Function decode_snapshot_chunk 

pub fn decode_snapshot_chunk(buf: &[u8]) -> Result<(&[u8], usize), WireError>

Decode the next snapshot chunk ($L\r\n<L bytes>\r\n) at the front of buf. Returns:

• Ok((chunk_bytes, used)) — chunk_bytes borrows from buf; used bytes were consumed.
• Err(WireError::Truncated) — not enough bytes for a complete chunk yet.
• Err(WireError::BadEnvelope) — header wasn’t $L\r\n, L exceeded SNAPSHOT_CHUNK_MAX, L parsed as non-numeric, or the trailing CRLF was missing.