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    #![cfg_attr(not(feature = "net"), allow(unreachable_pub))]

    use std::fmt;
    use std::ops;

    const READABLE: usize = 0b0_01;
    const WRITABLE: usize = 0b0_10;
    const READ_CLOSED: usize = 0b0_0100;
    const WRITE_CLOSED: usize = 0b0_1000;

    /// Describes the readiness state of an I/O resources.
    ///
    /// `Ready` tracks which operation an I/O resource is ready to perform.
    #[cfg_attr(docsrs, doc(cfg(feature = "net")))]
    #[derive(Clone, Copy, PartialEq, PartialOrd)]
    pub struct Ready(usize);

    impl Ready {
        /// Returns the empty `Ready` set.
        pub const EMPTY: Ready = Ready(0);

        /// Returns a `Ready` representing readable readiness.
        pub const READABLE: Ready = Ready(READABLE);

        /// Returns a `Ready` representing writable readiness.
        pub const WRITABLE: Ready = Ready(WRITABLE);

        /// Returns a `Ready` representing read closed readiness.
        pub const READ_CLOSED: Ready = Ready(READ_CLOSED);

        /// Returns a `Ready` representing write closed readiness.
        pub const WRITE_CLOSED: Ready = Ready(WRITE_CLOSED);

        /// Returns a `Ready` representing readiness for all operations.
        pub const ALL: Ready = Ready(READABLE | WRITABLE | READ_CLOSED | WRITE_CLOSED);

        // Must remain crate-private to avoid adding a public dependency on Mio.
        pub(crate) fn from_mio(event: &mio::event::Event) -> Ready {
            let mut ready = Ready::EMPTY;

            if event.is_readable() {
                ready |= Ready::READABLE;
            }

            if event.is_writable() {
                ready |= Ready::WRITABLE;
            }

            if event.is_read_closed() {
                ready |= Ready::READ_CLOSED;
            }

            if event.is_write_closed() {
                ready |= Ready::WRITE_CLOSED;
            }

            ready
        }

        /// Returns true if `Ready` is the empty set
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::Ready;
        ///
        /// assert!(Ready::EMPTY.is_empty());
        /// assert!(!Ready::READABLE.is_empty());
        /// ```
        pub fn is_empty(self) -> bool {
            self == Ready::EMPTY
        }

        /// Returns `true` if the value includes `readable`
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::Ready;
        ///
        /// assert!(!Ready::EMPTY.is_readable());
        /// assert!(Ready::READABLE.is_readable());
        /// assert!(Ready::READ_CLOSED.is_readable());
        /// assert!(!Ready::WRITABLE.is_readable());
        /// ```
        pub fn is_readable(self) -> bool {
            self.contains(Ready::READABLE) || self.is_read_closed()
        }

        /// Returns `true` if the value includes writable `readiness`
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::Ready;
        ///
        /// assert!(!Ready::EMPTY.is_writable());
        /// assert!(!Ready::READABLE.is_writable());
        /// assert!(Ready::WRITABLE.is_writable());
        /// assert!(Ready::WRITE_CLOSED.is_writable());
        /// ```
        pub fn is_writable(self) -> bool {
            self.contains(Ready::WRITABLE) || self.is_write_closed()
        }

        /// Returns `true` if the value includes read-closed `readiness`
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::Ready;
        ///
        /// assert!(!Ready::EMPTY.is_read_closed());
        /// assert!(!Ready::READABLE.is_read_closed());
        /// assert!(Ready::READ_CLOSED.is_read_closed());
        /// ```
        pub fn is_read_closed(self) -> bool {
            self.contains(Ready::READ_CLOSED)
        }

        /// Returns `true` if the value includes write-closed `readiness`
        ///
        /// # Examples
        ///
        /// ```
        /// use tokio::io::Ready;
        ///
        /// assert!(!Ready::EMPTY.is_write_closed());
        /// assert!(!Ready::WRITABLE.is_write_closed());
        /// assert!(Ready::WRITE_CLOSED.is_write_closed());
        /// ```
        pub fn is_write_closed(self) -> bool {
            self.contains(Ready::WRITE_CLOSED)
        }

        /// Returns true if `self` is a superset of `other`.
        ///
        /// `other` may represent more than one readiness operations, in which case
        /// the function only returns true if `self` contains all readiness
        /// specified in `other`.
        pub(crate) fn contains<T: Into<Self>>(self, other: T) -> bool {
            let other = other.into();
            (self & other) == other
        }

        /// Create a `Ready` instance using the given `usize` representation.
        ///
        /// The `usize` representation must have been obtained from a call to
        /// `Readiness::as_usize`.
        ///
        /// This function is mainly provided to allow the caller to get a
        /// readiness value from an `AtomicUsize`.
        pub(crate) fn from_usize(val: usize) -> Ready {
            Ready(val & Ready::ALL.as_usize())
        }

        /// Returns a `usize` representation of the `Ready` value.
        ///
        /// This function is mainly provided to allow the caller to store a
        /// readiness value in an `AtomicUsize`.
        pub(crate) fn as_usize(self) -> usize {
            self.0
        }
    }

    cfg_io_readiness! {
        use crate::io::Interest;

        impl Ready {
            pub(crate) fn from_interest(interest: Interest) -> Ready {
                let mut ready = Ready::EMPTY;

                if interest.is_readable() {
                    ready |= Ready::READABLE;
                    ready |= Ready::READ_CLOSED;
                }

                if interest.is_writable() {
                    ready |= Ready::WRITABLE;
                    ready |= Ready::WRITE_CLOSED;
                }

                ready
            }

            pub(crate) fn intersection(self, interest: Interest) -> Ready {
                Ready(self.0 & Ready::from_interest(interest).0)
            }

            pub(crate) fn satisfies(self, interest: Interest) -> bool {
                self.0 & Ready::from_interest(interest).0 != 0
            }
        }
    }

    impl ops::BitOr<Ready> for Ready {
        type Output = Ready;

        #[inline]
        fn bitor(self, other: Ready) -> Ready {
            Ready(self.0 | other.0)
        }
    }

    impl ops::BitOrAssign<Ready> for Ready {
        #[inline]
        fn bitor_assign(&mut self, other: Ready) {
            self.0 |= other.0;
        }
    }

    impl ops::BitAnd<Ready> for Ready {
        type Output = Ready;

        #[inline]
        fn bitand(self, other: Ready) -> Ready {
            Ready(self.0 & other.0)
        }
    }

    impl ops::Sub<Ready> for Ready {
        type Output = Ready;

        #[inline]
        fn sub(self, other: Ready) -> Ready {
            Ready(self.0 & !other.0)
        }
    }

    impl fmt::Debug for Ready {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            fmt.debug_struct("Ready")
                .field("is_readable", &self.is_readable())
                .field("is_writable", &self.is_writable())
                .field("is_read_closed", &self.is_read_closed())
                .field("is_write_closed", &self.is_write_closed())
                .finish()
        }
    }