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
186
187
188
189
190
191
192
193
194
195
196
197
198

use std::io::{Cursor, Read};

use byteorder::{ByteOrder, ReadBytesExt};

#[cfg(test)]
use nearly_eq::NearlyEq;

#[derive(Eq, PartialEq, Copy, Clone, Default, Debug)]
#[repr(transparent)]
pub struct Sample<Raw>(Raw);

impl From<i16> for Sample<i16> {
    #[inline]
    fn from(raw: i16) -> Self {
        Self(raw)
    }
}

impl From<f32> for Sample<f32> {
    #[inline]
    fn from(raw: f32) -> Self {
        Self(raw.clamp(-1.0, 1.0))
    }
}

macro_rules! impl_from_sample_for_raw {
    ($raw:ty) => {
        impl From<Sample<$raw>> for $raw {
            #[inline]
            fn from(sample: Sample<$raw>) -> $raw {
                sample.0
            }
        }
    };
}

impl_from_sample_for_raw!(i16);
impl_from_sample_for_raw!(f32);

// impl From<Sample<i16>> for Sample<i64> {
//     #[inline]
//     fn from(sample: Sample<i16>) -> Self {
//         // Fast but imprecise approach:
//         // Perform crude but fast upsample by bit-shifting the raw value:
//         Self::from((sample.0 as i64) << 16)

//         // Slow but precise approach:
//         // Perform a proper but expensive lerp from
//         // i16::MIN..i16::MAX to i32::MIN..i32::MAX:

//         // let value = sample.0 as i64;

//         // let from = if value <= 0 { i16::MIN } else { i16::MAX } as i64;
//         // let to = if value <= 0 { i32::MIN } else { i32::MAX } as i64;

//         // Self::from((value * to + from / 2) / from)
//     }
// }

impl From<Sample<i16>> for Sample<f32> {
    #[inline]
    fn from(sample: Sample<i16>) -> Self {
        let divisor = if sample.0 < 0 {
            i16::MIN as f32
        } else {
            i16::MAX as f32
        }
        .abs();
        Self::from((sample.0 as f32) / divisor)
    }
}

impl From<Sample<f32>> for Sample<i16> {
    #[inline]
    fn from(sample: Sample<f32>) -> Self {
        let multiplier = if sample.0 < 0.0 {
            i16::MIN as f32
        } else {
            i16::MAX as f32
        }
        .abs();
        Self::from((sample.0 * multiplier) as i16)
    }
}

trait FromBytes: Sized {
    fn from_reader<B: ByteOrder, R: Read>(reader: &mut R) -> Result<Self, std::io::Error>;

    fn from_bytes<B: ByteOrder>(bytes: &[u8]) -> Result<Self, std::io::Error> {
        let mut cursor = Cursor::new(bytes);
        Self::from_reader::<B, _>(&mut cursor)
    }
}

impl FromBytes for Sample<i16> {
    fn from_reader<B: ByteOrder, R: Read>(reader: &mut R) -> Result<Self, std::io::Error> {
        reader.read_i16::<B>().map(Self::from)
    }
}

impl FromBytes for Sample<f32> {
    fn from_reader<B: ByteOrder, R: Read>(reader: &mut R) -> Result<Self, std::io::Error> {
        reader.read_f32::<B>().map(Self::from)
    }
}

#[cfg(test)]
impl<Raw> NearlyEq<Self, Raw> for Sample<Raw>
where
    Raw: NearlyEq<Raw, Raw>,
{
    fn eps() -> Raw {
        Raw::eps()
    }

    fn eq(&self, other: &Self, eps: &Raw) -> bool {
        NearlyEq::eq(&self.0, &other.0, eps)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    use nearly_eq::assert_nearly_eq;

    #[test]
    fn sample_i16_from_i16() {
        // i16:
        assert_eq!(Sample::<i16>::from(i16::MIN).0, i16::MIN);
        assert_eq!(Sample::<i16>::from(i16::MIN / 2).0, i16::MIN / 2);
        assert_eq!(Sample::<i16>::from(0).0, 0);
        assert_eq!(Sample::<i16>::from(i16::MAX / 2).0, i16::MAX / 2);
        assert_eq!(Sample::<i16>::from(i16::MAX).0, i16::MAX);
    }

    #[test]
    fn sample_f32_from_f32() {
        assert_eq!(Sample::<f32>::from(-1.0).0, -1.0);
        assert_eq!(Sample::<f32>::from(-0.5).0, -0.5);
        assert_eq!(Sample::<f32>::from(0.0).0, 0.0);
        assert_eq!(Sample::<f32>::from(0.5).0, 0.5);
        assert_eq!(Sample::<f32>::from(1.0).0, 1.0);

        // For any values outside of -1.0..=1.0 we expect clamping:
        assert_eq!(Sample::<f32>::from(f32::MIN).0, -1.0);
        assert_eq!(Sample::<f32>::from(f32::MAX).0, 1.0);
    }

    #[test]
    fn sample_i16_from_sample_f32() {
        assert_nearly_eq!(
            Sample::<i16>::from(Sample::<f32>::from(-1.0)),
            Sample::from(i16::MIN)
        );
        assert_nearly_eq!(
            Sample::<i16>::from(Sample::<f32>::from(-0.5)),
            Sample::from(i16::MIN / 2)
        );
        assert_nearly_eq!(
            Sample::<i16>::from(Sample::<f32>::from(0.0)),
            Sample::from(0)
        );
        assert_nearly_eq!(
            Sample::<i16>::from(Sample::<f32>::from(0.5)),
            Sample::from(i16::MAX / 2)
        );
        assert_nearly_eq!(
            Sample::<i16>::from(Sample::<f32>::from(1.0)),
            Sample::from(i16::MAX)
        );
    }

    #[test]
    fn sample_f32_from_sample_i16() {
        assert_nearly_eq!(
            Sample::<f32>::from(Sample::<i16>::from(i16::MIN)),
            Sample::from(-1.0)
        );
        assert_nearly_eq!(
            Sample::<f32>::from(Sample::<i16>::from(i16::MIN / 2)),
            Sample::from(-0.5)
        );
        assert_nearly_eq!(
            Sample::<f32>::from(Sample::<i16>::from(0)),
            Sample::from(0.0)
        );
        assert_nearly_eq!(
            Sample::<f32>::from(Sample::<i16>::from(i16::MAX / 2)),
            Sample::from(0.5),
            0.0001 // rounding error due to i16::MAX being odd
        );
        assert_nearly_eq!(
            Sample::<f32>::from(Sample::<i16>::from(i16::MAX)),
            Sample::from(1.0)
        );
    }
}