use std::collections::VecDeque;
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll};
use async_trait::async_trait;
use bytes::Bytes;
use log::trace;
use futures::AsyncWriteExt;
use kuska_handshake::async_std::BoxStreamWrite;
use tokio::sync::mpsc;
use crate::error::*;
use crate::message::*;
use crate::stream::*;
// Messages are sent by chunks
// Chunk format:
// - u32 BE: request id (same for request and response)
// - u16 BE: chunk length, possibly with CHUNK_HAS_CONTINUATION flag
// when this is not the last chunk of the message
// - [u8; chunk_length] chunk data
pub(crate) type RequestID = u32;
pub(crate) type ChunkLength = u16;
pub(crate) const MAX_CHUNK_LENGTH: ChunkLength = 0x3FF0;
pub(crate) const ERROR_MARKER: ChunkLength = 0x4000;
pub(crate) const CHUNK_HAS_CONTINUATION: ChunkLength = 0x8000;
struct SendQueue {
items: Vec<(u8, VecDeque<SendQueueItem>)>,
}
struct SendQueueItem {
id: RequestID,
prio: RequestPriority,
data: ByteStreamReader,
}
impl SendQueue {
fn new() -> Self {
Self {
items: Vec::with_capacity(64),
}
}
fn push(&mut self, item: SendQueueItem) {
let prio = item.prio;
let pos_prio = match self.items.binary_search_by(|(p, _)| p.cmp(&prio)) {
Ok(i) => i,
Err(i) => {
self.items.insert(i, (prio, VecDeque::new()));
i
}
};
self.items[pos_prio].1.push_back(item);
}
fn is_empty(&self) -> bool {
self.items.iter().all(|(_k, v)| v.is_empty())
}
// this is like an async fn, but hand implemented
fn next_ready(&mut self) -> SendQueuePollNextReady<'_> {
SendQueuePollNextReady { queue: self }
}
}
struct SendQueuePollNextReady<'a> {
queue: &'a mut SendQueue,
}
impl<'a> futures::Future for SendQueuePollNextReady<'a> {
type Output = (RequestID, DataFrame);
fn poll(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Self::Output> {
for (i, (_prio, items_at_prio)) in self.queue.items.iter_mut().enumerate() {
let mut ready_item = None;
for (j, item) in items_at_prio.iter_mut().enumerate() {
let mut item_reader = item.data.read_exact_or_eos(MAX_CHUNK_LENGTH as usize);
match Pin::new(&mut item_reader).poll(ctx) {
Poll::Pending => (),
Poll::Ready(ready_v) => {
ready_item = Some((j, ready_v));
break;
}
}
}
if let Some((j, bytes_or_err)) = ready_item {
let item = items_at_prio.remove(j).unwrap();
let id = item.id;
let eos = item.data.eos();
let data_frame = match bytes_or_err {
Ok(bytes) => {
trace!(
"send queue poll next ready: id {} eos {:?} bytes {}",
id,
eos,
bytes.len()
);
DataFrame::Data(bytes, !eos)
}
Err(e) => DataFrame::Error(match e {
ReadExactError::Stream(code) => {
trace!(
"send queue poll next ready: id {} eos {:?} ERROR {}",
id,
eos,
code
);
code
}
_ => unreachable!(),
}),
};
if !eos && !matches!(data_frame, DataFrame::Error(_)) {
items_at_prio.push_back(item);
} else if items_at_prio.is_empty() {
self.queue.items.remove(i);
}
return Poll::Ready((id, data_frame));
}
}
// If the queue is empty, this futures is eternally pending.
// This is ok because we use it in a select with another future
// that can interrupt it.
Poll::Pending
}
}
enum DataFrame {
/// a fixed size buffer containing some data + a boolean indicating whether
/// there may be more data comming from this stream. Can be used for some
/// optimization. It's an error to set it to false if there is more data, but it is correct
/// (albeit sub-optimal) to set it to true if there is nothing coming after
Data(Bytes, bool),
/// An error code automatically signals the end of the stream
Error(u8),
}
impl DataFrame {
fn header(&self) -> [u8; 2] {
let header_u16 = match self {
DataFrame::Data(data, false) => data.len() as u16,
DataFrame::Data(data, true) => data.len() as u16 | CHUNK_HAS_CONTINUATION,
DataFrame::Error(e) => *e as u16 | ERROR_MARKER,
};
ChunkLength::to_be_bytes(header_u16)
}
fn data(&self) -> &[u8] {
match self {
DataFrame::Data(ref data, _) => &data[..],
DataFrame::Error(_) => &[],
}
}
}
/// The SendLoop trait, which is implemented both by the client and the server
/// connection objects (ServerConna and ClientConn) adds a method `.send_loop()`
/// that takes a channel of messages to send and an asynchronous writer,
/// and sends messages from the channel to the async writer, putting them in a queue
/// before being sent and doing the round-robin sending strategy.
///
/// The `.send_loop()` exits when the sending end of the channel is closed,
/// or if there is an error at any time writing to the async writer.
#[async_trait]
pub(crate) trait SendLoop: Sync {
async fn send_loop<W>(
self: Arc<Self>,
mut msg_recv: mpsc::UnboundedReceiver<(RequestID, RequestPriority, ByteStream)>,
mut write: BoxStreamWrite<W>,
) -> Result<(), Error>
where
W: AsyncWriteExt + Unpin + Send + Sync,
{
let mut sending = SendQueue::new();
let mut should_exit = false;
while !should_exit || !sending.is_empty() {
let recv_fut = msg_recv.recv();
futures::pin_mut!(recv_fut);
let send_fut = sending.next_ready();
// recv_fut is cancellation-safe according to tokio doc,
// send_fut is cancellation-safe as implemented above?
use futures::future::Either;
match futures::future::select(recv_fut, send_fut).await {
Either::Left((sth, _send_fut)) => {
if let Some((id, prio, data)) = sth {
trace!("send_loop: add stream {} to send", id);
sending.push(SendQueueItem {
id,
prio,
data: ByteStreamReader::new(data),
});
} else {
should_exit = true;
};
}
Either::Right(((id, data), _recv_fut)) => {
trace!(
"send_loop: id {}, send {} bytes, header_size {}",
id,
data.data().len(),
hex::encode(data.header())
);
let header_id = RequestID::to_be_bytes(id);
write.write_all(&header_id[..]).await?;
write.write_all(&data.header()).await?;
write.write_all(data.data()).await?;
write.flush().await?;
}
}
}
let _ = write.goodbye().await;
Ok(())
}
}
