/*
    -- l_queue.h -- Tony Givargis
    Linked list Queue implementation for medium to large memory models.
*/

#ifndef __l_queue_h__
#define __l_queue_h__

/*---------------------------------------------------------------------------*/

#include <stddef.h>

/*---------------------------------------------------------------------------*/

/*
    EL_QueueNode

    Used by queue functions.
*/
typedef struct EL_QueueNode {

    void* element;
    struct EL_QueueNode* link;

} EL_QueueNode;

/*---------------------------------------------------------------------------*/

/*
    EL_Queue

    Returned by EL_QueueCreate function as the ADT identifier (handle) of a
    queue.
*/
typedef struct EL_Queue {

    EL_QueueNode* head;
    EL_QueueNode* tail;
    unsigned int size;		/* number of items in the list */

} EL_Queue;

/*---------------------------------------------------------------------------*/

/*
    EL_QueueCreate

    Creates an empty queue and returns an EL_Queue* ADT to caller. This ADT
    is passed to subsequent queue functions as the identifier (handle) of
    this particular queue. Returns EL_Queue* on success, NULL otherwise.
    O(1)
*/
EL_Queue* EL_QueueCreate(void);

/*---------------------------------------------------------------------------*/

/*
    EL_QueueDestroy

    Destroys queue (q).
    --> O(n)
*/
void EL_QueueDestroy(EL_Queue* q);

/*---------------------------------------------------------------------------*/

/*
    EL_QueuePush

    Pushes data (element) onto the queue (q). Retruns data element on
    success, NULL otherwise.
    --> O(1)
*/
void* EL_QueuePush(EL_Queue* q, void* element);

/*---------------------------------------------------------------------------*/

/*
    EL_QueuePop

    Pops data element from the queue (q). Returns data element on success,
    NULL otherwise.
    --> O(1)
*/
void* EL_QueuePop(EL_Queue* q);

/*---------------------------------------------------------------------------*/

/*
    EL_QueueSize

    Returns the number of data elements in queue (q).
    --> O(1)
*/
#define EL_QueueSize(q)		((q)->size)

/*---------------------------------------------------------------------------*/

#endif