geng_rodio/source/
periodic.rs

1use std::time::Duration;
2
3use crate::{Sample, Source};
4
5/// Internal function that builds a `PeriodicAccess` object.
6pub fn periodic<I, F>(source: I, period: Duration, modifier: F) -> PeriodicAccess<I, F>
7where
8    I: Source,
9    I::Item: Sample,
10{
11    // TODO: handle the fact that the samples rate can change
12    // TODO: generally, just wrong
13    let update_ms = period.as_secs() as u32 * 1_000 + period.subsec_millis();
14    let update_frequency = (update_ms * source.sample_rate()) / 1000 * source.channels() as u32;
15
16    PeriodicAccess {
17        input: source,
18        modifier,
19        // Can overflow when subtracting if this is 0
20        update_frequency: if update_frequency == 0 {
21            1
22        } else {
23            update_frequency
24        },
25        samples_until_update: 1,
26    }
27}
28
29/// Calls a function on a source every time a period elapsed.
30#[derive(Clone, Debug)]
31pub struct PeriodicAccess<I, F> {
32    // The inner source.
33    input: I,
34
35    // Closure that gets access to `inner`.
36    modifier: F,
37
38    // The frequency with which local_volume should be updated by remote_volume
39    update_frequency: u32,
40
41    // How many samples remain until it is time to update local_volume with remote_volume.
42    samples_until_update: u32,
43}
44
45impl<I, F> PeriodicAccess<I, F>
46where
47    I: Source,
48    I::Item: Sample,
49    F: FnMut(&mut I),
50{
51    /// Returns a reference to the inner source.
52    #[inline]
53    pub fn inner(&self) -> &I {
54        &self.input
55    }
56
57    /// Returns a mutable reference to the inner source.
58    #[inline]
59    pub fn inner_mut(&mut self) -> &mut I {
60        &mut self.input
61    }
62
63    /// Returns the inner source.
64    #[inline]
65    pub fn into_inner(self) -> I {
66        self.input
67    }
68}
69
70impl<I, F> Iterator for PeriodicAccess<I, F>
71where
72    I: Source,
73    I::Item: Sample,
74    F: FnMut(&mut I),
75{
76    type Item = I::Item;
77
78    #[inline]
79    fn next(&mut self) -> Option<I::Item> {
80        self.samples_until_update -= 1;
81        if self.samples_until_update == 0 {
82            (self.modifier)(&mut self.input);
83            self.samples_until_update = self.update_frequency;
84        }
85
86        self.input.next()
87    }
88
89    #[inline]
90    fn size_hint(&self) -> (usize, Option<usize>) {
91        self.input.size_hint()
92    }
93}
94
95impl<I, F> Source for PeriodicAccess<I, F>
96where
97    I: Source,
98    I::Item: Sample,
99    F: FnMut(&mut I),
100{
101    #[inline]
102    fn current_frame_len(&self) -> Option<usize> {
103        self.input.current_frame_len()
104    }
105
106    #[inline]
107    fn channels(&self) -> u16 {
108        self.input.channels()
109    }
110
111    #[inline]
112    fn sample_rate(&self) -> u32 {
113        self.input.sample_rate()
114    }
115
116    #[inline]
117    fn total_duration(&self) -> Option<Duration> {
118        self.input.total_duration()
119    }
120}
121
122#[cfg(test)]
123mod tests {
124    use std::cell::RefCell;
125    use std::time::Duration;
126
127    use crate::buffer::SamplesBuffer;
128    use crate::source::Source;
129
130    #[test]
131    fn stereo_access() {
132        // Stereo, 1Hz audio buffer
133        let inner = SamplesBuffer::new(2, 1, vec![10i16, -10, 10, -10, 20, -20]);
134
135        let cnt = RefCell::new(0);
136
137        let mut source = inner.periodic_access(Duration::from_millis(1000), |_src| {
138            *cnt.borrow_mut() += 1;
139        });
140
141        assert_eq!(*cnt.borrow(), 0);
142        // Always called on first access!
143        assert_eq!(source.next(), Some(10));
144        assert_eq!(*cnt.borrow(), 1);
145        // Called every 1 second afterwards
146        assert_eq!(source.next(), Some(-10));
147        assert_eq!(*cnt.borrow(), 1);
148        assert_eq!(source.next(), Some(10));
149        assert_eq!(*cnt.borrow(), 2);
150        assert_eq!(source.next(), Some(-10));
151        assert_eq!(*cnt.borrow(), 2);
152        assert_eq!(source.next(), Some(20));
153        assert_eq!(*cnt.borrow(), 3);
154        assert_eq!(source.next(), Some(-20));
155        assert_eq!(*cnt.borrow(), 3);
156    }
157
158    #[test]
159    fn fast_access_overflow() {
160        // 1hz is lower than 0.5 samples per 5ms
161        let inner = SamplesBuffer::new(1, 1, vec![10i16, -10, 10, -10, 20, -20]);
162        let mut source = inner.periodic_access(Duration::from_millis(5), |_src| {});
163
164        source.next();
165        source.next(); // Would overflow here.
166    }
167}
geng_rodio/source/periodic.rs

geng_rodio/source/
periodic.rs
