Singly-Linked Lists

Singly-Linked Lists — linked lists containing integer values or pointers to data, limited to iterating over the list in one direction

Synopsis

#include <glib.h>

struct              GSList;

GSList *            g_slist_alloc                       (void);
GSList *            g_slist_append                      (GSList *list,
                                                         gpointer data);
GSList *            g_slist_prepend                     (GSList *list,
                                                         gpointer data);
GSList *            g_slist_insert                      (GSList *list,
                                                         gpointer data,
                                                         gint position);
GSList *            g_slist_insert_before               (GSList *slist,
                                                         GSList *sibling,
                                                         gpointer data);
GSList *            g_slist_insert_sorted               (GSList *list,
                                                         gpointer data,
                                                         GCompareFunc func);
GSList *            g_slist_remove                      (GSList *list,
                                                         gconstpointer data);
GSList *            g_slist_remove_link                 (GSList *list,
                                                         GSList *link_);
GSList *            g_slist_delete_link                 (GSList *list,
                                                         GSList *link_);
GSList *            g_slist_remove_all                  (GSList *list,
                                                         gconstpointer data);
void                g_slist_free                        (GSList *list);
void                g_slist_free_full                   (GSList *list,
                                                         GDestroyNotify free_func);
void                g_slist_free_1                      (GSList *list);
#define             g_slist_free1

guint               g_slist_length                      (GSList *list);
GSList *            g_slist_copy                        (GSList *list);
GSList *            g_slist_reverse                     (GSList *list);
GSList *            g_slist_insert_sorted_with_data     (GSList *list,
                                                         gpointer data,
                                                         GCompareDataFunc func,
                                                         gpointer user_data);
GSList *            g_slist_sort                        (GSList *list,
                                                         GCompareFunc compare_func);
GSList *            g_slist_sort_with_data              (GSList *list,
                                                         GCompareDataFunc compare_func,
                                                         gpointer user_data);
GSList *            g_slist_concat                      (GSList *list1,
                                                         GSList *list2);
void                g_slist_foreach                     (GSList *list,
                                                         GFunc func,
                                                         gpointer user_data);

GSList *            g_slist_last                        (GSList *list);
#define             g_slist_next                        (slist)
GSList *            g_slist_nth                         (GSList *list,
                                                         guint n);
gpointer            g_slist_nth_data                    (GSList *list,
                                                         guint n);

GSList *            g_slist_find                        (GSList *list,
                                                         gconstpointer data);
GSList *            g_slist_find_custom                 (GSList *list,
                                                         gconstpointer data,
                                                         GCompareFunc func);
gint                g_slist_position                    (GSList *list,
                                                         GSList *llink);
gint                g_slist_index                       (GSList *list,
                                                         gconstpointer data);

void                g_slist_push_allocator              (gpointer dummy);
void                g_slist_pop_allocator               (void);

Description

The GSList structure and its associated functions provide a standard singly-linked list data structure.

Each element in the list contains a piece of data, together with a pointer which links to the next element in the list. Using this pointer it is possible to move through the list in one direction only (unlike the Doubly-Linked Lists which allow movement in both directions).

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 from the slice allocator, which is more efficient than allocating elements individually.

Note that most of the GSList 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 GSList. NULL is considered to be the empty list so you simply set a GSList* to NULL.

To add elements, use g_slist_append(), g_slist_prepend(), g_slist_insert() and g_slist_insert_sorted().

To remove elements, use g_slist_remove().

To find elements in the list use g_slist_last(), g_slist_next(), g_slist_nth(), g_slist_nth_data(), g_slist_find() and g_slist_find_custom().

To find the index of an element use g_slist_position() and g_slist_index().

To call a function for each element in the list use g_slist_foreach().

To free the entire list, use g_slist_free().

Details

struct GSList

struct GSList {
  gpointer data;
  GSList *next;
};

The GSList struct is used for each element in the singly-linked list.

gpointer data;

 holds the element's data, which can be a pointer to any kind of data, or any integer value using the Type Conversion Macros.

GSList *next;

 contains the link to the next element in the list.

g_slist_alloc ()

GSList *            g_slist_alloc                       (void);

Allocates space for one GSList element. It is called by the g_slist_append(), g_slist_prepend(), g_slist_insert() and g_slist_insert_sorted() functions and so is rarely used on its own.

Returns :

 a pointer to the newly-allocated GSList element.

g_slist_append ()

GSList *            g_slist_append                      (GSList *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.

Note

Note that g_slist_append() has to traverse the entire list to find the end, which is inefficient when adding multiple elements. A common idiom to avoid the inefficiency is to prepend the elements and reverse the list when all elements have been added. 

