Struct StreamBitReader 

pub struct StreamBitReader<R> { /* private fields */ }

Available on crate feature std only.

A forward-only bit reader over any std::io::Read — the streaming counterpart to the in-memory BitReader, for a stream you read once and don’t seek.

It is bounded on Read only, not Seek, so it works over inputs that can’t seek (a socket, or a &[u8], which is Read but not Seek). A message that needs to seek (#[br(restore_position)]) won’t decode through it — use a BufSource or SeekReader for that. Reads up to 128 bits per call (the Source width ceiling); running out mid-message yields ErrorKind::Incomplete (“read more and retry”).

Examples

use bnb::{bin, StreamBitReader};

#[bin(big)]
#[derive(Debug, PartialEq)]
struct Word { value: u32 }

// `&[u8]` is `Read` but not `Seek` — exactly the forward-only case.
let data: &[u8] = &[0x12, 0x34, 0x56, 0x78];
let mut s = StreamBitReader::new(data);
assert_eq!(Word::decode(&mut s).unwrap(), Word { value: 0x1234_5678 });

Implementations

impl<R: Read> StreamBitReader<R>

pub fn new(inner: R) -> Self

Wraps a byte source, decoding in the default MSB-first, big-endian order. For a #[bin(little)]/bits = lsb message, use with_layout with that type’s LAYOUT, or the decode reads the wrong order.

pub fn with_layout(inner: R, layout: Layout) -> Self

Wraps a byte source, decoding in the given Layout (bit + byte order) — pass a message’s LAYOUT so a non-default-order #[bin] type round-trips over a stream.

pub fn bit_pos(&self) -> usize

The total number of bits consumed so far.

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

Reads n (<= 128) bits in the source’s bit order, pulling bytes from the source as needed. This matches every other Source: byte order is applied to whole values by read / Source::read, not here.

Errors

ErrorKind::TooWide if n > 128; ErrorKind::Incomplete if the source runs out mid-field (read more and retry). Either carries the bit offset.

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

Reads one Bits value (width <= 128) of its declared width, applying the source’s byte order to whole values — matching BitReader::read and Source::read, so sr.read::<T>() agrees with T::decode(&mut sr).

Errors

As read_bits.

Trait Implementations

impl<R: Debug> Debug for StreamBitReader<R>

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

Formats the value using the given formatter.

impl<R: Read> Source for StreamBitReader<R>

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,

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.