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/*
* Copyright (c) 2014, Volkan Yazıcı <volkan.yazici@gmail.com>
* Copyright (c) 2023, Marvin Borner <dev@marvinborner.de>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <pqueue.h>
#define left(i) ((i) << 1)
#define right(i) (((i) << 1) + 1)
#define parent(i) ((i) >> 1)
struct pqueue *pqueue_init(size_t n, pqueue_cmp_pri_f cmppri,
pqueue_get_pri_f getpri, pqueue_set_pos_f setpos)
{
struct pqueue *q;
if (!(q = malloc(sizeof(struct pqueue))))
return NULL;
/* Need to allocate n+1 elements since element 0 isn't used. */
if (!(q->d = malloc((n + 1) * sizeof(void *)))) {
free(q);
return NULL;
}
q->size = 1;
q->avail = q->step = (n + 1); /* see comment above about n+1 */
q->cmppri = cmppri;
q->getpri = getpri;
q->setpos = setpos;
return q;
}
void pqueue_free(struct pqueue *q)
{
free(q->d);
free(q);
}
size_t pqueue_size(struct pqueue *q)
{
/* queue element 0 exists but doesn't count since it isn't used. */
return (q->size - 1);
}
static void bubble_up(struct pqueue *q, size_t i)
{
size_t parent_node;
void *moving_node = q->d[i];
pqueue_pri_t moving_pri = q->getpri(moving_node);
for (parent_node = parent(i);
((i > 1) && q->cmppri(q->getpri(q->d[parent_node]), moving_pri));
i = parent_node, parent_node = parent(i)) {
q->d[i] = q->d[parent_node];
q->setpos(q->d[i], i);
}
q->d[i] = moving_node;
q->setpos(moving_node, i);
}
static size_t maxchild(struct pqueue *q, size_t i)
{
size_t child_node = left(i);
if (child_node >= q->size)
return 0;
if ((child_node + 1) < q->size &&
q->cmppri(q->getpri(q->d[child_node]),
q->getpri(q->d[child_node + 1])))
child_node++; /* use right child instead of left */
return child_node;
}
static void percolate_down(struct pqueue *q, size_t i)
{
size_t child_node;
void *moving_node = q->d[i];
pqueue_pri_t moving_pri = q->getpri(moving_node);
while ((child_node = maxchild(q, i)) &&
q->cmppri(moving_pri, q->getpri(q->d[child_node]))) {
q->d[i] = q->d[child_node];
q->setpos(q->d[i], i);
i = child_node;
}
q->d[i] = moving_node;
q->setpos(moving_node, i);
}
int pqueue_insert(struct pqueue *q, void *d)
{
void *tmp;
size_t i;
size_t newsize;
if (!q)
return 1;
/* allocate more memory if necessary */
if (q->size >= q->avail) {
newsize = q->size + q->step;
if (!(tmp = realloc(q->d, sizeof(void *) * newsize)))
return 1;
q->d = tmp;
q->avail = newsize;
}
/* insert item */
i = q->size++;
q->d[i] = d;
bubble_up(q, i);
return 0;
}
void *pqueue_pop(struct pqueue *q)
{
void *head;
if (!q || q->size == 1)
return NULL;
head = q->d[1];
q->d[1] = q->d[--q->size];
percolate_down(q, 1);
return head;
}
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