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

use cpal::Sample as CpalSample;
use std::marker::PhantomData;

/// Converts the samples data type to `O`.
#[derive(Clone, Debug)]
pub struct DataConverter<I, O> {
    input: I,
    marker: PhantomData<O>,
}

impl<I, O> DataConverter<I, O> {
    /// Builds a new converter.
    #[inline]
    pub fn new(input: I) -> DataConverter<I, O> {
        DataConverter {
            input: input,
            marker: PhantomData,
        }
    }

    /// Destroys this iterator and returns the underlying iterator.
    #[inline]
    pub fn into_inner(self) -> I {
        self.input
    }
}

impl<I, O> Iterator for DataConverter<I, O>
where
    I: Iterator,
    I::Item: Sample,
    O: Sample,
{
    type Item = O;

    #[inline]
    fn next(&mut self) -> Option<O> {
        self.input.next().map(|s| CpalSample::from(&s))
    }

    #[inline]
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.input.size_hint()
    }
}

impl<I, O> ExactSizeIterator for DataConverter<I, O>
where
    I: ExactSizeIterator,
    I::Item: Sample,
    O: Sample,
{
}

/// Represents a value of a single sample.
///
/// This trait is implemented by default on three types: `i16`, `u16` and `f32`.
///
/// - For `i16`, silence corresponds to the value `0`. The minimum and maximum amplitudes are
///   represented by `i16::min_value()` and `i16::max_value()` respectively.
/// - For `u16`, silence corresponds to the value `u16::max_value() / 2`. The minimum and maximum
///   amplitudes are represented by `0` and `u16::max_value()` respectively.
/// - For `f32`, silence corresponds to the value `0.0`. The minimum and maximum amplitudes are
///  represented by `-1.0` and `1.0` respectively.
///
/// You can implement this trait on your own type as well if you wish so.
///
pub trait Sample: CpalSample {
    /// Linear interpolation between two samples.
    ///
    /// The result should be equal to
    /// `first * numerator / denominator + second * (1 - numerator / denominator)`.
    fn lerp(first: Self, second: Self, numerator: u32, denominator: u32) -> Self;
    /// Multiplies the value of this sample by the given amount.
    fn amplify(self, value: f32) -> Self;

    /// Calls `saturating_add` on the sample.
    fn saturating_add(self, other: Self) -> Self;

    /// Returns the value corresponding to the absence of sound.
    fn zero_value() -> Self;
}

impl Sample for u16 {
    #[inline]
    fn lerp(first: u16, second: u16, numerator: u32, denominator: u32) -> u16 {
        (first as u32 + (second as u32 - first as u32) * numerator / denominator) as u16
    }

    #[inline]
    fn amplify(self, value: f32) -> u16 {
        self.to_i16().amplify(value).to_u16()
    }

    #[inline]
    fn saturating_add(self, other: u16) -> u16 {
        self.saturating_add(other)
    }

    #[inline]
    fn zero_value() -> u16 {
        32768
    }
}

impl Sample for i16 {
    #[inline]
    fn lerp(first: i16, second: i16, numerator: u32, denominator: u32) -> i16 {
        (first as i32 + (second as i32 - first as i32) * numerator as i32 / denominator as i32)
            as i16
    }

    #[inline]
    fn amplify(self, value: f32) -> i16 {
        ((self as f32) * value) as i16
    }

    #[inline]
    fn saturating_add(self, other: i16) -> i16 {
        self.saturating_add(other)
    }

    #[inline]
    fn zero_value() -> i16 {
        0
    }
}

impl Sample for f32 {
    #[inline]
    fn lerp(first: f32, second: f32, numerator: u32, denominator: u32) -> f32 {
        first + (second - first) * numerator as f32 / denominator as f32
    }

    #[inline]
    fn amplify(self, value: f32) -> f32 {
        self * value
    }

    #[inline]
    fn saturating_add(self, other: f32) -> f32 {
        self + other
    }

    #[inline]
    fn zero_value() -> f32 {
        0.0
    }
}