add a pipe/FIFO audio backend

Makefile

@@ -9,7 +9,7 @@ endif
 
 PREFIX ?= /usr/local
 
-SRCS := shairport.c rtsp.c mdns.c common.c rtp.c player.c alac.c audio.c audio_dummy.c
+SRCS := shairport.c rtsp.c mdns.c common.c rtp.c player.c alac.c audio.c audio_dummy.c audio_pipe.c
 
 ifdef CONFIG_AO
 SRCS += audio_ao.c

audio.c

@@ -32,13 +32,14 @@
 #ifdef CONFIG_AO
 extern audio_output audio_ao;
 #endif
-extern audio_output audio_dummy;
+extern audio_output audio_dummy, audio_pipe;
 
 static audio_output *outputs[] = {
 #ifdef CONFIG_AO
     &audio_ao,
 #endif
     &audio_dummy,
+    &audio_pipe,
     NULL
 };
 

audio_pipe.c

@@ -0,0 +1,87 @@
+/*
+ * 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"
+
+int fd = -1;
+
+char *pipename = NULL;
+
+static void start(int sample_rate) {
+    fd = open(pipename, O_WRONLY);
+    if (fd < 0) {
+        perror("open");
+        die("could not open specified pipe for writing");
+    }
+}
+
+static void play(short buf[], int samples) {
+    write(fd, buf, samples*4);
+}
+
+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
+};