REQ/CNF) FB" implementations of all the standard character string functions defined in IEC 61499, including implementations for both
WSTRING(16-bit character strings) and
STRING(8-bit character strings) types.
WSTRINGis implemented as a container for the Java
Stringclass, whose instances are immutable, and
STRINGis implemented as a wrapper for a mutable array of bytes. This gives the latter the following practical advantages:
- Significantly less object creation and garbage collection overhead
- Smaller (approaching 50%) payload sizes for PUBLISH/SUBSCRIBE and CLIENT/SERVER packets, with correspondingly smaller encode/decode times.
STRINGs can only represent 256 characters - usually the "C0 Controls and Basic Latin" (0000-007F) and "C1 Controls and Latin-1 Supplement" (0080-00FF) defined in ISO/IEC 10646. For a richer, multilingual character set,
WSTRINGwith its attendant overhead costs must be used.
Documentation for these FB types can be found in the
stringsfolder of the FBNavigator.