Several code review fixes

src/source/chirp.rs

@@ -0,0 +1,79 @@
+//! Chirp/sweep source.
+
+use std::time::Duration;
+
+use crate::Source;
+
+/// Convenience function to create a new `Chirp` source.
+#[inline]
+pub fn chirp(
+    sample_rate: cpal::SampleRate,
+    start_frequency: f32,
+    end_frequency: f32,
+    duration: Duration,
+) -> Chirp {
+    Chirp::new(sample_rate, start_frequency, end_frequency, duration)
+}
+
+/// Generate a sine wave with an instantaneous frequency that changes/sweeps linearly over time.
+/// At the end of the chirp, once the `end_frequency` is reached, the source is exhausted.
+#[derive(Clone, Debug)]
+pub struct Chirp {
+    start_frequency: f32,
+    end_frequency: f32,
+    sample_rate: cpal::SampleRate,
+    total_samples: u64,
+    elapsed_samples: u64,
+}
+
+impl Chirp {
+    fn new(
+        sample_rate: cpal::SampleRate,
+        start_frequency: f32,
+        end_frequency: f32,
+        duration: Duration,
+    ) -> Self {
+        Self {
+            sample_rate,
+            start_frequency,
+            end_frequency,
+            total_samples: (duration.as_secs_f64() * (sample_rate.0 as f64)) as u64,
+            elapsed_samples: 0,
+        }
+    }
+}
+
+impl Iterator for Chirp {
+    type Item = f32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let i = self.elapsed_samples;
+        self.elapsed_samples += 1;
+
+
+        todo!()
+    }
+}
+
+impl Source for Chirp {
+    fn current_frame_len(&self) -> Option<usize> {
+        None
+    }
+
+    fn channels(&self) -> u16 {
+        1
+    }
+
+    fn sample_rate(&self) -> u32 {
+        self.sample_rate.0
+    }
+
+    fn total_duration(&self) -> Option<Duration> {
+        let secs: f64 = self.total_samples as f64 / self.sample_rate.0 as f64;
+        Some(Duration::new(1,0).mul_f64(secs))
+    }
+
+    fn try_seek(&mut self, pos: Duration) -> Result<(), super::SeekError> {
+        todo!()
+    }
+}

src/source/mod.rs

@@ -10,6 +10,7 @@ pub use self::amplify::Amplify;
 pub use self::blt::BltFilter;
 pub use self::buffered::Buffered;
 pub use self::channel_volume::ChannelVolume;
+pub use self::chirp::{chirp, Chirp};
 pub use self::crossfade::Crossfade;
 pub use self::delay::Delay;
 pub use self::done::Done;
@@ -41,6 +42,7 @@ pub use self::zero::Zero;
 mod amplify;
 mod blt;
 mod buffered;
+mod chirp;
 mod channel_volume;
 mod crossfade;
 mod delay;

src/source/noise.rs

@@ -8,13 +8,13 @@ use super::SeekError;
 use rand::rngs::SmallRng;
 use rand::{RngCore, SeedableRng};
 
-/// Create a new `WhiteNoise` noise source.
+/// Convenience function to create a new `WhiteNoise` noise source.
 #[inline]
 pub fn white(sample_rate: cpal::SampleRate) -> WhiteNoise {
     WhiteNoise::new(sample_rate)
 }
 
-/// Create a new `PinkNoise` noise source.
+/// Convenience function to create a new `PinkNoise` noise source.
 #[inline]
 pub fn pink(sample_rate: cpal::SampleRate) -> PinkNoise {
     PinkNoise::new(sample_rate)
@@ -51,8 +51,8 @@ impl Iterator for WhiteNoise {
 
     #[inline]
     fn next(&mut self) -> Option<Self::Item> {
-        let randf = self.rng.next_u32() as f32 / u32::MAX as f32;
+        let rand = self.rng.next_u32() as f32 / u32::MAX as f32;
-        let scaled = randf * 2.0 - 1.0;
+        let scaled = rand * 2.0 - 1.0;
         Some(scaled)
     }
 }
@@ -85,19 +85,22 @@ impl Source for WhiteNoise {
     }
 }
 
