GLib Reference Manual | |||
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The GList structure and its associated functions provide a standard doubly-linked list data structure.
Each element in the list contains a piece of data, together with pointers which link to the previous and next elements in the list. Using these pointers it is possible to move through the list in both directions (unlike the Singly-Linked Lists which only allows movement through the list in the forward direction).
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.
List elements are allocated in blocks using a GListAllocator, which is more efficient than allocating elements individually.
Note that most of the GList functions expect to be passed a pointer to the first element in the list. The functions which insert elements return the new start of the list, which may have changed.
There is no function to create a GList. NULL is considered to be the empty list so you simply set a GList* to NULL.
To add elements, use g_list_append(), g_list_prepend(), g_list_insert() and g_list_insert_sorted().
To remove elements, use g_list_remove().
To find elements in the list use g_list_first(), g_list_last(), g_list_next(), g_list_previous(), g_list_nth(), g_list_nth_data(), g_list_find() and g_list_find_custom().
To find the index of an element use g_list_position() and g_list_index().
To call a function for each element in the list use g_list_foreach().
To free the entire list, use g_list_free().
struct GList { gpointer data; GList *next; GList *prev; }; |
The GList struct is used for each element in a doubly-linked list. The data field holds the element's data, which can be a pointer to any kind of data, or any integer value using the Type Conversion Macros. The next and prev pointers are the links to the next and previous elements in the list.
GList* g_list_append (GList *list, gpointer data); |
Adds a new element on to the end of the list.
Note: The return value is the new start of the list, which may have changed, so make sure you store the new value.
/* Notice that these are initialized to the empty list. */ GList *list = NULL, *number_list = NULL; /* This is a list of strings. */ list = g_list_append (list, "first"); list = g_list_append (list, "second"); /* This is a list of integers. */ number_list = g_list_append (number_list, GINT_TO_POINTER (27)); number_list = g_list_append (number_list, GINT_TO_POINTER (14)); |
GList* g_list_prepend (GList *list, gpointer data); |
Adds a new element on to the start of the list.
Note: The return value is the new start of the list, which may have changed, so make sure you store the new value.
/* Notice that it is initialized to the empty list. */ GList *list = NULL; list = g_list_prepend (list, "last"); list = g_list_prepend (list, "first"); |
GList* g_list_insert (GList *list, gpointer data, gint position); |
Inserts a new element into the list at the given position.
GList* g_list_insert_sorted (GList *list, gpointer data, GCompareFunc func); |
Inserts a new element into the list, using the given comparison function to determine its position.
GList* g_list_remove (GList *list, gpointer data); |
Removes an element from a GList. If two elements contain the same data, only the first is removed. If none of the elements contain the data, the GList is unchanged.
GList* g_list_remove_link (GList *list, GList *llink); |
Removes an element from a GList, without freeing the element. The removed element's prev and next links are set to NULL, so that it becomes a self-contained list with one element.
void g_list_free (GList *list); |
Frees all of the memory used by a GList. The freed elements are added to the GListAllocator free list.
Note: If list elements contain dynamically-allocated memory, they should be freed first.
list : |
GList* g_list_alloc (void); |
Allocates space for one GList element. It is called by g_list_append(), g_list_prepend(), g_list_insert() and g_list_insert_sorted() and so is rarely used on its own.
Returns : | a pointer to the newly-allocated GList element. |
void g_list_free_1 (GList *list); |
Frees one GList element. It is usually used after g_list_remove_link().
list : | a GList element. |
GList* g_list_copy (GList *list); |
Copies a GList.
Note that this is a "shallow" copy. If the list elements consist of pointers to data, the pointers are copied but the actual data isn't.
list : | a GList. |
Returns : | a copy of list. |
GList* g_list_reverse (GList *list); |
Reverses a GList. It simply switches the next and prev pointers of each element.
GList* g_list_sort (GList *list, GCompareFunc compare_func); |
Sorts a GList using the given comparison function.
list : | a GList. |
compare_func : | the comparison function used to sort the GList. This function is passed 2 elements of the GList and should return 0 if they are equal, a negative value if the first element comes before the second, or a positive value if the first element comes after the second. |
Returns : | the start of the sorted GList. |
GList* g_list_concat (GList *list1, GList *list2); |
Adds the second GList onto the end of the first GList. Note that the elements of the second GList are not copied. They are used directly.
void g_list_foreach (GList *list, GFunc func, gpointer user_data); |
Calls a function for each element of a GList.
list : | a GList. |
func : | the function to call with each element's data. |
user_data : | user data to pass to the function. |
void (*GFunc) (gpointer data, gpointer user_data); |
Specifies the type of functions passed to g_list_foreach() and g_slist_foreach().
data : | the element's data. |
user_data : | user data passed to g_list_foreach() or g_slist_foreach(). |
#define g_list_previous(list) |
A convenience macro to gets the previous element in a GList.
list : | an element in a GList. |
Returns : | the previous element, or NULL if there are no previous elements. |
#define g_list_next(list) |
A convenience macro to gets the next element in a GList.
list : | an element in a GList. |
Returns : | the next element, or NULL if there are no more elements. |
GList* g_list_nth (GList *list, guint n); |
Gets the element at the given position in a GList.
gpointer g_list_nth_data (GList *list, guint n); |
Gets the data of the element at the given position.
GList* g_list_find (GList *list, gpointer data); |
Finds the element in a GList which contains the given data.
GList* g_list_find_custom (GList *list, gpointer data, GCompareFunc func); |
Finds an element in a GList, using a supplied function to find the desired element. It iterates over the list, calling the given function which should return 0 when the desired element is found. The function takes two gconstpointer arguments, the GList element's data and the given user data.
gint g_list_position (GList *list, GList *llink); |
Gets the position of the given element in the GList (starting from 0).
gint g_list_index (GList *list, gpointer data); |
Gets the position of the element containing the given data (starting from 0).
list : | a GList. |
data : | the data to find. |
Returns : | the index of the element containing the data, or -1 if the data is not found. |
void g_list_push_allocator (GAllocator *allocator); |
Sets the allocator to use to allocate GList elements. Use g_list_pop_allocator() to restore the previous allocator.
allocator : | the GAllocator to use when allocating GList elements. |
void g_list_pop_allocator (void); |
Restores the previous GAllocator, used when allocating GList elements.