Struct PartialAsyncRead

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

Available on crate feature futures03 only.

A wrapper that breaks inner AsyncRead instances up according to the provided iterator.

Available with the futures03 feature for futures traits, and with the tokio1 feature for tokio traits.

Examples

This example uses tokio.

use partial_io::{PartialAsyncRead, PartialOp};
use std::io::{self, Cursor};
use tokio::io::AsyncReadExt;

#[tokio::main]
async fn main() -> io::Result<()> {
    let reader = Cursor::new(vec![1, 2, 3, 4]);
    // Sequential calls to `poll_read()` and the other `poll_` methods simulate the following behavior:
    let iter = vec![
        PartialOp::Err(io::ErrorKind::WouldBlock),   // A not-ready state.
        PartialOp::Limited(2),                       // Only allow 2 bytes to be read.
        PartialOp::Err(io::ErrorKind::InvalidData),  // Error from the underlying stream.
        PartialOp::Unlimited,                        // Allow as many bytes to be read as possible.
    ];
    let mut partial_reader = PartialAsyncRead::new(reader, iter);
    let mut out = vec![0; 256];

    // This causes poll_read to be called twice, yielding after the first call (WouldBlock).
    assert_eq!(partial_reader.read(&mut out).await?, 2, "first read with Limited(2)");
    assert_eq!(&out[..4], &[1, 2, 0, 0]);

    // This next call returns an error.
    assert_eq!(
        partial_reader.read(&mut out[2..]).await.unwrap_err().kind(),
        io::ErrorKind::InvalidData,
    );

    // And this one causes the last two bytes to be written.
    assert_eq!(partial_reader.read(&mut out[2..]).await?, 2, "second read with Unlimited");
    assert_eq!(&out[..4], &[1, 2, 3, 4]);

    Ok(())
}

Implementations

impl<R> PartialAsyncRead<R>

pub fn new<I>(inner: R, iter: I) -> Self

where I: IntoIterator<Item = PartialOp> + 'static, I::IntoIter: Send,

Creates a new PartialAsyncRead wrapper over the reader with the specified PartialOps.

pub fn set_ops<I>(&mut self, iter: I) -> &mut Self

where I: IntoIterator<Item = PartialOp> + 'static, I::IntoIter: Send,

Sets the PartialOps for this reader.

pub fn pin_set_ops<I>(self: Pin<&mut Self>, iter: I) -> Pin<&mut Self>

where I: IntoIterator<Item = PartialOp> + 'static, I::IntoIter: Send,

Sets the PartialOps for this reader in a pinned context.

pub fn get_ref(&self) -> &R

Returns a shared reference to the underlying reader.

pub fn get_mut(&mut self) -> &mut R

Returns a mutable reference to the underlying reader.

pub fn pin_get_mut(self: Pin<&mut Self>) -> Pin<&mut R>

Returns a pinned mutable reference to the underlying reader.

pub fn into_inner(self) -> R

Consumes this wrapper, returning the underlying reader.

Trait Implementations

impl<R> AsyncBufRead for PartialAsyncRead<R>

where R: AsyncBufRead,

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

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read.

impl<R> AsyncBufRead for PartialAsyncRead<R>

where R: AsyncBufRead,

Available on crate feature tokio1 only.

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

Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read.

impl<R> AsyncRead for PartialAsyncRead<R>

where R: AsyncRead,

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<R> AsyncRead for PartialAsyncRead<R>

where R: AsyncRead,

Available on crate feature tokio1 only.

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

Attempts to read from the AsyncRead into buf.

impl<R> AsyncSeek for PartialAsyncRead<R>

where R: AsyncSeek,

This is a forwarding impl to support duplex structs.

fn poll_seek( self: Pin<&mut Self>, cx: &mut Context<'_>, pos: SeekFrom, ) -> Poll<Result<u64>>

Attempt to seek to an offset, in bytes, in a stream.

impl<R> AsyncSeek for PartialAsyncRead<R>

where R: AsyncSeek,

Available on crate feature tokio1 only.

This is a forwarding impl to support duplex structs.

fn start_seek(self: Pin<&mut Self>, position: SeekFrom) -> Result<()>

Attempts to seek to an offset, in bytes, in a stream.

fn poll_complete( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<u64>>

Waits for a seek operation to complete.

impl<R> AsyncWrite for PartialAsyncRead<R>

where R: AsyncWrite,

This is a forwarding impl to support duplex structs.

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

Attempt to write bytes from buf into the object.

fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempt to flush the object, ensuring that any buffered data reach their destination.

fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempt to close the object.

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

Attempt to write bytes from bufs into the object using vectored IO operations.

impl<R> AsyncWrite for PartialAsyncRead<R>

where R: AsyncWrite,

Available on crate feature tokio1 only.

This is a forwarding impl to support duplex structs.

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

Attempt to write bytes from buf into the object.

fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

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

Like poll_write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

impl<R> Debug for PartialAsyncRead<R>

where R: Debug,

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

Formats the value using the given formatter.

impl<'pin, R> Unpin for PartialAsyncRead<R>

where PinnedFieldsOf<__PartialAsyncRead<'pin, R>>: Unpin,