typedef int (* XPLMGetDatai_f)( void * inRefcon);
Data provider function pointers.
These define the function pointers you provide to get or set data. Note that you are passed a generic pointer for each one. This is the same pointer you pass in your register routine; you can use it to find global variables, etc.
The semantics of your callbacks are the same as the dataref accessor above - basically routines like XPLMGetDatai are just pass-throughs from a caller to your plugin. Be particularly mindful in implementing array dataref read-write accessors; you are responsible for avoiding overruns, supporting offset read/writes, and handling a read with a NULL buffer.