HP 3000 Manuals

HP C/iX Library Reference Manual

Foptions 

The structure tag fop names a structure that describes the bit positions
of the MPE/iX FOPEN intrinsic's foptions.  The structure is:

     struct fop {
         unsigned short reserved:2;      /* for MPE/iX */
         unsigned short typer:3;         /* file type */
         unsigned short no_f_equ:1;      /* no file equations */
         unsigned short label:1;         /* labeled tape option */
         unsigned short carriage:1;      /* carriage control needed */
         unsigned short format:2;        /* record format */
         unsigned short designator:3;    /* default designator */
         unsigned short ascii:1;         /* ASCII(1)/binary(0) */
         unsigned short domain:2;        /* file domain */
     };

In addition to the fop structure, <mpe.h> contains a typedef called
foptions that is the union of an unsigned short and an fop structure.
The typedef is:

     typedef union {
         struct fop fs;
         unsigned short fv;
     } foptions;

This typedef is useful for declaring regions of storage that are to serve
as foptions.  If a variable f is declared as being type foptions, then
f.fv accesses the unsigned short version of the foptions while f.fs
accesses the structural definition of the foptions.  For example:

     #include <mpe.h>
     #pragma intrinsic FOPEN MPE_FOPEN

     main
     {
       foptions f;         /* declare f as an foption variable */
        . . .
       f.fv = 0;                     /* clear all options to 0 */
       f.fs.ascii = 1;               /* set ASCII foption to true */
       f.fs.no_f_equ = 1;            /* disallow file equations */
       MPE_FOPEN(. . , f.fv, . . .); /* pass foptions */
        . . .
     }

Note, in the above example, the foptions variable can be accessed as
named bit-fields using the f.fs construct or as a 16-bit unsigned short
value using the f.fv construct.  Also, notice the FOPEN intrinsic has
been given the name MPE_FOPEN in this example to avoid confusion with the
C library function fopen.

MPE/iX 5.0 Documentation