rodio/source/
periodic.rs

1use std::time::Duration;
2
3use crate::{Sample, Source};
4
5use super::SeekError;
6
7/// Internal function that builds a `PeriodicAccess` object.
8pub fn periodic<I, F>(source: I, period: Duration, modifier: F) -> PeriodicAccess<I, F>
9where
10    I: Source,
11    I::Item: Sample,
12{
13    // TODO: handle the fact that the samples rate can change
14    // TODO: generally, just wrong
15    let update_ms = period.as_secs() as u32 * 1_000 + period.subsec_millis();
16    let update_frequency = (update_ms * source.sample_rate()) / 1000 * source.channels() as u32;
17
18    PeriodicAccess {
19        input: source,
20        modifier,
21        // Can overflow when subtracting if this is 0
22        update_frequency: if update_frequency == 0 {
23            1
24        } else {
25            update_frequency
26        },
27        samples_until_update: 1,
28    }
29}
30
31/// Calls a function on a source every time a period elapsed.
32#[derive(Clone, Debug)]
33pub struct PeriodicAccess<I, F> {
34    // The inner source.
35    input: I,
36
37    // Closure that gets access to `inner`.
38    modifier: F,
39
40    // The frequency with which local_volume should be updated by remote_volume
41    update_frequency: u32,
42
43    // How many samples remain until it is time to update local_volume with remote_volume.
44    samples_until_update: u32,
45}
46
47impl<I, F> PeriodicAccess<I, F>
48where
49    I: Source,
50    I::Item: Sample,
51    F: FnMut(&mut I),
52{
53    /// Returns a reference to the inner source.
54    #[inline]
55    pub fn inner(&self) -> &I {
56        &self.input
57    }
58
59    /// Returns a mutable reference to the inner source.
60    #[inline]
61    pub fn inner_mut(&mut self) -> &mut I {
62        &mut self.input
63    }
64
65    /// Returns the inner source.
66    #[inline]
67    pub fn into_inner(self) -> I {
68        self.input
69    }
70}
71
72impl<I, F> Iterator for PeriodicAccess<I, F>
73where
74    I: Source,
75    I::Item: Sample,
76    F: FnMut(&mut I),
77{
78    type Item = I::Item;
79
80    #[inline]
81    fn next(&mut self) -> Option<I::Item> {
82        self.samples_until_update -= 1;
83        if self.samples_until_update == 0 {
84            (self.modifier)(&mut self.input);
85            self.samples_until_update = self.update_frequency;
86        }
87
88        self.input.next()
89    }
90
91    #[inline]
92    fn size_hint(&self) -> (usize, Option<usize>) {
93        self.input.size_hint()
94    }
95}
96
97impl<I, F> Source for PeriodicAccess<I, F>
98where
99    I: Source,
100    I::Item: Sample,
101    F: FnMut(&mut I),
102{
103    #[inline]
104    fn current_frame_len(&self) -> Option<usize> {
105        self.input.current_frame_len()
106    }
107
108    #[inline]
109    fn channels(&self) -> u16 {
110        self.input.channels()
111    }
112
113    #[inline]
114    fn sample_rate(&self) -> u32 {
115        self.input.sample_rate()
116    }
117
118    #[inline]
119    fn total_duration(&self) -> Option<Duration> {
120        self.input.total_duration()
121    }
122
123    #[inline]
124    fn try_seek(&mut self, pos: Duration) -> Result<(), SeekError> {
125        self.input.try_seek(pos)
126    }
127}
128
129#[cfg(test)]
130mod tests {
131    use std::cell::RefCell;
132    use std::time::Duration;
133
134    use crate::buffer::SamplesBuffer;
135    use crate::source::Source;
136
137    #[test]
138    fn stereo_access() {
139        // Stereo, 1Hz audio buffer
140        let inner = SamplesBuffer::new(2, 1, vec![10i16, -10, 10, -10, 20, -20]);
141
142        let cnt = RefCell::new(0);
143
144        let mut source = inner.periodic_access(Duration::from_millis(1000), |_src| {
145            *cnt.borrow_mut() += 1;
146        });
147
148        assert_eq!(*cnt.borrow(), 0);
149        // Always called on first access!
150        assert_eq!(source.next(), Some(10));
151        assert_eq!(*cnt.borrow(), 1);
152        // Called every 1 second afterwards
153        assert_eq!(source.next(), Some(-10));
154        assert_eq!(*cnt.borrow(), 1);
155        assert_eq!(source.next(), Some(10));
156        assert_eq!(*cnt.borrow(), 2);
157        assert_eq!(source.next(), Some(-10));
158        assert_eq!(*cnt.borrow(), 2);
159        assert_eq!(source.next(), Some(20));
160        assert_eq!(*cnt.borrow(), 3);
161        assert_eq!(source.next(), Some(-20));
162        assert_eq!(*cnt.borrow(), 3);
163    }
164
165    #[test]
166    fn fast_access_overflow() {
167        // 1hz is lower than 0.5 samples per 5ms
168        let inner = SamplesBuffer::new(1, 1, vec![10i16, -10, 10, -10, 20, -20]);
169        let mut source = inner.periodic_access(Duration::from_millis(5), |_src| {});
170
171        source.next();
172        source.next(); // Would overflow here.
173    }
174}
rodio/source/periodic.rs

rodio/source/
periodic.rs
