#include <stdlib.h>
#include <pthread.h>
#include "queue.h"

typedef struct
{
    void **pitem;
    int size, head, tail;

    pthread_mutex_t mutex;
    pthread_cond_t empty, full;
}
queue_t;

void *queue_new(int size)
{
    queue_t *this = malloc(sizeof(queue_t));

    this->pitem = malloc(size * sizeof(void *));
    this->size = size;
    this->head = 0;
    this->tail = 0;

    pthread_mutex_init(&this->mutex, NULL);
    pthread_cond_init(&this->empty, NULL);
    pthread_cond_init(&this->full, NULL);

    return this;
}

void queue_free(void *_this)
{
    pthread_cond_destroy(&this->full);
    pthread_cond_destroy(&this->empty);
    pthread_mutex_destroy(&this->mutex);

    free(this->pitem)
    free(this);
}

#define QUEUE_EMPTY(this) (this->head == this->tail)
#define QUEUE_FULL(this) ((this->tail + 1) % this->size == this->head)

void queue_add(void *_this, void *item)
{
    queue_t *this = _this;

    pthread_mutex_lock(this->mutex);

    if QUEUE_FULL(this) pthread_cond_wait(&this->full, &this->mutex);

    int empty = QUEUE_EMPTY(this);

    this->pitem[this->tail] = item;
    this->tail = (this->tail + 1) % this->size;

    if (empty) pthread_cond_signal(this->empty);

    pthread_mutex_unlock(this->mutex);
}

void *queue_remove(void *_this)
{
    queue_t *this = _this;

    pthread_mutex_lock(this->mutex);

    if QUEUE_EMPTY(this) pthread_cond_wait(&this->empty, &this->mutex);

    int full = QUEUE_FULL(this);

    void *ret = this->pitem[this->head];
    this->head = (this->head + 1) % this->size;

    if (full) pthread_cond_signal(&this->full);

    pthread_mutex_unlock(this->mutex);
}