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    use crate::frame::*;

    #[derive(Debug, Eq, PartialEq)]
    pub struct Priority {
        stream_id: StreamId,
        dependency: StreamDependency,
    }

    #[derive(Debug, Eq, PartialEq)]
    pub struct StreamDependency {
        /// The ID of the stream dependency target
        dependency_id: StreamId,

        /// The weight for the stream. The value exposed (and set) here is always in
        /// the range [0, 255], instead of [1, 256] (as defined in section 5.3.2.)
        /// so that the value fits into a `u8`.
        weight: u8,

        /// True if the stream dependency is exclusive.
        is_exclusive: bool,
    }

    impl Priority {
        pub fn load(head: Head, payload: &[u8]) -> Result<Self, Error> {
            let dependency = StreamDependency::load(payload)?;

            if dependency.dependency_id() == head.stream_id() {
                return Err(Error::InvalidDependencyId);
            }

            Ok(Priority {
                stream_id: head.stream_id(),
                dependency,
            })
        }
    }

    impl<B> From<Priority> for Frame<B> {
        fn from(src: Priority) -> Self {
            Frame::Priority(src)
        }
    }

    // ===== impl StreamDependency =====

    impl StreamDependency {
        pub fn new(dependency_id: StreamId, weight: u8, is_exclusive: bool) -> Self {
            StreamDependency {
                dependency_id,
                weight,
                is_exclusive,
            }
        }

        pub fn load(src: &[u8]) -> Result<Self, Error> {
            if src.len() != 5 {
                return Err(Error::InvalidPayloadLength);
            }

            // Parse the stream ID and exclusive flag
            let (dependency_id, is_exclusive) = StreamId::parse(&src[..4]);

            // Read the weight
            let weight = src[4];

            Ok(StreamDependency::new(dependency_id, weight, is_exclusive))
        }

        pub fn dependency_id(&self) -> StreamId {
            self.dependency_id
        }
    }