Add source::Empty and source::Zero

src/source/empty.rs

@@ -0,0 +1,46 @@
+use std::marker::PhantomData;
+use std::time::Duration;
+use Sample;
+use Source;
+
+/// An empty source.
+#[derive(Debug, Copy, Clone)]
+pub struct Empty<S>(PhantomData<S>);
+
+impl<S> Empty<S> {
+    #[inline]
+    pub fn new() -> Empty<S> {
+        Empty(PhantomData)
+    }
+}
+
+impl<S> Iterator for Empty<S> {
+    type Item = S;
+
+    #[inline]
+    fn next(&mut self) -> Option<S> {
+        None
+    }
+}
+
+impl<S> Source for Empty<S> where S: Sample {
+    #[inline]
+    fn get_current_frame_len(&self) -> Option<usize> {
+        None
+    }
+
+    #[inline]
+    fn get_channels(&self) -> u16 {
+        1
+    }
+
+    #[inline]
+    fn get_samples_rate(&self) -> u32 {
+        48000
+    }
+
+    #[inline]
+    fn get_total_duration(&self) -> Option<Duration> {
+        Some(Duration::new(0, 0))
+    }
+}

src/source/mod.rs

@@ -5,6 +5,7 @@ use Sample;
 pub use self::amplify::Amplify;
 pub use self::buffered::Buffered;
 pub use self::delay::Delay;
+pub use self::empty::Empty;
 pub use self::fadein::FadeIn;
 pub use self::mix::Mix;
 pub use self::pauseable::Pauseable;
@@ -14,10 +15,12 @@ pub use self::speed::Speed;
 pub use self::take::TakeDuration;
 pub use self::uniform::UniformSourceIterator;
 pub use self::volume_filter::VolumeFilter;
+pub use self::zero::Zero;
 
 mod amplify;
 mod buffered;
 mod delay;
+mod empty;
 mod fadein;
 mod mix;
 mod pauseable;
@@ -27,6 +30,7 @@ mod speed;
 mod take;
 mod uniform;
 mod volume_filter;
+mod zero;
 
 /// A source of samples.
 pub trait Source: Iterator

src/source/zero.rs

@@ -0,0 +1,54 @@
+use std::marker::PhantomData;
+use std::time::Duration;
+use Sample;
+use Source;
+
+/// An infinite source that produces zero.
+#[derive(Clone, Debug)]
+pub struct Zero<S> {
+    channels: u16,
+    samples_rate: u32,
+    marker: PhantomData<S>,
+}
+
+impl<S> Zero<S> {
+    #[inline]
+    pub fn new(channels: u16, samples_rate: u32) -> Zero<S> {
+        Zero {
+            channels: channels,
+            samples_rate: samples_rate,
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<S> Iterator for Zero<S> where S: Sample {
+    type Item = S;
+
+    #[inline]
+    fn next(&mut self) -> Option<S> {
+        Some(S::zero_value())
+    }
+}
+
+impl<S> Source for Zero<S> where S: Sample {
+    #[inline]
+    fn get_current_frame_len(&self) -> Option<usize> {
+        None
+    }
+
+    #[inline]
+    fn get_channels(&self) -> u16 {
+        self.channels
+    }
+
+    #[inline]
+    fn get_samples_rate(&self) -> u32 {
+        self.samples_rate
+    }
+
+    #[inline]
+    fn get_total_duration(&self) -> Option<Duration> {
+        None
+    }
+}