shadow_utils/
codec.rs

1//! Packet encoding/decoding utilities
2
3use shadow_core::error::{Result, ShadowError};
4use bytes::Bytes;
5
6/// Encode packet with length prefix
7pub fn encode_packet(data: &[u8]) -> Bytes {
8    let mut buf = Vec::with_capacity(4 + data.len());
9    
10    // Write length prefix (4 bytes)
11    buf.extend_from_slice(&(data.len() as u32).to_be_bytes());
12    
13    // Write data
14    buf.extend_from_slice(data);
15    
16    Bytes::from(buf)
17}
18
19/// Decode packet with length prefix
20pub fn decode_packet(data: &[u8]) -> Result<Bytes> {
21    if data.len() < 4 {
22        return Err(ShadowError::InvalidPacket("Too short".into()));
23    }
24    
25    let length = u32::from_be_bytes([data[0], data[1], data[2], data[3]]) as usize;
26    
27    if data.len() < 4 + length {
28        return Err(ShadowError::InvalidPacket(format!(
29            "Incomplete packet: expected {}, got {}",
30            length,
31            data.len() - 4
32        )));
33    }
34    
35    Ok(Bytes::copy_from_slice(&data[4..4 + length]))
36}
37
38/// Frame multiple packets into a single buffer
39pub fn frame_packets(packets: &[&[u8]]) -> Bytes {
40    let total_size: usize = packets.iter().map(|p| 4 + p.len()).sum();
41    let mut buf = Vec::with_capacity(total_size);
42    
43    for packet in packets {
44        buf.extend_from_slice(&(packet.len() as u32).to_be_bytes());
45        buf.extend_from_slice(packet);
46    }
47    
48    Bytes::from(buf)
49}
50
51/// Unframe multiple packets from a buffer
52pub fn unframe_packets(data: &[u8]) -> Result<Vec<Bytes>> {
53    let mut packets = Vec::new();
54    let mut buf = data;
55    
56    while buf.len() >= 4 {
57        let length = u32::from_be_bytes([buf[0], buf[1], buf[2], buf[3]]) as usize;
58        buf = &buf[4..];
59        
60        if buf.len() < length {
61            return Err(ShadowError::InvalidPacket("Truncated packet".into()));
62        }
63        
64        packets.push(Bytes::copy_from_slice(&buf[..length]));
65        buf = &buf[length..];
66    }
67    
68    if !buf.is_empty() {
69        return Err(ShadowError::InvalidPacket("Trailing bytes".into()));
70    }
71    
72    Ok(packets)
73}
74
75#[cfg(test)]
76mod tests {
77    use super::*;
78
79    #[test]
80    fn test_encode_decode() {
81        let data = b"Hello, World!";
82        let encoded = encode_packet(data);
83        let decoded = decode_packet(&encoded).unwrap();
84        
85        assert_eq!(decoded.as_ref(), data);
86    }
87
88    #[test]
89    fn test_frame_unframe() {
90        let packets = vec![b"First" as &[u8], b"Second", b"Third"];
91        
92        let framed = frame_packets(&packets);
93        let unframed = unframe_packets(&framed).unwrap();
94        
95        assert_eq!(unframed.len(), 3);
96        assert_eq!(unframed[0].as_ref(), b"First");
97        assert_eq!(unframed[1].as_ref(), b"Second");
98        assert_eq!(unframed[2].as_ref(), b"Third");
99    }
100
101    #[test]
102    fn test_decode_invalid() {
103        // Too short
104        assert!(decode_packet(&[0, 1]).is_err());
105        
106        // Incomplete (says 100 bytes but only has 7 + header)
107        let mut buf = Vec::new();
108        buf.extend_from_slice(&100u32.to_be_bytes());
109        buf.extend_from_slice(b"Only 10");
110        assert!(decode_packet(&buf).is_err());
111    }
112}
shadow_utils/codec.rs

shadow_utils/
codec.rs
