Struct bitstream_io::write::BitWriter

pub struct BitWriter<W: Write, E: Endianness> { /* private fields */ }

For writing bit values to an underlying stream in a given endianness.

Because this only writes whole bytes to the underlying stream, it is important that output is byte-aligned before the bitstream writer’s lifetime ends. Partial bytes will be lost if the writer is disposed of before they can be written.

Implementations

impl<W: Write, E: Endianness> BitWriter<W, E>

pub fn new(writer: W) -> BitWriter<W, E>

Wraps a BitWriter around something that implements Write

pub fn endian(writer: W, _endian: E) -> BitWriter<W, E>

Wraps a BitWriter around something that implements Write with the given endianness.

pub fn into_writer(self) -> W

Unwraps internal writer and disposes of BitWriter. Any unwritten partial bits are discarded.

pub fn write_bit(&mut self, bit: bool) -> Result<()>

Writes a single bit to the stream. true indicates 1, false indicates 0

Errors

Passes along any I/O error from the underlying stream.

Examples

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write_bit(true).unwrap();
writer.write_bit(false).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(false).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(true).unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

use std::io::Write;
use bitstream_io::{LittleEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), LittleEndian);
writer.write_bit(true).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(false).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(true).unwrap();
writer.write_bit(false).unwrap();
writer.write_bit(true).unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

pub fn write<U>(&mut self, bits: u32, value: U) -> Result<()>where
    U: Numeric,

Writes an unsigned value to the stream using the given number of bits.

Errors

Passes along any I/O error from the underlying stream. Returns an error if the input type is too small to hold the given number of bits. Returns an error if the value is too large to fit the given number of bits.

Examples

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write(1, 0b1).unwrap();
writer.write(2, 0b01).unwrap();
writer.write(5, 0b10111).unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

use std::io::Write;
use bitstream_io::{LittleEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), LittleEndian);
writer.write(1, 0b1).unwrap();
writer.write(2, 0b11).unwrap();
writer.write(5, 0b10110).unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

use std::io::{Write, sink};
use bitstream_io::{BigEndian, BitWriter};
let mut w = BitWriter::endian(sink(), BigEndian);
assert!(w.write(9, 0u8).is_err());    // can't write  u8 in 9 bits
assert!(w.write(17, 0u16).is_err());  // can't write u16 in 17 bits
assert!(w.write(33, 0u32).is_err());  // can't write u32 in 33 bits
assert!(w.write(65, 0u64).is_err());  // can't write u64 in 65 bits
assert!(w.write(1, 2).is_err());      // can't write   2 in 1 bit
assert!(w.write(2, 4).is_err());      // can't write   4 in 2 bits
assert!(w.write(3, 8).is_err());      // can't write   8 in 3 bits
assert!(w.write(4, 16).is_err());     // can't write  16 in 4 bits

pub fn write_signed<S>(&mut self, bits: u32, value: S) -> Result<()>where
    S: SignedNumeric,

Writes a twos-complement signed value to the stream with the given number of bits.

Errors

Passes along any I/O error from the underlying stream. Returns an error if the input type is too small to hold the given number of bits. Returns an error if the value is too large to fit the given number of bits.

Examples

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write_signed(4, -5).unwrap();
writer.write_signed(4, 7).unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

use std::io::Write;
use bitstream_io::{LittleEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), LittleEndian);
writer.write_signed(4, 7).unwrap();
writer.write_signed(4, -5).unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

pub fn write_bytes(&mut self, buf: &[u8]) -> Result<()>

Writes the entirety of a byte buffer to the stream. If the stream is already byte-aligned, it will map to a faster write_all call. Otherwise it will write bytes individually in 8-bit increments.

Errors

Passes along any I/O error from the underlying stream.

Example

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write(8, 0x66).unwrap();
writer.write(8, 0x6F).unwrap();
writer.write(8, 0x6F).unwrap();
writer.write_bytes(b"bar").unwrap();
assert_eq!(writer.into_writer(), b"foobar");

pub fn write_huffman<T>(
    &mut self,
    tree: &WriteHuffmanTree<E, T>,
    symbol: T
) -> Result<()>where
    T: Ord + Copy,

Writes Huffman code for the given symbol to the stream.

