Struct BitReader 

pub struct BitReader<'a> { /* private fields */ }

A cursor that reads values at arbitrary bit offsets from a byte slice, in a chosen BitOrder (MSB-first by default — bit 0 is the high bit of byte 0, the RFC/ETSI ASCII-art convention; LSB-first for serial/PHY layers).

Examples

use bnb::{BitReader, u4, u12};

let mut r = BitReader::new(&[0xAB, 0xCD]);
assert_eq!(r.read::<u4>().unwrap(), u4::new(0xA)); // 4 bits
assert_eq!(r.read::<u12>().unwrap(), u12::new(0xBCD)); // the next 12, straddling a byte
assert_eq!(r.remaining_bits(), 0);

Implementations

impl<'a> BitReader<'a>

pub fn new(bytes: &'a [u8]) -> Self

Wraps bytes, positioned at bit 0, MSB-first, big-endian.

pub fn with_order(bytes: &'a [u8], order: BitOrder) -> Self

Wraps bytes, positioned at bit 0, in the given bit order (big-endian).

pub fn with_layout(bytes: &'a [u8], layout: Layout) -> Self

Wraps bytes, positioned at bit 0, in the given Layout (bit + byte order).

pub fn bit_pos(&self) -> usize

The current absolute bit offset.

pub fn remaining_bits(&self) -> usize

Bits not yet consumed.

pub fn read_bits(&mut self, n: u32) -> Result<u128, BitError>

Reads n (<= 128) bits into the low bits of a u128, in the reader’s bit order (MSB-first by default).

Errors

ErrorKind::TooWide if n > 128; ErrorKind::UnexpectedEof if fewer than n bits remain. Either carries the current bit offset.

pub fn read<T: Bits>(&mut self) -> Result<T, BitError>

Reads one Bits value of its declared width, applying the byte order to a byte-multiple value.

Errors

As read_bits.

pub fn seek_to_bit(&mut self, pos: usize) -> Result<(), BitError>

Moves the cursor to absolute bit pos. This needs no Seek trait — the whole buffer is in hand, so a seek is just cursor arithmetic. (Enables e.g. DNS name-compression pointers.)

Errors

ErrorKind::UnexpectedEof if pos is past the end of the buffer.

pub fn align_to_byte(&mut self)

Advances the cursor to the next byte boundary (a no-op if already aligned).

Trait Implementations

impl<'a> Clone for BitReader<'a>

fn clone(&self) -> BitReader<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for BitReader<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl SeekSource for BitReader<'_>

impl Source for BitReader<'_>

fn read_bits(&mut self, n: u32) -> Result<u128, BitError>

Reads n (<= 128) bits into the low bits of a u128, in the source’s bit order (MSB-first by default).

fn bit_pos(&self) -> usize

The current absolute bit offset (for position-aware errors).

fn byte_order(&self) -> ByteOrder

The byte order applied to a byte-multiple value (default big-endian).

fn bit_order(&self) -> BitOrder

The bit order this source reads in (default MSB-first). Paired with byte_order to decide whether a byte-multiple value needs its bytes swapped — each bit order has a natural byte layout (big-endian under MSB, little-endian under LSB), and only the opposite declaration swaps.

fn seek_to_bit(&mut self, pos: usize) -> Result<(), BitError>

Moves the cursor to absolute bit pos. The default — for a forward-only source — fails with ErrorKind::NotSeekable; seekable sources (the slice BitReader) override it. A SeekSource guarantees this works.

fn read<T: Bits>(&mut self) -> Result<T, BitError>

Reads one Bits value of its declared width, applying the byte order.

fn read_bytes(&mut self, n: usize) -> Result<Vec<u8>, BitError>

Reads n bytes into a fresh Vec (at any bit offset — the bytes need not be aligned). The bulk form of the per-byte read::<u8>() loop, for blob/payload reads in custom codecs and container formats.

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

Fills buf with bytes from the source — the no-alloc dual of read_bytes, for fixed scratch buffers and tight no_std paths.

fn as_read(&mut self) -> SourceReader<'_, Self>

where Self: Sized,

Available on crate feature std only.

Borrows this source as a std::io::Read over its bytes — for handing the cursor to std::io-based code from a #[br(parse_with = …)] (e.g. a decoder, or a Read-based parser). Reads 8 bits per byte; see SourceReader. Only with the std feature.