audio_pipe.c

/*
 * pipe output driver. This file is part of Shairport.
 * Copyright (c) James Laird 2013
 * All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <memory.h>
#include "common.h"
#include "audio.h"

static int fd = -1;
static char *pipename = NULL;
static int Fs;

static void start(int sample_rate) {
	int readfd;
	
	Fs = sample_rate;
	
	readfd = open(pipename, O_RDONLY | O_NONBLOCK);
	if (readfd < 0) {
		perror("open");
		die("could not open specified pipe for reading");
	}
	fd = open(pipename, O_WRONLY);
	if (fd < 0) {
        perror("open");
        die("could not open specified pipe for writing");
    }
	close(readfd);
}

static void play(short buf[], int samples) {
	int rc;
 
	rc = write(fd, buf, samples*4);
	if (rc <=0) usleep(1e6 * samples / Fs);
}

static void stop(void) {
	close(fd);
}

static int init(int argc, char **argv) {
    if (argc != 1)
        die("bad argument(s) to pipe");

    pipename = strdup(argv[0]);

	// test open pipe so we error on startup if it's going to fail
	start(44100);
	stop();
	
    return 0;
}

static void deinit(void) {
    if (fd > 0)
        close(fd);
    if (pipename)
        free(pipename);
}

static void help(void) {
    printf("    pipe takes 1 argument: the name of the FIFO to write to.\n");
}

audio_output audio_pipe = {
    .name = "pipe",
    .help = &help,
    .init = &init,
    .deinit = &deinit,
    .start = &start,
    .stop = &stop,
    .play = &play,
    .volume = NULL
};