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

// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Abstract interface for bit-based output.

use bitvec::prelude::BitOrder;
use bitvec::prelude::BitSlice;
use bitvec::prelude::BitStore;
use bitvec::prelude::BitVec;
use bitvec::prelude::Msb0;
use bitvec::view::BitView;

/// Storage-agnostic interface trait for bit-based output.
pub trait BitSink: Sized {
    fn write_bitslice<T: BitStore, O: BitOrder>(&mut self, other: &BitSlice<T, O>);

    fn align_to_byte(&mut self) -> usize;

    // Type signature may change. Don't override.
    #[inline]
    fn write_lsbs<T: Into<u64>>(&mut self, val: T, nbits: usize) {
        let val: u64 = val.into();
        self.write_bitslice(&val.view_bits::<Msb0>()[64 - nbits..]);
    }

    #[inline]
    fn write_msbs<T: BitStore>(&mut self, val: T, nbits: usize) {
        self.write_bitslice(&val.view_bits::<Msb0>()[0..nbits]);
    }

    #[inline]
    fn write<T: BitView>(&mut self, val: T) {
        self.write_bitslice(val.view_bits::<Msb0>());
    }

    #[inline]
    fn write_twoc<T: Into<i64>>(&mut self, val: T, bits_per_sample: usize) {
        let shifted = (val.into() << (64 - bits_per_sample)) as u64;
        self.write_msbs(shifted, bits_per_sample);
    }
}

impl<T2, O2> BitSink for BitVec<T2, O2>
where
    T2: BitStore,
    O2: BitOrder,
{
    fn write_bitslice<T: BitStore, O: BitOrder>(&mut self, other: &BitSlice<T, O>) {
        self.extend_from_bitslice(other);
    }

    fn align_to_byte(&mut self) -> usize {
        let npad = 8 - self.len() % 8;
        if npad == 8 {
            return 0;
        }
        self.write_lsbs(0u8, npad);
        npad
    }
}

pub struct Tee<'a, L: BitSink, R: BitSink> {
    primary: &'a mut L,
    secondary: &'a mut R,
}

impl<'a, L: BitSink, R: BitSink> Tee<'a, L, R> {
    #[allow(dead_code)]
    pub fn new(primary: &'a mut L, secondary: &'a mut R) -> Self {
        Tee { primary, secondary }
    }
}

impl<'a, L: BitSink, R: BitSink> BitSink for Tee<'a, L, R> {
    fn write_bitslice<T: BitStore, O: BitOrder>(&mut self, other: &BitSlice<T, O>) {
        self.primary.write_bitslice(other);
        self.secondary.write_bitslice(other);
    }

    fn align_to_byte(&mut self) -> usize {
        let padded = self.primary.align_to_byte();
        self.secondary.write_lsbs(0u8, padded);
        padded
    }
}

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

    use bitvec::prelude::bits;
    use bitvec::prelude::Lsb0;

    #[test]
    fn align_to_byte_with_bitvec() {
        let mut sink: BitVec<u8> = BitVec::new();
        sink.write_lsbs(0x01u8, 1);
        sink.align_to_byte();
        assert_eq!(sink.len(), 8);
        sink.align_to_byte();
        assert_eq!(sink.len(), 8);
        sink.write_lsbs(0x01u8, 2);
        assert_eq!(sink.len(), 10);
        sink.align_to_byte();
        assert_eq!(sink.len(), 16);
    }

    #[test]
    fn write_with_tee() {
        let mut sink: BitVec<u8> = BitVec::new();
        sink.write_lsbs(0x01u8, 1);
        let mut aux_sink: BitVec<u16> = BitVec::new();
        let mut tee = Tee::new(&mut sink, &mut aux_sink);
        tee.write_lsbs(0x01u8, 1);
        tee.align_to_byte();
        assert_eq!(sink.len(), 8);
        assert_eq!(aux_sink.len(), 7);
        assert_eq!(sink, bits![1, 1, 0, 0, 0, 0, 0, 0]);
        assert!(aux_sink[0]);
        assert!(!aux_sink[1]);
    }

    #[test]
    fn twoc_writing() {
        let mut sink: BitVec<u8> = BitVec::new();
        sink.write_twoc(-7, 4);
        assert_eq!(sink, bits![1, 0, 0, 1]);
    }
}