msg-wire 0.1.6

Wire formats for msg-rs
Documentation 
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

use bytes::{Buf, BufMut, Bytes};
use thiserror::Error;
use tokio_util::codec::{Decoder, Encoder};

/// The ID of the auth codec on the wire.
const WIRE_ID: u8 = 0x01;

#[derive(Debug, Error)]
pub enum Error {
    #[error("IO error: {0:?}")]
    Io(#[from] std::io::Error),
    #[error("Invalid wire ID: {0}")]
    WireId(u8),
    #[error("Rejected")]
    Rejected,
}

/// Authentication codec.
pub struct Codec {
    state: State,
}

impl Codec {
    /// Creates a new authentication codec for a client. This will put the
    /// codec in the `Ack` state since it will be waiting for an ack.
    pub fn new_client() -> Self {
        Self { state: State::Ack }
    }

    /// Creates a new authentication codec for a server. This will put the
    /// codec in the `AuthReceive` state since it will be waiting for the
    /// client to send its ID.
    pub fn new_server() -> Self {
        Self { state: State::AuthReceive }
    }
}

#[derive(Debug, Clone)]
enum State {
    /// Waiting for the client to send its ID
    AuthReceive,
    /// Waiting for the server to send an ACK
    Ack,
}

#[derive(Debug, Clone)]
pub enum Message {
    /// The client sends the ID to the server
    Auth(Bytes),
    /// The server responds with an ACK
    Ack,
    /// We reject the client
    Reject,
}

impl Decoder for Codec {
    type Item = Message;
    type Error = Error;

    fn decode(&mut self, src: &mut bytes::BytesMut) -> Result<Option<Self::Item>, Self::Error> {
        match self.state {
            // We are the server, waiting for the client to send its auth message
            State::AuthReceive => {
                // We need at least 5 bytes to read the wire ID and the auth ID
                if src.is_empty() {
                    return Ok(None);
                }

                // Wire ID check (without advancing the cursor)
                let wire_id = u8::from_be_bytes([src[0]]);
                if wire_id != WIRE_ID {
                    return Err(Error::WireId(wire_id));
                }

                if src.len() < 4 {
                    return Ok(None);
                }

                let id_size = u32::from_be_bytes([src[1], src[2], src[3], src[4]]);
                if src.len() < id_size as usize {
                    return Ok(None);
                }

                src.advance(1);
                src.advance(4);

                let id = src.split_to(id_size as usize).freeze();
                self.state = State::Ack;
                Ok(Some(Message::Auth(id)))
            }
            // We are the client, and we are waiting for the server to send an ACK
            State::Ack => {
                if src.len() < 2 {
                    return Ok(None);
                }

                // Wire ID check (without advancing the cursor)
                let wire_id = u8::from_be_bytes([src[0]]);
                if wire_id != WIRE_ID {
                    return Err(Error::WireId(wire_id));
                }

                src.advance(1);

                let ack = src.get_u8();

                if ack == 0 {
                    return Err(Error::Rejected);
                }

                Ok(Some(Message::Ack))
            }
        }
    }
}

impl Encoder<Message> for Codec {
    type Error = std::io::Error;

    fn encode(&mut self, item: Message, dst: &mut bytes::BytesMut) -> Result<(), Self::Error> {
        match item {
            // We are the client, and we are sending the ID to the server
            Message::Auth(id) => {
                self.state = State::Ack;
                dst.reserve(1 + 4 + id.len());
                dst.put_u8(WIRE_ID);
                dst.put_u32(id.len() as u32);
                dst.put(id);
            }
            // We are the server, and we are sending an ACK to the client
            Message::Ack => {
                dst.reserve(1 + 1);
                dst.put_u8(WIRE_ID);
                dst.put_u8(1);
            }
            Message::Reject => {
                dst.reserve(1 + 1);
                dst.put_u8(WIRE_ID);
                dst.put_u8(0);
            }
        }

        Ok(())
    }
}