/* Copyright (C) 2010, 2011 Tony Garnock-Jones. All rights reserved. */

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

#include "dataq.h"

#define QLINK(q,x)	(*((void **)(((char *) x) + (q)->link_offset)))

void enqueue(queue_t *q, void *x) {
  QLINK(q, x) = NULL;
  if (q->head == NULL) {
    q->head = x;
  } else {
    QLINK(q, q->tail) = x;
  }
  q->tail = x;
  q->count++;
}

void *dequeue(queue_t *q) {
  if (q->head == NULL) {
    return NULL;
  } else {
    void *x = q->head;
    q->head = QLINK(q, x);
    QLINK(q, x) = NULL;
    if (q->head == NULL) {
      q->tail = NULL;
    }
    q->count--;
    return x;
  }
}

void queue_append(queue_t *q1, queue_t *q2) {
  assert(q1->link_offset == q2->link_offset);

  if (q2->head != NULL) {
    if (q1->head != NULL) {
      QLINK(q1, q1->tail) = q2->head;
    } else {
      q1->head = q2->head;
    }
    q1->tail = q2->tail;
    q2->head = NULL;
    q2->tail = NULL;
  }
}