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    use crate::hpack;

    use bytes::Bytes;

    use std::fmt;

    /// A helper macro that unpacks a sequence of 4 bytes found in the buffer with
    /// the given identifier, starting at the given offset, into the given integer
    /// type. Obviously, the integer type should be able to support at least 4
    /// bytes.
    ///
    /// # Examples
    ///
    /// ```rust
    /// let buf: [u8; 4] = [0, 0, 0, 1];
    /// assert_eq!(1u32, unpack_octets_4!(buf, 0, u32));
    /// ```
    #[macro_escape]
    macro_rules! unpack_octets_4 {
        // TODO: Get rid of this macro
        ($buf:expr, $offset:expr, $tip:ty) => {
            (($buf[$offset + 0] as $tip) << 24)
                | (($buf[$offset + 1] as $tip) << 16)
                | (($buf[$offset + 2] as $tip) << 8)
                | (($buf[$offset + 3] as $tip) << 0)
        };
    }

    mod data;
    mod go_away;
    mod head;
    mod headers;
    mod ping;
    mod priority;
    mod reason;
    mod reset;
    mod settings;
    mod stream_id;
    mod util;
    mod window_update;

    pub use self::data::Data;
    pub use self::go_away::GoAway;
    pub use self::head::{Head, Kind};
    pub use self::headers::{
        parse_u64, Continuation, Headers, Pseudo, PushPromise, PushPromiseHeaderError,
    };
    pub use self::ping::Ping;
    pub use self::priority::{Priority, StreamDependency};
    pub use self::reason::Reason;
    pub use self::reset::Reset;
    pub use self::settings::Settings;
    pub use self::stream_id::{StreamId, StreamIdOverflow};
    pub use self::window_update::WindowUpdate;

    #[cfg(feature = "unstable")]
    pub use crate::hpack::BytesStr;

    // Re-export some constants

    pub use self::settings::{
        DEFAULT_INITIAL_WINDOW_SIZE, DEFAULT_MAX_FRAME_SIZE, DEFAULT_SETTINGS_HEADER_TABLE_SIZE,
        MAX_INITIAL_WINDOW_SIZE, MAX_MAX_FRAME_SIZE,
    };

    pub type FrameSize = u32;

    pub const HEADER_LEN: usize = 9;

    #[derive(Eq, PartialEq)]
    pub enum Frame<T = Bytes> {
        Data(Data<T>),
        Headers(Headers),
        Priority(Priority),
        PushPromise(PushPromise),
        Settings(Settings),
        Ping(Ping),
        GoAway(GoAway),
        WindowUpdate(WindowUpdate),
        Reset(Reset),
    }

    impl<T> Frame<T> {
        pub fn map<F, U>(self, f: F) -> Frame<U>
        where
            F: FnOnce(T) -> U,
        {
            use self::Frame::*;

            match self {
                Data(frame) => frame.map(f).into(),
                Headers(frame) => frame.into(),
                Priority(frame) => frame.into(),
                PushPromise(frame) => frame.into(),
                Settings(frame) => frame.into(),
                Ping(frame) => frame.into(),
                GoAway(frame) => frame.into(),
                WindowUpdate(frame) => frame.into(),
                Reset(frame) => frame.into(),
            }
        }
    }

    impl<T> fmt::Debug for Frame<T> {
        fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
            use self::Frame::*;

            match *self {
                Data(ref frame) => fmt::Debug::fmt(frame, fmt),
                Headers(ref frame) => fmt::Debug::fmt(frame, fmt),
                Priority(ref frame) => fmt::Debug::fmt(frame, fmt),
                PushPromise(ref frame) => fmt::Debug::fmt(frame, fmt),
                Settings(ref frame) => fmt::Debug::fmt(frame, fmt),
                Ping(ref frame) => fmt::Debug::fmt(frame, fmt),
                GoAway(ref frame) => fmt::Debug::fmt(frame, fmt),
                WindowUpdate(ref frame) => fmt::Debug::fmt(frame, fmt),
                Reset(ref frame) => fmt::Debug::fmt(frame, fmt),
            }
        }
    }

    /// Errors that can occur during parsing an HTTP/2 frame.
    #[derive(Debug, Clone, PartialEq, Eq)]
    pub enum Error {
        /// A length value other than 8 was set on a PING message.
        BadFrameSize,

        /// The padding length was larger than the frame-header-specified
        /// length of the payload.
        TooMuchPadding,

        /// An invalid setting value was provided
        InvalidSettingValue,

        /// An invalid window update value
        InvalidWindowUpdateValue,

        /// The payload length specified by the frame header was not the
        /// value necessary for the specific frame type.
        InvalidPayloadLength,

        /// Received a payload with an ACK settings frame
        InvalidPayloadAckSettings,

        /// An invalid stream identifier was provided.
        ///
        /// This is returned if a SETTINGS or PING frame is received with a stream
        /// identifier other than zero.
        InvalidStreamId,

        /// A request or response is malformed.
        MalformedMessage,

        /// An invalid stream dependency ID was provided
        ///
        /// This is returned if a HEADERS or PRIORITY frame is received with an
        /// invalid stream identifier.
        InvalidDependencyId,

        /// Failed to perform HPACK decoding
        Hpack(hpack::DecoderError),
    }