as many others, I'm sure, I am DATA space starved. We have, for backwards compatibility to process 'old files" (E1 format) which have the structures with the following pointers:
E1_SEIN xdata *E1_SEINp; E1_MAIN xdata *GE1_MAINp; E1_TXCH xdata *GE1_TXCHp;
now when the data is loaded it is immediately recognized which format the data is in and if it is the new E2 format the above structures do not exist, but these do:
E2_CHIF xdata *GE2_CHIFp; E2_DHDR xdata *GE2_DHDRp; E2_FTHD xdata *GE2_FTHDp;
now, since the two formats are mutually exclusive, I could gain 6 DATA slots by overlaying them. YES, I can do it with a union, but since these pointers are used all over the place this will be rather messy and I would like to use something like:
E1_SEIN xdata *E1_SEINp; E1_MAIN xdata *GE1_MAINp; E1_TXCH xdata *GE1_TXCHp; #define E2_CHIF xdata *GE2_CHIFp *E1_SEINp #define E2_DHDR xdata *GE2_DHDRp *GE1_MAINp #define E2_FTHD xdata *GE2_FTHDp *GE1_TXCHp
which, of course do not work.
any 'elegant' way to do this. #define with typecasst"??.
Erik
the code must be universal, no #if, #ifedef or such.
Define the unions, then use #defines to alias the individual members to look like ordinary variables.
You may wish to change this to
E1_SEIN xdata *E1_SEINp; E1_MAIN xdata *GE1_MAINp; E1_TXCH xdata *GE1_TXCHp; #define GE2_CHIFp ((E2_CHIF xdata *) E1_SEINp) #define GE2_DHDRp ((E2_DHDR xdata *) GE1_MAINp) #define GE2_FTHDp ((E2_FTHD xdata *) GE1_TXCHp)
This makes the two sets of variables overlay with macro's doing the work.