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audio_pipe.c
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audio_pipe.c
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/*
* 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 <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include "common.h"
#include "audio.h"
static int fd = -1;
static char *pipename = NULL;
static int Fs;
static long long starttime, samples_played;
static void stop(void) {
close(fd);
fd = -1;
}
static void start(int sample_rate) {
if (fd >= 0)
stop();
fd = open(pipename, O_WRONLY | O_NONBLOCK);
if ((fd < 0) && (errno != ENXIO)) {
perror("open");
die("could not open specified pipe for writing");
}
// The other end is ready, reopen with blocking
if (fd >= 0) {
close(fd);
fd = open(pipename, O_WRONLY);
}
Fs = sample_rate;
starttime = 0;
samples_played = 0;
}
// Wait procedure taken from audio_dummy.c
static void wait_samples(int samples) {
struct timeval tv;
// this is all a bit expensive but it's long-term stable.
gettimeofday(&tv, NULL);
long long nowtime = tv.tv_usec + 1e6*tv.tv_sec;
if (!starttime)
starttime = nowtime;
samples_played += samples;
long long finishtime = starttime + samples_played * 1e6 / Fs;
usleep(finishtime - nowtime);
}
static void play(short buf[], int samples) {
if (fd < 0) {
wait_samples(samples);
// check if the other end is ready every 5 seconds
if (samples_played > 5 * Fs)
start(Fs);
return;
}
if (write(fd, buf, samples*4) < 0)
stop();
}
static int init(int argc, char **argv) {
struct stat sb;
if (argc != 1)
die("bad argument(s) to pipe");
pipename = strdup(argv[0]);
if (stat(pipename, &sb) < 0)
die("could not stat() pipe");
if (!S_ISFIFO(sb.st_mode))
die("not a pipe");
return 0;
}
static void deinit(void) {
if (fd >= 0)
stop();
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
};