Pastable version of Linked lists implementation

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 <pre class="sunburst">#ifndef _LINKED_LIST_H_
#define _LINKED_LIST_H_
#include &quot;common.h&quot;

typedef struct _s_list list_t;
/* TODO: add comments */

/* Description: Creates a list, this function sets the list to empty,
 * Arguments:
 * 		no arguments
 * Return: Returns a pointer to the empty list, the list has type 'list_t'
 * Errors: On error, NULL is returned, errno is set accordingly and an error
 * is printed to stderr
 * Depends:
 * void *malloc(size_t size); &lt;stdlib.h&gt;
 */
list_t* DLL_EXPORT list_create ( void );

/* Description: Deletes a list, this function frees all of the list occupied
 * 		memory
 * Arguments:
 * 		list_t* _list: a pointer to the list to be deleted
 * Return: returns no value
 * Depends:
 * void free(void *ptr); &lt;stdlib.h&gt;
 */
void DLL_EXPORT list_delete ( list_t* _list );

/* Description: Gets the first element of a list, the element is not removed
 * 		from the list
 * Arguments:
 * 		list_t* _list: a pointer to the list where the first element
 * 		is to be fetched
 * Return: Returns a pointer to the first element of the list, the list
 * 	 element has type list_t*
 * Errors: On error, NULL is returned and the error is printed to stderr
 * Depends:
 */

list_t* DLL_EXPORT list_gethead ( list_t *const _list ) __ATTR_CONST;

/* Description: Gets the elements that preceeds the first element of the list,
 * 		the first element is not removed from the list
 * Arguments:
 * 		list_t* _list: a pointer to the list where the elements are to
 * 		be fetched
 * Return: Returns a pointer to the next element of the first element of the
 * 	 list, this element has type list_t*
 * Errors: On error, NULL is returned and the error is printed to stderr
 * Depends:
 */
list_t* DLL_EXPORT list_gettail ( const list_t *const _list ) __ATTR_CONST;

/* Description: Gets the last element of the list
 * Arguments:
 * 		list_t* _list: a pointer to the list where the last element is
 * 		to be fetched
 * Return: Returns a pointer to the last element of the list, this element has
 * 	 type list_t*
 * Errors: On error, NULL is returned and the error is printed to stderr
 * Depends:
 */
list_t* DLL_EXPORT list_getend ( list_t *const _list ) __ATTR_CONST;

/* Description: Inserts an element to the end of the list
 * Arguments:
 * 		list_t* _list: a pointer to the list where the element is to be *		inserted
 * 		void* _elem: a pointer to the element to insert
 * Return: Returns a pointer to the last element of the list, this element has
 * 	 type list_t*
 * Errors: On error, NULL is returned, errno is set accordingly, and the error
 * 	 is printed to stderr
 * Depends:
 * void *malloc(size_t size); &lt;stdlib.h&gt;
 * list_t* list_get_end(list_t* _list); &quot;linked_list.h&quot;
 */
list_t* DLL_EXPORT list_appendelement ( list_t*const _list, void*const _elem );

/* Description: Inserts an element to the start of the list
 * Arguments:
 * 		list_t* _list: a pointer to the list where the element is to be *		inserted
 * 		void* _elem: a pointer to the element to insert
 * Return: Returns a pointer to the first element of the list, this element has
 * 	 type list_t*
 * Errors: On error, NULL is returned, errno is set accordingly, and the error
 * 	 is printed to stderr
 * Depends:
 * void *malloc(size_t size); &lt;stdlib.h&gt;
 * list_t* list_get_head(list_t* _list); &quot;linked_list.h&quot;
 */
list_t* DLL_EXPORT list_insertelement ( list_t*const _list, void* _elem );

/* Description: Deletes an element from the list
 * Arguments:
 * 		list_t* _list: a pointer to the list where the element is to be *		deleted
 * 		list_t* _elem: a pointer to the element to delete
 * Return: Returns no value
 * Errors: On error, NULL is returned, errno is set accordingly, and the error
 * 	 is printed to stderr
 * Depends:
 * void free(void *ptr); &lt;stdlib.h&gt;
 * list_t* list_get_tail(list_t* _list); &quot;linked_list.h&quot;
 */
void DLL_EXPORT list_deleteelement ( list_t* _list, list_t* _elem );

/* Description: Gets the data from the list element
 * Arguments:
 * 		list_t* _elem: a pointer to the list position where the data
 * 		is going to be read
 * Return: Returns a pointer to the data, this pointer has type void*
 */
void* DLL_EXPORT list_getdata ( list_t const* _elem) __ATTR_CONST;

/* Description: Determines if the list has at least one more element
 * Arguments:
 * 		list_t* _elem: a pointer to the list
 * Return: Returns true if the list has at least one more element, false
 * otherwise
 */
GLboolean DLL_EXPORT list_hasnext ( list_t const* _list ) __ATTR_CONST;

