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
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185

use std::cmp;
use std::time::Duration;

use crate::conversions::{ChannelCountConverter, DataConverter, SampleRateConverter};
use crate::{Sample, Source};

/// An iterator that reads from a `Source` and converts the samples to a specific rate and
/// channels count.
///
/// It implements `Source` as well, but all the data is guaranteed to be in a single frame whose
/// channels and samples rate have been passed to `new`.
#[derive(Clone)]
pub struct UniformSourceIterator<I, D>
where
    I: Source,
    I::Item: Sample,
    D: Sample,
{
    inner: Option<DataConverter<ChannelCountConverter<SampleRateConverter<Take<I>>>, D>>,
    target_channels: u16,
    target_sample_rate: u32,
    total_duration: Option<Duration>,
}

impl<I, D> UniformSourceIterator<I, D>
where
    I: Source,
    I::Item: Sample,
    D: Sample,
{
    #[inline]
    pub fn new(
        input: I,
        target_channels: u16,
        target_sample_rate: u32,
    ) -> UniformSourceIterator<I, D> {
        let total_duration = input.total_duration();
        let input = UniformSourceIterator::bootstrap(input, target_channels, target_sample_rate);

        UniformSourceIterator {
            inner: Some(input),
            target_channels,
            target_sample_rate,
            total_duration,
        }
    }

    #[inline]
    fn bootstrap(
        input: I,
        target_channels: u16,
        target_sample_rate: u32,
    ) -> DataConverter<ChannelCountConverter<SampleRateConverter<Take<I>>>, D> {
        // Limit the frame length to something reasonable
        let frame_len = input.current_frame_len().map(|x| x.min(32768));

        let from_channels = input.channels();
        let from_sample_rate = input.sample_rate();

        let input = Take {
            iter: input,
            n: frame_len,
        };
        let input = SampleRateConverter::new(
            input,
            cpal::SampleRate(from_sample_rate),
            cpal::SampleRate(target_sample_rate),
            from_channels,
        );
        let input = ChannelCountConverter::new(input, from_channels, target_channels);

        DataConverter::new(input)
    }
}

impl<I, D> Iterator for UniformSourceIterator<I, D>
where
    I: Source,
    I::Item: Sample,
    D: Sample,
{
    type Item = D;

    #[inline]
    fn next(&mut self) -> Option<D> {
        if let Some(value) = self.inner.as_mut().unwrap().next() {
            return Some(value);
        }

        let input = self
            .inner
            .take()
            .unwrap()
            .into_inner()
            .into_inner()
            .into_inner()
            .iter;

        let mut input =
            UniformSourceIterator::bootstrap(input, self.target_channels, self.target_sample_rate);

        let value = input.next();
        self.inner = Some(input);
        value
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.inner.as_ref().unwrap().size_hint().0, None)
    }
}

impl<I, D> Source for UniformSourceIterator<I, D>
where
    I: Iterator + Source,
    I::Item: Sample,
    D: Sample,
{
    #[inline]
    fn current_frame_len(&self) -> Option<usize> {
        None
    }

    #[inline]
    fn channels(&self) -> u16 {
        self.target_channels
    }

    #[inline]
    fn sample_rate(&self) -> u32 {
        self.target_sample_rate
    }

    #[inline]
    fn total_duration(&self) -> Option<Duration> {
        self.total_duration
    }
}

#[derive(Clone, Debug)]
struct Take<I> {
    iter: I,
    n: Option<usize>,
}

impl<I> Iterator for Take<I>
where
    I: Iterator,
{
    type Item = <I as Iterator>::Item;

    #[inline]
    fn next(&mut self) -> Option<<I as Iterator>::Item> {
        if let Some(n) = &mut self.n {
            if *n != 0 {
                *n -= 1;
                self.iter.next()
            } else {
                None
            }
        } else {
            self.iter.next()
        }
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        if let Some(n) = self.n {
            let (lower, upper) = self.iter.size_hint();

            let lower = cmp::min(lower, n);

            let upper = match upper {
                Some(x) if x < n => Some(x),
                _ => Some(n),
            };

            (lower, upper)
        } else {
            self.iter.size_hint()
        }
    }
}

impl<I> ExactSizeIterator for Take<I> where I: ExactSizeIterator {}