feat: "Constant" sound source for testing and debugging

src/sources/constant.rs

@@ -0,0 +1,44 @@
+use rodio::Source;
+use std::time::Duration;
+
+/// Constant source
+pub struct Constant {
+    sample_rate: u32,
+    value: f32,
+}
+
+impl Constant {
+    pub fn new(value: f32, sample_rate: u32) -> Self {
+        Constant { sample_rate, value }
+    }
+}
+
+impl Iterator for Constant {
+    type Item = f32;
+
+    fn next(&mut self) -> Option<f32> {
+        Some(self.value)
+    }
+}
+
+impl Source for Constant {
+    #[inline(always)]
+    fn current_frame_len(&self) -> Option<usize> {
+        None
+    }
+
+    #[inline(always)]
+    fn channels(&self) -> u16 {
+        1
+    }
+
+    #[inline(always)]
+    fn sample_rate(&self) -> u32 {
+        self.sample_rate
+    }
+
+    #[inline(always)]
+    fn total_duration(&self) -> Option<Duration> {
+        None
+    }
+}

src/sources/mod.rs

@@ -1,5 +1,7 @@
 //! Useful implementations of `rodio::Source`
 
 mod noise;
+mod constant;
 
 pub use self::noise::Noise;
+pub use self::constant::Constant;