Dear MPD-developers,
Lately I fantasized about a CGI like mechanism that is called when a song
changes for example. External programs can then be notified without listening
all the time, a push basis.
For example it can be used to:
- Log data about playing behaviour.
- Change the wallpaper of the system.
- Output playing information to an external device like a character LCD
display.
- Scrobble to last.fm like services.Anyways, I was not sure whether this was in the scope of the project and what other thought about it. But since it was an easy hack I've include a patch anyhow that supplies this functionality. An example program that uses the functionality can be found here: https://github.com/dopefishh/mpdcgilog Best, Mart
diff --git a/AUTHORS b/AUTHORS
index 09eb11c..d620531 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -30,3 +30,4 @@ The following people have contributed code to MPD:
Jurgen Kramer <gtmkra...@xs4all.nl>
Jean-Francois Dockes <j...@dockes.org>
Yue Wang <yuleo...@gmail.com>
+ Mart Lubbers <m...@martlubbers.net>
diff --git a/Makefile.am b/Makefile.am
index ef65231..e34d069 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1403,6 +1403,12 @@ liboutput_plugins_a_SOURCES += \
src/output/plugins/FifoOutputPlugin.hxx
endif
+if ENABLE_CGI_OUTPUT
+liboutput_plugins_a_SOURCES += \
+ src/output/plugins/CgiOutputPlugin.cxx \
+ src/output/plugins/CgiOutputPlugin.hxx
+endif
+
if HAVE_SNDIO
liboutput_plugins_a_SOURCES += \
src/output/plugins/SndioOutputPlugin.cxx \
diff --git a/configure.ac b/configure.ac
index d94cad3..6c21026 100644
--- a/configure.ac
+++ b/configure.ac
@@ -334,6 +334,11 @@ AC_ARG_ENABLE(fifo,
[disable support for writing audio to a FIFO (default: enable)]),,
enable_fifo=yes)
+AC_ARG_ENABLE(cgi-output,
+ AS_HELP_STRING([--enable-cgi-output],
+ [enable support for writing audio/events to a CGI script (default: disabled)]),,
+ enable_cgi_output=yes)
+
AC_ARG_ENABLE(sndio,
AS_HELP_STRING([--enable-sndio],
[enable support for sndio output plugin (default: auto)]),,
@@ -1119,6 +1124,10 @@ fi
MPD_DEFINE_CONDITIONAL(enable_fifo, HAVE_FIFO,
[support for writing audio to a FIFO])
+dnl ----------------------------------- CGI -----------------------------------
+MPD_DEFINE_CONDITIONAL(enable_cgi_output, ENABLE_CGI_OUTPUT, [CGI output])
+
+
dnl ----------------------------------- SNDIO ----------------------------------
if test x$enable_sndio = xauto; then
AC_CHECK_HEADER(sndio.h,
@@ -1453,6 +1462,7 @@ results(id3,[ID3])
printf '\nPlayback support:\n\t'
results(alsa,ALSA)
results(fifo,FIFO)
+results(cgi_output,CGI)
results(sndio,[SNDIO])
results(recorder_output,[File Recorder])
results(haiku,[Haiku])
diff --git a/doc/mpdconf.example b/doc/mpdconf.example
index 7f9ddde..8d8c67d 100644
--- a/doc/mpdconf.example
+++ b/doc/mpdconf.example
@@ -335,6 +335,13 @@ input {
# format "44100:16:2"
#}
#
+## Example "cgi" output:
+#audio_output {
+# type "cgi"
+# name "my cgi"
+# command "/path/to/some/script.sh"
+#}
+#
## An example of a null output (for no audio output):
#
#audio_output {
diff --git a/doc/user.xml b/doc/user.xml
index c86458f..d72d3b2 100644
--- a/doc/user.xml
+++ b/doc/user.xml
@@ -2828,6 +2828,39 @@ buffer_size: 16384</programlisting>
</section>
<section>
+ <title><varname>cgi</varname></title>
+
+ <para>
+ The <varname>cgi</varname> plugin writes the metadata of the
+ files and events to a <varname>cgi</varname> script.
+ </para>
+
+ <informaltable>
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>Setting</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ <varname>command</varname>
+ <parameter>CMD</parameter>
+ </entry>
+ <entry>
+ This specifies the path of the script to write to.