-/// Generate an infinite stream of pink noise samples in [-1.0, 1.0].
+/// Generates an infinite stream of pink noise samples in [-1.0, 1.0].
 ///
-/// The output of this source is the result of taking the output of the `WhiteNoise` source and
+/// The output of the source is the result of taking the output of the `WhiteNoise` source and
-/// filtering it according to a weighted-sum of seven FIR filters after [Paul Kellett](https://www.musicdsp.org/en/latest/Filters/76-pink-noise-filter.html).
+/// filtering it according to a weighted-sum of seven FIR filters after [Paul Kellett's
+/// method][pk_method] from *musicdsp.org*.
+///
+/// [pk_method]: https://www.musicdsp.org/en/latest/Filters/76-pink-noise-filter.html
 pub struct PinkNoise {
-    noise: WhiteNoise,
+    white_noise: WhiteNoise,
     b: [f32; 7],
 }
 
 impl PinkNoise {
     pub fn new(sample_rate: cpal::SampleRate) -> Self {
         Self {
-            noise: WhiteNoise::new(sample_rate),
+            white_noise: WhiteNoise::new(sample_rate),
             b: [0.0f32, 0.0f32, 0.0f32, 0.0f32, 0.0f32, 0.0f32, 0.0f32],
         }
     }
@@ -107,7 +110,7 @@ impl Iterator for PinkNoise {
     type Item = f32;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let white = self.noise.next().unwrap();
+        let white = self.white_noise.next().unwrap();
         self.b[0] = 0.99886 * self.b[0] + white * 0.0555179;
         self.b[1] = 0.99332 * self.b[1] + white * 0.0750759;
         self.b[2] = 0.969 * self.b[2] + white * 0.153852;
@@ -140,7 +143,7 @@ impl Source for PinkNoise {
     }
 
     fn sample_rate(&self) -> u32 {
-        self.noise.sample_rate()
+        self.white_noise.sample_rate()
     }
 
     fn total_duration(&self) -> Option<std::time::Duration> {

src/source/sine.rs

@@ -12,7 +12,7 @@ const SAMPLE_RATE: u32 = 48000;
 /// Always has a rate of 48kHz and one channel.
 #[derive(Clone, Debug)]
 pub struct SineWave {
-    synth: TestWaveform,
+    test_sine: TestWaveform,
 }
 
 impl SineWave {
@@ -21,7 +21,7 @@ impl SineWave {
     pub fn new(freq: f32) -> SineWave {
         let sr = cpal::SampleRate(SAMPLE_RATE);
         SineWave {
-            synth: TestWaveform::new(sr, freq, TestWaveformFunction::Sine),
+            test_sine: TestWaveform::new(sr, freq, TestWaveformFunction::Sine),
         }
     }
 }
@@ -31,7 +31,7 @@ impl Iterator for SineWave {
 
     #[inline]
     fn next(&mut self) -> Option<f32> {
-        self.synth.next()
+        self.test_sine.next()
     }
 }
 
@@ -58,6 +58,6 @@ impl Source for SineWave {
 
     #[inline]
     fn try_seek(&mut self, pos: Duration) -> Result<(), SeekError> {
-        self.synth.try_seek(pos)
+        self.test_sine.try_seek(pos)
     }
 }

src/source/test_waveform.rs

@@ -1,8 +1,8 @@
 //! Generator sources for various periodic test waveforms.
 //!
 //! This module provides several periodic, deterministic waveforms for testing other sources and
-//! for simple additive sound synthesis. Every source is monoaural and in the codomain `[-1.0f32,
+//! for simple additive sound synthesis. Every source is monoaural and in the codomain [-1.0f32,
-//! 1.0f32]` 
+//! 1.0f32].
 //!
 //! # Example
 //!
@@ -17,12 +17,12 @@ use std::time::Duration;
 use super::SeekError;
 use crate::Source;
 
