Singly-Linked Lists

Singly-Linked Lists — linked lists that can be iterated in one direction

Types and Values

struct GSList
#define g_slist_free1

Includes

#include <glib.h>

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 double-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().

Functions

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.

The return value is the new start of the list, which may have changed, so make sure you store the new value.

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));

Parameters

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.

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");

Parameters

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.

Parameters

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 .

Parameters

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.

Parameters

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.

Parameters

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.

Removing arbitrary nodes from a singly-linked list requires time that is proportional to the length of the list (ie. O(n)). If you find yourself using g_slist_remove_link() frequently, you should consider a different data structure, such as the doubly-linked GList.

Parameters

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.

Removing arbitrary nodes from a singly-linked list requires time that is proportional to the length of the list (ie. O(n)). If you find yourself using g_slist_delete_link() frequently, you should consider a different data structure, such as the doubly-linked GList.

Parameters

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.

Parameters

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.

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

Parameters

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.

Parameters

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().

Parameters

list

a GSList element

 

g_slist_length ()

guint
g_slist_length (GSList *list);

Gets the number of elements in a GSList.

This function iterates over the whole list to count its elements. To check whether the list is non-empty, it is faster to check list against NULL.

Parameters

list

a GSList

 

Returns

the number of elements in the GSList


g_slist_copy ()

GSList *
g_slist_copy (GSList *list);

Copies a GSList.

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. See g_slist_copy_deep() if you need to copy the data as well.

Parameters

list

a GSList

 

Returns

a copy of list


g_slist_copy_deep ()

GSList *
g_slist_copy_deep (GSList *list,
                   GCopyFunc func,
                   gpointer user_data);

Makes a full (deep) copy of a GSList.

In contrast with g_slist_copy(), this function uses func to make a copy of each list element, in addition to copying the list container itself.

func , as a GCopyFunc, takes two arguments, the data to be copied and a user pointer. It's safe to pass NULL as user_data, if the copy function takes only one argument.

For instance, if list holds a list of GObjects, you can do:

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another_list = g_slist_copy_deep (list, (GCopyFunc) g_object_ref, NULL);

And, to entirely free the new list, you could do:

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g_slist_free_full (another_list, g_object_unref);

Parameters

list

a GSList

 

func

a copy function used to copy every element in the list

 

user_data

user data passed to the copy function func , or NULL

 

Returns

a full copy of list , use g_slist_free_full to free it

Since: 2.34


g_slist_reverse ()

GSList *
g_slist_reverse (GSList *list);

Reverses a GSList.

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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.

This function iterates over the whole list.

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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.

Parameters

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).

Parameters

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).

Parameters

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

Types and Values

struct GSList

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

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

Members

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_free1

#define             g_slist_free1

A macro which does the same as g_slist_free_1().

Since: 2.10