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//! Unix-specific I/O extensions.

use cfg_if::cfg_if;

cfg_if! {
    if #[cfg(feature = "docs")] {
        /// Raw file descriptors.
        pub type RawFd = std::os::raw::c_int;

        /// A trait to extract the raw unix file descriptor from an underlying
        /// object.
        ///
        /// This is only available on unix platforms and must be imported in order
        /// to call the method. Windows platforms have a corresponding `AsRawHandle`
        /// and `AsRawSocket` set of traits.
        pub trait AsRawFd {
            /// Extracts the raw file descriptor.
            ///
            /// This method does **not** pass ownership of the raw file descriptor
            /// to the caller. The descriptor is only guaranteed to be valid while
            /// the original object has not yet been destroyed.
            fn as_raw_fd(&self) -> RawFd;
        }

        /// A trait to express the ability to construct an object from a raw file
        /// descriptor.
        pub trait FromRawFd {
            /// Constructs a new instance of `Self` from the given raw file
            /// descriptor.
            ///
            /// This function **consumes ownership** of the specified file
            /// descriptor. The returned object will take responsibility for closing
            /// it when the object goes out of scope.
            ///
            /// This function is also unsafe as the primitives currently returned
            /// have the contract that they are the sole owner of the file
            /// descriptor they are wrapping. Usage of this function could
            /// accidentally allow violating this contract which can cause memory
            /// unsafety in code that relies on it being true.
            unsafe fn from_raw_fd(fd: RawFd) -> Self;
        }

        /// A trait to express the ability to consume an object and acquire ownership of
        /// its raw file descriptor.
        pub trait IntoRawFd {
            /// Consumes this object, returning the raw underlying file descriptor.
            ///
            /// This function **transfers ownership** of the underlying file descriptor
            /// to the caller. Callers are then the unique owners of the file descriptor
            /// and must close the descriptor once it's no longer needed.
            fn into_raw_fd(self) -> RawFd;
        }
    } else {
        pub use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
    }
}