aven_protocol/
codec.rs

1//! Canonical framing shared by the sync formats. Domain-separated inputs
2//! must stay byte-identical across every format that uses them.
3use sha2::{Digest, Sha256};
4
5/// Appends `value` with its u32 big-endian length.
6pub fn bytes(out: &mut Vec<u8>, value: &[u8]) {
7    // Every framed field is bounded far below 4 GiB.
8    out.extend_from_slice(
9        &u32::try_from(value.len())
10            .expect("framed field fits u32")
11            .to_be_bytes(),
12    );
13    out.extend_from_slice(value);
14}
15
16/// Canonical concatenation: the label, then each field, all length-framed.
17pub fn cce(label: &str, fields: &[&[u8]]) -> Vec<u8> {
18    let mut out = Vec::new();
19    bytes(&mut out, label.as_bytes());
20    for field in fields {
21        bytes(&mut out, field);
22    }
23    out
24}
25
26pub fn hash(value: &[u8]) -> [u8; 32] {
27    Sha256::digest(value).into()
28}
29
30#[cfg(test)]
31mod tests {
32    #[test]
33    fn canonical_fields_keep_their_length_prefixes() {
34        assert_eq!(
35            super::cce("x", &[b"yz", b""]),
36            vec![0, 0, 0, 1, b'x', 0, 0, 0, 2, b'y', b'z', 0, 0, 0, 0],
37        );
38    }
39}
aven_protocol/codec.rs

aven_protocol/
codec.rs
