Struct PeekReader 

struct PeekReader<R: Read> {
    inner: R,
    lookahead: Vec<u8>,
    lookahead_pos: usize,
    count: u64,
}

A Read that can look ahead without consuming, and counts what it has handed out.

Both are needed for segmented traces: the lookahead is how a segment boundary is spotted before an event decoder eats the magic bytes, and the count is how a clean end-of-file is told apart from a stream that stopped half-way through an event.

Fields

inner: R

lookahead: Vec<u8>

Bytes read from inner but not yet handed to a caller of read.

lookahead_pos: usize

count: u64

Bytes handed out so far, excluding whatever is still in lookahead.

Implementations

impl<R: Read> PeekReader<R>

fn new(inner: R) -> Self

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

Borrow the next n bytes without consuming them. The returned slice is shorter than n only at end of stream.

fn next_byte(&mut self) -> Result<Option<u8>>

Consume and return one byte, or None at end of stream.

Trait Implementations

impl<R: Debug + Read> Debug for PeekReader<R>

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

Formats the value using the given formatter.

impl<R: Read> Read for PeekReader<R>

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

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Reads all bytes until EOF in this source, appending them to buf.

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

Reads the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_, u8>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact( &mut self, cursor: BorrowedCursor<'_, u8>, ) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Reads the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Read.

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

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

where Self: Sized,

🔬This is a nightly-only experimental API. (read_array)

Read and return a fixed array of bytes from this source.

fn read_le<T>(&mut self) -> Result<T, Error>

where T: FromEndianBytes, Self: Sized,

🔬This is a nightly-only experimental API. (read_le)

Read and return a type (e.g. an integer) in little-endian order.

fn read_be<T>(&mut self) -> Result<T, Error>

where T: FromEndianBytes, Self: Sized,

🔬This is a nightly-only experimental API. (read_le)

Read and return a type (e.g. an integer) in big-endian order.