Struct async_read_util::MappedReader

pub struct MappedReader<R, F> { /* fields omitted */ }

An async reader which allows a closure to map the output of the inner async reader into a new buffer. This allows things like compression/encryption to be layered on top of a normal reader.

NOTE: The closure must consume at least 1 byte for the reader to continue.

SAFETY: This currently creates the equivalent of Box<[MaybeUninit<u8>]>, but does so through use of accessing the allocator directly. Once new_uninit is available on stable, Box::new_uninit_slice will be used. This will still utilize unsafe. A uninitialized buffer is acceptable because it’s contents are only ever written to before reading only the written section.

ref: https://github.com/rust-lang/rust/issues/63291

Implementations

impl<R, F> MappedReader<R, F> where
    R: AsyncRead,
    F: FnMut(&[u8], &mut [u8]) -> (usize, usize), 

pub fn new(inner: R, f: F) -> Self

pub fn with_capacity(capacity: usize, inner: R, f: F) -> Self

Trait Implementations

impl<R, F> AsyncRead for MappedReader<R, F> where
    R: AsyncRead,
    F: FnMut(&[u8], &mut [u8]) -> (usize, usize), 

fn poll_read(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>,
    buf: &mut [u8]
) -> Poll<Result<usize>>

Attempt to read from the AsyncRead into buf.

pub fn poll_read_vectored(
    self: Pin<&mut Self>,
    cx: &mut Context<'_>,
    bufs: &mut [IoSliceMut<'_>]
) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into bufs using vectored IO operations.

impl<'pin, R, F> Unpin for MappedReader<R, F> where
    __MappedReader<'pin, R, F>: Unpin,