mpd/src/output/fifo_plugin.c

/* the Music Player Daemon (MPD)
 * Copyright (C) 2003-2007 by Warren Dukes (warren.dukes@gmail.com)
 * This project's homepage is: http://www.musicpd.org
 *
 * This program 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 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "../output_api.h"
#include "../utils.h"
#include "../timer.h"

#include <glib.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#undef G_LOG_DOMAIN
#define G_LOG_DOMAIN "fifo"

#define FIFO_BUFFER_SIZE 65536 /* pipe capacity on Linux >= 2.6.11 */

typedef struct _FifoData {
	char *path;
	int input;
	int output;
	int created;
	Timer *timer;
} FifoData;

static FifoData *newFifoData(void)
{
	FifoData *ret;

	ret = xmalloc(sizeof(FifoData));

	ret->path = NULL;
	ret->input = -1;
	ret->output = -1;
	ret->created = 0;
	ret->timer = NULL;
	
	return ret;
}

static void freeFifoData(FifoData *fd)
{
	if (fd->path)
		free(fd->path);

	if (fd->timer)
		timer_free(fd->timer);

	free(fd);
}

static void removeFifo(FifoData *fd)
{
	g_debug("Removing FIFO \"%s\"", fd->path);

	if (unlink(fd->path) < 0) {
		g_warning("Could not remove FIFO \"%s\": %s",
			  fd->path, strerror(errno));
		return;
	}

	fd->created = 0;
}

static void closeFifo(FifoData *fd)
{
	struct stat st;

	if (fd->input >= 0) {
		close(fd->input);
		fd->input = -1;
	}

	if (fd->output >= 0) {
		close(fd->output);
		fd->output = -1;
	}

	if (fd->created && (stat(fd->path, &st) == 0))
		removeFifo(fd);
}

static int makeFifo(FifoData *fd)
{
	if (mkfifo(fd->path, 0666) < 0) {
		g_warning("Couldn't create FIFO \"%s\": %s",
			  fd->path, strerror(errno));
		return -1;
	}

	fd->created = 1;

	return 0;
}

static int checkFifo(FifoData *fd)
{
	struct stat st;

	if (stat(fd->path, &st) < 0) {
		if (errno == ENOENT) {
			/* Path doesn't exist */
			return makeFifo(fd);
		}

		g_warning("Failed to stat FIFO \"%s\": %s",
			  fd->path, strerror(errno));
		return -1;
	}

	if (!S_ISFIFO(st.st_mode)) {
		g_warning("\"%s\" already exists, but is not a FIFO",
			  fd->path);
		return -1;
	}

	return 0;
}

static bool openFifo(FifoData *fd)
{
	if (checkFifo(fd) < 0)
		return false;

	fd->input = open(fd->path, O_RDONLY|O_NONBLOCK);
	if (fd->input < 0) {
		g_warning("Could not open FIFO \"%s\" for reading: %s",
			  fd->path, strerror(errno));
		closeFifo(fd);
		return false;
	}

	fd->output = open(fd->path, O_WRONLY|O_NONBLOCK);
	if (fd->output < 0) {
		g_warning("Could not open FIFO \"%s\" for writing: %s",
			  fd->path, strerror(errno));
		closeFifo(fd);
		return false;
	}

	return true;
}

static void *fifo_initDriver(G_GNUC_UNUSED struct audio_output *ao,
			     G_GNUC_UNUSED const struct audio_format *audio_format,
			     ConfigParam *param)
{
	FifoData *fd;
	BlockParam *blockParam;
	char *path;

	blockParam = getBlockParam(param, "path");
	if (!blockParam) {
		g_error("No \"path\" parameter specified for fifo output "
			"defined at line %i", param->line);
	}

	path = parsePath(blockParam->value);
	if (!path) {
		g_error("Could not parse \"path\" parameter for fifo output "
			"at line %i", blockParam->line);
	}

	fd = newFifoData();
	fd->path = path;

	if (!openFifo(fd)) {
		freeFifoData(fd);
		return NULL;
	}

	return fd;
}

static void fifo_finishDriver(void *data)
{
	FifoData *fd = (FifoData *)data;

	closeFifo(fd);
	freeFifoData(fd);
}

static bool fifo_openDevice(void *data,
			   struct audio_format *audio_format)
{
	FifoData *fd = (FifoData *)data;

	if (fd->timer)
		timer_free(fd->timer);

	fd->timer = timer_new(audio_format);

	return true;
}

static void fifo_closeDevice(void *data)
{
	FifoData *fd = (FifoData *)data;

	if (fd->timer) {
		timer_free(fd->timer);
		fd->timer = NULL;
	}
}

static void fifo_dropBufferedAudio(void *data)
{
	FifoData *fd = (FifoData *)data;
	char buf[FIFO_BUFFER_SIZE];
	int bytes = 1;

	timer_reset(fd->timer);

	while (bytes > 0 && errno != EINTR)
		bytes = read(fd->input, buf, FIFO_BUFFER_SIZE);

	if (bytes < 0 && errno != EAGAIN) {
		g_warning("Flush of FIFO \"%s\" failed: %s",
			  fd->path, strerror(errno));
	}
}

static bool
fifo_playAudio(void *data, const char *playChunk, size_t size)
{
	FifoData *fd = (FifoData *)data;
	size_t offset = 0;
	ssize_t bytes;

	if (!fd->timer->started)
		timer_start(fd->timer);
	else
		timer_sync(fd->timer);

	timer_add(fd->timer, size);

	while (size) {
		bytes = write(fd->output, playChunk + offset, size);
		if (bytes < 0) {
			switch (errno) {
			case EAGAIN:
				/* The pipe is full, so empty it */
				fifo_dropBufferedAudio(fd);
				continue;
			case EINTR:
				continue;
			}

			g_warning("Closing FIFO output \"%s\" due to write error: %s",
				  fd->path, strerror(errno));
			return false;
		}

		size -= bytes;
		offset += bytes;
	}

	return true;
}

const struct audio_output_plugin fifoPlugin = {
	.name = "fifo",
	.init = fifo_initDriver,
	.finish = fifo_finishDriver,
	.open = fifo_openDevice,
	.play = fifo_playAudio,
	.cancel = fifo_dropBufferedAudio,
	.close = fifo_closeDevice,
};