Adding elements to Eina_List

Creating an Eina_List and adding elements to it is very easy and can be understood from an example: First thing is always to include Eina.h, for this example we also include stdio.h so we can use printf.

#include <stdio.h>
#include <Eina.h>
Eina Utility library.

Just some boilerplate code, declaring some variable and initializing eina.

int
main(int argc, char **argv)
{
Eina_List *list = NULL;
void *list_data;
int eina_init(void)
Initialize the Eina library.
Definition eina_main.c:244
Type for a generic double linked list.
Definition eina_list.h:321

Here we add a sequence of elements to our list. By using append we add elements to the end of the list, so the list will look like this:
Full-size

list = eina_list_append(list, "tigh");
list = eina_list_append(list, "adar");
list = eina_list_append(list, "baltar");
list = eina_list_append(list, "roslin");
Eina_List * eina_list_append(Eina_List *list, const void *data)
Append the given data to the given linked list.
Definition eina_list.c:530

There are a couple of interesting things happening here, first is that we are passing a NULL pointer to the first eina_list_append() call, when this is done a list is created. The other very important detail to notice is that the return value is attributed to the list variable, this needs to be done every time we use a a function that alters the contents of the list.

Now that we have a list with some elements in it we can look at it's contents.

EINA_LIST_FOREACH(list, l, list_data)
printf("%s\n", (char*)list_data);
#define EINA_LIST_FOREACH(list, l, data)
Macro to iterate over a list.
Definition eina_list.h:1399

There are many ways of accessing elements in the list, including by it's index:

printf("\n");
l = eina_list_nth_list(list, 1);
Eina_List * eina_list_nth_list(const Eina_List *list, unsigned int n)
Get the nth member's list node in a list.
Definition eina_list.c:927
Note
It should be noted that the index starts at 0.

eina_list_append() is not the only way to add elements to a a list. A common requirement is to add an element in a specific position this can be accomplished using eina_list_append_relative() and eina_list_append_relative_list():

list = eina_list_append_relative_list(list, "cain", l);
list = eina_list_append_relative(list, "zarek", "cain");
Eina_List * eina_list_append_relative_list(Eina_List *list, const void *data, Eina_List *relative)
Append a list node to a linked list after the specified member.
Definition eina_list.c:606
Eina_List * eina_list_append_relative(Eina_List *list, const void *data, const void *relative)
Insert the given data into the given linked list after the specified data.
Definition eina_list.c:586

First "cain" is added after the second element(remember that indexes are 0 based) and then we add "zarek" after "cain".

Eina_List also has prepend analogs to append functions we have used so far:

list = eina_list_prepend(list, "adama");
list = eina_list_prepend_relative(list, "gaeta", "cain");
list = eina_list_prepend_relative_list(list, "lampkin", l);
Eina_List * eina_list_prepend_relative(Eina_List *list, const void *data, const void *relative)
Prepend a data pointer to a linked list before the specified member.
Definition eina_list.c:639
Eina_List * eina_list_prepend_relative_list(Eina_List *list, const void *data, Eina_List *relative)
Prepend a list node to a linked list before the specified member.
Definition eina_list.c:658
Eina_List * eina_list_prepend(Eina_List *list, const void *data)
Prepends the given data to the given linked list.
Definition eina_list.c:560

With this additions our list now looks like this:
Full-size

Once done using the list it needs to be freed, and since we are done with eina that also need to be shutdown:

EINA_LIST_FOREACH(list, l, list_data)
printf("%s\n", (char*)list_data);
return 0;
}
Eina_List * eina_list_free(Eina_List *list)
Free an entire list and all the nodes, ignoring the data contained.
Definition eina_list.c:754
int eina_shutdown(void)
Shut down the Eina library.
Definition eina_main.c:315

The full source code can be found on the examples folder on the eina_list_01.c file.