Struct MappedReader

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

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.

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 PinnedFieldsOf<__MappedReader<'pin, R, F>>: Unpin,