User exits allow direct references to assembler routines known as modes. These are generally not needed for new applications and are provided primarily for backwards compatibility and specialty utilities that must access internal structures.
The unumber syntax is the standard way to call pre-defined user exits. The number is a 4-digit hexadecimal number. Leading zeros can be omitted.
Users with assembly accounts can also enter their code via user exits. The standard way to do this is with the u$mode.name syntax that jumps directly into the mode called mode.name. Every user exit call of this type requires an ABS lookup.
The user can initially use the u?mode.name syntax and store the result in a FlashBASIC variable. This does not execute the user exit, but returns a direct pointer to its location. After this, the mode can be repeatedly called by using that variables value as the conversion. This is much faster than the u?mode.name syntax because no further ABS lookups are needed. If the u?mode.name call returns a null, then the mode cannot be located.
A numeric user exit that is not found in the user exit table is converted to a FlashBASIC call to a subroutine named u followed by the number (for example, u123). If the system(0) function is executed at the beginning of this subroutine, it returns a 1 for an iconv() call or a 0 for an oconv() call.
Syntax
unumber u$mode.name u?mode.name |
WARNING |
User exits are dangerous. Extreme caution is advised when using them. They can cause the application to run slower than if it was coded entirely in FlashBASIC. |
See Also
iconv() Function, oconv() Function, PROC User Exits, system() Function, u005b User Exit, u017e User Exit, u8193 User Exit, User Exits