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Make sure there is only ever one allocation when converting

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Collect is probably fine but for code that's this hot it's worth the couple extra lines to make certain there's only ever one allocation when it comes to the returned Vec.
This commit is contained in:
JasonLG1979 2023-06-23 12:00:42 -05:00
parent 5da8ddf5e2
commit 46b8f84d6a
1 changed files with 41 additions and 17 deletions
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58
playback/src/convert.rs
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@ -80,36 +80,60 @@ impl Converter {
} }
pub fn f64_to_f32(&mut self, samples: &[f64]) -> Vec<f32> { pub fn f64_to_f32(&mut self, samples: &[f64]) -> Vec<f32> {
samples.iter().map(|sample| *sample as f32).collect() let mut output = Vec::with_capacity(samples.len());
output.extend(samples.iter().map(|sample| *sample as f32));
output
} }
pub fn f64_to_s32(&mut self, samples: &[f64]) -> Vec<i32> { pub fn f64_to_s32(&mut self, samples: &[f64]) -> Vec<i32> {
samples let mut output = Vec::with_capacity(samples.len());
.iter()
.map(|sample| self.scale(*sample, Self::SCALE_S32) as i32) output.extend(
.collect() samples
.iter()
.map(|sample| self.scale(*sample, Self::SCALE_S32) as i32),
);
output
} }
// S24 is 24-bit PCM packed in an upper 32-bit word // S24 is 24-bit PCM packed in an upper 32-bit word
pub fn f64_to_s24(&mut self, samples: &[f64]) -> Vec<i32> { pub fn f64_to_s24(&mut self, samples: &[f64]) -> Vec<i32> {
samples let mut output = Vec::with_capacity(samples.len());
.iter()
.map(|sample| self.clamping_scale(*sample, Self::SCALE_S24) as i32) output.extend(
.collect() samples
.iter()
.map(|sample| self.clamping_scale(*sample, Self::SCALE_S24) as i32),
);
output
} }
// S24_3 is 24-bit PCM in a 3-byte array // S24_3 is 24-bit PCM in a 3-byte array
pub fn f64_to_s24_3(&mut self, samples: &[f64]) -> Vec<i24> { pub fn f64_to_s24_3(&mut self, samples: &[f64]) -> Vec<i24> {
samples let mut output = Vec::with_capacity(samples.len());
.iter()
.map(|sample| i24::from_s24(self.clamping_scale(*sample, Self::SCALE_S24) as i32)) output.extend(
.collect() samples
.iter()
.map(|sample| i24::from_s24(self.clamping_scale(*sample, Self::SCALE_S24) as i32)),
);
output
} }
pub fn f64_to_s16(&mut self, samples: &[f64]) -> Vec<i16> { pub fn f64_to_s16(&mut self, samples: &[f64]) -> Vec<i16> {
samples let mut output = Vec::with_capacity(samples.len());
.iter()
.map(|sample| self.scale(*sample, Self::SCALE_S16) as i16) output.extend(
.collect() samples
.iter()
.map(|sample| self.scale(*sample, Self::SCALE_S16) as i16),
);
output
} }
} }