NAME¶
gd_mconstants — retrieve a list of constant values from a dirfile
SYNOPSIS¶
#include <getdata.h>
const void *gd_mconstants(DIRFILE *dirfile,
const char *parent, gd_type_t
return_type);
DESCRIPTION¶
The
gd_mconstants() function queries a
dirfile(5) database specified by
dirfile and returns a read-only list of values of the all
CONST
type metafields for the supplied
parent field after type conversion to
the data type specified by
return_type.
The
dirfile argument must point to a valid DIRFILE object previously
created by a call to
gd_open(3).
The array returned will be de-allocated by a call to
gd_close(3) and
should not be de-allocated by the caller. The list returned should not be
assumed to be in any particular order, although it is guaranteed to be in the
same order as the list of
CONST fields returned by
gd_mfield_list_by_type(3). The array is unterminated. The number of
values in the array can be obtained from a call to
gd_nmfields_by_type(3).
The caller may not modify any values in the array, or the array itself. Doing so
may cause database corruption. The pointer returned is guaranteed to be valid
until
gd_mconstants() is called again, or until the array is
de-allocated by a call to
gd_close(3).
A corresponding list of names for these fields may be obtained by calling
gd_mfield_list_by_type(3).
RETURN VALUE¶
Upon successful completion,
gd_mconstants() returns a pointer to an array
of values containing the values of all the
CONST metafields for the
supplied parent field. If the parent field has no constant metafields, NULL is
returned. On error it returns NULL and sets the dirfile error to a non-zero
error value. Possible error values are:
- GD_E_ALLOC
- The library was unable to allocate memory.
- GD_E_BAD_CODE
- The supplied parent field code was not found, or referred to a metafield
itself.
- GD_E_BAD_DIRFILE
- The supplied dirfile was invalid.
- GD_E_BAD_TYPE
- The return_type specified was invalid.
The dirfile error may be retrieved by calling
gd_error(3). A descriptive
error string for the last error encountered can be obtained from a call to
gd_error_string(3).
SEE ALSO¶
dirfile(5),
gd_error(3),
gd_error_string(3),
gd_field_list_by_type(3),
gd_nfields_by_type(3),
gd_mcarrays(3),
gd_open(3)