+ Several environment variables are made available to
+ the script in the same fashion as web cgi scripts.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </section>
+
+ <section>
<title><varname>jack</varname></title>
<para>
diff --git a/src/output/Registry.cxx b/src/output/Registry.cxx
index 9d8d826..9500f06 100644
--- a/src/output/Registry.cxx
+++ b/src/output/Registry.cxx
@@ -23,6 +23,7 @@
#include "plugins/AlsaOutputPlugin.hxx"
#include "plugins/AoOutputPlugin.hxx"
#include "plugins/FifoOutputPlugin.hxx"
+#include "plugins/CgiOutputPlugin.hxx"
#include "plugins/SndioOutputPlugin.hxx"
#include "plugins/httpd/HttpdOutputPlugin.hxx"
#include "plugins/HaikuOutputPlugin.hxx"
@@ -53,6 +54,9 @@ const AudioOutputPlugin *const audio_output_plugins[] = {
#ifdef HAVE_FIFO
&fifo_output_plugin,
#endif
+#ifdef ENABLE_CGI_OUTPUT
+ &cgi_output_plugin,
+#endif
#ifdef HAVE_SNDIO
&sndio_output_plugin,
#endif
diff --git a/src/output/plugins/CgiOutputPlugin.cxx b/src/output/plugins/CgiOutputPlugin.cxx
new file mode 100644
index 0000000..ab8baf2
--- /dev/null
+++ b/src/output/plugins/CgiOutputPlugin.cxx
@@ -0,0 +1,166 @@
+/*
+ * Copyright 2003-2016 The Music Player Daemon Project
+ * 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.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "CgiOutputPlugin.hxx"
+#include "../OutputAPI.hxx"
+#include "../Wrapper.hxx"
+#include "util/StringUtil.hxx"
+#include "config/ConfigError.hxx"
+#include "util/Error.hxx"
+
+#include <string>
+#include <string.h>
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static char **make_env(const Tag &tag)
+{
+ char **env = new char*[tag.num_items+1];
+ unsigned short i = 0;
+ const char *ntag;
+ char *uptag;
+ size_t elen;
+ for (const auto &item : tag) {
+ ntag = tag_item_names[item.type];
+ uptag = new char[strlen(ntag)+1];
+ ToUpperASCII(uptag, tag_item_names[item.type], strlen(ntag)+1);
+
+ env[i] = new char[elen = strlen(uptag)+strlen(item.value)+2];
+ env[i][0] = '\0';
+
+ strcat(env[i], uptag);
+ strcat(env[i], "=");
+ strcat(env[i], item.value);
+
+ delete[] uptag;
+ i++;
+ }
+ for(;i<tag.num_items; i++){
+ env[i] = nullptr;
+ }
+ env[i] = nullptr;
+ return env;
+}
+
+class CgiOutput {
+ friend struct AudioOutputWrapper<CgiOutput>;
+
+ AudioOutput base;
+
+ std::string cmd;
+ pid_t previous_pid = 0;
+ char **env = nullptr;
+
+ CgiOutput()
+ :base(cgi_output_plugin) {}
+
+ bool Configure(const ConfigBlock &block, Error &error)
+ {
+ if (!base.Configure(block, error))
+ return false;
+
+ cmd = block.GetBlockValue("command", "");
+ if (cmd.empty()) {
+ error.Set(config_domain,
+ "No \"command\" parameter specified");
+ return false;
+ }
+
+ return true;
+ }
+
+public:
+ static CgiOutput *Create(const ConfigBlock &block, Error &error)
+ {
+ CgiOutput *co = new CgiOutput();
+
+ if (!co->Configure(block, error)) {
+ delete co;
+ return nullptr;
+ }
+
+ return co;
+ }
+
+ bool Open(gcc_unused AudioFormat &audio_format, gcc_unused Error &error)
+ {
+ return true;
+ }
+
+ void Close()
+ {
+ if(env != nullptr){
+ delete[] env;
+ env = nullptr;
+ }
+ }
+
+ void SendTag(const Tag &tag)
+ {
+ int wp = waitpid(previous_pid, nullptr, WNOHANG);
+ if(previous_pid != 0 && wp == 0){
+ exit(0);
+ //Child still alive
+ } else if(previous_pid != 0 && wp == -1){
+ exit(0);
+ //Error
+ } else {
+ //Nothing is wrong
+ Close();
+
+ env = make_env(tag);
+ char *argv[1] = {nullptr};
+ pid_t p = fork();
+ if(p == 0){
+ execvpe(cmd.c_str(), argv, env);
+ } else {
+ Close();
+ previous_pid = p;
+ }
+ }
+ }
+
+ size_t Play(gcc_unused const void *chunk, size_t size, gcc_unused Error &error)
+ {
+ return size;
+ }
+};
+
+typedef AudioOutputWrapper<CgiOutput> Wrapper;
+
+const struct AudioOutputPlugin cgi_output_plugin = {
+ "cgi-output",
+ nullptr, //Test
+ &Wrapper::Init, //Init
+ &Wrapper::Finish, //Finish
+ nullptr, //Enable
+ nullptr, //Disable
+ &Wrapper::Open, //Open
+ &Wrapper::Close, //Close
+ nullptr, //Delay
+ &Wrapper::SendTag, //Send tag
+ &Wrapper::Play, //Play
+ nullptr, //Drain
+ nullptr, //Cancel
+ nullptr, //Pause
+ nullptr, //MixerPlugin
+};
diff --git a/src/output/plugins/CgiOutputPlugin.hxx b/src/output/plugins/CgiOutputPlugin.hxx
new file mode 100644
index 0000000..2479794
--- /dev/null
+++ b/src/output/plugins/CgiOutputPlugin.hxx
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2003-2016 The Music Player Daemon Project
+ * 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.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_CGI_OUTPUT_PLUGIN_HXX
+#define MPD_CGI_OUTPUT_PLUGIN_HXX
+
+extern const struct AudioOutputPlugin cgi_output_plugin;
+
+#endif
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