Add Voice::get_period()

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "cpal"
-version = "0.2.5"
+version = "0.2.6"
 authors = ["Pierre Krieger <pierre.krieger1708@gmail.com>"]
 description = "Cross-platform audio playing library in pure Rust."
 repository = "https://github.com/tomaka/cpal"

src/alsa/mod.rs

@@ -174,6 +174,7 @@ pub struct Voice {
     channel: Mutex<*mut alsa::snd_pcm_t>,
     num_channels: u16,
     buffer_len: usize,      // number of samples that can fit in the buffer
+    period_len: usize,      // minimum number of samples to put in the buffer
 }
 
 pub struct Buffer<'a, T> {
@@ -232,18 +233,21 @@ impl Voice {
 
             check_errors(alsa::snd_pcm_prepare(playback_handle)).unwrap();
 
-            let buffer_len = {
-                let mut dummy = mem::uninitialized();
-                let mut val = mem::uninitialized();
-                check_errors(alsa::snd_pcm_get_params(playback_handle, &mut val, &mut dummy)).unwrap();
-                assert!(val != 0);
-                val as usize * format.channels.len()
+            let (buffer_len, period_len) = {
+                let mut buffer = mem::uninitialized();
+                let mut period = mem::uninitialized();
+                check_errors(alsa::snd_pcm_get_params(playback_handle, &mut buffer, &mut period)).unwrap();
+                assert!(buffer != 0);
+                let buffer = buffer as usize * format.channels.len();
+                let period = period as usize * format.channels.len();
+                (buffer, period)
             };
 
             Ok(Voice {
                 channel: Mutex::new(playback_handle),
                 num_channels: format.channels.len() as u16,
                 buffer_len: buffer_len,
+                period_len: period_len,
             })
         }
     }
@@ -283,6 +287,11 @@ impl Voice {
         unimplemented!()
     }
 
+    #[inline]
+    pub fn get_period(&self) -> usize {
+        self.period_len
+    }
+
     pub fn get_pending_samples(&self) -> usize {
         let available = {
             let channel = self.channel.lock().unwrap();

src/lib.rs

@@ -324,6 +324,16 @@ impl Voice {
         self.format().data_type
     }
 
+    /// Returns the minimum number of samples that should be put in a buffer before it is
+    /// processable by the audio output.
+    ///
+    /// If you put less than this value in the buffer, the buffer will not be processed and you
+    /// risk an underrun.
+    #[inline]
+    pub fn get_period(&self) -> usize {
+        self.voice.get_period()
+    }
+
     /// Adds some PCM data to the voice's buffer.
     ///
     /// This function indirectly returns a `Buffer` object that must be filled with the audio data.

src/null/mod.rs

@@ -72,6 +72,11 @@ impl Voice {
     pub fn pause(&mut self) {
     }
 
+    #[inline]
+    pub fn get_period(&self) -> usize {
+        0
+    }
+
     #[inline]
     pub fn get_pending_samples(&self) -> usize {
         unreachable!()

src/wasapi/voice.rs

@@ -193,6 +193,11 @@ impl Voice {
         }
     }
 
+    #[inline]
+    pub fn get_period(&self) -> usize {
+        0
+    }
+
     pub fn get_pending_samples(&self) -> usize {
         unsafe {
             let mut padding = mem::uninitialized();