PURPOSE

Fvnull, Fvnull32 - check if a structure element is null

SYNOPSIS

#include <stdio.h>
#include "fml.h"
int
Fvnull(char *cstruct, char *cname, FLDOCC oc, char *view)
#include "fml32.h"
int
Fvnull32(char *cstruct, char *cname, FLDOCC32 oc, char *view)

DESCRIPTION

Fvnull() is used to determine if an occurrence of a structure element is null. cstruct is a pointer to a C structure. cname is a pointer to the name of an element within cstruct. oc is the occurrence number of the element. view is a pointer to the name of a compiled view description.

Options of Fvopt(3fml) such as do not affect this function.

Fvnull32 is used for views defined with viewc32 or VIEW32 typed buffers for larger views with more fields.

RETURN VALUES

Fvnull() returns 1, if the specified cname in a C structure is null and returns 0 if not null. This function returns -1 on error and sets Ferror to indicate the error condition.

ERRORS

Under the following conditions, Fvnull() fails and sets Ferror to:

[FBADVIEW]

"cannot find or get view"
The view description specified was not found in the files specified by VIEWDIR or VIEWFILES.

 

[FNOCNAME]

"cname not found"
The C structure field name is not found in the view description.

SEE ALSO

Fintro(3fml),
Fvopt(3fml),
viewfile(5)