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>

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

int
main(int argc, char **argv)
{
   (void)argc;
   (void)argv;
   Eina_List *list = NULL;
   Eina_List *l;
   void *list_data;

   eina_init();

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:

   list = eina_list_append(list, "tigh");
   list = eina_list_append(list, "adar");
   list = eina_list_append(list, "baltar");
   list = eina_list_append(list, "roslin");

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 its contents.

   EINA_LIST_FOREACH(list, l, list_data)
     printf("%s\n", (char*)list_data);

There are many ways of accessing elements in the list, including by its index:

   printf("\n");

   l = eina_list_nth_list(list, 1);

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");

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);

With this additions our list now looks like this:

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);

   eina_list_free(list);

   eina_shutdown();

   return 0;
}

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