/* Description: Searches a list for a given element, a comparator is specified
 * 		as an argument that is used to find the given element
 * Arguments:
 * 		list_t* _list: a pointer to the list
 *		bool (*_compare)( list_t* _list_elem ): a pointer to the
 *		comparator function
 * Return: Returns the given element if it is found, NULL otherwise
 * Depends:
 * list_t* list_get_tail(list_t* _list); &quot;linked_list.h&quot;
 * list_t* list_get_head(list_t* _list); &quot;linked_list.h&quot;
 */
list_t* DLL_EXPORT list_findelement ( list_t *const _list,
				bool (*_compare)( list_t* _list_elem ) );

/* Description: Simple print function for lists, only prints lists that are
 * 		made of elementary data types
 * Arguments:
 * 		list_t* _list: a pointer to the list to be printed
 *		type_t _data_type: elementary data type of the list elements
 * Return: Returns no value
 * Depends:
 */
void list_print ( list_t *_list, type_t _data_type );
#endif

// FILE linked_list.c
#include &quot;data_structures/linked_list.h&quot;
struct _s_list
{
	void* data;	/* the data this list will hold */

/* double linked */
	struct list* next;
	struct list* previous;
};

/* PRIVATE FUNCTIONS */
static GLboolean list_ishead ( const list_t *const _list ) __ATTR_CONST;
static void list_initializehead ( list_t *const _list );
static GLboolean list_isempty ( const list_t *const _list ) __ATTR_CONST;
static list_t* list_movetofront ( list_t* _list, list_t* _elem );

static GLboolean list_ishead ( const list_t *const _list )
{
	if ( _list-&gt;previous == NULL )
	{
		return GL_TRUE;
	}
	return GL_FALSE;

}

static void list_initializehead ( list_t *const _list )
{
	/* low priority error checking */
	if ( unlikely ( _list == NULL ) )
	{
		perror(&quot;list_initializehead()&quot;);
		return;
	}
	/* end of error checking */
	_list-&gt;data = NULL;
	_list-&gt;next = NULL;
	_list-&gt;previous = NULL;
}

static GLboolean list_isempty ( const list_t *const _list )
{
	/* low priority error checking */
	if ( unlikely ( _list == NULL ) )
	{
		perror(&quot;list_isempty()&quot;);
	}
	/* end of error checking */

return (!_list-&gt;data &amp;&amp; !_list-&gt;next &amp;&amp; !_list-&gt;previous);
}

static list_t* list_movetofront ( list_t* _list, list_t* _elem )
{
	list_t* list_head;
	list_t* list_tail;
	list_t* previous_of_elem;
	/* low priority error checking */
	if ( unlikely ( _list == NULL || _elem == NULL) )
	{

}
	/* end of error checking */

list_head = list_gethead ( _list );
	list_tail = list_gettail ( _list );
	previous_of_elem = _elem-&gt;previous;
	if ( _elem-&gt;next == NULL ) /* _elem is at the end of the list */
	{
		if ( _elem-&gt;previous == NULL )
		{
			return _list; /* list has only one element (which is
					 the one we are trying to move into the
					 front of the list) */
		}
		previous_of_elem-&gt;next = NULL;
	}
	else if ( _elem-&gt;previous != NULL ) /* _elem is on the middle */
	{
		list_t* next_of_elem = _elem-&gt;next;
		next_of_elem-&gt;previous = _elem-&gt;previous;
	}
	else if ( _elem-&gt;previous == NULL )
	{
		return _list; /* the element we are trying to move into the
				 front of the list is already there */
	}
	previous_of_elem-&gt;next = _elem-&gt;next;
	list_head-&gt;previous = _elem;
	_elem-&gt;next = list_head;
	_elem-&gt;previous = NULL;

return _elem;
}

/* PUBLIC FUNCTIONS */
list_t* list_create ( void )
{
	list_t* list;
	list = (list_t*) malloc ( sizeof ( list_t ) );
	/* low priority error checking */
	if ( unlikely ( list == NULL ) )
	{
		fprintf(stderr, &quot;list_create() malloc()&quot;);
		return NULL;
	}
	/* end of error checking */

list_initializehead ( list );

return list;
}

void list_delete ( list_t* _list )
{
	/* high priority error checking */
	if ( !list_ishead ( _list ) )
	{
		/* begin traversing list backwise */
		list_t* tmp_list = _list-&gt;previous;
		do
		{
			list_t* last_pointer = tmp_list;
			free ( tmp_list-&gt;data );
			tmp_list = tmp_list-&gt;previous;
			free ( last_pointer );

} while ( tmp_list != NULL );

