue *queue,
                        GList *link_);

Adds a new element at the head of the queue.

Parameters

queue

a GQueue

 

link_

a single GList element, not a list with more than one element

 

g_queue_push_tail_link ()

void
g_queue_push_tail_link (GQueue *queue,
                        GList *link_);

Adds a new element at the tail of the queue.

Parameters

queue

a GQueue

 

link_

a single GList element, not a list with more than one element

 

g_queue_push_nth_link ()

void
g_queue_push_nth_link (GQueue *queue,
                       gint n,
                       GList *link_);

Inserts link into queue at the given position.

Parameters

queue

a GQueue

 

n

the position to insert the link. If this is negative or larger than the number of elements in queue , the link is added to the end of queue .

 

link_

the link to add to queue

 

Since: 2.4


g_queue_pop_head_link ()

GList *
g_queue_pop_head_link (GQueue *queue);

Removes and returns the first element of the queue.

Parameters

queue

a GQueue

 

Returns

the GList element at the head of the queue, or NULL if the queue is empty


g_queue_pop_tail_link ()

GList *
g_queue_pop_tail_link (GQueue *queue);

Removes and returns the last element of the queue.

Parameters

queue

a GQueue

 

Returns

the GList element at the tail of the queue, or NULL if the queue is empty


g_queue_pop_nth_link ()

GList *
g_queue_pop_nth_link (GQueue *queue,
                      guint n);

Removes and returns the link at the given position.

Parameters

queue

a GQueue

 

n

the link's position

 

Returns

the n 'th link, or NULL if n is off the end of queue

Since: 2.4


g_queue_peek_head_link ()

GList *
g_queue_peek_head_link (GQueue *queue);

Returns the first link in queue .

Parameters

queue

a GQueue

 

Returns

the first link in queue , or NULL if queue is empty

Since: 2.4


g_queue_peek_tail_link ()

GList *
g_queue_peek_tail_link (GQueue *queue);

Returns the last link in queue .

Parameters

queue

a GQueue

 

Returns

the last link in queue , or NULL if queue is empty

Since: 2.4


g_queue_peek_nth_link ()

GList *
g_queue_peek_nth_link (GQueue *queue,
                       guint n);

Returns the link at the given position

Parameters

queue

a GQueue

 

n

the position of the link

 

Returns

the link at the n 'th position, or NULL if n is off the end of the list

Since: 2.4


g_queue_link_index ()

gint
g_queue_link_index (GQueue *queue,
                    GList *link_);

Returns the position of link_ in queue .

Parameters

queue

a GQueue

 

link_

a GList link

 

Returns

the position of link_ , or -1 if the link is not part of queue

Since: 2.4


g_queue_unlink ()

void
g_queue_unlink (GQueue *queue,
                GList *link_);

Unlinks link_ so that it will no longer be part of queue . The link is not freed.

link_ must be part of queue .

Parameters

queue

a GQueue

 

link_

a GList link that must be part of queue

 

Since: 2.4


g_queue_delete_link ()

void
g_queue_delete_link (GQueue *queue,
                     GList *link_);

Removes link_ from queue and frees it.

link_ must be part of queue .

Parameters

queue

a GQueue

 

link_

a GList link that must be part of queue

 

Since: 2.4

Types and Values

struct GQueue

struct GQueue {
  GList *head;
  GList *tail;
  guint  length;
};

Contains the public fields of a Queue.

Members

GList *head;

a pointer to the first element of the queue

 

GList *tail;

a pointer to the last element of the queue

 

guint length;

the number of elements in the queue

 

G_QUEUE_INIT

#define G_QUEUE_INIT { NULL, NULL, 0 }

A statically-allocated GQueue must be initialized with this macro before it can be used. This macro can be used to initialize a variable, but it cannot be assigned to a variable. In that case you have to use g_queue_init().

1
GQueue my_queue = G_QUEUE_INIT;

Since: 2.14