libpriqueue/libpriqueue.c File Reference

#include <stdlib.h>
#include <stdio.h>
#include "libpriqueue.h"

Functions
void	priqueue_init (priqueue_t *q, int(*comparer)(const void *, const void *))
	Initializes the priqueue_t data structure.
int	priqueue_offer (priqueue_t *q, void *ptr)
	Inserts the specified element into this priority queue.
void *	priqueue_peek (priqueue_t *q)
	Retrieves, but does not remove, the head of this queue, returning NULL if this queue is empty.
void *	priqueue_poll (priqueue_t *q)
	Retrieves and removes the head of this queue, or NULL if this queue is empty.
void *	priqueue_at (priqueue_t *q, int index)
	Returns the element at the specified position in this list, or NULL if the queue does not contain an index'th element.
int	priqueue_remove (priqueue_t *q, void *ptr)
	Removes all instances of ptr from the queue.
void *	priqueue_remove_at (priqueue_t *q, int index)
	Removes the specified index from the queue, moving later elements up a spot in the queue to fill the gap.
int	priqueue_size (priqueue_t *q)
	Returns the number of elements in the queue.
void	priqueue_destroy (priqueue_t *q)
	Destroys and frees all the memory associated with q.

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Detailed Description

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Function Documentation

void* priqueue_at	(	priqueue_t *	q,
		int	index
	)

Returns the element at the specified position in this list, or NULL if the queue does not contain an index'th element.

Parameters:

q	a pointer to an instance of the priqueue_t data structure
index	position of retrieved element

Returns:

the index'th element in the queue

NULL if the queue does not contain the index'th element

void priqueue_destroy

(

priqueue_t *

q

)

Destroys and frees all the memory associated with q.

Parameters:

q	a pointer to an instance of the priqueue_t data structure

void priqueue_init	(	priqueue_t *	q,
		int(*)(const void *, const void *)	comparer
	)

Initializes the priqueue_t data structure.

Assumtions

• You may assume this function will only be called once per instance of priqueue_t
• You may assume this function will be the first function called using an instance of priqueue_t.

  Parameters:

  q	a pointer to an instance of the priqueue_t data structure
  comparer	a function pointer that compares two elements. See also Compare Function

int priqueue_offer	(	priqueue_t *	q,
		void *	ptr
	)

Inserts the specified element into this priority queue.

Parameters:

q	a pointer to an instance of the priqueue_t data structure
ptr	a pointer to the data to be inserted into the priority queue

Returns:

The zero-based index where ptr is stored in the priority queue, where 0 indicates that ptr was stored at the front of the priority queue.

void* priqueue_peek

(

priqueue_t *

q

)

Retrieves, but does not remove, the head of this queue, returning NULL if this queue is empty.

Parameters:

q	a pointer to an instance of the priqueue_t data structure

Returns:

pointer to element at the head of the queue

NULL if the queue is empty

void* priqueue_poll

(

priqueue_t *

q

)

Retrieves and removes the head of this queue, or NULL if this queue is empty.

Parameters:

q	a pointer to an instance of the priqueue_t data structure

Returns:

the head of this queue

NULL if this queue is empty

int priqueue_remove	(	priqueue_t *	q,
		void *	ptr
	)

Removes all instances of ptr from the queue.

This function should not use the comparer function, but check if the data contained in each element of the queue is equal (==) to ptr.

Parameters:

q	a pointer to an instance of the priqueue_t data structure
ptr	address of element to be removed

Returns:

the number of entries removed

void* priqueue_remove_at	(	priqueue_t *	q,
		int	index
	)

Removes the specified index from the queue, moving later elements up a spot in the queue to fill the gap.

Parameters:

q	a pointer to an instance of the priqueue_t data structure
index	position of element to be removed

Returns:

the element removed from the queue

NULL if the specified index does not exist

int priqueue_size

(

priqueue_t *

q

)

Returns the number of elements in the queue.

Parameters:

q	a pointer to an instance of the priqueue_t data structure

Returns:

the number of elements in the queue