Function encode_snapshot_chunk

nodedb-raft/src/snapshot_framing.rs:117–132

Encode a single snapshot chunk into the framed wire format. The CRC-32C is computed over the two `engine_id` bytes followed by all `payload` bytes, then the result is prefixed with the fixed header.

(engine_id: SnapshotEngineId, payload: &[u8])

/// The CRC-32C is computed over the two `engine_id` bytes followed by
/// all `payload` bytes, then the result is prefixed with the fixed header.
pub fn encode_snapshot_chunk(engine_id: SnapshotEngineId, payload: &[u8]) -> Vec<u8> {
    let engine_bytes = (engine_id as u16).to_be_bytes();
    let crc = {
        let mut h = crc32c::crc32c(&engine_bytes);
        h = crc32c::crc32c_append(h, payload);
        h
    };

    let mut out = Vec::with_capacity(HEADER_LEN + payload.len());
    out.extend_from_slice(&SNAPSHOT_MAGIC);
    out.extend_from_slice(&SNAPSHOT_FORMAT_VERSION.to_be_bytes());
    out.extend_from_slice(&engine_bytes);
    out.extend_from_slice(&crc.to_be_bytes());
    out.extend_from_slice(payload);
    out
}

/// Decode a framed snapshot chunk, returning the engine id and a slice
/// into the original buffer pointing at the payload (zero-copy).