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use futures::{AsyncRead, AsyncWrite, Sink, Stream};
use smallvec::SmallVec;
use crate::{
Negotiated, NegotiationError, ProtocolError,
protocol::{Message, MessageIO, Protocol},
};
use std::{
mem,
pin::Pin,
task::{Context, Poll},
};
#[pin_project::pin_project]
pub struct ListenerSelectFuture<R, N> {
// 使用 smallvec, 在堆上分配内存之前，它会在栈上存储一定数量的元素。
protocols: SmallVec<[(N, Protocol); 8]>,
state: State<R, N>,
}
impl<R, N> ListenerSelectFuture<R, N>
where
R: AsyncRead + AsyncWrite + Unpin,
N: AsRef<str> + Clone,
{
pub fn new<I>(io: R, protocols: I) -> Self
where
I: Iterator<Item = N>,
{
let protocols =
protocols
.into_iter()
.filter_map(|n| match Protocol::try_from(n.as_ref()) {
Ok(p) => Some((n, p)),
Err(_) => None,
});
ListenerSelectFuture {
protocols: SmallVec::from_iter(protocols),
state: State::RecvMessage {
io: MessageIO::new(io),
},
}
}
}
enum State<R, N> {
RecvMessage {
io: MessageIO<R>,
},
SendMessage {
io: MessageIO<R>,
message: Message,
protocol: Option<N>,
},
Flush {
io: MessageIO<R>,
protocol: Option<N>,
},
Done,
}
impl<R, N> Future for ListenerSelectFuture<R, N>
where
R: AsyncRead + AsyncWrite + Unpin,
N: AsRef<str> + Clone,
{
type Output = Result<(N, Negotiated<R>), NegotiationError>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = self.project();
loop {
match mem::replace(this.state, State::Done) {
State::RecvMessage { mut io } => {
let msg = match Pin::new(&mut io).poll_next(cx)? {
Poll::Ready(Some(msg)) => msg,
Poll::Ready(None) => {
return Poll::Ready(Err(NegotiationError::Failed));
}
Poll::Pending => {
*this.state = State::RecvMessage { io };
return Poll::Pending;
}
};
tracing::debug!("Received message: {:?}", msg);
match msg {
Message::Protocol(p) => {
// 查找匹配的协议
let protocol = this.protocols.iter().find_map(|(name, proto)| {
if &p == proto {
Some(name.clone())
} else {
None
}
});
let message = if protocol.is_some() {
Message::Protocol(p.clone())
} else {
Message::NotAvailable
};
*this.state = State::SendMessage {
io,
message,
protocol,
};
}
_ => return Poll::Ready(Err(ProtocolError::InvalidMessage.into())),
}
}
State::SendMessage {
mut io,
message,
protocol,
} => {
match Pin::new(&mut io).poll_ready(cx)? {
Poll::Ready(()) => {}
Poll::Pending => {
*this.state = State::SendMessage {
io,
message,
protocol,
};
return Poll::Pending;
}
};
if let Err(err) = Pin::new(&mut io).start_send(message) {
return Poll::Ready(Err(From::from(err)));
}
*this.state = State::Flush { io, protocol };
}
State::Flush { mut io, protocol } => {
match Pin::new(&mut io).poll_flush(cx)? {
Poll::Ready(()) => {}
Poll::Pending => {
*this.state = State::Flush { io, protocol };
return Poll::Pending;
}
};
if let Some(protocol) = protocol {
// 协议匹配成功，返回 Negotiated
let io = Negotiated::completed(io.into_inner());
tracing::trace!(
"Negotiation successful for protocol: {}",
protocol.as_ref()
);
return Poll::Ready(Ok((protocol, io)));
} else {
// 如果没有匹配的协议，继续接收消息
*this.state = State::RecvMessage { io }
}
}
_ => panic!("Unexpected state in ListenerSelectFuture"),
}
}
}
}