rust-libp2p/libp2p-swarm/src/muxing.rs

// Copyright 2017 Parity Technologies (UK) Ltd.
//
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use futures::future::{Future, FutureResult, ok};
use std::io::Error as IoError;
use tokio_io::{AsyncRead, AsyncWrite};

/// Implemented on objects that can be turned into a substream.
///
/// > **Note**: The methods of this trait consume the object, but if the object implements `Clone`
/// >           then you can clone it and keep the original in order to open additional substreams.
pub trait StreamMuxer {
    /// Type of the object that represents the raw substream where data can be read and written.
    type Substream: AsyncRead + AsyncWrite;
    /// Future that will be resolved when a new incoming substream is open.
    type InboundSubstream: Future<Item = Self::Substream, Error = IoError>;
    /// Future that will be resolved when the outgoing substream is open.
    type OutboundSubstream: Future<Item = Self::Substream, Error = IoError>;

    /// Produces a future that will be resolved when a new incoming substream arrives.
    fn inbound(self) -> Self::InboundSubstream;

    /// Opens a new outgoing substream, and produces a future that will be resolved when it becomes
    /// available.
    fn outbound(self) -> Self::OutboundSubstream;
}

impl<T> StreamMuxer for T where T: AsyncRead + AsyncWrite {
    type Substream = Self;
    type InboundSubstream = FutureResult<Self, IoError>;       // TODO: use !
    type OutboundSubstream = FutureResult<Self, IoError>;      // TODO: use !

    #[inline]
    fn inbound(self) -> Self::InboundSubstream {
        ok(self)
    }

    #[inline]
    fn outbound(self) -> Self::OutboundSubstream {
        ok(self)
    }
}