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

use std::io::{self, BufReader, BufWriter, SeekFrom, prelude::*};
use std::net::{ToSocketAddrs, TcpStream, TcpListener};
use std::convert::TryInto;

#[cfg(test)]
mod tests;

const OPERATION_READ: u8 = 0xFF;
const OPERATION_SEEK: u8 = 0xFE;

const SEEK_FROM_START: u8 = 0;
const SEEK_FROM_END: u8 = 1;
const SEEK_FROM_CURRENT: u8 = 2;

const RESULT_OK: u8 = 0;
const RESULT_ERR: u8 = 1;

pub struct Networked<R: Read + Seek> {
    listener: TcpListener,
    reader: R,
}

impl<R: Read + Seek> Networked<R> {
    pub fn new<S: ToSocketAddrs>(reader: R, socket: S) -> io::Result<Self> {
        Ok(Self {
            reader,
            listener: TcpListener::bind(socket)?
        })
    }
    
    pub fn new_buffered<S: ToSocketAddrs>(reader: R, socket: S) -> io::Result<Networked<BufReader<R>>> {
        Ok(Networked {
            reader: BufReader::new(reader),
            listener: TcpListener::bind(socket)?
        })
    }
    
    pub fn listen(mut self) -> io::Result<()> {
        for connection in self.listener.incoming() {
            let mut connection = connection?;
            let mut buf = [0u8];
            while connection.read_exact(&mut buf).is_ok() {
                match buf[0] {
                    OPERATION_SEEK => {
                        let mut buf = [0u8; 9];
                        let pos = match connection.read_exact(&mut buf) {
                            Ok(_) => {
                                let offset = i64::from_be_bytes(buf[1..].try_into().unwrap());
                                match buf[0] {
                                    0 => SeekFrom::Start(offset as u64),
                                    1 => SeekFrom::End(offset),
                                    2 => SeekFrom::Current(offset),
                                    _ => continue
                                }
                            },
                            Err(_) => continue,
                        };

                        match self.reader.seek(pos) {
                            Ok(ret) => {
                                connection.write_all(&[RESULT_OK])?;
                                connection.write_all(&u64::to_be_bytes(ret))?;
                            }
                            Err(_) => {
                                connection.write_all(&[RESULT_ERR])?;
                            }
                        }
                        connection.flush()?;
                    }
                    OPERATION_READ => {
                        let mut buf = [0u8; 8];
                        let amount = match connection.read_exact(&mut buf) {
                            Ok(_) => u64::from_be_bytes(buf),
                            Err(_) => continue,
                        };
                        
                        let mut writer = BufWriter::new(&mut connection);
                        let reader = &mut self.reader;
                        let size = io::copy(&mut reader.take(amount), &mut writer)?;

                        io::copy(&mut io::repeat(0).take(amount - size), &mut writer)?;
                        writer.write_all(&size.to_be_bytes())?;
                        writer.flush()?;
                    }
                    _ => continue
                }
            }
        }
        Ok(())
    }
}

pub struct NetworkReader(TcpStream);

impl NetworkReader {
    pub fn new<Addr: ToSocketAddrs>(addr: Addr) -> io::Result<Self> {
        TcpStream::connect(addr).map(Self)
    }
}

impl Seek for NetworkReader {
    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
        self.0.write_all(&[OPERATION_SEEK])?;
        self.0.write_all(&[match pos {
            SeekFrom::Start(_) => SEEK_FROM_START,
            SeekFrom::End(_) => SEEK_FROM_END,
            SeekFrom::Current(_) => SEEK_FROM_CURRENT,
        }])?;
        self.0.write_all(&match pos {
            SeekFrom::Start(offset) => offset.to_be_bytes(),
            SeekFrom::End(offset) | SeekFrom::Current(offset) => offset.to_be_bytes(),
        })?;
        self.0.flush()?;

        let mut result = [0u8];
        self.0.read_exact(&mut result)?;

        if result == [RESULT_OK] {
            let mut val = [0u8; 8];
            self.0.read_exact(&mut val)?;
            
            Ok(u64::from_be_bytes(val))
        } else {
            Err(io::Error::new(io::ErrorKind::Other, "server returned error"))
        }
    }
}

impl Read for NetworkReader {
    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
        self.0.write_all(&[OPERATION_READ])?;
        self.0.write_all(&(buf.len() as u64).to_be_bytes())?;
        
        self.0.read_exact(buf)?;

        let mut buf = [0u8; 8];
        self.0.read_exact(&mut buf)?;

        Ok(u64::from_be_bytes(buf) as usize)
    }
}