1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
use super::{Millisecond, Amplitude, SamplesPerSecond};
pub struct Line {
pub start: Amplitude,
pub end: Amplitude,
pub duration: Millisecond,
pub index: u32,
slope: f32,
samples: u32
}
impl Line {
pub fn new(
start: Amplitude, end: Amplitude, duration: Millisecond, sample_rate: SamplesPerSecond
) -> Self {
Self { start, end, duration, index: 0, slope: slope(start, end, ms_to_samples(duration, sample_rate)), samples: ms_to_samples(duration, sample_rate) }
}
}
impl Iterator for Line {
type Item = Amplitude;
fn next(&mut self) -> Option<Self::Item> {
let idx = self.index;
let val = self.slope * idx as f32 + self.start;
self.index += 1;
if idx <= self.samples {
Some(val)
} else {
None
}
}
}
fn slope(start: Amplitude, end: Amplitude, duration: Millisecond) -> f32 {
return (end - start) / duration as f32 ;
}
fn ms_to_samples(ms: Millisecond, sample_rate: SamplesPerSecond) -> u32 {
let multiplier = sample_rate as u32 / 1000;
multiplier * ms
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_calculates_a_slope() {
let expected = 0.5;
let slope = slope(0.0, 0.5, 1);
assert_eq! (expected, slope)
}
#[test]
fn it_calculates_the_next_values() {
let mut line = Line::new(0.0, 0.5, 1, 5000.0);
assert_eq!(0.0, line.next().unwrap());
assert_eq!(0.1, line.next().unwrap());
assert_eq!(0.2, line.next().unwrap());
assert_eq!(0.3, line.next().unwrap());
assert_eq!(0.4, line.next().unwrap());
assert_eq!(0.5, line.next().unwrap());
assert_eq!(None, line.next());
}
}
|
