.\" gd_validate.3.  The gd_validate man page.
.\"
.\" Copyright (C) 2009, 2010 D. V. Wiebe
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.TH gd_validate 3 "3 November 2010" "Version 0.7.0" "GETDATA"
.SH NAME
gd_validate \(em check a dirfile field code for validity
.SH SYNOPSIS
.B #include <getdata.h>
.HP
.nh
.ad l
.BI "int gd_validate(DIRFILE *" dirfile ", const char *" field_code );
.hy
.ad n
.SH DESCRIPTION
The
.BR gd_validate ()
function queries a dirfile(5) database specified by
.I dirfile
and checks whether
.IR field_code ,
which may contain a representation suffix, specifies a valid field.

The 
.I dirfile
argument must point to a valid DIRFILE object previously created by a call to
.BR gd_open (3).

This function checks whether the field and its input fields (if any) are found,
whether the representation suffix (if any) is valid, and also that all
non-literal parameters specify valid scalar fields.

.SH RETURN VALUE
If all checks pass,
.BR gd_validate ()
returns zero.  On error, it returns -1 and sets the dirfile error to a non-zero
error value.  Possible error values are:
.TP 8
.B GD_E_BAD_CODE
The field specified by
.I field_code
or one of the fields it uses as input was not found in the database.
.TP
.B GD_E_BAD_DIRFILE
The supplied dirfile was invalid.
.TP
.B GD_E_BAD_REPR
The representation suffix specified in
.I field_code
was not recognised.
.TP
.B GD_E_BAD_SCALAR
A non-literal scalar used in the definition of the field or one of its inputs
was not found, or was not a
.B CONST
or
.B CARRAY
field.
.TP
.B GD_E_DIMENSION
A scalar field was found where a vector field was expected.
.TP
.B GD_E_RECURSE_LEVEL
Too many levels of recursion were encountered while trying to resolve
.IR field_code .
This usually indicates a circular dependency in field specification in the
dirfile.
.PP
The dirfile error may be retrieved by calling
.BR gd_error (3).
A descriptive error string for the last error encountered can be obtained from
a call to
.BR gd_error_string (3).
.SH NOTES
It is not necessary to call this function before passing a field code to another
GetData function: all functions which accept field codes perform these checks
themselves.
.SH SEE ALSO
.BR dirfile (5),
.BR gd_getdata (3),
.BR gd_error (3),
.BR gd_error_string (3),
.BR gd_open (3)