/*
 * fifo.c
 *
 * (c) 2012 Thomas White <taw@bitwiz.org.uk>
 *
 * This file is part of MIDInator.
 *
 * MIDInator is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MIDInator is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MIDInator.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

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

#include "fifo.h"

struct _fifo
{
	pthread_mutex_t lock;

	unsigned char *buf;
	size_t sz;
	size_t n_used;

	size_t r;  /* Read pointer */
	size_t w;  /* Write pointer */
};


FIFO *fifo_new()
{
	FIFO *f;

	f = malloc(sizeof(struct _fifo));
	if ( f == NULL ) return NULL;

	f->sz = 64*1024;
	f->buf = malloc(f->sz);
	if ( f->buf == NULL ) {
		free(f);
		return NULL;
	}

	f->r = 0;
	f->w = 0;
	f->n_used = 0;

	pthread_mutex_init(&f->lock, NULL);

	return f;
}


void fifo_push(FIFO *f, unsigned char c)
{
	pthread_mutex_lock(&f->lock);

	f->buf[f->w++] = c;
	f->n_used++;

	if ( f->w == f->sz ) {
		f->w = 0;
	}

	pthread_mutex_unlock(&f->lock);
}


unsigned char fifo_pop(FIFO *f, int *err)
{
	unsigned char c;

	pthread_mutex_lock(&f->lock);

	if ( f->n_used == 0 ) {
		pthread_mutex_unlock(&f->lock);
		*err = 1;
		return 0;
	}

	*err = 0;
	c = f->buf[f->r++];
	f->n_used--;

	pthread_mutex_unlock(&f->lock);

	return c;
}