Cross-Platform Binary Protocols

When designing binary protocols for cross-platform use, always explicitly specify big. Network byte order is the universal standard, and failing to use it has caused countless bugs throughout computing history (though admittedly fewer than the confusion caused by time zones).

(defun encode-packet (type-id data)
  "Encode a packet with proper network byte order."
  (let ((data-size (byte_size data)))
    (binary ((#xDEAD (size 16) big)              ; Magic number
             (type-id (size 8))                   ; Type (single byte, no endianness)
             (data-size (size 32) big)            ; Length field
             (data binary)))))                    ; Payload

(defun decode-packet (packet)
  "Decode a packet, expecting network byte order."
  (binary ((#xDEAD (size 16) big)
           (type-id (size 8))
           (data-size (size 32) big)
           (data (size data-size) binary)
           rest binary)
          packet)
  `#m(type ,type-id data ,data rest ,rest))