Adding the `into_stdio` make async-process more flexible. (#13)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "async-process"
-version = "1.0.2"
+version = "1.1.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2018"
 description = "Async interface for working with processes"
@@ -19,6 +19,7 @@ once_cell = "1.4.1"
 
 [target.'cfg(unix)'.dependencies]
 async-io = "1.0.0"
+libc = "0.2.88"
 
 [target.'cfg(unix)'.dependencies.signal-hook]
 version = "0.3.0"
@@ -33,5 +34,5 @@ version = "0.3.9"
 default-features = false
 features = [
   "winbase",
-  "winnt",
+  "winnt"
 ]

src/lib.rs

@@ -60,8 +60,12 @@ use std::thread;
 
 #[cfg(unix)]
 use async_io::Async;
+#[cfg(unix)]
+use std::os::unix::io::AsRawFd;
+
 #[cfg(windows)]
 use blocking::Unblock;
+
 use event_listener::Event;
 use futures_lite::{future, io, prelude::*};
 use once_cell::sync::Lazy;
@@ -443,6 +447,38 @@ pub struct ChildStdin(
     #[cfg(unix)] Async<std::process::ChildStdin>,
 );
 
+impl ChildStdin {
+    /// Convert async_process::ChildStdin into std::process::Stdio.
+    ///
+    /// You can use it to associate to the next process.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # futures_lite::future::block_on(async {
+    /// use async_process::Command;
+    /// use std::process::Stdio;
+    ///
+    /// let mut ls_child = Command::new("ls").stdin(Stdio::piped()).spawn()?;
+    /// let stdio:Stdio = ls_child.stdin.take().unwrap().into_stdio().await?;
+    ///
+    /// let mut echo_child = Command::new("echo").arg("./").stdout(stdio).spawn()?;
+    ///
+    /// # std::io::Result::Ok(()) });
+    /// ```
+    pub async fn into_stdio(self) -> io::Result<std::process::Stdio> {
+        cfg_if::cfg_if! {
+            if #[cfg(windows)] {
+                Ok(self.0.into_inner().await.into())
+            } else if #[cfg(unix)] {
+                let child_stdin = self.0.into_inner()?;
+                blocking_fd(child_stdin.as_raw_fd())?;
+                Ok(child_stdin.into())
+            }
+        }
+    }
+}
+
 impl io::AsyncWrite for ChildStdin {
     fn poll_write(
         mut self: Pin<&mut Self>,
@@ -470,6 +506,41 @@ pub struct ChildStdout(
     #[cfg(unix)] Async<std::process::ChildStdout>,
 );
 
+impl ChildStdout {
+    /// Convert async_process::ChildStdout into std::process::Stdio.
+    ///
+    /// You can use it to associate to the next process.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # futures_lite::future::block_on(async {
+    /// use async_process::Command;
+    /// use std::process::Stdio;
+    /// use std::io::Read;
+    /// use futures_lite::AsyncReadExt;
+    ///
+    /// let mut ls_child = Command::new("ls").stdout(Stdio::piped()).spawn()?;
+    /// let stdio:Stdio = ls_child.stdout.take().unwrap().into_stdio().await?;
+    ///
+    /// let mut echo_child = Command::new("echo").stdin(stdio).stdout(Stdio::piped()).spawn()?;
+    /// let mut buf = vec![];
+    /// echo_child.stdout.take().unwrap().read(&mut buf).await;
+    /// # std::io::Result::Ok(()) });
+    /// ```
+    pub async fn into_stdio(self) -> io::Result<std::process::Stdio> {
+        cfg_if::cfg_if! {
+            if #[cfg(windows)] {
+                Ok(self.0.into_inner().await.into())
+            } else if #[cfg(unix)] {
+                let child_stdout = self.0.into_inner()?;
+                blocking_fd(child_stdout.as_raw_fd())?;
+                Ok(child_stdout.into())
+            }
+        }
+    }
+}
+
 impl io::AsyncRead for ChildStdout {
     fn poll_read(
         mut self: Pin<&mut Self>,
@@ -489,6 +560,37 @@ pub struct ChildStderr(
     #[cfg(unix)] Async<std::process::ChildStderr>,
 );
 
+impl ChildStderr {
+    /// Convert async_process::ChildStderr into std::process::Stdio.
+    ///
+    /// You can use it to associate to the next process.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # futures_lite::future::block_on(async {
+    /// use async_process::Command;
+    /// use std::process::Stdio;
+    ///
+    /// let mut ls_child = Command::new("ls").arg("x").stderr(Stdio::piped()).spawn()?;
+    /// let stdio:Stdio = ls_child.stderr.take().unwrap().into_stdio().await?;
+    ///
+    /// let mut echo_child = Command::new("echo").stdin(stdio).spawn()?;
+    /// # std::io::Result::Ok(()) });
+    /// ```
+    pub async fn into_stdio(self) -> io::Result<std::process::Stdio> {
+        cfg_if::cfg_if! {
+            if #[cfg(windows)] {
+                Ok(self.0.into_inner().await.into())
+            } else if #[cfg(unix)] {
+                let child_stderr = self.0.into_inner()?;
+                blocking_fd(child_stderr.as_raw_fd())?;
+                Ok(child_stderr.into())
+            }
+        }
+    }
+}
+
 impl io::AsyncRead for ChildStderr {
     fn poll_read(
         mut self: Pin<&mut Self>,
@@ -837,3 +939,63 @@ impl Command {
         async { child?.output().await }
     }
 }
+
+#[cfg(unix)]
+/// Moves `Fd` out of nonblocking mode.
+fn blocking_fd(fd: std::os::unix::io::RawFd) -> io::Result<()> {
+    // Helper macro to execute a system call that returns an `io::Result`.
+    macro_rules! syscall {
+    ($fn: ident ( $($arg: expr),* $(,)* ) ) => {{
+            let res = unsafe { libc::$fn($($arg, )*) };
+            if res == -1 {
+                return Err(std::io::Error::last_os_error());
+            } else {
+                res
+            }
+        }};
+    }
+
+    let res = syscall!(fcntl(fd, libc::F_GETFL));
+    syscall!(fcntl(fd, libc::F_SETFL, res & !libc::O_NONBLOCK));
+
+    Ok(())
+}
+
+#[cfg(unix)]
+mod test {
+
+    #[test]
+    fn test_into_inner() {
+        futures_lite::future::block_on(async {
+            use crate::Command;
+
+            use std::io::Result;
+            use std::process::Stdio;
+            use std::str::from_utf8;
+
+            use futures_lite::AsyncReadExt;
+
+            let mut ls_child = Command::new("cat")
+                .arg("Cargo.toml")
+                .stdout(Stdio::piped())
+                .spawn()?;
+
+            let stdio: Stdio = ls_child.stdout.take().unwrap().into_stdio().await?;
+
+            let mut echo_child = Command::new("grep")
+                .arg("async")
+                .stdin(stdio)
+                .stdout(Stdio::piped())
+                .spawn()?;
+
+            let mut buf = vec![];
+            let mut stdout = echo_child.stdout.take().unwrap();
+
+            stdout.read_to_end(&mut buf).await?;
+            dbg!(from_utf8(&buf).unwrap_or(""));
+
+            Result::Ok(())
+        })
+        .unwrap();
+    }
+}