/***********************************************************************
* linkedlist.h
*
* Header file for a simple inplementation of an expandable queue
*
* Written by Paul Bonamy - 23 May 2010
* Rewritten in pure C - 20 July 2010
************************************************************************/

#ifndef EQUEUE_H
#define EQUEUE_H

/***********************************************************************
 * C doesn't understand classes, so we'll use a struct for the node
 *
 * We normally need to refer to a struct specifically as
 * 'struct Node', rather than just as 'Node'. The typedef allows us
 * to refer to a Node as a 'NODE', which requires rather less typing.
 ***********************************************************************/
typedef struct Node {
    // note that we aren't explicitly declaring these public
    // struct members are always automatically public
    int value;      // value stored in the list
    struct Node * next;    // next node in the list. set to 0 if last node
    struct Node * prev;    // previous node in the list, 0 if first node
    // note that there's no longer a constructor. We'll have
    // to set up left = right = 0 on our own from here on out.
} NODE;

/***********************************************************************
 * The EQueue class used to live here. We can't use classes in C,
 * so we'll have to make do with a struct to manage the head and
 * tail pointers and a bunch of global functions.
 *
 * Note, however, that I'm leaving function prototypes here
 *
 * Passing around a pointer to an equeue seems a little ugly, but
 * it means we can have as many equeues as we want. It also means
 * we don't need global variables, which is always a plus
 ***********************************************************************/
typedef struct EQueue {
    NODE * head;    // address of first node in the list
    NODE * tail;    // address of last node in the list
} EQUEUE;
    
void equeue_init(EQUEUE *queue);   // initialize the given queue
void equeue_cleanup(EQUEUE *queue);  // empty out the given queue
int equeue_enqueue(EQUEUE *queue, int v); // insert v into queue
int equeue_dequeue(EQUEUE *queue, int *v); // pull a value from queue into v
void equeue_empty(EQUEUE *queue);   // delete all values in queue

#endif