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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

//! Process-global interrupt handling
//!
//! This module contains facilities to globally request an interrupt, which will cause supporting computations to
//! abort once it is observed.
//! Such checks for interrupts are provided in custom implementations of various traits to transparently add interrupt
//! support to methods who wouldn't otherwise by injecting it. see [`Read`].

#[cfg(all(feature = "interrupt-handler", not(feature = "disable-interrupts")))]
mod _impl {
    use std::{
        io,
        sync::atomic::{AtomicUsize, Ordering},
    };

    /// Initialize a signal handler to listen to SIGINT and SIGTERM and trigger our [`trigger()`][super::trigger()] that way.
    ///
    /// When `Ctrl+C` is pressed, a message will be sent to `message_channel` to inform the user about it being registered, after all
    /// actually responding to it is implementation dependent and might thus take some time (or not work at all).
    ///
    /// # Note
    ///
    /// This implementation is available only with the **interrupt-handler** feature toggle with the **disable-interrupts** feature disabled.
    pub fn init_handler(mut message_channel: impl io::Write + Send + 'static) {
        ctrlc::set_handler(move || {
            const MESSAGES: &[&str] = &[
                "interrupt requested", 
                "please wait…", 
                "the program will respond soon…", 
                "if the program doesn't respond quickly enough, please let us know here: https://github.com/Byron/gitoxide/issues"
            ];
            static CURRENT_MESSAGE: AtomicUsize = AtomicUsize::new(0);
            if !super::is_triggered() {
                CURRENT_MESSAGE.store(0, Ordering::Relaxed);
            }
            let msg_idx = CURRENT_MESSAGE.fetch_add(1, Ordering::Relaxed);
            super::IS_INTERRUPTED.store(true, Ordering::Relaxed);
            writeln!(message_channel, "{}", MESSAGES[msg_idx % MESSAGES.len()]).ok();
        })
        .expect("it is up to the application to ensure only one interrupt handler is installed, and this function is called only once.")
    }
}
use std::io;
#[cfg(not(feature = "disable-interrupts"))]
use std::sync::atomic::{AtomicBool, Ordering};

#[cfg(any(feature = "disable-interrupts", not(feature = "interrupt-handler")))]
mod _impl {
    use std::io;

    /// Does nothing, as the **disable-interrupts** feature is enabled while the **interrupt-handler** feature is not present.
    pub fn init_handler(_message_channel: impl io::Write + Send + 'static) {}
}
pub use _impl::init_handler;

/// A wrapper for implementors of [`std::io::Read`] or [`std::io::BufRead`] with interrupt support.
///
/// It fails a [read][`std::io::Read::read`] while an interrupt was requested.
pub struct Read<R> {
    /// The actual implementor of [`std::io::Read`] to which interrupt support will be added.
    pub inner: R,
}

impl<R> io::Read for Read<R>
where
    R: io::Read,
{
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        if is_triggered() {
            return Err(io::Error::new(io::ErrorKind::Other, "interrupted by user"));
        }
        self.inner.read(buf)
    }
}

impl<R> io::BufRead for Read<R>
where
    R: io::BufRead,
{
    fn fill_buf(&mut self) -> io::Result<&[u8]> {
        self.inner.fill_buf()
    }

    fn consume(&mut self, amt: usize) {
        self.inner.consume(amt)
    }
}

#[cfg(not(feature = "disable-interrupts"))]
static IS_INTERRUPTED: AtomicBool = AtomicBool::new(false);

/// Returns true if an interrupt is requested.
///
/// Only implemented if the **disable-interrupts** feature toggle is not present.
#[cfg(not(feature = "disable-interrupts"))]
pub fn is_triggered() -> bool {
    IS_INTERRUPTED.load(Ordering::Relaxed)
}

/// Returns always false if the **disable-interrupts** feature is present.
#[cfg(feature = "disable-interrupts")]
pub fn is_triggered() -> bool {
    false
}

/// Trigger an interrupt, signalling to those checking for [`is_triggered()`] to stop what they are doing.
///
/// # Note
/// Only effective if the **disable-interrupts** feature is **not** present.
pub fn trigger() {
    #[cfg(not(feature = "disable-interrupts"))]
    IS_INTERRUPTED.store(true, Ordering::Relaxed);
}
/// Sets the interrupt request to false, thus allowing those checking for [`is_triggered()`] to proceed.
///
/// Call this in code that is able to trigger an interrupt.
/// This may also be performed by the [`ResetOnDrop`] helper to assure the trigger state is returned
/// to its original state.
///
/// # Note
/// Only effective if the **disable-interrupts** feature is **not** present.
pub fn reset() {
    #[cfg(not(feature = "disable-interrupts"))]
    IS_INTERRUPTED.store(false, Ordering::Relaxed);
}

/// Useful if some parts of the program set the interrupt programmatically to cause others to stop, while
/// assuring the interrupt state is reset at the end of the function to avoid other side-effects.
///
/// Note that this is inherently racy and that this will only work deterministically if there is only one
/// top-level function running in a process.
pub struct ResetOnDrop {
    was_interrupted: bool,
}

impl Default for ResetOnDrop {
    fn default() -> Self {
        ResetOnDrop {
            was_interrupted: is_triggered(),
        }
    }
}

impl Drop for ResetOnDrop {
    fn drop(&mut self) {
        if self.was_interrupted {
            trigger()
        } else {
            reset()
        }
    }
}