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

#[macro_use] 
extern crate failure;

use async_std::io::{BufReader, Read};
use async_std::prelude::*;

use bitqueue::BitQueue;
use byte_reader::{ReadFromBigEndian};
use error::Result;

use bit_reverse::LookupReverse;

/// BitReader reads data from a byte slice at the granularity of a single bit.
pub struct BitReader<R : Read + std::marker::Unpin + std::marker::Send> {
    reader : BufReader<R>,
    buffer : BitQueue,
    byte_count : usize
}

mod bitqueue;
mod truncate;
mod byte_reader;

pub mod error;

impl<R : Read + std::marker::Unpin + std::marker::Send> BitReader<R>
{
    pub fn new(reader : R) -> BitReader<R>
    {
        BitReader
        {
            reader : BufReader::new(reader),
            buffer : BitQueue::new(),
            byte_count : 0usize
        }
    }

    pub fn is_aligned(&self) -> bool { self.buffer.is_empty() }

    pub async fn read_u8_slice_aligned(&mut self, count : usize) -> Result<Vec<u8>>
    {
        let mut result : Vec<u8> = vec![0; count];
        self.reader.read_exact(result.as_mut_slice()).await?;

        self.byte_count += count;

        Ok(result)
    }

    //should be aligned before this is called
    //Reads a T from the Bitreader and increments position accordingly
    pub async fn read_aligned_be<T>(&mut self) -> Result<T>
    where T : Sized + ReadFromBigEndian + std::marker::Unpin + std::marker::Send
    {
        //check if its aligned to the byte mark
        assert!(self.buffer.is_empty());
        let num = <T>::read_be(&mut self.reader).await?;
        self.byte_count += std::mem::size_of::<T>();
        Ok(num)
    }

    pub fn byte_count(&self) -> usize
    {
        self.byte_count.clone()
    }

    pub async fn read_be_bits(&mut self, count: usize) -> Result<u8> 
    {
        if self.buffer.len() < count
        {
            //TODO: expand this to allow for bitstruct types bigger than one byte
            let mut buf : [u8; 1] = [0;1];

            self.reader.read_exact(&mut buf).await?;

            self.byte_count += 1;

            let new_bytes : u8 = u8::from_ne_bytes(buf);

            //we need to refil the buffer
            self.buffer.push(new_bytes);
        }

        Ok(self.buffer.pop(count))
    }

    //TODO: come back and make this generic
    //If some protocol needs it
    pub async fn read_le_bits(&mut self, count: usize) -> Result<u8>
    {
        if self.buffer.len() < count
        {
            //TODO: expand this to allow for bitstruct types bigger than one byte
            let mut buf : [u8; 1] = [0;1];

            self.reader.read_exact(&mut buf).await?;

            self.byte_count += 1;

            let new_bytes : u8 = u8::from_ne_bytes(buf);

            //we need to refil the buffer
            self.buffer.push(new_bytes);
        }

        let trailing_0s = (std::mem::size_of::<u8>() * 8) - count;

        let result = self.buffer.pop(count).swap_bits() >> trailing_0s;

        println!("LE Bits : {:#010b}", result);

        Ok(result)
    }
}

#[cfg(test)]
mod tests
{
    use super::*;
    use async_std::io::BufReader;
    use async_std::task;

    #[test]
    fn read_be() 
    {
        task::block_on(async {
            let bytes = [25u8,25u8,25u8,25u8];

            let underlying_reader : BufReader<&[u8]> = BufReader::new(&bytes);

            let mut reader = BitReader::<BufReader<&[u8]>>::new(underlying_reader);

            let num = reader.read_aligned_be::<u16>().await.unwrap();

            assert_eq!(num, 6425u16);

            let num2 = reader.read_aligned_be::<u8>().await.unwrap();

            assert_eq!(num2, 25u8);
        });
    }

    #[test]
    fn read_test_connect_fixed_header()
    {
        task::block_on(async {
            let bytes = [0b00010000];

            let underlying_reader : BufReader<&[u8]> = BufReader::new(&bytes);

            let mut reader = BitReader::<BufReader<&[u8]>>::new(underlying_reader);


            assert_eq!(0b0001, reader.read_be_bits(4).await.unwrap());
            assert_eq!(0b0, reader.read_be_bits(1).await.unwrap());
            assert_eq!(0b00, reader.read_be_bits(2).await.unwrap());
            assert_eq!(0b0, reader.read_be_bits(1).await.unwrap());
        });
    }

    #[test]
    fn read_test_connect_flags()
    {
        task::block_on(async {
            let bytes = [0b11001110];

            let underlying_reader : BufReader<&[u8]> = BufReader::new(&bytes);

            let mut reader = BitReader::<BufReader<&[u8]>>::new(underlying_reader);


            assert_eq!(0b1, reader.read_be_bits(1).await.unwrap());
            assert_eq!(0b1, reader.read_be_bits(1).await.unwrap());
            assert_eq!(0b0, reader.read_be_bits(1).await.unwrap());
            assert_eq!(0b01, reader.read_be_bits(2).await.unwrap());
            assert_eq!(0b1, reader.read_be_bits(1).await.unwrap());
            assert_eq!(0b1, reader.read_be_bits(1).await.unwrap());
            assert_eq!(0b0, reader.read_be_bits(1).await.unwrap());
        });
    }
}