rust-libp2p/core/src/muxing.rs

// Copyright 2017 Parity Technologies (UK) Ltd.
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use futures::future::Future;
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.
    ///
    /// A `None` item signals that the underlying resource has been exhausted and
    /// no more substreams can be created.
    type InboundSubstream: Future<Item = Option<Self::Substream>, Error = IoError>;

    /// Future that will be resolved when the outgoing substream is open.
    ///
    /// A `None` item signals that the underlying resource has been exhausted and
    /// no more substreams can be created.
    type OutboundSubstream: Future<Item = Option<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;
}