Returns the field bytes (useful for binary fields such as DE64).
Returns the field as text (digits for N/XN, windows-1256-decoded text for ASCII
fields), with any trailing NUL padding removed. Use getBin for the raw bytes.
Pack without touching the MAC (DE64 used as-is if present).
Pack and append the SSP1126 DE64 CBC-MAC. Returns the full on-wire message.
Staticunpack
Packed ISO-8583 message. Field values are stored as their logical "content bytes".