Errors

Passes along any I/O error from the underlying stream.

Example

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
use bitstream_io::huffman::compile_write_tree;
let tree = compile_write_tree(
    vec![('a', vec![0]),
         ('b', vec![1, 0]),
         ('c', vec![1, 1, 0]),
         ('d', vec![1, 1, 1])]).unwrap();
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write_huffman(&tree, 'b').unwrap();
writer.write_huffman(&tree, 'c').unwrap();
writer.write_huffman(&tree, 'd').unwrap();
assert_eq!(writer.into_writer(), [0b10110111]);

pub fn write_unary0(&mut self, value: u32) -> Result<()>

Writes value number of 1 bits to the stream and then writes a 0 bit. This field is variably-sized.

Errors

Passes along any I/O error from the underyling stream.

Examples

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write_unary0(0).unwrap();
writer.write_unary0(3).unwrap();
writer.write_unary0(10).unwrap();
assert_eq!(writer.into_writer(), [0b01110111, 0b11111110]);

use std::io::Write;
use bitstream_io::{LittleEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), LittleEndian);
writer.write_unary0(0).unwrap();
writer.write_unary0(3).unwrap();
writer.write_unary0(10).unwrap();
assert_eq!(writer.into_writer(), [0b11101110, 0b01111111]);

pub fn write_unary1(&mut self, value: u32) -> Result<()>

Writes value number of 0 bits to the stream and then writes a 1 bit. This field is variably-sized.

Errors

Passes along any I/O error from the underyling stream.

Example

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write_unary1(0).unwrap();
writer.write_unary1(3).unwrap();
writer.write_unary1(10).unwrap();
assert_eq!(writer.into_writer(), [0b10001000, 0b00000001]);

use std::io::Write;
use bitstream_io::{LittleEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), LittleEndian);
writer.write_unary1(0).unwrap();
writer.write_unary1(3).unwrap();
writer.write_unary1(10).unwrap();
assert_eq!(writer.into_writer(), [0b00010001, 0b10000000]);

pub fn byte_aligned(&self) -> bool

Returns true if the stream is aligned at a whole byte.

Example

use std::io::{Write, sink};
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(sink(), BigEndian);
assert_eq!(writer.byte_aligned(), true);
writer.write(1, 0).unwrap();
assert_eq!(writer.byte_aligned(), false);
writer.write(7, 0).unwrap();
assert_eq!(writer.byte_aligned(), true);

pub fn byte_align(&mut self) -> Result<()>

Pads the stream with 0 bits until it is aligned at a whole byte. Does nothing if the stream is already aligned.

Errors

Passes along any I/O error from the underyling stream.

Example

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut writer = BitWriter::endian(Vec::new(), BigEndian);
writer.write(1, 0).unwrap();
writer.byte_align().unwrap();
writer.write(8, 0xFF).unwrap();
assert_eq!(writer.into_writer(), [0x00, 0xFF]);

pub fn into_unwritten(self) -> (u32, u8)

Consumes writer and returns any un-written partial byte as a (bits, value) tuple.

Examples

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut data = Vec::new();
let (bits, value) = {
    let mut writer = BitWriter::endian(&mut data, BigEndian);
    writer.write(15, 0b1010_0101_0101_101).unwrap();
    writer.into_unwritten()
};
assert_eq!(data, [0b1010_0101]);
assert_eq!(bits, 7);
assert_eq!(value, 0b0101_101);

use std::io::Write;
use bitstream_io::{BigEndian, BitWriter};
let mut data = Vec::new();
let (bits, value) = {
    let mut writer = BitWriter::endian(&mut data, BigEndian);
    writer.write(8, 0b1010_0101).unwrap();
    writer.into_unwritten()
};
assert_eq!(data, [0b1010_0101]);
assert_eq!(bits, 0);
assert_eq!(value, 0);