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    use crate::io::blocking::Blocking;
    use crate::io::stdio_common::SplitByUtf8BoundaryIfWindows;
    use crate::io::AsyncWrite;

    use std::io;
    use std::pin::Pin;
    use std::task::Context;
    use std::task::Poll;

    cfg_io_std! {
        /// A handle to the standard error stream of a process.
        ///
        /// Concurrent writes to stderr must be executed with care: Only individual
        /// writes to this [`AsyncWrite`] are guaranteed to be intact. In particular
        /// you should be aware that writes using [`write_all`] are not guaranteed
        /// to occur as a single write, so multiple threads writing data with
        /// [`write_all`] may result in interleaved output.
        ///
        /// Created by the [`stderr`] function.
        ///
        /// [`stderr`]: stderr()
        /// [`AsyncWrite`]: AsyncWrite
        /// [`write_all`]: crate::io::AsyncWriteExt::write_all()
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::{self, AsyncWriteExt};
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let mut stderr = io::stdout();
        ///     stderr.write_all(b"Print some error here.").await?;
        ///     Ok(())
        /// }
        /// ```
        #[derive(Debug)]
        pub struct Stderr {
            std: SplitByUtf8BoundaryIfWindows<Blocking<std::io::Stderr>>,
        }

        /// Constructs a new handle to the standard error of the current process.
        ///
        /// The returned handle allows writing to standard error from the within the
        /// Tokio runtime.
        ///
        /// Concurrent writes to stderr must be executed with care: Only individual
        /// writes to this [`AsyncWrite`] are guaranteed to be intact. In particular
        /// you should be aware that writes using [`write_all`] are not guaranteed
        /// to occur as a single write, so multiple threads writing data with
        /// [`write_all`] may result in interleaved output.
        ///
        /// [`AsyncWrite`]: AsyncWrite
        /// [`write_all`]: crate::io::AsyncWriteExt::write_all()
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::{self, AsyncWriteExt};
        ///
        /// #[tokio::main]
        /// async fn main() -> io::Result<()> {
        ///     let mut stderr = io::stderr();
        ///     stderr.write_all(b"Print some error here.").await?;
        ///     Ok(())
        /// }
        /// ```
        pub fn stderr() -> Stderr {
            let std = io::stderr();
            Stderr {
                std: SplitByUtf8BoundaryIfWindows::new(Blocking::new(std)),
            }
        }
    }

    #[cfg(unix)]
    impl std::os::unix::io::AsRawFd for Stderr {
        fn as_raw_fd(&self) -> std::os::unix::io::RawFd {
            std::io::stderr().as_raw_fd()
        }
    }

    #[cfg(windows)]
    impl std::os::windows::io::AsRawHandle for Stderr {
        fn as_raw_handle(&self) -> std::os::windows::io::RawHandle {
            std::io::stderr().as_raw_handle()
        }
    }

    impl AsyncWrite for Stderr {
        fn poll_write(
            mut self: Pin<&mut Self>,
            cx: &mut Context<'_>,
            buf: &[u8],
        ) -> Poll<io::Result<usize>> {
            Pin::new(&mut self.std).poll_write(cx, buf)
        }

        fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
            Pin::new(&mut self.std).poll_flush(cx)
        }

        fn poll_shutdown(
            mut self: Pin<&mut Self>,
            cx: &mut Context<'_>,
        ) -> Poll<Result<(), io::Error>> {
            Pin::new(&mut self.std).poll_shutdown(cx)
        }
    }