-/// Test waveform functions.
+/// Waveform functions.
 #[derive(Clone, Debug)]
-pub enum TestWaveformFunction {
+pub enum Function {
     /// A sinusoidal waveform.
     Sine,
-    /// A triangle wave.
+    /// A triangle waveform.
     Triangle,
     /// A square wave, rising edge at t=0.
     Square,
@@ -30,7 +30,7 @@ pub enum TestWaveformFunction {
     Sawtooth,
 }
 
-impl TestWaveformFunction {
+impl Function {
     /// Create a single sample for the given waveform
     #[inline]
     fn render(&self, i: u64, period: f32) -> f32 {
@@ -38,7 +38,7 @@ impl TestWaveformFunction {
 
         match self {
             Self::Sine => (TAU * i_div_p).sin(),
-            Self::Triangle => 04.0f32 * (i_div_p - (i_div_p + 0.5f32).floor()).abs() - 1f32,
+            Self::Triangle => 4.0f32 * (i_div_p - (i_div_p + 0.5f32).floor()).abs() - 1f32,
             Self::Square => {
                 if i_div_p % 1.0f32 < 0.5f32 {
                     1.0f32
@@ -56,24 +56,29 @@ impl TestWaveformFunction {
 pub struct TestWaveform {
     sample_rate: cpal::SampleRate,
     period: f32,
-    f: TestWaveformFunction,
+    function: Function,
     i: u64,
 }
 
 impl TestWaveform {
     /// Create a new `TestWaveform` object that generates an endless waveform
     /// `f`.
+    ///
+    /// # Panics
+    ///
+    /// Will panic if `frequency` is equal to zero.
     #[inline]
     pub fn new(
         sample_rate: cpal::SampleRate,
         frequency: f32,
-        f: TestWaveformFunction,
+        f: Function,
     ) -> TestWaveform {
+        assert!(frequency != 0.0, "frequency must be greater than zero");
         let period = sample_rate.0 as f32 / frequency;
         TestWaveform {
             sample_rate,
             period,
-            f,
+            function: f,
             i: 0,
         }
     }
@@ -86,7 +91,7 @@ impl Iterator for TestWaveform {
     fn next(&mut self) -> Option<f32> {
         let this_i = self.i;
         self.i += 1;
-        Some(self.f.render(this_i, self.period))
+        Some(self.function.render(this_i, self.period))
     }
 }
 
@@ -120,7 +125,7 @@ impl Source for TestWaveform {
 
 #[cfg(test)]
 mod tests {
-    use crate::source::{TestWaveform, TestWaveformFunction};
+    use crate::source::{TestWaveform, Function};
     use approx::assert_abs_diff_eq;
 
     #[test]
@@ -128,7 +133,7 @@ mod tests {
         let mut wf = TestWaveform::new(
             cpal::SampleRate(2000),
             500.0f32,
-            TestWaveformFunction::Square,
+            Function::Square,
         );
         assert_eq!(wf.next(), Some(1.0f32));
         assert_eq!(wf.next(), Some(1.0f32));
@@ -145,7 +150,7 @@ mod tests {
         let mut wf = TestWaveform::new(
             cpal::SampleRate(8000),
             1000.0f32,
-            TestWaveformFunction::Triangle,
+            Function::Triangle,
         );
         assert_eq!(wf.next(), Some(-1.0f32));
         assert_eq!(wf.next(), Some(-0.5f32));
@@ -170,7 +175,7 @@ mod tests {
         let mut wf = TestWaveform::new(
             cpal::SampleRate(200),
             50.0f32,
-            TestWaveformFunction::Sawtooth,
+            Function::Sawtooth,
         );
         assert_eq!(wf.next(), Some(0.0f32));
         assert_eq!(wf.next(), Some(0.5f32));
@@ -183,7 +188,7 @@ mod tests {
 
     #[test]
     fn sine() {
-        let mut wf = TestWaveform::new(cpal::SampleRate(1000), 100f32, TestWaveformFunction::Sine);
+        let mut wf = TestWaveform::new(cpal::SampleRate(1000), 100f32, Function::Sine);
 
         assert_abs_diff_eq!(wf.next().unwrap(), 0.0f32);
         assert_abs_diff_eq!(wf.next().unwrap(), 0.58778525f32);