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use futures::ready;
use std::{io, marker, mem, pin, task};
use std::future::Future;
use tokio::io::{AsyncBufRead, AsyncRead, BufReader};
const ABUSE_ERR: &str = "Bad client, bad! >:(";
const UTF8_ERR: &str = "This was definitely not UTF-8...";
const TOO_LONG_ERR: &str = "Kyaa! Your message is too long!";
const MAX_READ_PER_MESSAGE: u8 = 4;
const MAX_TAG_LENGTH: usize = 4096;
pub struct IrcReader<R> {
inner: BufReader<R>,
message_max: usize,
}
impl<R: AsyncRead> IrcReader<R> {
pub fn new(r: R, message_max: usize) -> Self {
Self { inner: BufReader::new(r), message_max }
}
pub fn read_message<'a>(&'a mut self, buf: &'a mut String) -> ReadMessage<'a, R>
where Self: marker::Unpin,
{
ReadMessage {
reader: &mut self.inner,
bytes: unsafe { mem::replace(buf.as_mut_vec(), Vec::new()) },
buf,
n: ReadInfo {
read: 0,
limit: 0,
message_max: self.message_max,
count: 0,
},
}
}
}
#[derive(Debug)]
struct ReadInfo {
read: usize,
limit: usize,
message_max: usize,
count: u8,
}
#[must_use = "futures do nothing unless polled or .await'ed"]
#[derive(Debug)]
pub struct ReadMessage<'a, R> {
reader: &'a mut BufReader<R>,
bytes: Vec<u8>,
buf: &'a mut String,
n: ReadInfo,
}
impl<R: AsyncRead + marker::Unpin> Future for ReadMessage<'_, R> {
type Output = io::Result<usize>;
fn poll(mut self: pin::Pin<&mut Self>, cx: &mut task::Context<'_>) -> task::Poll<Self::Output> {
let Self { reader, buf, bytes, n } = &mut *self;
read_message(pin::Pin::new(reader), cx, buf, bytes, n)
}
}
fn read_message<R>(reader: pin::Pin<&mut BufReader<R>>, cx: &mut task::Context<'_>,
buf: &mut String, bytes: &mut Vec<u8>, n: &mut ReadInfo)
-> task::Poll<io::Result<usize>>
where R: AsyncRead,
{
let ret = ready!(read_line(reader, cx, bytes, n))?;
if std::str::from_utf8(&bytes).is_err() {
task::Poll::Ready(
Err(io::Error::new(io::ErrorKind::InvalidData, UTF8_ERR))
)
} else {
mem::swap(unsafe { buf.as_mut_vec() }, bytes);
task::Poll::Ready(Ok(ret))
}
}
fn read_line<R>(mut reader: pin::Pin<&mut BufReader<R>>, cx: &mut task::Context<'_>,
bytes: &mut Vec<u8>, n: &mut ReadInfo)
-> task::Poll<io::Result<usize>>
where R: AsyncRead,
{
loop {
if MAX_READ_PER_MESSAGE <= n.count {
return task::Poll::Ready(Err(io::Error::new(io::ErrorKind::TimedOut, ABUSE_ERR)));
}
if 0 < n.limit && n.limit <= n.read {
return task::Poll::Ready(Err(io::Error::new(io::ErrorKind::TimedOut, TOO_LONG_ERR)));
}
let (done, used) = {
let available = ready!(reader.as_mut().poll_fill_buf(cx))?;
if n.limit == 0 && !available.is_empty() {
if available[0] == b'@' {
n.limit = MAX_TAG_LENGTH;
}
n.limit += n.message_max;
}
if let Some(i) = memchr::memchr2(b'\r', b'\n', available) {
bytes.extend_from_slice(&available[..=i]);
if i + 1 < available.len() && available[i + 1] == b'\n' {
(true, i + 2)
} else {
(true, i + 1)
}
} else {
bytes.extend_from_slice(available);
(false, available.len())
}
};
reader.as_mut().consume(used);
n.read += used;
if done || used == 0 {
return task::Poll::Ready(Ok(mem::replace(&mut n.read, 0)));
}
n.count += 1;
}
}