1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168


use std::collections::vec_deque::VecDeque;
use std::task::Poll::*;
//use std::io::BufRead;
use std::pin::Pin;
use std::default::Default;
use std::fmt::{self,Display,Formatter};
use std::result;
use std::ops::{Deref,DerefMut};
use tokio::io::{ReadHalf,WriteHalf};

use thiserror::Error;

use futures_util::future;

use tokio::io::{AsyncRead,AsyncWrite};

pub struct Communicator<RW : AsyncRead + AsyncWrite> (
  CommunicatorSplit<ReadHalf<RW>, WriteHalf<RW>>
);

impl<RW : AsyncRead + AsyncWrite> Deref for Communicator<RW> {
  type Target = CommunicatorSplit<ReadHalf<RW>,WriteHalf<RW>>;
  fn deref(&self) -> &Self::Target { &self.0 }
}
impl<RW : AsyncRead + AsyncWrite> DerefMut for Communicator<RW> {
  fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 }
}

pub struct CommunicatorSplit<R : AsyncRead, W : AsyncWrite> {
  write_buffer  : VecDeque<u8>,
  read_expected : usize,
  conn_r        : Pin<Box<R>>,
  conn_w        : Pin<Box<W>>,
}

type Result<T> = tokio::io::Result<T>;

#[derive(Error,Debug)]
struct PeerDisconnected { }
impl Display for PeerDisconnected {
  fn fmt(&self, fmt: &mut Formatter) -> result::Result<(), fmt::Error> {
    write!(fmt,"PeerDisconnected")
  }
}

trait Outputter {
  type BufObj;
  fn buf<'a>(&'a mut self, expected : usize,
             bo : &'a mut Self::BufObj) -> &'a mut [u8];
  fn bufobj(&self) -> Self::BufObj;
}

impl Outputter for &mut [u8] {
  type BufObj = ();
  fn buf<'a>(&'a mut self, remaining : usize,
             _bo : &'a mut Self::BufObj) -> &'a mut [u8] {
    self.split_at_mut( self.len() - remaining ).1
  }
  fn bufobj(&self) -> Self::BufObj { Default::default() }
}

impl Outputter for () {
  type BufObj = [u8;20];
  fn buf<'a>(&'a mut self, _remaining : usize,
             bo : &'a mut Self::BufObj) -> &'a mut [u8] { bo }
  fn bufobj(&self) -> Self::BufObj { Default::default() }
}

impl<RW : AsyncRead + AsyncWrite + Unpin> Communicator<RW> {
  pub fn new(connection : RW) -> Communicator<RW> {
    let (conn_r, conn_w) = tokio::io::split(connection);
    Communicator( CommunicatorSplit::new(conn_r, conn_w) )
  }

  pub fn into_inner(self) -> RW {
    self.assert_idle();
    let (r, w) = self.0.into_inner();
    r.unsplit(w)
  }
}

impl<R : AsyncRead + Unpin, W : AsyncWrite + Unpin> CommunicatorSplit<R,W> {
  pub fn new(conn_r : R, conn_w : W) -> CommunicatorSplit<R,W> {
    CommunicatorSplit {
      write_buffer  : VecDeque::new(),
      read_expected : 0,
      conn_r        : Box::pin(conn_r),
      conn_w        : Box::pin(conn_w),
    }
  }

  pub async fn communicate(&mut self, cmdvec : &[&[u8]],
                           mut response : &mut [u8])
                           -> Result<()> {
    self.drain_write_buffer().await?;
    self.ignore_stale_responses().await?;
    self.assert_idle();
    for &cmd in cmdvec { self.write_buffer.extend(cmd); }
    self.read_expected = response.len();
    self.drain_write_buffer().await?;
    read_into(&mut self.conn_r, &mut self.read_expected,
              &mut response).await?;
    self.assert_idle();
    Ok(())
  }

  pub fn into_inner(self) -> (R, W) {
    self.assert_idle();
    ( *Pin::into_inner(self.conn_r),
      *Pin::into_inner(self.conn_w) )
  }

  fn assert_idle(&self) {
    assert!(self.write_buffer.is_empty());
    assert!(self.read_expected == 0);
  }

  async fn drain_write_buffer(&mut self) -> Result<()> {
    loop {
      if self.write_buffer.len() == 0 { break }
      future::poll_fn(|cx|{
        let (slice1, slice2) = self.write_buffer.as_slices();
        let slice = if slice1.is_empty() { slice2 } else { slice1 };
        let got = self.conn_w.as_mut().poll_write(cx, slice);
        match got {
          Ready(Ok(n)) => {
            self.write_buffer.drain(0..n);
            Ready(<Result<()>>::Ok(()))
          },
          Ready(Err(e)) => Err(e)?,
          Pending => Pending,
        }
      }).await?;
    }
    Ok(())
  }

  async fn ignore_stale_responses(&mut self) -> Result<()> {
    read_into(&mut self.conn_r, &mut self.read_expected, &mut ()).await
  }
}

//impl<RW : AsyncWrite + AsyncRead, O : Outputter> Communicator<RW> {
//  async fn read_into(&mut self, o : &mut O) -> Result<()> {
async fn read_into<R : AsyncRead, O : Outputter>
  (c : &mut Pin<Box<R>>, remaining : &mut usize, o : &mut O) -> Result<()> {
    let mut bo = o.bufobj();
    future::poll_fn(|cx|{
      loop {
        if *remaining == 0 { return Ready(Ok(())) }
        let got = c.as_mut().poll_read(cx, o.buf(*remaining, &mut bo));
        match got {
          Ready(Ok(0)) => {
            return Ready(Err(
              tokio::io::Error::new(
                tokio::io::ErrorKind::UnexpectedEof, PeerDisconnected{}
              )
            ))
          },
          Ready(Ok(n)) => { *remaining -= n; },
          Ready(Err(e)) => return Err(e)?,
          Pending => return Pending,
        }
      }
    }).await?;
    Ok(())
  }