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//! cancelable syscall apis.

use crate::handle::Handle;

/// The returns type of [`WouldBlock`](std::io::ErrorKind::WouldBlock) operations.
pub enum CancelablePoll<T> {
    /// Operation is ready, returns operation result.
    Ready(T),
    /// Operation is pending, returns operation cancel handle.
    ///
    /// When pending handle drops, the syscall implementation should cancel
    /// the pending operation referenced by this handle.
    Pending(Handle),
}

/// Create a ready status of [`CancelablePoll`] from `F: FnOnce() -> T`.
pub fn ready<T, F>(f: F) -> CancelablePoll<T>
where
    F: FnOnce() -> T,
{
    CancelablePoll::Ready(f())
}