Singly-Linked List module

This is my simple singly-linked list module with basic functionality for handling multiple c-strings in your projects.

Usage

• Include the module

  #include "SLList.h"

• Declare list variable

  struct SLList source_list;

• Initialize working with list

  sll_init(&source_list);

• Do with your list what you want

  • add new string to list's end

    sll_push(&source_list, "some_text");

  • remove string from list's end

    sll_pop(&source_list);

  • get list's size

    sll_size(&source_list);

  • find out if the list is empty

    sll_is_empty(&source_list);

• Terminate working with list

  sll_terminate(&source_list);

Note: all the functions, processing list, works with pointer on list. So I advice to use a pointer-variable. This makes & using unnecessary. An example is given below:

struct SLList *source_list = malloc(sizeof(struct SLList*));

sll_init(source_list);

...
   
sll_terminate(source_list);
	
free(source_list);

Code Example

#include <stdio.h>
#include <stdlib.h>

#include "SLList.h"

int main(int argc, char *argv[])
{
	struct SLList *source_list = malloc(sizeof(struct SLList*));

	sll_init(source_list);

	printf("%d\n", sll_size(source_list));

	sll_push(source_list, "First string");
	sll_push(source_list, "Second string");
	sll_push(source_list, "Third string");

	printf("%d\n", sll_size(source_list)); 
	
	
	struct Node *temp = source_list->head;

	while (temp->next != NULL)
	{
		printf("%s\n", temp->next->value);

		temp = temp->next;
	}

	sll_terminate(source_list);
	
	free(source_list);

	return 0;
}

/*
	OUTPUT:
	0
	3
	First string
	Second string
	Third string
*/

Sentinel Using

If you want to find some value in list, you have to use while loop.

struct Node *temp = source_list->head; 

while (temp != NULL)
{
	if (temp->value == some_found_value)
	{
		...
	}

	temp = temp->next;
}

At the moment everything is allright. But if want to pop last element, you need to use:

struct Node *temp = source_list->head;

while (temp != NULL)
{
	temp = temp->next;
}

Here you found last element, but you need to redirect previous Node "next" field to NULL. because of list is singly-linked, you cannot address previous Node

To resolve it I use a sentinel in the list's begin. Sentinel is an empty Node containing nothing. It provides me an opportunity to use code:

struct Node *temp = source_list->head;

while (temp->next->next != NULL)
{
	temp = temp->next;
}

temp->next = NULL;

Here temp pointers to penultimate element and we can delete the last element.

The following is the structure of singly-linked list with sentinel node

To learn more about lists with sentinels you can visit this Wikipage.