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add io::cursor

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Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>
This commit is contained in:
Yoshua Wuyts 2019-09-09 00:23:13 +02:00
parent 3054509fd0
commit 0bc39e6e6c
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3 changed files with 267 additions and 4 deletions
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261
src/io/cursor.rs Normal file
View file

@ -0,0 +1,261 @@
use futures_io::{AsyncRead, AsyncSeek, AsyncWrite};
use std::io::{self, IoSlice, IoSliceMut, SeekFrom};
use std::pin::Pin;
use std::task::{Context, Poll};
/// A `Cursor` wraps an in-memory buffer and provides it with a
/// [`Seek`] implementation.
///
/// `Cursor`s are used with in-memory buffers, anything implementing
/// `AsRef<[u8]>`, to allow them to implement [`Read`] and/or [`Write`],
/// allowing these buffers to be used anywhere you might use a reader or writer
/// that does actual I/O.
///
/// The standard library implements some I/O traits on various types which
/// are commonly used as a buffer, like `Cursor<`[`Vec`]`<u8>>` and
/// `Cursor<`[`&[u8]`][bytes]`>`.
///
/// [`Seek`]: trait.Seek.html
/// [`Read`]: trait.Read.html
/// [`Write`]: trait.Write.html
/// [`Vec`]: https://doc.rust-lang.org/std/vec/struct.Vec.html
/// [bytes]: https://doc.rust-lang.org/std/primitive.slice.html
/// [`File`]: struct.File.html
#[derive(Clone, Debug, Default)]
pub struct Cursor<T> {
inner: std::io::Cursor<T>,
}
impl<T> Cursor<T> {
/// Creates a new cursor wrapping the provided underlying in-memory buffer.
///
/// Cursor initial position is `0` even if underlying buffer (e.g., `Vec`)
/// is not empty. So writing to cursor starts with overwriting `Vec`
/// content, not with appending to it.
///
/// # Examples
///
/// ```
/// use async_std::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
/// ```
pub fn new(inner: T) -> Cursor<T> {
Cursor {
inner: std::io::Cursor::new(inner),
}
}
/// Consumes this cursor, returning the underlying value.
///
/// # Examples
///
/// ```
/// use async_std::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let vec = buff.into_inner();
/// ```
pub fn into_inner(self) -> T {
self.inner.into_inner()
}
/// Gets a reference to the underlying value in this cursor.
///
/// # Examples
///
/// ```
/// use async_std::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let reference = buff.get_ref();
/// ```
pub fn get_ref(&self) -> &T {
self.inner.get_ref()
}
/// Gets a mutable reference to the underlying value in this cursor.
///
/// Care should be taken to avoid modifying the internal I/O state of the
/// underlying value as it may corrupt this cursor's position.
///
/// # Examples
///
/// ```
/// use async_std::io::Cursor;
///
/// let mut buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let reference = buff.get_mut();
/// ```
pub fn get_mut(&mut self) -> &mut T {
self.inner.get_mut()
}
/// Returns the current position of this cursor.
///
/// # Examples
///
/// ```
/// use async_std::io::Cursor;
/// use async_std::io::prelude::*;
/// use async_std::io::SeekFrom;
///
/// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
///
/// assert_eq!(buff.position(), 0);
///
/// buff.seek(SeekFrom::Current(2)).unwrap();
/// assert_eq!(buff.position(), 2);
///
/// buff.seek(SeekFrom::Current(-1)).unwrap();
/// assert_eq!(buff.position(), 1);
/// ```
pub fn position(&self) -> u64 {
self.inner.position()
}
/// Sets the position of this cursor.
///
/// # Examples
///
/// ```
/// use async_std::io::Cursor;
///
/// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
///
/// assert_eq!(buff.position(), 0);
///
/// buff.set_position(2);
/// assert_eq!(buff.position(), 2);
///
/// buff.set_position(4);
/// assert_eq!(buff.position(), 4);
/// ```
pub fn set_position(&mut self, pos: u64) {
self.inner.set_position(pos)
}
}
impl<T> AsyncSeek for Cursor<T>
where
T: AsRef<[u8]> + Unpin,
{
fn poll_seek(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
pos: SeekFrom,
) -> Poll<io::Result<u64>> {
Poll::Ready(io::Seek::seek(&mut self.inner, pos))
}
}
impl<T> AsyncRead for Cursor<T>
where
T: AsRef<[u8]> + Unpin,
{
fn poll_read(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Read::read(&mut self.inner, buf))
}
fn poll_read_vectored(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Read::read_vectored(&mut self.inner, bufs))
}
}
// impl<T> AsyncBufRead for Cursor<T>
// where
// T: AsRef<[u8]> + Unpin,
// {
// fn poll_fill_buf(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
// // let amt = cmp::min(self.position(), self.as_ref().len() as u64);
// // Poll::Ready(Ok(&self.inner.as_ref()[(amt as usize)..]))
// let res = io::BufRead::fill_buf(&mut self.inner);
// Poll::Ready(res)
// }
// fn consume(mut self: Pin<&mut Self>, amt: usize) {
// io::BufRead::consume(&mut self.inner, amt)
// }
// }
impl AsyncWrite for Cursor<&mut [u8]> {
fn poll_write(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Write::write(&mut self.inner, buf))
}
fn poll_write_vectored(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
bufs: &[IoSlice<'_>],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Write::write_vectored(&mut self.inner, bufs))
}
fn poll_flush(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
Poll::Ready(io::Write::flush(&mut self.inner))
}
fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
self.poll_flush(cx)
}
}
impl AsyncWrite for Cursor<&mut Vec<u8>> {
fn poll_write(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Write::write(&mut self.inner, buf))
}
fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
self.poll_flush(cx)
}
fn poll_flush(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
Poll::Ready(io::Write::flush(&mut self.inner))
}
}
impl AsyncWrite for Cursor<Vec<u8>> {
fn poll_write(
mut self: Pin<&mut Self>,
_: &mut Context<'_>,
buf: &[u8],
) -> Poll<io::Result<usize>> {
Poll::Ready(io::Write::write(&mut self.inner, buf))
}
fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
self.poll_flush(cx)
}
fn poll_flush(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<io::Result<()>> {
Poll::Ready(io::Write::flush(&mut self.inner))
}
}

2
src/io/mod.rs
View file

@ -28,6 +28,7 @@ pub use std::io::{Error, ErrorKind, Result, SeekFrom};
pub use buf_read::{BufRead, Lines};
pub use buf_reader::BufReader;
pub use copy::copy;
pub use cursor::Cursor;
pub use empty::{empty, Empty};
pub use read::Read;
pub use seek::Seek;
@ -41,6 +42,7 @@ pub use write::Write;
mod buf_read;
mod buf_reader;
mod copy;
mod cursor;
mod empty;
mod read;
mod seek;

8
src/io/prelude.rs
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@ -9,10 +9,10 @@
//! ```
#[doc(no_inline)]
pub use super::BufRead as _;
pub use super::BufRead;
#[doc(no_inline)]
pub use super::Read as _;
pub use super::Read;
#[doc(no_inline)]
pub use super::Seek as _;
pub use super::Seek;
#[doc(no_inline)]
pub use super::Write as _;
pub use super::Write;