Start work on ALSA driver.

git-svn-id: https://svn.code.sf.net/p/freetel/code@1417 01035d8c-6547-0410-b346-abe4f91aad63

diff --git a/freedv-server/source/platform/linux/audio_out_alsa.cpp b/freedv-server/source/platform/linux/audio_out_alsa.cpp
new file mode 100644 (file)
index 0000000..b2a78ab
--- /dev/null
+++ b/freedv-server/source/platform/linux/audio_out_alsa.cpp
@@ -0,0 +1,77 @@
+/// The ALSA audio output driver. 
+
+#include "drivers.h"
+#include <alsa/asoundlib.h>
+#include <sstream>
+#include <stdexcept>
+
+namespace FreeDV {
+  /// Audio output "sink", discards the audio, for testing.
+  class AudioOutALSA : public AudioOutput {
+  private:
+    snd_pcm_t * handle;
+
+  public:
+
+       /// Instantiate the audio sink.
+               AudioOutALSA(const char * parameters);
+               ~AudioOutALSA();
+
+       /// Return the number of audio samples the device can handle in
+       /// a write without blocking.
+        virtual std::size_t
+               ready();
+
+        /// Write audio into the "short" type.
+       virtual std::size_t
+               write16(const std::int16_t * array, std::size_t length);
+  };
+
+  AudioOutALSA::AudioOutALSA(const char * p)
+  : AudioOutput("alsa", p)
+  {
+    const int error = snd_pcm_open(
+     &handle,
+     p,
+     SND_PCM_STREAM_PLAYBACK,
+     0);
+
+    if ( error ) {
+      std::ostringstream str;
+
+      str << "Can't open audio device " << p << ": " << snd_strerror(error);
+      throw std::runtime_error(str.str().c_str());
+    }
+  }
+
+  AudioOutALSA::~AudioOutALSA()
+  {
+  }
+
+  // Write audio into the "short" type.
+  std::size_t
+  AudioOutALSA::write16(const std::int16_t * array, std::size_t length)
+  {
+    return length;
+  }
+
+  AudioOutput *
+  Driver::AudioOutALSA(const char * parameter)
+  {
+    return new ::FreeDV::AudioOutALSA(parameter);
+  }
+
+  std::size_t
+  AudioOutALSA::ready()
+  {
+    return SIZE_MAX;
+  }
+
+  static bool
+  initializer()
+  {
+    driver_manager()->register_audio_output("alsa", Driver::AudioOutALSA);
+    return true;
+  }
+  static const bool initialized = initializer();
+}