Merge pull request #334 from k-nasa/add_stdin_lock

Locking for stdin

Author: yoshuawuyts

src/io/mod.rs

@@ -282,9 +282,9 @@ pub use read::Read;
 pub use repeat::{repeat, Repeat};
 pub use seek::Seek;
 pub use sink::{sink, Sink};
-pub use stderr::{stderr, Stderr};
-pub use stdin::{stdin, Stdin};
-pub use stdout::{stdout, Stdout};
+pub use stderr::{stderr, Stderr, StderrLock};
+pub use stdin::{stdin, Stdin, StdinLock};
+pub use stdout::{stdout, Stdout, StdoutLock};
 pub use timeout::timeout;
 pub use write::Write;
 

src/io/stderr.rs

@@ -1,10 +1,15 @@
+use std::io::Write as StdWrite;
 use std::pin::Pin;
 use std::sync::Mutex;
 
 use crate::future::Future;
 use crate::io::{self, Write};
 use crate::task::{spawn_blocking, Context, JoinHandle, Poll};
 
+cfg_unstable! {
+    use once_cell::sync::Lazy;
+}
+
 /// Constructs a new handle to the standard error of the current process.
 ///
 /// This function is an async version of [`std::io::stderr`].
@@ -53,6 +58,16 @@ pub fn stderr() -> Stderr {
 #[derive(Debug)]
 pub struct Stderr(Mutex<State>);
 
+/// A locked reference to the Stderr handle.
+/// This handle implements the [`Write`] traits, and is constructed via the [`Stderr::lock`] method.
+///
+/// [`Write`]: trait.Read.html
+/// [`Stderr::lock`]: struct.Stderr.html#method.lock
+#[derive(Debug)]
+pub struct StderrLock<'a>(std::io::StderrLock<'a>);
+
+unsafe impl Send for StderrLock<'_> {}
+
 /// The state of the asynchronous stderr.
 ///
 /// The stderr can be either idle or busy performing an asynchronous operation.
@@ -87,6 +102,35 @@ enum Operation {
     Flush(io::Result<()>),
 }
 
+impl Stderr {
+    /// Locks this handle to the standard error stream, returning a writable guard.
+    ///
+    /// The lock is released when the returned lock goes out of scope. The returned guard also implements the Write trait for writing data.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
+    /// #
+    /// use async_std::io;
+    /// use async_std::prelude::*;
+    ///
+    /// let stderr = io::stderr();
+    /// let mut handle = stderr.lock().await;
+    ///
+    /// handle.write_all(b"hello world").await?;
+    /// #
+    /// # Ok(()) }) }
+    /// ```
+    #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+    #[cfg(any(feature = "unstable", feature = "docs"))]
+    pub async fn lock(&self) -> StderrLock<'static> {
+        static STDERR: Lazy<std::io::Stderr> = Lazy::new(std::io::stderr);
+
+        spawn_blocking(move || StderrLock(STDERR.lock())).await
+    }
+}
+
 impl Write for Stderr {
     fn poll_write(
         mut self: Pin<&mut Self>,
@@ -189,3 +233,21 @@ cfg_windows! {
         }
     }
 }
+
+impl Write for StderrLock<'_> {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        Poll::Ready(self.0.write(buf))
+    }
+
+    fn poll_flush(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(self.0.flush())
+    }
+
+    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        self.poll_flush(cx)
+    }
+}

src/io/stdin.rs

@@ -5,6 +5,10 @@ use crate::future::{self, Future};
 use crate::io::{self, Read};
 use crate::task::{spawn_blocking, Context, JoinHandle, Poll};
 
+cfg_unstable! {
+    use once_cell::sync::Lazy;
+}
+
 /// Constructs a new handle to the standard input of the current process.
 ///
 /// This function is an async version of [`std::io::stdin`].
@@ -54,6 +58,16 @@ pub fn stdin() -> Stdin {
 #[derive(Debug)]
 pub struct Stdin(Mutex<State>);
 
