twang 0.9.0

Library for pure Rust advanced audio synthesis.
Documentation 
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

// Copyright © 2018-2022 The Twang Contributors.
//
// Licensed under any of:
// - Apache License, Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0)
// - Boost Software License, Version 1.0 (https://www.boost.org/LICENSE_1_0.txt)
// - MIT License (https://mit-license.org/)
// At your choosing (See accompanying files LICENSE_APACHE_2_0.txt,
// LICENSE_MIT.txt and LICENSE_BOOST_1_0.txt).

use fon::chan::Ch16;

// Constants PFIRA and PFIRB
include!(concat!(env!("OUT_DIR"), "/pink.rs"));

#[inline(always)]
fn pnmask(pncnt: u8) -> u8 {
    match pncnt % 16 {
        _x if _x % 2 != 0 => 0x80,
        _x if _x % 4 != 0 => 0x40,
        _x if _x % 8 != 0 => 0x20,
        8 => 0x10, // _x if _x % 16 != 0
        _ => match pncnt / 16 {
            // only 0
            _x if _x % 2 != 0 => 8,
            _x if _x % 4 != 0 => 4,
            _x if _x % 8 != 0 => 2,
            8 => 1, // _x if _x % 16 != 0
            _ => 0, // only 0
        },
    }
}

/// Pink Noise Generator using algorithm described in research paper
/// [A New Shade of Pink](https://github.com/Stenzel/newshadeofpink/blob/master/newshadeofpink.pdf).
#[derive(Debug, Copy, Clone)]
pub struct Pink {
    lfsr: i32,
    inc: i32,
    dec: i32,
    accu: i32,
    pncnt: u8,
    which: u8,
    bit: i32,
}

impl Default for Pink {
    #[inline(always)]
    fn default() -> Self {
        Self::new()
    }
}

impl Pink {
    /// Create a new Pink Noise Sampler.
    #[inline(always)]
    pub fn new() -> Self {
        Self {
            lfsr: 0x5eed41f5i32,
            inc: 0xccc,
            dec: 0xccc,
            accu: 0,
            pncnt: 0,
            which: 0,
            bit: 0,
        }
    }

    fn a(&mut self) -> i16 {
        self.bit = self.lfsr >> 31i32;
        self.dec &= !0x800i32;
        self.lfsr <<= 1;
        self.dec |= self.inc & 0x800i32;
        self.inc ^= self.bit & 0x800i32;
        self.b()
    }

    fn b(&mut self) -> i16 {
        self.accu += self.inc - self.dec;
        self.lfsr ^= self.bit & 0x46000001i32;
        (self.accu
            + PFIRA[(self.lfsr & 0x3fi32) as usize]
            + PFIRB[(self.lfsr >> 6i32 & 0x3fi32) as usize]) as i16
    }

    fn c(&mut self) -> i16 {
        self.bit = self.lfsr >> 31i32;
        self.dec &= !0x400i32;
        self.lfsr <<= 1;
        self.dec |= self.inc & 0x400i32;
        self.inc ^= self.bit & 0x400i32;
        self.b()
    }

    fn d(&mut self) -> i16 {
        self.bit = self.lfsr >> 31i32;
        self.dec &= !0x200i32;
        self.lfsr <<= 1;
        self.dec |= self.inc & 0x200i32;
        self.inc ^= self.bit & 0x200i32;
        self.b()
    }

    fn e(&mut self) -> i16 {
        self.bit = self.lfsr >> 31i32;
        self.dec &= !0x100i32;
        self.lfsr <<= 1;
        self.dec |= self.inc & 0x100i32;
        self.inc ^= self.bit & 0x100i32;
        self.b()
    }

    fn f(&mut self, mask: i32) -> i16 {
        self.bit = self.lfsr >> 31i32;
        self.dec &= !mask;
        self.lfsr <<= 1;
        self.dec |= self.inc & mask;
        self.inc ^= self.bit & mask;
        self.b()
    }

    /// Get next sample from the noise generator.
    #[inline(always)]
    pub fn step(&mut self) -> fon::chan::Ch32 {
        // Different functions for each sample.
        let pink = match self.which {
            _x if _x % 2 != 0 => self.a(), // odd #s
            _x if _x % 4 != 0 => self.c(),
            _x if _x % 8 != 0 => self.d(),
            0 => {
                let mask = pnmask(self.pncnt).into();
                self.pncnt = self.pncnt.wrapping_add(1);
                self.f(mask)
            }
            8 => self.e(),
            _ => unreachable!(),
        };
        self.which += 1;
        self.which %= 16;

        Ch16::new(pink).into()
    }
}