Struct ReadBuf

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

Expand description

Cursor over an immutable byte slice with a tracked read position.

§Example

use wire_codec::ReadBuf;

let mut buf = ReadBuf::new(&[0xDE, 0xAD, 0xBE, 0xEF]);
assert_eq!(buf.read_u16_be().unwrap(), 0xDEAD);
assert_eq!(buf.read_u16_be().unwrap(), 0xBEEF);
assert_eq!(buf.remaining(), 0);

Implementations§

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impl<'a> ReadBuf<'a>

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

Wrap bytes in a new cursor positioned at the start of the slice.

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pub const fn position(&self) -> usize

Current read offset within the backing slice.

Because every read is atomic, after an error this is the offset of the value that failed to decode, which makes it useful in diagnostics.

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pub const fn remaining(&self) -> usize

Number of bytes still available for reading.

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pub const fn is_empty(&self) -> bool

Whether the cursor has consumed every byte of the backing slice.

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pub fn remaining_slice(&self) -> &'a [u8] ⓘ

Slice of bytes that have not yet been consumed.

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pub fn peek(&self, n: usize) -> Result<&'a [u8]>

Look at the next n bytes without advancing the cursor.

§Errors

Returns Error::UnexpectedEof when fewer than n bytes remain.

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pub fn peek_u8(&self) -> Result<u8>

Look at the next byte without advancing the cursor.

§Errors

Returns Error::UnexpectedEof when the cursor is exhausted.

§Example

use wire_codec::ReadBuf;

let buf = ReadBuf::new(&[0x7F]);
assert_eq!(buf.peek_u8().unwrap(), 0x7F);
assert_eq!(buf.position(), 0);

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pub fn read_bytes(&mut self, n: usize) -> Result<&'a [u8]>

Read the next n bytes and advance the cursor by n.

§Errors

Returns Error::UnexpectedEof when fewer than n bytes remain.

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pub fn read_array<const N: usize>(&mut self) -> Result<[u8; N]>

Read the next N bytes as a fixed-size array (copied).

§Errors

Returns Error::UnexpectedEof when fewer than N bytes remain.

§Example

use wire_codec::ReadBuf;

let mut buf = ReadBuf::new(b"GIF89a...");
let magic: [u8; 6] = buf.read_array().unwrap();
assert_eq!(&magic, b"GIF89a");

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pub fn read_array_ref<const N: usize>(&mut self) -> Result<&'a [u8; N]>

Borrow the next N bytes as a fixed-size array reference (zero-copy).

§Errors

Returns Error::UnexpectedEof when fewer than N bytes remain.

§Example

use wire_codec::ReadBuf;

let data = [1, 2, 3, 4, 5];
let mut buf = ReadBuf::new(&data);
let head: &[u8; 4] = buf.read_array_ref().unwrap();
assert_eq!(head, &[1, 2, 3, 4]);

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pub fn split_to(&mut self, n: usize) -> Result<ReadBuf<'a>>

Split off the next n bytes as an independent cursor and advance past them.

Useful for a length-delimited sub-record: decode it from the returned cursor, then check ReadBuf::is_empty to make sure it was consumed exactly.

§Errors

Returns Error::UnexpectedEof when fewer than n bytes remain.

§Example

use wire_codec::ReadBuf;

let mut buf = ReadBuf::new(&[0x02, 0xAA, 0xBB, 0xCC]);
let len = usize::from(buf.read_u8().unwrap());
let mut record = buf.split_to(len).unwrap();
assert_eq!(record.read_u16_be().unwrap(), 0xAABB);
assert!(record.is_empty());
assert_eq!(buf.remaining_slice(), &[0xCC]);