async_buf_read 0.1.3

Async Buffer Reader for IO
Documentation 
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use std::{
    io,
    pin::Pin,
    task::{Context, Poll},
};

use async_buf_read::{AsyncBufPassthrough, AsyncBufReadExt, AsyncBufReader};
use futures::poll;
use tokio::{
    io::{AsyncRead, AsyncReadExt, ReadBuf},
    pin,
};

struct MaybePending<'a> {
    inner: &'a [u8],
    ready_read: bool,
}

impl<'a> MaybePending<'a> {
    fn new(inner: &'a [u8]) -> Self {
        Self {
            inner,
            ready_read: false,
        }
    }
}

impl AsyncRead for MaybePending<'_> {
    fn poll_read(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        if self.ready_read {
            self.ready_read = false;
            Pin::new(&mut self.inner).poll_read(cx, buf)
        } else {
            self.ready_read = true;
            cx.waker().wake_by_ref();
            Poll::Pending
        }
    }
}

struct AlwaysPending<'a> {
    inner: &'a [u8],
    ready_read: bool,
}

impl<'a> AlwaysPending<'a> {
    fn new(inner: &'a [u8]) -> Self {
        Self {
            inner,
            ready_read: true,
        }
    }
}

impl AsyncRead for AlwaysPending<'_> {
    fn poll_read(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<io::Result<()>> {
        if self.ready_read {
            self.ready_read = false;
            Pin::new(&mut self.inner).poll_read(cx, buf)
        } else {
            cx.waker().wake_by_ref();
            Poll::Pending
        }
    }
}

#[tokio::test]
async fn test_buf_reader_read_basic() {
    let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
    let mut reader = AsyncBufReader::with_chunk_size(3, inner);

    let mut buf = [0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 3);
    assert_eq!(buf, [5, 6, 7]);
    assert_eq!(reader.buffer(), []);

    let mut buf = [0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 2);
    assert_eq!(buf, [0, 1]);
    assert_eq!(reader.buffer(), [2]);

    let mut buf = [0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 1);
    assert_eq!(buf, [2]);
    assert_eq!(reader.buffer(), []);

    let mut buf = [0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 2);
    assert_eq!(buf, [3, 4, 0]);
    assert_eq!(reader.buffer(), []);

    assert_eq!(reader.read(&mut buf).await.unwrap(), 0);
}

#[tokio::test]
async fn test_buf_reader_read_expand() {
    let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4, 11, 10, 9, 8, 13, 12, 14, 15];
    let mut reader = AsyncBufReader::with_chunk_size(5, inner);

    let mut buf = [0, 0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 4);
    assert_eq!(buf, [5, 6, 7, 0]);
    assert_eq!(reader.capacity(), 1);
    assert_eq!(reader.buffer(), [1]);

    let mut buf = [0, 0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 4);
    assert_eq!(buf, [1, 2, 3, 4]);
    assert_eq!(reader.capacity(), 2);
    assert_eq!(reader.buffer(), [11, 10]);

    let mut buf = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 2);
    assert_eq!(buf, [11, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
    assert_eq!(reader.capacity(), 0);
    assert_eq!(reader.buffer(), []);

    let mut buf = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 6);
    assert_eq!(buf, [9, 8, 13, 12, 14, 15, 0, 0, 0, 0, 0, 0]);
    assert_eq!(reader.capacity(), 0);
    assert_eq!(reader.buffer(), []);

    assert_eq!(reader.read(&mut buf).await.unwrap(), 0);
}

#[tokio::test]
async fn test_buf_reader_peek() {
    let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4, 11, 10];
    let mut reader = AsyncBufReader::with_chunk_size(5, inner);

    let buf = reader.peek(4).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0]);
    assert_eq!(reader.capacity(), 5);
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1]);

    let buf = reader.peek(8).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0, 1, 2, 3, 4]);
    assert_eq!(reader.capacity(), 10);
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);

    let buf = reader.peek(12).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);
    assert_eq!(reader.capacity(), 20);
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);

    let buf = reader.peek(24).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);
    assert_eq!(reader.capacity(), 20);
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);
}

