Add get_volume and set_volume methods

This uses the global volume for the audio/mixer device. This isn't
ideal, but to my understanding follows what the alsa and oss plugins
do as well. Audacious already provides a software volume control in
Settings -> Audio, which despite saying "not recommended," doesn't
seem to have any issues.

TODO

@@ -1,6 +1,5 @@
 * Determine if audio open/close should happen in open_audio
   and close_audio
-* Support get_volume/set_volume
 * Support 24-bit LPCM -> 32-bit
 * Create a settings panel so users can select their output
   device

src/netbsdout.cc

@@ -50,7 +50,7 @@ __attribute__((visibility("default"))) NetBSDOutput aud_plugin_instance;
 static String audio_path;
 static int audio_fd;
 
-static bool audio_paused, audio_prebuffer, audio_flushed;
+static bool audio_paused, audio_flushed;
 
 static pthread_mutex_t nbout_mutex = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t nbout_cond = PTHREAD_COND_INITIALIZER;
@@ -97,7 +97,7 @@ NetBSDOutput::init ()
     audio_fd = open (audio_path, O_WRONLY);
 
     if (audio_fd == -1) {
-        AUDERR ("Failed to open %s: %s.\n", audio_path, strerror (errno));
+        AUDERR ("Failed to open %s: %s.\n", (const char *) audio_path, strerror (errno));
         return false;
     }
 
@@ -142,14 +142,14 @@ NetBSDOutput::open_audio (int format,
     if (ioctl (audio_fd, AUDIO_GETPROPS, & props) == -1) {
         error = String (str_printf
             ("Failed to get audio properties on %s: %s.",
-            audio_path, strerror (errno)));
+            (const char *) audio_path, strerror (errno)));
         return false;
     }
 
-    if (props | AUDIO_PROP_PLAYBACK != AUDIO_PROP_PLAYBACK) {
+    if ((props | AUDIO_PROP_PLAYBACK) != AUDIO_PROP_PLAYBACK) {
         error = String (str_printf
             ("Device %s does not support playback.",
-            audio_path));
+            (const char *) audio_path));
     }
 
     AUDIO_INITINFO (&info);
@@ -178,7 +178,7 @@ NetBSDOutput::open_audio (int format,
     if (ioctl (audio_fd, AUDIO_SETINFO, & info) == -1) {
         error = String (str_printf
              ("Failed to set track info on %s: %s.\n",
-             audio_path, strerror (errno)));
+             (const char *) audio_path, strerror (errno)));
         return false;
     }
 
@@ -238,8 +238,7 @@ NetBSDOutput::period_wait ()
 void
 NetBSDOutput::pause (bool pause)
 {
-    int res, len;
+    int res;
-    audio_info_t info;
 
     AUDDBG ("Setting pause = %s.\n", pause ? "true" : "false");
 
@@ -333,14 +332,32 @@ NetBSDOutput::flush ()
 StereoVolume
 NetBSDOutput::get_volume ()
 {
-    /* too noisy, even for debug... */
+    audio_info_t info;
-    // AUDDBG ("get_volume: Stub!\n");
+    int aud_vol;
 
-    return {100, 100}; // XXX
+    if (ioctl (audio_fd, AUDIO_GETINFO, & info) != 0) {
+        AUDERR ("Unable to get volume: %s.\n", strerror (errno));
+        return { 0, 0 };
+    }
+
+    aud_vol = aud::rescale ((int)info.play.gain - AUDIO_MIN_GAIN,
+                            AUDIO_MAX_GAIN - AUDIO_MIN_GAIN,
+                            100);
+
+    return { aud_vol, aud_vol };
 }
 
 void
 NetBSDOutput::set_volume (StereoVolume volume)
 {
-    AUDDBG ("set_volume: Stub!\n"); // XXX
+    audio_info_t info;
+
+    AUDIO_INITINFO (& info);
+    info.play.gain = aud::rescale (aud::max
+        (volume.left, volume.right), 100,
+        AUDIO_MAX_GAIN) + AUDIO_MIN_GAIN;
+
+    if (ioctl(audio_fd, AUDIO_SETINFO, & info) != 0) {
+        AUDERR ("Unable to set volume: %s.\n", strerror (errno));
+    }
 }