+/// A locked reference to the Stdin handle.
+/// This handle implements the [`Read`] traits, and is constructed via the [`Stdin::lock`] method.
+///
+/// [`Read`]: trait.Read.html
+/// [`Stdin::lock`]: struct.Stdin.html#method.lock
+#[derive(Debug)]
+pub struct StdinLock<'a>(std::io::StdinLock<'a>);
+
+unsafe impl Send for StdinLock<'_> {}
+
 /// The state of the asynchronous stdin.
 ///
 /// The stdin can be either idle or busy performing an asynchronous operation.
@@ -142,6 +156,35 @@ impl Stdin {
         })
         .await
     }
+
+    /// Locks this handle to the standard input stream, returning a readable guard.
+    ///
+    /// The lock is released when the returned lock goes out of scope. The returned guard also implements the Read trait for accessing the underlying data.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
+    /// #
+    /// use async_std::io;
+    /// use crate::async_std::prelude::*;
+    ///
+    /// let mut buffer = String::new();
+    ///
+    /// let stdin = io::stdin();
+    /// let mut handle = stdin.lock().await;
+    ///
+    /// handle.read_to_string(&mut buffer).await?;
+    /// #
+    /// # Ok(()) }) }
+    /// ```
+    #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+    #[cfg(any(feature = "unstable", feature = "docs"))]
+    pub async fn lock(&self) -> StdinLock<'static> {
+        static STDIN: Lazy<std::io::Stdin> = Lazy::new(std::io::stdin);
+
+        spawn_blocking(move || StdinLock(STDIN.lock())).await
+    }
 }
 
 impl Read for Stdin {
@@ -213,3 +256,15 @@ cfg_windows! {
         }
     }
 }
+
+impl Read for StdinLock<'_> {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut [u8],
+    ) -> Poll<io::Result<usize>> {
+        use std::io::Read as StdRead;
+
+        Poll::Ready(self.0.read(buf))
+    }
+}

src/io/stdout.rs

@@ -1,10 +1,15 @@
+use std::io::Write as StdWrite;
 use std::pin::Pin;
 use std::sync::Mutex;
 
 use crate::future::Future;
 use crate::io::{self, Write};
 use crate::task::{spawn_blocking, Context, JoinHandle, Poll};
 
+cfg_unstable! {
+    use once_cell::sync::Lazy;
+}
+
 /// Constructs a new handle to the standard output of the current process.
 ///
 /// This function is an async version of [`std::io::stdout`].
@@ -53,6 +58,16 @@ pub fn stdout() -> Stdout {
 #[derive(Debug)]
 pub struct Stdout(Mutex<State>);
 
+/// A locked reference to the Stderr handle.
+/// This handle implements the [`Write`] traits, and is constructed via the [`Stdout::lock`] method.
+///
+/// [`Write`]: trait.Read.html
+/// [`Stdout::lock`]: struct.Stdout.html#method.lock
+#[derive(Debug)]
+pub struct StdoutLock<'a>(std::io::StdoutLock<'a>);
+
+unsafe impl Send for StdoutLock<'_> {}
+
 /// The state of the asynchronous stdout.
 ///
 /// The stdout can be either idle or busy performing an asynchronous operation.
@@ -87,6 +102,35 @@ enum Operation {
     Flush(io::Result<()>),
 }
 
+impl Stdout {
+    /// Locks this handle to the standard error stream, returning a writable guard.
+    ///
+    /// The lock is released when the returned lock goes out of scope. The returned guard also implements the Write trait for writing data.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
+    /// #
+    /// use async_std::io;
+    /// use async_std::prelude::*;
+    ///
+    /// let stdout = io::stdout();
+    /// let mut handle = stdout.lock().await;
+    ///
+    /// handle.write_all(b"hello world").await?;
+    /// #
+    /// # Ok(()) }) }
+    /// ```
+    #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
+    #[cfg(any(feature = "unstable", feature = "docs"))]
+    pub async fn lock(&self) -> StdoutLock<'static> {
+        static STDOUT: Lazy<std::io::Stdout> = Lazy::new(std::io::stdout);
+
+        spawn_blocking(move || StdoutLock(STDOUT.lock())).await
+    }
+}
+
 impl Write for Stdout {
     fn poll_write(
         mut self: Pin<&mut Self>,
@@ -189,3 +233,21 @@ cfg_windows! {
         }
     }
 }
+
+impl Write for StdoutLock<'_> {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        Poll::Ready(self.0.write(buf))
+    }
+
+    fn poll_flush(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(self.0.flush())
+    }
+
+    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        self.poll_flush(cx)
+    }
+}