Adding renamed signal_generator.rs

src/source/signal_generator.rs

@@ -0,0 +1,185 @@
+//! 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,
+//! 1.0f32].
+//!
+//! # Example
+//!
+//! ```
+//! use rodio::source::{SignalGenerator,Function};
+//!
+//! let tone = SignalGenerator::new(cpal::SampleRate(48000), 440.0, Function::Sine);
+//! ```
+use std::f32::consts::TAU;
+use std::time::Duration;
+
+use super::SeekError;
+use crate::Source;
+
+/// Waveform functions.
+#[derive(Clone, Debug)]
+pub enum Function {
+    /// A sinusoidal waveform.
+    Sine,
+    /// A triangle waveform.
+    Triangle,
+    /// A square wave, rising edge at t=0.
+    Square,
+    /// A rising sawtooth wave.
+    Sawtooth,
+}
+
+impl Function {
+    /// Create a single sample for the given waveform
+    #[inline]
+    fn render(&self, i: u64, period: f32) -> f32 {
+        let cycle_pos: f32 = i as f32 / period;
+
+        match self {
+            Self::Sine => (TAU * cycle_pos).sin(),
+            Self::Triangle => 4.0f32 * (cycle_pos - (cycle_pos + 0.5f32).floor()).abs() - 1f32,
+            Self::Square => {
+                if cycle_pos % 1.0f32 < 0.5f32 {
+                    1.0f32
+                } else {
+                    -1.0f32
+                }
+            }
+            Self::Sawtooth => 2.0f32 * (cycle_pos - (cycle_pos + 0.5f32).floor()),
+        }
+    }
+}
+
+/// An infinite source that produces one of a selection of test waveforms.
+#[derive(Clone, Debug)]
+pub struct SignalGenerator {
+    sample_rate: cpal::SampleRate,
+    period: f32,
+    function: Function,
+    i: u64,
+}
+
+impl SignalGenerator {
+    /// 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: Function) -> SignalGenerator {
+        assert!(frequency != 0.0, "frequency must be greater than zero");
+        let period = sample_rate.0 as f32 / frequency;
+        SignalGenerator {
+            sample_rate,
+            period,
+            function: f,
+            i: 0,
+        }
+    }
+}
+
+impl Iterator for SignalGenerator {
+    type Item = f32;
+
+    #[inline]
+    fn next(&mut self) -> Option<f32> {
+        let val = Some(self.function.render(self.i, self.period));
+        self.i += 1;
+        val
+    }
+}
+
+impl Source for SignalGenerator {
+    #[inline]
+    fn current_frame_len(&self) -> Option<usize> {
+        None
+    }
+
+    #[inline]
+    fn channels(&self) -> u16 {
+        1
+    }
+
+    #[inline]
+    fn sample_rate(&self) -> u32 {
+        self.sample_rate.0
+    }
+
+    #[inline]
+    fn total_duration(&self) -> Option<Duration> {
+        None
+    }
+
+    #[inline]
+    fn try_seek(&mut self, duration: Duration) -> Result<(), SeekError> {
+        self.i = (self.sample_rate.0 as f32 * duration.as_secs_f32()) as u64;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::source::{Function, SignalGenerator};
+    use approx::assert_abs_diff_eq;
+
+    #[test]
+    fn square() {
+        let mut wf = SignalGenerator::new(cpal::SampleRate(2000), 500.0f32, Function::Square);
+        assert_eq!(wf.next(), Some(1.0f32));
+        assert_eq!(wf.next(), Some(1.0f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+        assert_eq!(wf.next(), Some(1.0f32));
+        assert_eq!(wf.next(), Some(1.0f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+    }
+
+    #[test]
+    fn triangle() {
+        let mut wf = SignalGenerator::new(cpal::SampleRate(8000), 1000.0f32, Function::Triangle);
+        assert_eq!(wf.next(), Some(-1.0f32));
+        assert_eq!(wf.next(), Some(-0.5f32));
+        assert_eq!(wf.next(), Some(0.0f32));
+        assert_eq!(wf.next(), Some(0.5f32));
+        assert_eq!(wf.next(), Some(1.0f32));
+        assert_eq!(wf.next(), Some(0.5f32));
+        assert_eq!(wf.next(), Some(0.0f32));
+        assert_eq!(wf.next(), Some(-0.5f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+        assert_eq!(wf.next(), Some(-0.5f32));
+        assert_eq!(wf.next(), Some(0.0f32));
+        assert_eq!(wf.next(), Some(0.5f32));
+        assert_eq!(wf.next(), Some(1.0f32));
+        assert_eq!(wf.next(), Some(0.5f32));
+        assert_eq!(wf.next(), Some(0.0f32));
+        assert_eq!(wf.next(), Some(-0.5f32));
+    }
+
+    #[test]
+    fn saw() {
+        let mut wf = SignalGenerator::new(cpal::SampleRate(200), 50.0f32, Function::Sawtooth);
+        assert_eq!(wf.next(), Some(0.0f32));
+        assert_eq!(wf.next(), Some(0.5f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+        assert_eq!(wf.next(), Some(-0.5f32));
+        assert_eq!(wf.next(), Some(0.0f32));
+        assert_eq!(wf.next(), Some(0.5f32));
+        assert_eq!(wf.next(), Some(-1.0f32));
+    }
+
+    #[test]
+    fn sine() {
+        let mut wf = SignalGenerator::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);
+        assert_abs_diff_eq!(wf.next().unwrap(), 0.95105652f32);
+        assert_abs_diff_eq!(wf.next().unwrap(), 0.95105652f32);
+        assert_abs_diff_eq!(wf.next().unwrap(), 0.58778525f32);
+        assert_abs_diff_eq!(wf.next().unwrap(), 0.0f32);
+        assert_abs_diff_eq!(wf.next().unwrap(), -0.58778554f32);
+    }
+}