Function decode_context_payload 

pub fn decode_context_payload(
    datagram: &[u8],
) -> Result<(ContextId, &[u8]), ContextPayloadError>

Available on crate feature masque only.

Split an HTTP Datagram payload into its Context ID and the rest (RFC 9298 §5).

Non-minimal Context ID encodings are accepted. A context-0 payload longer than MAX_UDP_PAYLOAD is an error the caller must answer by aborting the stream; payloads of other contexts are returned as they are.