# upgrade.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/hyper-0.14.4/src/upgrade.rs`.
Keywords: rust, rustlang, rust-lang

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    //! HTTP Upgrades
    //!
    //! See [this example][example] showing how upgrades work with both
    //! Clients and Servers.
    //!
    //! [example]: https://github.com/hyperium/hyper/blob/master/examples/upgrades.rs

    use std::any::TypeId;
    use std::error::Error as StdError;
    use std::fmt;
    use std::io;
    use std::marker::Unpin;

    use bytes::Bytes;
    use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
    use tokio::sync::oneshot;

    use crate::common::io::Rewind;
    use crate::common::{task, Future, Pin, Poll};

    /// An upgraded HTTP connection.
    ///
    /// This type holds a trait object internally of the original IO that
    /// was used to speak HTTP before the upgrade. It can be used directly
    /// as a `Read` or `Write` for convenience.
    ///
    /// Alternatively, if the exact type is known, this can be deconstructed
    /// into its parts.
    pub struct Upgraded {
        io: Rewind<Box<dyn Io + Send>>,
    }

    /// A future for a possible HTTP upgrade.
    ///
    /// If no upgrade was available, or it doesn't succeed, yields an `Error`.
    pub struct OnUpgrade {
        rx: Option<oneshot::Receiver<crate::Result<Upgraded>>>,
    }

    /// The deconstructed parts of an [`Upgraded`](Upgraded) type.
    ///
    /// Includes the original IO type, and a read buffer of bytes that the
    /// HTTP state machine may have already read before completing an upgrade.
    #[derive(Debug)]
    pub struct Parts<T> {
        /// The original IO object used before the upgrade.
        pub io: T,
        /// A buffer of bytes that have been read but not processed as HTTP.
        ///
        /// For instance, if the `Connection` is used for an HTTP upgrade request,
        /// it is possible the server sent back the first bytes of the new protocol
        /// along with the response upgrade.
        ///
        /// You will want to check for any existing bytes if you plan to continue
        /// communicating on the IO object.
        pub read_buf: Bytes,
        _inner: (),
    }

    /// Gets a pending HTTP upgrade from this message.
    pub fn on<T: sealed::CanUpgrade>(msg: T) -> OnUpgrade {
        msg.on_upgrade()
    }

    #[cfg(feature = "http1")]
    pub(super) struct Pending {
        tx: oneshot::Sender<crate::Result<Upgraded>>,
    }

    #[cfg(feature = "http1")]
    pub(super) fn pending() -> (Pending, OnUpgrade) {
        let (tx, rx) = oneshot::channel();
        (Pending { tx }, OnUpgrade { rx: Some(rx) })
    }

    // ===== impl Upgraded =====

    impl Upgraded {
        #[cfg(any(feature = "http1", test))]
        pub(super) fn new<T>(io: T, read_buf: Bytes) -> Self
        where
            T: AsyncRead + AsyncWrite + Unpin + Send + 'static,
        {
            Upgraded {
                io: Rewind::new_buffered(Box::new(io), read_buf),
            }
        }

        /// Tries to downcast the internal trait object to the type passed.
        ///
        /// On success, returns the downcasted parts. On error, returns the
        /// `Upgraded` back.
        pub fn downcast<T: AsyncRead + AsyncWrite + Unpin + 'static>(self) -> Result<Parts<T>, Self> {
            let (io, buf) = self.io.into_inner();
            match io.__hyper_downcast() {
                Ok(t) => Ok(Parts {
                    io: *t,
                    read_buf: buf,
                    _inner: (),
                }),
                Err(io) => Err(Upgraded {
                    io: Rewind::new_buffered(io, buf),
                }),
            }
        }
    }

    impl AsyncRead for Upgraded {
        fn poll_read(
            mut self: Pin<&mut Self>,
            cx: &mut task::Context<'_>,
            buf: &mut ReadBuf<'_>,
        ) -> Poll<io::Result<()>> {
            Pin::new(&mut self.io).poll_read(cx, buf)
        }
    }

    impl AsyncWrite for Upgraded {
        fn poll_write(
            mut self: Pin<&mut Self>,
            cx: &mut task::Context<'_>,
            buf: &[u8],
        ) -> Poll<io::Result<usize>> {
            Pin::new(&mut self.io).poll_write(cx, buf)
        }

        fn poll_write_vectored(
            mut self: Pin<&mut Self>,
            cx: &mut task::Context<'_>,
            bufs: &[io::IoSlice<'_>],
        ) -> Poll<io::Result<usize>> {
            Pin::new(&mut self.io).poll_write_vectored(cx, bufs)
        }

        fn poll_flush(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<io::Result<()>> {
            Pin::new(&mut self.io).poll_flush(cx)
        }

        fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<io::Result<()>> {
            Pin::new(&mut self.io).poll_shutdown(cx)
        }

        fn is_write_vectored(&self) -> bool {
            self.io.is_write_vectored()
        }
    }

    impl fmt::Debug for Upgraded {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.debug_struct("Upgraded").finish()
        }
    }

    // ===== impl OnUpgrade =====

    impl OnUpgrade {
        pub(super) fn none() -> Self {
            OnUpgrade { rx: None }
        }

