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

#![crate_name = "craftping"]

use std::io::{Cursor, Error, ErrorKind, Read, Result, Write};

trait ReadPacket {
    fn read_packet(&mut self) -> Result<CraftPacket>;
    fn read_varint(&mut self) -> Result<(i32, usize)>;
}

struct CraftPacket(i32, Box<[u8]>);

impl<R: Read> ReadPacket for R {
    fn read_packet(&mut self) -> Result<CraftPacket> {
        let length = self.read_varint()?.0 as usize;
        let (packet_id, id_length) = self.read_varint()?;
        let mut buffer = vec![0; length - id_length];
        self.read_exact(&mut buffer)?;
        Ok(CraftPacket(packet_id, buffer.into_boxed_slice()))
    }

    fn read_varint(&mut self) -> Result<(i32, usize)> {
        let mut read = 0;
        let mut result = 0;
        let mut buffer = [0];
        loop {
            self.read_exact(&mut buffer)?;
            let value = buffer[0] & 0b0111_1111;
            result |= (value as i32) << (7 * read);
            read += 1;
            if read > 5 {
                return Err(Error::from(ErrorKind::InvalidData));
            }
            if (buffer[0] & 0b1000_0000) == 0 {
                return Ok((result, read as usize));
            }
        }
    }
}

trait WritePacket {
    fn write_packet(&mut self, packet: CraftPacket) -> Result<()>;
    fn write_varint(&mut self, int: i32) -> Result<usize>;
}

impl<W: Write> WritePacket for W {
    fn write_packet(&mut self, packet: CraftPacket) -> Result<()> {
        let mut buffer: Cursor<Vec<u8>> = Cursor::new(Vec::new());
        buffer.write_varint(packet.0)?;
        buffer.write_all(&packet.1)?;
        buffer.set_position(0);
        let mut inner = buffer.into_inner();
        self.write_varint(inner.len() as i32)?;
        self.write_all(&mut inner)?;
        Ok(())
    }

    fn write_varint(&mut self, int: i32) -> Result<usize> {
        let mut int = (int as i64) & 0xFFFF_FFFF;
        let mut written = 0;
        let mut buffer = [0; 5];
        loop {
            let temp = (int & 0b0111_1111) as u8;
            int >>= 7;
            if int != 0 {
                buffer[written] = temp | 0b1000_0000;
            } else {
                buffer[written] = temp;
            }
            written += 1;
            if int == 0 {
                break;
            }
        }
        self.write_all(&mut buffer[0..written])?;
        Ok(written)
    }
}

/// Execute a server list ping (for version > 1.6) Synchronously.
/// Returns ping response in JSON format.
///
/// # Arguments
/// * `addr` - A string slice that represents the host without port
/// * `port` - port number to ping on
pub fn ping(addr: &str, port: u16) -> Result<String> {
    use std::net::TcpStream;
    let mut stream = TcpStream::connect(format!("{}:{}", addr, port))?;
    {
        let mut buffer = Cursor::new(Vec::<u8>::new());
        buffer.write_varint(-1)?;
        buffer.write_varint(addr.len() as i32)?;
        buffer.write_all(addr.as_bytes())?;
        let u16_buffer = [(port >> 8) as u8, (port & 0xFF) as u8];
        buffer.write_all(&u16_buffer)?;
        buffer.write_varint(1)?;
        let consumed = buffer.into_inner();
        stream.write_packet(CraftPacket(0, consumed.into_boxed_slice()))?;
    }
    stream.write_packet(CraftPacket(0, Box::new([])))?;
    stream.flush()?;
    {
        let CraftPacket(packet_id, data) = stream.read_packet()?;
        if packet_id != 0 {
            return Err(Error::from(ErrorKind::InvalidData));
        }
        let mut reader = Cursor::new(data);
        let (length, _) = reader.read_varint()?;
        let mut buffer = vec![0; length as usize];
        reader.read_exact(&mut buffer)?;
        String::from_utf8(buffer).map_err(|e| Error::new(ErrorKind::Other, e))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn test_varint() {
        let test_cases: [(i32, Vec<u8>); 5] = [
            (0, vec![0x00]),
            (1, vec![0x01]),
            (127, vec![0x7f]),
            (128, vec![0x80, 0x01]),
            (-2147483648, vec![0x80, 0x80, 0x80, 0x80, 0x08]),
        ];

        for (num, result) in &test_cases {
            let mut buffer = Cursor::new(Vec::new());
            buffer.write_varint(*num).unwrap();
            let inner = buffer.into_inner();
            assert_eq!(&inner, result);
            let mut buffer = Cursor::new(inner);
            let (varint, _) = buffer.read_varint().unwrap();
            assert_eq!(varint, *num);
        }
    }
}