layer_mtproto/
message.rs

1//! MTProto message framing types.
2
3use std::time::{SystemTime, UNIX_EPOCH};
4
5/// A 64-bit MTProto message identifier.
6///
7/// Per the spec: the lower 32 bits are derived from the current Unix time;
8/// the upper 32 bits are a monotonically increasing counter within the second.
9/// The least significant two bits must be zero for client messages.
10#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
11pub struct MessageId(pub u64);
12
13impl MessageId {
14    /// Generate a new message ID using the system clock.
15    ///
16    /// Call this from the session rather than directly so that the
17    /// counter is properly sequenced.
18    pub(crate) fn generate(counter: u32) -> Self {
19        let unix_secs = SystemTime::now()
20            .duration_since(UNIX_EPOCH)
21            .unwrap_or_default()
22            .as_secs();
23        // Lower 32 bits = seconds, upper 32 bits = intra-second counter × 4
24        // (the two LSBs must be 0b00 for client messages)
25        let id = (unix_secs << 32) | (u64::from(counter) << 2);
26        Self(id)
27    }
28}
29
30/// A framed MTProto message ready to be sent.
31#[derive(Debug)]
32pub struct Message {
33    /// Unique identifier for this message.
34    pub id: MessageId,
35    /// Session-scoped sequence number (even for content-unrelated, odd for content-related).
36    pub seq_no: i32,
37    /// The serialized TL body (constructor ID + fields).
38    pub body: Vec<u8>,
39}
40
41impl Message {
42    /// Construct a new plaintext message (used before key exchange).
43    pub fn plaintext(id: MessageId, seq_no: i32, body: Vec<u8>) -> Self {
44        Self { id, seq_no, body }
45    }
46
47    /// Serialize the message into the plaintext wire format:
48    ///
49    /// ```text
50    /// auth_key_id:long  (0 for plaintext)
51    /// message_id:long
52    /// message_data_length:int
53    /// message_data:bytes
54    /// ```
55    pub fn to_plaintext_bytes(&self) -> Vec<u8> {
56        let mut buf = Vec::with_capacity(8 + 8 + 4 + self.body.len());
57        buf.extend(0i64.to_le_bytes());           // auth_key_id = 0
58        buf.extend(self.id.0.to_le_bytes());      // message_id
59        buf.extend((self.body.len() as u32).to_le_bytes()); // length
60        buf.extend(&self.body);
61        buf
62    }
63}
layer_mtproto/message.rs

layer_mtproto/
message.rs