        #[cfg(feature = "http1")]
        pub(super) fn is_none(&self) -> bool {
            self.rx.is_none()
        }
    }

    impl Future for OnUpgrade {
        type Output = Result<Upgraded, crate::Error>;

        fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
            match self.rx {
                Some(ref mut rx) => Pin::new(rx).poll(cx).map(|res| match res {
                    Ok(Ok(upgraded)) => Ok(upgraded),
                    Ok(Err(err)) => Err(err),
                    Err(_oneshot_canceled) => Err(crate::Error::new_canceled().with(UpgradeExpected)),
                }),
                None => Poll::Ready(Err(crate::Error::new_user_no_upgrade())),
            }
        }
    }

    impl fmt::Debug for OnUpgrade {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.debug_struct("OnUpgrade").finish()
        }
    }

    // ===== impl Pending =====

    #[cfg(feature = "http1")]
    impl Pending {
        pub(super) fn fulfill(self, upgraded: Upgraded) {
            trace!("pending upgrade fulfill");
            let _ = self.tx.send(Ok(upgraded));
        }

        /// Don't fulfill the pending Upgrade, but instead signal that
        /// upgrades are handled manually.
        pub(super) fn manual(self) {
            trace!("pending upgrade handled manually");
            let _ = self.tx.send(Err(crate::Error::new_user_manual_upgrade()));
        }
    }

    // ===== impl UpgradeExpected =====

    /// Error cause returned when an upgrade was expected but canceled
    /// for whatever reason.
    ///
    /// This likely means the actual `Conn` future wasn't polled and upgraded.
    #[derive(Debug)]
    struct UpgradeExpected;

    impl fmt::Display for UpgradeExpected {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.write_str("upgrade expected but not completed")
        }
    }

    impl StdError for UpgradeExpected {}

    // ===== impl Io =====

    pub(super) trait Io: AsyncRead + AsyncWrite + Unpin + 'static {
        fn __hyper_type_id(&self) -> TypeId {
            TypeId::of::<Self>()
        }
    }

    impl<T: AsyncRead + AsyncWrite + Unpin + 'static> Io for T {}

    impl dyn Io + Send {
        fn __hyper_is<T: Io>(&self) -> bool {
            let t = TypeId::of::<T>();
            self.__hyper_type_id() == t
        }

        fn __hyper_downcast<T: Io>(self: Box<Self>) -> Result<Box<T>, Box<Self>> {
            if self.__hyper_is::<T>() {
                // Taken from `std::error::Error::downcast()`.
                unsafe {
                    let raw: *mut dyn Io = Box::into_raw(self);
                    Ok(Box::from_raw(raw as *mut T))
                }
            } else {
                Err(self)
            }
        }
    }

    mod sealed {
        use super::OnUpgrade;

        pub trait CanUpgrade {
            fn on_upgrade(self) -> OnUpgrade;
        }

        impl CanUpgrade for http::Request<crate::Body> {
            fn on_upgrade(mut self) -> OnUpgrade {
                self.extensions_mut()
                    .remove::<OnUpgrade>()
                    .unwrap_or_else(OnUpgrade::none)
            }
        }

        impl CanUpgrade for &'_ mut http::Request<crate::Body> {
            fn on_upgrade(self) -> OnUpgrade {
                self.extensions_mut()
                    .remove::<OnUpgrade>()
                    .unwrap_or_else(OnUpgrade::none)
            }
        }

        impl CanUpgrade for http::Response<crate::Body> {
            fn on_upgrade(mut self) -> OnUpgrade {
                self.extensions_mut()
                    .remove::<OnUpgrade>()
                    .unwrap_or_else(OnUpgrade::none)
            }
        }

        impl CanUpgrade for &'_ mut http::Response<crate::Body> {
            fn on_upgrade(self) -> OnUpgrade {
                self.extensions_mut()
                    .remove::<OnUpgrade>()
                    .unwrap_or_else(OnUpgrade::none)
            }
        }
    }

    #[cfg(test)]
    mod tests {
        use super::*;

        #[test]
        fn upgraded_downcast() {
            let upgraded = Upgraded::new(Mock, Bytes::new());

            let upgraded = upgraded.downcast::<std::io::Cursor<Vec<u8>>>().unwrap_err();

            upgraded.downcast::<Mock>().unwrap();
        }

        // TODO: replace with tokio_test::io when it can test write_buf
        struct Mock;

        impl AsyncRead for Mock {
            fn poll_read(
                self: Pin<&mut Self>,
                _cx: &mut task::Context<'_>,
                _buf: &mut ReadBuf<'_>,
            ) -> Poll<io::Result<()>> {
                unreachable!("Mock::poll_read")
            }
        }

        impl AsyncWrite for Mock {
            fn poll_write(
                self: Pin<&mut Self>,
                _: &mut task::Context<'_>,
                buf: &[u8],
            ) -> Poll<io::Result<usize>> {
                // panic!("poll_write shouldn't be called");
                Poll::Ready(Ok(buf.len()))
            }

            fn poll_flush(self: Pin<&mut Self>, _cx: &mut task::Context<'_>) -> Poll<io::Result<()>> {
                unreachable!("Mock::poll_flush")
            }

            fn poll_shutdown(
                self: Pin<&mut Self>,
                _cx: &mut task::Context<'_>,
            ) -> Poll<io::Result<()>> {
                unreachable!("Mock::poll_shutdown")
            }
        }
    }