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use std::collections::{HashMap, VecDeque};
use std::sync::Arc;
use log::trace;
use futures::{AsyncReadExt, AsyncWriteExt};
use tokio::sync::mpsc;
use async_trait::async_trait;
use crate::error::*;
/// Priority of a request (click to read more about priorities).
///
/// This priority value is used to priorize messages
/// in the send queue of the client, and their responses in the send queue of the
/// server. Lower values mean higher priority.
///
/// This mechanism is usefull for messages bigger than the maximum chunk size
/// (set at `0x4000` bytes), such as large file transfers.
/// In such case, all of the messages in the send queue with the highest priority
/// will take turns to send individual chunks, in a round-robin fashion.
/// Once all highest priority messages are sent successfully, the messages with
/// the next highest priority will begin being sent in the same way.
///
/// The same priority value is given to a request and to its associated response.
pub type RequestPriority = u8;
/// Priority class: high
pub const PRIO_HIGH: RequestPriority = 0x20;
/// Priority class: normal
pub const PRIO_NORMAL: RequestPriority = 0x40;
/// Priority class: background
pub const PRIO_BACKGROUND: RequestPriority = 0x80;
/// Priority: primary among given class
pub const PRIO_PRIMARY: RequestPriority = 0x00;
/// Priority: secondary among given class (ex: `PRIO_HIGH | PRIO_SECONDARY`)
pub const PRIO_SECONDARY: RequestPriority = 0x01;
const MAX_CHUNK_SIZE: usize = 0x4000;
pub(crate) type RequestID = u16;
struct SendQueueItem {
id: RequestID,
prio: RequestPriority,
data: Vec<u8>,
cursor: usize,
}
struct SendQueue {
items: VecDeque<(u8, VecDeque<SendQueueItem>)>,
}
impl SendQueue {
fn new() -> Self {
Self {
items: VecDeque::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 pop(&mut self) -> Option<SendQueueItem> {
match self.items.pop_front() {
None => None,
Some((prio, mut items_at_prio)) => {
let ret = items_at_prio.pop_front();
if !items_at_prio.is_empty() {
self.items.push_front((prio, items_at_prio));
}
ret.or_else(|| self.pop())
}
}
}
fn is_empty(&self) -> bool {
self.items.iter().all(|(_k, v)| v.is_empty())
}
}
#[async_trait]
pub(crate) trait SendLoop: Sync {
async fn send_loop<W>(
self: Arc<Self>,
mut msg_recv: mpsc::UnboundedReceiver<Option<(RequestID, RequestPriority, Vec<u8>)>>,
mut write: 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() {
if let Ok(sth) = msg_recv.try_recv() {
if let Some((id, prio, data)) = sth {
trace!("send_loop: got {}, {} bytes", id, data.len());
sending.push(SendQueueItem {
id,
prio,
data,
cursor: 0,
});
} else {
should_exit = true;
}
} else if let Some(mut item) = sending.pop() {
trace!(
"send_loop: sending bytes for {} ({} bytes, {} already sent)",
item.id,
item.data.len(),
item.cursor
);
let header_id = u16::to_be_bytes(item.id);
write.write_all(&header_id[..]).await?;
if item.data.len() - item.cursor > MAX_CHUNK_SIZE {
let header_size = u16::to_be_bytes(MAX_CHUNK_SIZE as u16 | 0x8000);
write.write_all(&header_size[..]).await?;
let new_cursor = item.cursor + MAX_CHUNK_SIZE as usize;
write.write_all(&item.data[item.cursor..new_cursor]).await?;
item.cursor = new_cursor;
sending.push(item);
} else {
let send_len = (item.data.len() - item.cursor) as u16;
let header_size = u16::to_be_bytes(send_len);
write.write_all(&header_size[..]).await?;
write.write_all(&item.data[item.cursor..]).await?;
}
write.flush().await?;
} else {
let sth = msg_recv
.recv()
.await
.ok_or_else(|| Error::Message("Connection closed.".into()))?;
if let Some((id, prio, data)) = sth {
trace!("send_loop: got {}, {} bytes", id, data.len());
sending.push(SendQueueItem {
id,
prio,
data,
cursor: 0,
});
} else {
should_exit = true;
}
}
}
Ok(())
}
}
#[async_trait]
pub(crate) trait RecvLoop: Sync + 'static {
// Returns true if we should stop receiving after this
async fn recv_handler(self: Arc<Self>, id: RequestID, msg: Vec<u8>);
async fn recv_loop<R>(self: Arc<Self>, mut read: R) -> Result<(), Error>
where
R: AsyncReadExt + Unpin + Send + Sync,
{
let mut receiving = HashMap::new();
loop {
trace!("recv_loop: reading packet");
let mut header_id = [0u8; 2];
read.read_exact(&mut header_id[..]).await?;
let id = RequestID::from_be_bytes(header_id);
trace!("recv_loop: got header id: {:04x}", id);
let mut header_size = [0u8; 2];
read.read_exact(&mut header_size[..]).await?;
let size = RequestID::from_be_bytes(header_size);
trace!("recv_loop: got header size: {:04x}", size);
let has_cont = (size & 0x8000) != 0;
let size = size & !0x8000;
let mut next_slice = vec![0; size as usize];
read.read_exact(&mut next_slice[..]).await?;
trace!("recv_loop: read {} bytes", next_slice.len());
let mut msg_bytes: Vec<_> = receiving.remove(&id).unwrap_or_default();
msg_bytes.extend_from_slice(&next_slice[..]);
if has_cont {
receiving.insert(id, msg_bytes);
} else {
tokio::spawn(self.clone().recv_handler(id, msg_bytes));
}
}
}
}
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