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/* Notice that these are initialized to the empty list. */
GSList *list = NULL, *number_list = NULL;

/* This is a list of strings. */
list = g_slist_append (list, "first");
list = g_slist_append (list, "second");

/* This is a list of integers. */
number_list = g_slist_append (number_list, GINT_TO_POINTER (27));
number_list = g_slist_append (number_list, GINT_TO_POINTER (14));

list :

 a GSList

data :

 the data for the new element

Returns :

 the new start of the GSList

g_slist_prepend ()

GSList *            g_slist_prepend                     (GSList *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. 

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/* Notice that it is initialized to the empty list. */
GSList *list = NULL;
list = g_slist_prepend (list, "last");
list = g_slist_prepend (list, "first");

list :

 a GSList

data :

 the data for the new element

Returns :

 the new start of the GSList

g_slist_insert ()

GSList *            g_slist_insert                      (GSList *list,
                                                         gpointer data,
                                                         gint position);

Inserts a new element into the list at the given position.

list :

 a GSList

data :

 the data for the new element

position :

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

Returns :

 the new start of the GSList

g_slist_insert_before ()

GSList *            g_slist_insert_before               (GSList *slist,
                                                         GSList *sibling,
                                                         gpointer data);

Inserts a node before sibling containing data.

slist :

 a GSList

sibling :

 node to insert data before

data :

 data to put in the newly-inserted node

Returns :

 the new head of the list.

g_slist_insert_sorted ()

GSList *            g_slist_insert_sorted               (GSList *list,
                                                         gpointer data,
                                                         GCompareFunc func);

Inserts a new element into the list, using the given comparison function to determine its position.

list :

 a GSList

data :

 the data for the new element

func :

 the function to compare elements in the list. It should return a number > 0 if the first parameter comes after the second parameter in the sort order.

Returns :

 the new start of the GSList

g_slist_remove ()

GSList *            g_slist_remove                      (GSList *list,
                                                         gconstpointer data);

Removes an element from a GSList. If two elements contain the same data, only the first is removed. If none of the elements contain the data, the GSList is unchanged.

list :

 a GSList

data :

 the data of the element to remove

Returns :

 the new start of the GSList

g_slist_remove_link ()

GSList *            g_slist_remove_link                 (GSList *list,
                                                         GSList *link_);

Removes an element from a GSList, without freeing the element. The removed element's next link is set to NULL, so that it becomes a self-contained list with one element.

list :

 a GSList

link_ :

 an element in the GSList

Returns :

 the new start of the GSList, without the element

g_slist_delete_link ()

GSList *            g_slist_delete_link                 (GSList *list,
                                                         GSList *link_);

Removes the node link_ from the list and frees it. Compare this to g_slist_remove_link() which removes the node without freeing it.

list :

 a GSList

link_ :

 node to delete

Returns :

 the new head of list

g_slist_remove_all ()

GSList *            g_slist_remove_all                  (GSList *list,
                                                         gconstpointer data);

Removes all list nodes with data equal to data. Returns the new head of the list. Contrast with g_slist_remove() which removes only the first node matching the given data.

list :

 a GSList

data :

 data to remove

Returns :

 new head of list

g_slist_free ()

void                g_slist_free                        (GSList *list);

Frees all of the memory used by a GSList. The freed elements are returned to the slice allocator.

Note

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

list :

 a GSList

g_slist_free_full ()

void                g_slist_free_full                   (GSList *list,
                                                         GDestroyNotify free_func);

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

list :

 a pointer to a GSList

free_func :

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

Since 2.28

g_slist_free_1 ()

void                g_slist_free_1                      (GSList *list);

Frees one GSList element. It is usually used after g_slist_remove_link().

list :

 a GSList element

g_slist_free1

#define             g_slist_free1

A macro which does the same as g_slist_free_1().

Since 2.10

g_slist_length ()

guint               g_slist_length                      (GSList *list);

Gets the number of elements in a GSList.

Note

This function iterates over the whole list to count its elements.

list :

 a GSList

Returns :

 the number of elements in the GSList

g_slist_copy ()

GSList *            g_slist_copy                        (GSList *list);

Copies a GSList.

