pqueue.h

// SPDX-License-Identifier: BSD-2-Clause
/*
 * Copyright (c) 2014, Volkan Yazıcı <volkan.yazici@gmail.com>
 * All rights reserved.
 */

/**
 * @file  pqueue.h
 * @brief Priority Queue function declarations
 *
 * @{
 */

#ifndef PQUEUE_H
#define PQUEUE_H

/** priority data type */
typedef unsigned long long pqueue_pri_t;

/** callback functions to get/set/compare the priority of an element */
typedef pqueue_pri_t (*pqueue_get_pri_f)(void *a);
typedef void (*pqueue_set_pri_f)(void *a, pqueue_pri_t pri);
typedef int (*pqueue_cmp_pri_f)(pqueue_pri_t next, pqueue_pri_t curr);

/** callback functions to get/set the position of an element */
typedef size_t (*pqueue_get_pos_f)(void *a);
typedef void (*pqueue_set_pos_f)(void *a, size_t pos);

// /** debug callback function to print a entry */
// typedef void (*pqueue_print_entry_f)(FILE *out, void *a);

/** the priority queue handle */
typedef struct pqueue_t {
	size_t size; /**< number of elements in this queue */
	size_t avail; /**< slots available in this queue */
	size_t step; /**< growth stepping setting */
	pqueue_cmp_pri_f cmppri; /**< callback to compare nodes */
	pqueue_get_pri_f getpri; /**< callback to get priority of a node */
	pqueue_set_pri_f setpri; /**< callback to set priority of a node */
	pqueue_get_pos_f getpos; /**< callback to get position of a node */
	pqueue_set_pos_f setpos; /**< callback to set position of a node */
	void **d; /**< The actualy queue in binary heap form */
} pqueue_t;

/**
 * initialize the queue
 *
 * @param n the initial estimate of the number of queue items for which memory
 *     should be preallocated
 * @param cmppri The callback function to run to compare two elements
 *     This callback should return 0 for 'lower' and non-zero
 *     for 'higher', or vice versa if reverse priority is desired
 * @param setpri the callback function to run to assign a score to an element
 * @param getpri the callback function to run to set a score to an element
 * @param getpos the callback function to get the current element's position
 * @param setpos the callback function to set the current element's position
 *
 * @return the handle or NULL for insufficent memory
 */
pqueue_t *pqueue_init(size_t n, pqueue_cmp_pri_f cmppri, pqueue_get_pri_f getpri,
		      pqueue_set_pri_f setpri, pqueue_get_pos_f getpos, pqueue_set_pos_f setpos);

/**
 * free all memory used by the queue
 * @param q the queue
 */
void pqueue_free(pqueue_t *q);

/**
 * return the size of the queue.
 * @param q the queue
 */
size_t pqueue_size(pqueue_t *q);

/**
 * insert an item into the queue.
 * @param q the queue
 * @param d the item
 * @return 0 on success
 */
int pqueue_insert(pqueue_t *q, void *d);

/**
 * move an existing entry to a different priority
 * @param q the queue
 * @param new_pri the new priority
 * @param d the entry
 */
void pqueue_change_priority(pqueue_t *q, pqueue_pri_t new_pri, void *d);

/**
 * pop the highest-ranking item from the queue.
 * @param q the queue
 * @return NULL on error, otherwise the entry
 */
void *pqueue_pop(pqueue_t *q);

/**
 * remove an item from the queue.
 * @param q the queue
 * @param d the entry
 * @return 0 on success
 */
int pqueue_remove(pqueue_t *q, void *d);

/**
 * access highest-ranking item without removing it.
 * @param q the queue
 * @return NULL on error, otherwise the entry
 */
void *pqueue_peek(pqueue_t *q);

// /**
//  * print the queue
//  * @internal
//  * DEBUG function only
//  * @param q the queue
//  * @param the callback function to print the entry
//  */
// void pqueue_print(pqueue_t *q, pqueue_print_entry_f print);

// /**
//  * dump the queue and it's internal structure
//  * @internal
//  * debug function only
//  * @param q the queue
//  * @param the callback function to print the entry
//  */
// void pqueue_dump(pqueue_t *q, pqueue_print_entry_f print);

/**
 * checks that the pq is in the right order, etc
 * @internal
 * debug function only
 * @param q the queue
 */
int pqueue_is_valid(pqueue_t *q);

#endif /* PQUEUE_H */
/** @} */