audio_pipe.c

   1 /*
   2  * pipe output driver. This file is part of Shairport.
   3  * Copyright (c) James Laird 2013
   4  * All rights reserved.
   5  *
   6  * Modifications for audio synchronisation
   7  * and related work, copyright (c) Mike Brady 2014
   8  * All rights reserved.
   9  *
  10  * Permission is hereby granted, free of charge, to any person
  11  * obtaining a copy of this software and associated documentation
  12  * files (the "Software"), to deal in the Software without
  13  * restriction, including without limitation the rights to use,
  14  * copy, modify, merge, publish, distribute, sublicense, and/or
  15  * sell copies of the Software, and to permit persons to whom the
  16  * Software is furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be
  19  * included in all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  23  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  25  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  26  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  27  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  28  * OTHER DEALINGS IN THE SOFTWARE.
  29  */
  30
  31 #include "audio.h"
  32 #include "common.h"
  33 #include <errno.h>
  34 #include <fcntl.h>
  35 #include <memory.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <sys/stat.h>
  39 #include <sys/types.h>
  40 #include <unistd.h>
  41
  42 static int fd = -1;
  43
  44 char *pipename = NULL;
  45 char *default_pipe_name = "/tmp/shairport-sync-audio";
  46
  47 static void start(__attribute__((unused)) int sample_rate,
  48                   __attribute__((unused)) int sample_format) {
  49
  50   // this will leave fd as -1 if a reader hasn't been attached to the pipe
  51   // we check that it's not a "real" error though. From the "man 2 open" page:
  52   // "ENXIO  O_NONBLOCK | O_WRONLY is set, the named file is a FIFO, and no process has the FIFO
  53   // open for reading."
  54
  55   fd = try_to_open_pipe_for_writing(pipename);
  56   // we check that it's not a "real" error. From the "man 2 open" page:
  57   // "ENXIO  O_NONBLOCK | O_WRONLY is set, the named file is a FIFO, and no process has the FIFO
  58   // open for reading." Which is okay.
  59   if ((fd == -1) && (errno != ENXIO)) {
  60     char errorstring[1024];
  61     strerror_r(errno, (char *)errorstring, sizeof(errorstring));
  62     debug(1, "audio_pipe start -- error %d (\"%s\") opening pipe: \"%s\".", errno,
  63           (char *)errorstring, pipename);
  64     warn("can not open audio pipe -- error %d (\"%s\") opening pipe: \"%s\".", errno,
  65          (char *)errorstring, pipename);
  66   }
  67 }
  68
  69 static int play(void *buf, int samples, __attribute__((unused)) int sample_type,
  70                 __attribute__((unused)) uint32_t timestamp,
  71                 __attribute__((unused)) uint64_t playtime) {
  72   // if the file is not open, try to open it.
  73   char errorstring[1024];
  74   if (fd == -1) {
  75     fd = try_to_open_pipe_for_writing(pipename);
  76   }
  77   // if it's got a reader, write to it.
  78   if (fd > 0) {
  79     // int rc = non_blocking_write(fd, buf, samples * 4);
  80     int rc = write(fd, buf, samples * 4);
  81     if ((rc < 0) && (errno != EPIPE)) {
  82       strerror_r(errno, (char *)errorstring, 1024);
  83       debug(1, "audio_pip play: error %d writing to the pipe named \"%s\": \"%s\".", errno,
  84             pipename, errorstring);
  85     }
  86   }
  87   return 0;
  88 }
  89
  90 static void stop(void) {
  91   // Don't close the pipe just because a play session has stopped.
  92 }
  93
  94 static int init(int argc, char **argv) {
  95   //  debug(1, "pipe init");
  96   //  const char *str;
  97   //  int value;
  98   //  double dvalue;
  99
 100   // set up default values first
 101
 102   config.audio_backend_buffer_desired_length = 1.0;
 103   config.audio_backend_latency_offset = 0;
 104
 105   // do the "general" audio  options. Note, these options are in the "general" stanza!
 106   parse_general_audio_options();
 107
 108   if (config.cfg != NULL) {
 109     /* Get the Output Pipename. */
 110     const char *str;
 111     if (config_lookup_string(config.cfg, "pipe.name", &str)) {
 112       pipename = (char *)str;
 113     }
 114   }
 115
 116   if (argc > 1)
 117     die("too many command-line arguments to pipe");
 118
 119   if (argc == 1)
 120     pipename = argv[0]; // command line argument has priority
 121
 122   if ((pipename) && (strcasecmp(pipename, "STDOUT") == 0))
 123     die("Can't use \"pipe\" backend for STDOUT. Use the \"stdout\" backend instead.");
 124
 125   if (pipename == NULL)
 126     pipename = default_pipe_name; // if none specified
 127
 128   // here, create the pipe
 129   mode_t oldumask = umask(000);
 130   if (mkfifo(pipename, 0666) && errno != EEXIST)
 131     die("Could not create audio pipe \"%s\"", pipename);
 132   umask(oldumask);
 133
 134   debug(1, "audio pipe name is \"%s\"", pipename);
 135
 136   return 0;
 137 }
 138
 139 static void deinit(void) {
 140   if (fd > 0)
 141     close(fd);
 142 }
 143
 144 static void help(void) {
 145   printf("    Provide the pipe's pathname. The default is \"%s\".\n", default_pipe_name);
 146 }
 147
 148 audio_output audio_pipe = {.name = "pipe",
 149                            .help = &help,
 150                            .init = &init,
 151                            .deinit = &deinit,
 152                            .prepare = NULL,
 153                            .start = &start,
 154                            .stop = &stop,
 155                            .is_running = NULL,
 156                            .flush = NULL,
 157                            .delay = NULL,
 158                            .stats = NULL,
 159                            .play = &play,
 160                            .volume = NULL,
 161                            .parameters = NULL,
 162                            .mute = NULL};