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/* Priority queue on top of gheap. */
/******************************************************************************
* Interface.
*****************************************************************************/
#include "gheap.h"
#include <stddef.h> /* for size_t */
/*
* Deletes the given item.
*/
typedef void (*gpriority_queue_item_deleter_t)(void *);
/*
* Opaque type for priority queue.
*/
struct gpriority_queue;
/*
* Creates an empty priority queue.
*
* The gheap context pointed by ctx must remain valid until
* gpriority_queue_delete() call.
*/
static inline struct gpriority_queue *gpriority_queue_create(
const struct gheap_ctx *ctx, gpriority_queue_item_deleter_t item_deleter);
/*
* Creates a pirority queue and copies items from the given array into
* the priority queue.
*/
static inline struct gpriority_queue *gpriority_queue_create_from_array(
const struct gheap_ctx *ctx, gpriority_queue_item_deleter_t item_deleter,
const void *a, size_t n);
/*
* Deletes the given priority queue.
*/
static inline void gpriority_queue_delete(struct gpriority_queue *q);
/*
* Returns non-zero if the given priority queue is empty.
* Otherwise returns zero.
*/
static inline int gpriority_queue_empty(struct gpriority_queue *q);
/*
* Returns the size of the given priority queue.
*/
static inline size_t gpriority_queue_size(struct gpriority_queue *q);
/*
* Returns a pointer to the top element in the priority queue.
*/
static inline const void *gpriority_queue_top(struct gpriority_queue *q);
/*
* Pushes a copy of the given item into priority queue.
*/
static inline void gpriority_queue_push(struct gpriority_queue *q,
const void *item);
/*
* Pops the top element from the priority queue.
*/
static inline void gpriority_queue_pop(struct gpriority_queue *q);
/******************************************************************************
* Implementation.
*****************************************************************************/
#include <stdint.h> /* for SIZE_MAX */
#include <stdio.h> /* for fprintf() */
#include <stdlib.h> /* for malloc(), free() */
struct gpriority_queue
{
const struct gheap_ctx *ctx;
gpriority_queue_item_deleter_t item_deleter;
void *base;
size_t size;
size_t capacity;
};
static inline struct gpriority_queue *gpriority_queue_create(
const struct gheap_ctx *const ctx,
const gpriority_queue_item_deleter_t item_deleter)
{
struct gpriority_queue *q = malloc(sizeof(*q));
q->ctx = ctx;
q->item_deleter = item_deleter;
q->base = malloc(ctx->item_size);
q->size = 0;
q->capacity = 1;
return q;
}
static inline struct gpriority_queue *gpriority_queue_create_from_array(
const struct gheap_ctx *const ctx,
const gpriority_queue_item_deleter_t item_deleter,
const void *const a, size_t n)
{
struct gpriority_queue *q = malloc(sizeof(*q));
q->ctx = ctx;
q->item_deleter = item_deleter;
assert(n <= SIZE_MAX / ctx->item_size);
q->base = malloc(n * ctx->item_size);
q->size = n;
q->capacity = n;
for (size_t i = 0; i < n; ++i) {
const void *const src = ((char *)a) + i * ctx->item_size;
void *const dst = ((char *)q->base) + i * ctx->item_size;
ctx->item_mover(dst, src);
}
gheap_make_heap(ctx, q->base, q->size);
return q;
}
static inline void gpriority_queue_delete(struct gpriority_queue *const q)
{
for (size_t i = 0; i < q->size; ++i) {
void *const item = ((char *)q->base) + i * q->ctx->item_size;
q->item_deleter(item);
}
free(q->base);
free(q);
}
static inline int gpriority_queue_empty(struct gpriority_queue *const q)
{
return (q->size == 0);
}
static inline size_t gpriority_queue_size(struct gpriority_queue *const q)
{
return q->size;
}
static inline const void *gpriority_queue_top(struct gpriority_queue *const q)
{
assert(q->size > 0);
return q->base;
}
static inline void gpriority_queue_push(struct gpriority_queue *const q,
const void *item)
{
if (q->size == q->capacity) {
if (q->capacity > SIZE_MAX / 2 / q->ctx->item_size) {
fprintf(stderr, "priority queue size overflow");
exit(EXIT_FAILURE);
}
q->capacity *= 2;
char *const new_base = malloc(q->capacity * q->ctx->item_size);
for (size_t i = 0; i < q->size; ++i) {
void *const dst = new_base + i * q->ctx->item_size;
const void *const src = ((char *)q->base) + i * q->ctx->item_size;
q->ctx->item_mover(dst, src);
}
free(q->base);
q->base = new_base;
}
assert(q->size < q->capacity);
void *const dst = ((char *)q->base) + q->size * q->ctx->item_size;
q->ctx->item_mover(dst, item);
++(q->size);
gheap_push_heap(q->ctx, q->base, q->size);
}
static inline void gpriority_queue_pop(struct gpriority_queue *const q)
{
assert(q->size > 0);
gheap_pop_heap(q->ctx, q->base, q->size);
--(q->size);
void *const item = ((char *)q->base) + q->size * q->ctx->item_size;
q->item_deleter(item);
}