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use crate::{stream, Buffer};
use dasp_sample::Sample;
use std;
/// A `Receiver` for converting audio delivered by the backend at varying buffer sizes into buffers
/// of a fixed size.
///
/// The `Receiver` works by calling `fill_buffer` with the requested buffer and sample rate from
/// the audio backend each time the callback is invoked.
pub struct Receiver<S> {
samples: Vec<S>,
num_frames: usize,
num_channels: usize,
}
impl<S> Receiver<S>
where
S: Sample,
{
/// Construct a `Receiver`.
///
/// Both `num_frames` and `num_channels` must be greater than `0`.
pub fn new(num_frames: usize, num_channels: usize) -> Self {
// We can't make any progress filling buffers of `0` frames.
assert!(num_frames > 0);
assert!(num_channels > 0);
let num_samples = num_frames + num_channels;
Receiver {
samples: Vec::with_capacity(num_samples),
num_frames: num_frames,
num_channels: num_channels,
}
}
/// Deliver samples from `input` to the given capture function in chunks of size `frames *
/// channels`.
///
/// **Panic!**s under any of the following conditions:
///
/// - `sample_rate` is not greater than `0`.
/// - The number of `channels` is different to that with which the receiver was initialised.
/// - The final input buffer frame does not contain a sample for every channel.
pub fn read_buffer<M, FC>(
&mut self,
mut model: M,
capture: &FC,
input: &[S],
channels: usize,
sample_rate: u32,
) -> M
where
FC: stream::input::CaptureFn<M, S>,
{
let Receiver {
ref mut samples,
num_frames,
num_channels,
} = *self;
// Ensure that the input length makes sense given the number of channels.
assert_eq!(
input.len() % channels,
0,
"the input length must be a multiple of the number of channels"
);
// Ensure that the number of channels has not changed.
assert_eq!(
channels, num_channels,
"the number of channels differs to that with which `Receiver` was initialised"
);
// An iterator yielding the input samples.
let mut input_samples = input.iter().cloned();
// The number of samples pass to the capture function at a time.
let num_samples = num_frames * channels;
// Append the given input and deliver it to the capture fn until we run out.
loop {
let num_to_take = num_samples - samples.len();
samples.extend(input_samples.by_ref().take(num_to_take));
// If there weren't enough samples remaining in the input for a full buffer we're done.
if samples.len() < num_samples {
break;
}
// Capture the input data and update the model.
let interleaved_samples = std::mem::replace(samples, Vec::new()).into_boxed_slice();
let buffer = Buffer {
interleaved_samples,
channels,
sample_rate,
};
capture(&mut model, &buffer);
std::mem::swap(samples, &mut buffer.interleaved_samples.into_vec());
samples.clear();
}
model
}
}