}
	/* end of error checking */

while ( _list != NULL )
	{
		list_t* last_pointer = _list; /* keep a copy to delete after
					 advancing the pointer */
		free ( _list-&gt;data );
		_list = _list-&gt;next; 	 /* advance the pointer */
		free ( last_pointer ); 	 /* and delete the last one */
	}
}

list_t* list_gethead ( list_t*const _list )
{
	/* medium periority error checking */
	if ( unlikely ( _list == NULL ) )
	{
		perror ( &quot;list_gethead ()&quot; );
		return NULL;
	}
	/* end of error checking */

if ( unlikely (list_ishead ( _list ) ) )
		return _list;
	return list_gethead ( _list-&gt;previous );
}

list_t* list_gettail ( const list_t *const _list )
{
	/* medium priority error checking */
	if ( unlikely ( _list == NULL ) )
	{
		perror ( &quot;list_gettail()&quot; );
		return NULL;
	}
	if ( unlikely ( _list-&gt;next == NULL ) )
	{
		return NULL;
	}
	/* end of error checking */

return _list-&gt;next;
}

list_t* list_getend ( list_t *const _list )
{
	/* medium priority error checking */
	if ( unlikely( _list == NULL ) )
	{
		fprintf(stderr, &quot;list_getend()&quot; );
		return NULL;
	}
	/* end of error checking */
	if ( _list-&gt;next == NULL ) return _list;
	return list_getend ( _list-&gt;next );
}

list_t* list_insertelement ( list_t*const _list, void* _elem )
{
	list_t* list_head;
	list_t* new_element;

/* medium priority error checking */
	if ( _list == NULL || _elem == NULL )
	{
		errno = EINVAL;
		return NULL;
	}
	/* end of error checking */
	list_head = list_gethead ( _list );

if ( !list_isempty ( _list ) ) /* list is not empty */
	{
		new_element = (list_t*) malloc( sizeof ( list_t ) );
		/* low priority error checking */
		if( unlikely ( new_element == NULL ) )
		{
			perror ( &quot;list_insertelement() malloc()&quot; );
		}
		/* end of error checking */

/* update pointers */
		list_head-&gt;previous = new_element;
	}
	else /* list is empty */
	{
		list_head = NULL;
		new_element = _list;
	}
	new_element-&gt;next = list_head;
	new_element-&gt;previous = NULL;

/* add our data */
	new_element-&gt;data = _elem;

return new_element;
}

list_t* list_appendelement ( list_t*const _list, void*const _elem )
{
	list_t* list_end;
	list_t* new_element;

/* medium priority error checking */
	if ( unlikely(_list == NULL || _elem == NULL ))
	{
		errno = EINVAL;
		return NULL;
	}
	/* end of error checking */
	list_end = list_getend ( _list );

if ( !list_isempty ( _list ) ) /* list is not empty */
	{
		new_element = (list_t*) malloc( sizeof ( list_t ) );
		/* low priority error checking */
		if( unlikely ( new_element == NULL ) )
		{
			perror ( &quot;list_insertelement() malloc()&quot; );
			return NULL;
		}
		/* end of error checking */

/* update pointers */
		list_end-&gt;next = new_element;
	}
	else /* list is empty */
	{
		list_end = NULL;
		new_element = _list;
	}
	new_element-&gt;next = NULL;
	new_element-&gt;previous = list_end;

return new_element;
}

void* list_getdata ( list_t const* _list )
{
	return _list-&gt;data;
}

GLboolean list_hasnext ( list_t const* _list )
{
	if ( _list != NULL &amp;&amp; _list-&gt;next == NULL ) return GL_FALSE;
	return GL_TRUE;
}

void list_deleteelement ( list_t* _list, list_t* _elem )
{
	list_t* new_list;
	list_t* final_list;
	/* medium priority error checking */
	if ( _list == NULL || _elem == NULL )
	{
		return;
	}
	/* end of error checking */

new_list = list_movetofront ( _list, _elem );
	final_list = list_gettail ( new_list );
	final_list-&gt;previous = NULL;
	free ( new_list-&gt;data );
	free ( new_list );
}

list_t* list_findelement ( list_t *const _list,
				GLboolean (*_compare)( list_t* _list_elem ) )
{
	list_t* list_iterator;

list_iterator = list_gethead ( _list );
	do
	{
		if (unlikely (_compare (list_iterator)))
		{
			return list_iterator;
		}
		list_iterator = list_gettail ( list_iterator );
	} while ( list_iterator != NULL );
	return NULL;
}

void list_print ( list_t* _list, type_t _data_type )
{
	int position;
	char ldatac;
	int ldatai;
	char* ldatas;
	double ldatad;
	list_t* tmp_list;
	printf ( &quot;printing list:\n&quot; );
	position = 0;
	tmp_list = _list;
	do
	{

printf ( &quot;list position %i:\t&quot;, position );
		switch ( _data_type )
		{
			case CHAR_T: case UNSIGNED_CHAR_T:
				ldatac = *( char* )list_getdata ( tmp_list );
				printf ( &quot;data: %c\n&quot;, ldatac);
			break;
			case DOUBLE_T: case FLOAT_T:
				ldatad = *( double* )list_getdata ( tmp_list );
				printf ( &quot;data: %f\n&quot;, ldatad);
			break;
			case CHAR_POINTER_T:
				ldatas = ( char * )list_getdata ( tmp_list );
				printf( &quot;data %s\n&quot;, ldatas);
			break;
			default:
				ldatai = *( int * )list_getdata( tmp_list );
				printf( &quot;data %i\n&quot;, ldatai);
		}
		position++;
	}
	while (
		(tmp_list = list_gettail(tmp_list)));

}
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Pastable version of Linked lists implementation