tokio/io/
stderr.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
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)]
mod sys {
    use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, RawFd};

    use super::Stderr;

    impl AsRawFd for Stderr {
        fn as_raw_fd(&self) -> RawFd {
            std::io::stderr().as_raw_fd()
        }
    }

    impl AsFd for Stderr {
        fn as_fd(&self) -> BorrowedFd<'_> {
            unsafe { BorrowedFd::borrow_raw(self.as_raw_fd()) }
        }
    }
}

cfg_windows! {
    use crate::os::windows::io::{AsHandle, BorrowedHandle, AsRawHandle, RawHandle};

    impl AsRawHandle for Stderr {
        fn as_raw_handle(&self) -> RawHandle {
            std::io::stderr().as_raw_handle()
        }
    }

    impl AsHandle for Stderr {
        fn as_handle(&self) -> BorrowedHandle<'_> {
            unsafe { BorrowedHandle::borrow_raw(self.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)
    }
}