Note

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 GSList

Returns :

 a copy of list

g_slist_reverse ()

GSList *            g_slist_reverse                     (GSList *list);

Reverses a GSList.

list :

 a GSList

Returns :

 the start of the reversed GSList

g_slist_insert_sorted_with_data ()

GSList *            g_slist_insert_sorted_with_data     (GSList *list,
                                                         gpointer data,
                                                         GCompareDataFunc func,
                                                         gpointer user_data);

Inserts a new element into the list, using the given comparison function to determine its position.

list :

 a GSList

data :

 the data for the new element

func :

 the function to compare elements in the list. It should return a number > 0 if the first parameter comes after the second parameter in the sort order.

user_data :

 data to pass to comparison function

Returns :

 the new start of the GSList

Since 2.10

g_slist_sort ()

GSList *            g_slist_sort                        (GSList *list,
                                                         GCompareFunc compare_func);

Sorts a GSList using the given comparison function.

list :

 a GSList

compare_func :

 the comparison function used to sort the GSList. This function is passed the data from 2 elements of the GSList 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 GSList

g_slist_sort_with_data ()

GSList *            g_slist_sort_with_data              (GSList *list,
                                                         GCompareDataFunc compare_func,
                                                         gpointer user_data);

Like g_slist_sort(), but the sort function accepts a user data argument.

list :

 a GSList

compare_func :

 comparison function

user_data :

 data to pass to comparison function

Returns :

 new head of the list

g_slist_concat ()

GSList *            g_slist_concat                      (GSList *list1,
                                                         GSList *list2);

Adds the second GSList onto the end of the first GSList. Note that the elements of the second GSList are not copied. They are used directly.

list1 :

 a GSList

list2 :

 the GSList to add to the end of the first GSList

Returns :

 the start of the new GSList

g_slist_foreach ()

void                g_slist_foreach                     (GSList *list,
                                                         GFunc func,
                                                         gpointer user_data);

Calls a function for each element of a GSList.

list :

 a GSList

func :

 the function to call with each element's data

user_data :

 user data to pass to the function

g_slist_last ()

GSList *            g_slist_last                        (GSList *list);

Gets the last element in a GSList.

Note

This function iterates over the whole list.

list :

 a GSList

Returns :

 the last element in the GSList, or NULL if the GSList has no elements

g_slist_next()

#define             g_slist_next(slist)

A convenience macro to get the next element in a GSList.

slist :

 an element in a GSList.

Returns :

 the next element, or NULL if there are no more elements.

g_slist_nth ()

GSList *            g_slist_nth                         (GSList *list,
                                                         guint n);

Gets the element at the given position in a GSList.

list :

 a GSList

n :

 the position of the element, counting from 0

Returns :

 the element, or NULL if the position is off the end of the GSList

g_slist_nth_data ()

gpointer            g_slist_nth_data                    (GSList *list,
                                                         guint n);

Gets the data of the element at the given position.

list :

 a GSList

n :

 the position of the element

Returns :

 the element's data, or NULL if the position is off the end of the GSList

g_slist_find ()

GSList *            g_slist_find                        (GSList *list,
                                                         gconstpointer data);

Finds the element in a GSList which contains the given data.

list :

 a GSList

data :

 the element data to find

Returns :

 the found GSList element, or NULL if it is not found

g_slist_find_custom ()

GSList *            g_slist_find_custom                 (GSList *list,
                                                         gconstpointer data,
                                                         GCompareFunc func);

Finds an element in a GSList, 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 GSList element's data as the first argument and the given user data.

list :

 a GSList

data :

 user data passed to the function

func :

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

Returns :

 the found GSList element, or NULL if it is not found

g_slist_position ()

gint                g_slist_position                    (GSList *list,
                                                         GSList *llink);

Gets the position of the given element in the GSList (starting from 0).

list :

 a GSList

llink :

 an element in the GSList

Returns :

 the position of the element in the GSList, or -1 if the element is not found

g_slist_index ()

gint                g_slist_index                       (GSList *list,
                                                         gconstpointer data);

Gets the position of the element containing the given data (starting from 0).

list :

 a GSList

data :

 the data to find

Returns :

 the index of the element containing the data, or -1 if the data is not found

g_slist_push_allocator ()

void                g_slist_push_allocator              (gpointer dummy);

Warning

g_slist_push_allocator has been deprecated since version 2.10 and should not be used in newly-written code. It does nothing, since GSList has been converted to the slice allocator

Sets the allocator to use to allocate GSList elements. Use g_slist_pop_allocator() to restore the previous allocator.

Note that this function is not available if GLib has been compiled with --disable-mem-pools

dummy :

 the GAllocator to use when allocating GSList elements.

g_slist_pop_allocator ()

void                g_slist_pop_allocator               (void);

Warning

g_slist_pop_allocator has been deprecated since version 2.10 and should not be used in newly-written code. It does nothing, since GSList has been converted to the slice allocator

Restores the previous GAllocator, used when allocating GSList elements.

Note that this function is not available if GLib has been compiled with --disable-mem-pools

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