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use num_complex::Complex;
use rustc_hash::{FxBuildHasher, FxHashSet};
/// I thought about doing this to avoid allocating new memory in the audio thread
pub struct RetainAlgorithm {
indexed_spectrum: Vec<(usize, Complex<f32>)>,
top_indices: FxHashSet<usize>,
}
impl RetainAlgorithm {
pub fn new() -> Self {
let max_size = (32768 / 2) + 1;
Self {
indexed_spectrum: Vec::with_capacity(max_size),
top_indices: FxHashSet::with_capacity_and_hasher(max_size, FxBuildHasher::default()),
}
}
pub fn calculate(&mut self, spectrum: &mut [Complex<f32>], n: usize, complement: bool) {
// you'd be keeping the entire signal
if n >= spectrum.len() && !complement {
return;
}
if n == 0 && complement {
return;
}
// keeping nothing at all
if n == 0 && !complement {
for phasor in spectrum {
*phasor = Complex::ZERO;
}
return;
}
if n >= spectrum.len() && complement {
for phasor in spectrum {
*phasor = Complex::ZERO;
}
return;
}
self.indexed_spectrum.clear();
for (i, phasor) in spectrum.iter().copied().enumerate() {
self.indexed_spectrum.push((i, phasor));
}
let target = spectrum.len() - n;
self.indexed_spectrum
.select_nth_unstable_by(target, |(_, c0), (_, c1)| c0.norm().total_cmp(&c1.norm()));
self.top_indices.clear();
for i in self.indexed_spectrum[target..].iter().map(|&(i, _)| i) {
self.top_indices.insert(i);
}
for (i, phasor) in spectrum.iter_mut().enumerate() {
if self.top_indices.contains(&i) && complement {
*phasor = Complex::ZERO;
}
if !self.top_indices.contains(&i) && !complement {
*phasor = Complex::ZERO;
}
}
}
}
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