#[tokio::test]
async fn test_buf_reader_passthrough() {
    let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4, 11, 10];
    let mut reader = AsyncBufReader::with_chunk_size(5, inner);

    let buf = reader.peek(4).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0]);
    assert_eq!(reader.capacity(), 5);
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1]);

    reader.passthrough(true);

    let mut buf = [0, 0, 0, 0, 0, 0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 5);
    assert_eq!(buf, [5, 6, 7, 0, 1, 0, 0, 0]);
    assert_eq!(reader.capacity(), 0);
    assert_eq!(reader.buffer(), []);

    let mut buf = [0, 0, 0, 0, 0, 0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 5);
    assert_eq!(buf, [2, 3, 4, 11, 10, 0, 0, 0]);
    assert_eq!(reader.capacity(), 0);
    assert_eq!(reader.buffer(), []);
}

#[tokio::test]
async fn test_buf_reader_pending() {
    let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
    let mut reader = AsyncBufReader::with_chunk_size(3, MaybePending::new(inner));

    let mut buf = [0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 3);
    assert_eq!(buf, [5, 6, 7]);
    assert_eq!(reader.buffer(), []);

    let mut buf = [0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 2);
    assert_eq!(buf, [0, 1]);
    assert_eq!(reader.buffer(), [2]);

    let mut buf = [0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 1);
    assert_eq!(buf, [2]);
    assert_eq!(reader.buffer(), []);

    let mut buf = [0, 0, 0];
    let nread = reader.read(&mut buf).await.unwrap();
    assert_eq!(nread, 2);
    assert_eq!(buf, [3, 4, 0]);
    assert_eq!(reader.buffer(), []);

    assert_eq!(reader.read(&mut buf).await.unwrap(), 0);
}

#[tokio::test]
async fn test_buf_reader_cancel_safety() {
    let buffer: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4, 11, 10];
    let inner = MaybePending::new(buffer);
    let mut reader = AsyncBufReader::with_chunk_size(4, inner);

    // Now try a new peek operation
    let buf = reader.peek(4).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0]);
    assert_eq!(reader.capacity(), 4);
    assert_eq!(reader.buffer(), [5, 6, 7, 0]);

    // Drop future
    {
        let future = reader.peek(8);
        pin!(future);
        let res = poll!(future);
        assert!(res.is_pending());
    }

    // Now try a new peek operation
    let buf = reader.peek(8).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0, 1, 2, 3, 4]);
    assert_eq!(reader.capacity(), 8);
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1, 2, 3, 4]);
}

#[tokio::test]
async fn test_buf_reader_always_pending() {
    let buffer: &[u8] = &[5, 6, 7, 0];
    let inner = AlwaysPending::new(buffer);
    let mut reader = AsyncBufReader::with_chunk_size(10, inner);

    // Peek once
    let buf = reader.peek(10).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0]);
    assert_eq!(reader.capacity(), 10);
    assert_eq!(reader.buffer(), [5, 6, 7, 0]);

    // Peek again future
    let future = reader.peek(10);
    pin!(future);
    let res = poll!(future);
    assert!(res.is_pending());
}

#[tokio::test]
async fn test_buf_reader_eof() {
    let buffer: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4, 11, 10];
    let inner = MaybePending::new(buffer);
    let mut reader = AsyncBufReader::with_chunk_size(20, inner);

    // Peek once
    let buf = reader.peek(20).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);
    assert_eq!(reader.capacity(), 20);
    assert!(!reader.ended());
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);

    // Peek once
    let buf = reader.peek(20).await.unwrap();
    assert_eq!(buf, [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);
    assert_eq!(reader.capacity(), 20);
    assert!(reader.ended());
    assert_eq!(reader.buffer(), [5, 6, 7, 0, 1, 2, 3, 4, 11, 10]);
}