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use tokio_util::codec::{Encoder, Decoder};
use bytes::{BytesMut, Buf, BufMut, Bytes};
use std::{
io
};
const SE: u8 = 240;
const SB: u8 = 250;
const WILL: u8 = 251;
const WONT: u8 = 252;
const DO: u8 = 253;
const DONT: u8 = 254;
const IAC: u8 = 255;
#[derive(Clone, Debug)]
pub enum TelnetEvent {
Negotiate(u8, u8),
SubNegotiate(u8, Bytes),
Data(Bytes),
Command(u8)
}
impl From<TelnetEvent> for Bytes {
fn from(src: TelnetEvent) -> Self {
let mut out = BytesMut::new();
match src {
TelnetEvent::Data(data) => {
out.reserve(data.len());
out.put(data);
},
TelnetEvent::Negotiate(comm, op) => {
out.reserve(3);
out.extend(&[IAC, comm, op]);
},
TelnetEvent::SubNegotiate(op, data) => {
out.reserve(5 + data.len());
out.extend(&[IAC, SB, op]);
out.extend(data);
out.extend(&[IAC, SB]);
},
TelnetEvent::Command(byte) => {
out.reserve(2);
out.extend(&[IAC, byte]);
}
}
out.freeze()
}
}
#[derive(Debug)]
pub struct TelnetCodec {
max_buffer: usize,
}
impl TelnetCodec {
pub fn new(max_buffer: usize) -> Self {
TelnetCodec {
max_buffer,
}
}
}
impl Default for TelnetCodec {
fn default() -> Self {
Self::new(1024)
}
}
impl Decoder for TelnetCodec {
type Item = TelnetEvent;
type Error = io::Error;
fn decode(&mut self, src: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> {
if src.is_empty() {
return Ok(None);
}
if src[0] == IAC {
if src.len() > 1 {
match src[1] {
IAC => {
src.advance(2);
let mut data = BytesMut::with_capacity(1);
data.put_u8(IAC);
return Ok(Some(TelnetEvent::Data(data.freeze())));
},
WILL | WONT | DO | DONT => {
if src.len() > 2 {
let answer = TelnetEvent::Negotiate(src[1], src[2]);
src.advance(3);
return Ok(Some(answer));
} else {
return Ok(None)
}
},
SB => {
if src.len() > 4 {
if let Some(ipos) = src.as_ref().windows(2).position(|b| b[0] == IAC && b[1] == SE) {
let mut data = src.split_to(ipos);
src.advance(2);
let discard = data.split_to(3);
let answer = TelnetEvent::SubNegotiate(discard[2], data.freeze());
return Ok(Some(answer))
} else {
return Ok(None)
}
} else {
return Ok(None)
}
},
_ => {
let cmd = src[1];
src.advance(2);
return Ok(Some(TelnetEvent::Command(cmd)))
}
}
} else {
return Ok(None)
}
} else {
if let Some(ipos) = src.as_ref().iter().position(|b| b == &IAC) {
return Ok(Some(TelnetEvent::Data(src.split_to(ipos).freeze())))
} else {
return Ok(Some(TelnetEvent::Data(src.split_to(src.len()).freeze())))
}
}
}
}
impl Encoder<TelnetEvent> for TelnetCodec {
type Error = io::Error;
fn encode(&mut self, item: TelnetEvent, dst: &mut BytesMut) -> Result<(), Self::Error> {
let out = Bytes::from(item);
dst.reserve(out.len());
dst.put(out.as_ref());
Ok(())
}
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
}