void
pqueue_heapify(pqueue_t *queue, size_t idx) {
/* left index, right index, largest */
void *tmp = NULL;
size_t l_idx, r_idx, lrg_idx;
if (queue == NULL)
return;
l_idx = LEFT(idx);
r_idx = RIGHT(idx);
/* left child exists, compare left child with its parent */
if (l_idx < queue->size && queue->cmp(queue->data[l_idx], queue->data[idx]) > 0) {
lrg_idx = l_idx;
} else {
lrg_idx = idx;
}
/* right child exists, compare right child with the largest element */
if (r_idx < queue->size && queue->cmp(queue->data[r_idx], queue->data[lrg_idx]) > 0) {
lrg_idx = r_idx;
}
/* at this point largest element was determined */
if (lrg_idx != idx) {
/* swap between the index at the largest element */
tmp = queue->data[lrg_idx];
queue->data[lrg_idx] = queue->data[idx];
queue->data[idx] = tmp;
/* heapify again */
pqueue_heapify(queue, lrg_idx);
}
}
/**
* * Turn an "almost-heap" into a heap .
* */
void pqueue_heapify(PQueue *q, size_t idx) {
/* left index, right index, largest */
void *tmp = NULL;
size_t l_idx, r_idx, lrg_idx;
NP_CHECK(q);
l_idx = LEFT(idx);
r_idx = RIGHT(idx);
/* Left child exists, compare left child with its parent */
if (l_idx < q->size && q->cmp(q->data[l_idx], q->data[idx]) < 0) {
lrg_idx = l_idx;
} else {
lrg_idx = idx;
}
/* Right child exists, compare right child with the largest element */
if (r_idx < q->size && q->cmp(q->data[r_idx], q->data[lrg_idx]) < 0) {
lrg_idx = r_idx;
}
/* At this point largest element was determined */
if (lrg_idx != idx) {
/* Swap between the index at the largest element */
tmp = q->data[lrg_idx];
q->data[lrg_idx] = q->data[idx];
q->data[idx] = tmp;
/* Heapify again */
pqueue_heapify(q, lrg_idx);
}
}
void
pqueue_replace_data(pqueue_t *queue, void *old_data, void *new_data, queue_cmp cmp, queue_swp swp) {
size_t i;
for(i=0; i<queue->size; ++i) {
if ((*cmp)(queue->data[i], old_data)) {
(*swp)(&queue->data[i], &new_data);
pqueue_heapify(queue, 0);
break;
}
}
}
void*
pqueue_dequeue(pqueue_t *queue) {
void *data = NULL;
if (queue == NULL || queue->size < 1)
return NULL;
data = queue->data[0];
queue->data[0] = queue->data[queue->size-1];
queue->size--;
/* restore heap property */
pqueue_heapify(queue, 0);
return (data);
}
/**
* * Returns the element with the biggest priority from the queue .
* */
void *pqueue_dequeue(PQueue *q) {
void *data = NULL;
NP_CHECK(q);
if (q->size < 1)
{ /* Priority Queue is empty */ //DEBUG("Priority Queue underflow . Cannot remove another element .");
return NULL;
}
data = q->data[0];
q->data[0] = q->data[q->size-1];
q->size--;
/* Restore heap property */
pqueue_heapify(q, 0);
return (data);
}
