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#ifndef MY_QUEUE_H
#define MY_QUEUE_H
#include <stdbool.h>
/**
* \file
*
* Fixed-size single-producer / single-consumer queue.
*
* This is a generic queue that supports a single producer thread and a
* single consumer thread. The implementation uses a fixed power-of-2 size
* circular buffer.
*
* The my_queue_insert() and my_queue_remove() functions are "non-blocking";
* that is, the policies for queue full / queue empty conditions are left to
* the caller. These functions return a boolean indicating whether the queue
* operation succeeded or not. For example, a producer that spins until an
* element is successfully enqueued might look like:
*
* void *item;
* produce_item(&item);
* while (!my_queue_insert(q, item, NULL));
*
* And a consumer that spins until an element is successfully dequeued
* might look like:
*
* void *item;
* while (!my_queue_remove(q, &item, NULL));
* consume_item(item);
*
* The my_queue_insert() and my_queue_remove() functions take an optional third
* parameter for returning the spaces remaining in the queue or the count of
* elements remaining, respectively. This allows for more complicated
* coordination between producer and consumer, for instance a consumer thread
* that sleeps when the queue is empty and is woken by the producer when it
* adds an element to an empty queue.
*/
struct my_queue;
/**
* Initialize a new queue.
*
* \param[in] num_entries Number of elements in the queue. Must be >=2, and a power-of-2.
* \param[in] size_entry Size in bytes of each queue entry.
* \return Opaque pointer that is NULL on failure or non-NULL on success.
*/
struct my_queue *
my_queue_init(unsigned num_entries, unsigned size_entry);
/**
* Destroy a queue.
*/
void
my_queue_destroy(struct my_queue **q);
/**
* Describe the queue implementation type.
*/
const char *
my_queue_impl_type(void);
/**
* Insert an element into the queue.
*
* \param[in] q Queue object.
* \param[in] elem Element object.
* \param[out] space If non-NULL, pointer to store the number of remaining
* spaces in the queue.
* \return true if the element was inserted into the queue,
* false if the queue is full.
*/
bool
my_queue_insert(struct my_queue *q, void *elem, unsigned *space);
/**
* Remove an element from the queue.
*
* \param[in] q Queue object.
* \param[out] elem Where the element object will be copied.
* \param[out] count If non-NULL, pointer to store the count of elements
* remaining in the queue.
* \return true if an element was removed from the queue,
* false if the queue is empty.
*/
bool
my_queue_remove(struct my_queue *q, void *elem, unsigned *count);
struct my_queue_ops {
struct my_queue *(*init)(unsigned, unsigned);
void (*destroy)(struct my_queue **);
const char *(*impl_type)(void);
bool (*insert)(struct my_queue *, void *, unsigned *);
bool (*remove)(struct my_queue *, void *, unsigned *);
};
#endif /* MY_QUEUE_H */
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