NAME

       gd_get_constant — retrieve a scalar constant from a dirfile database

SYNOPSIS

       #include <getdata.h>

       int gd_get_constant(DIRFILE *dirfile, const char *field_code, gd_type_t return_type, void
              *data_out);

DESCRIPTION

       The gd_get_constant() function queries a dirfile(5) database specified by dirfile for  the
       CONST  scalar  field_code,  which  may  contain  a representation suffix.  The constant is
       converted to the data type specified by  return_type,  and  stored  in  the  user-supplied
       buffer data_out.

       The  dirfile argument must point to a valid DIRFILE object previously created by a call to
       gd_open(3).  The argument data_out must point to a valid  memory  location  of  sufficient
       size to hold a value of the return type specified.

       The  return_type  argument  should  be  one  of the following symbols, which indicates the
       desired return type of the data:

              GD_UINT8   unsigned 8-bit integer

              GD_INT8    signed (two's complement) 8-bit integer

              GD_UINT16  unsigned 16-bit integer

              GD_INT16   signed (two's complement) 16-bit integer

              GD_UINT32  unsigned 32-bit integer

              GD_INT32   signed (two's complement) 32-bit integer

              GD_UINT64  unsigned 64-bit integer

              GD_INT64   signed (two's complement) 64-bit integer

              GD_FLOAT32 IEEE-754 standard 32-bit single precision floating point number

              GD_FLOAT64 IEEE-754 standard 64-bit double precision floating point number

              GD_COMPLEX64
                         C99-conformant 64-bit single precision complex number

              GD_COMPLEX128
                         C99-conformant 128-bit double precision complex number

              GD_NULL    the null type: the  database  is  queried  as  usual,  but  no  data  is
                         returned.  In this case, data_out is ignored and may be NULL.

       The return type of the constant need not be the same as the type of the data stored in the
       database.  Type conversion will be performed as necessary to return  the  requested  type.
       If  the field_code does not indicate a representation, but conversion from a complex value
       to a purely real one is required, only the real portion of the requested  vector  will  be
       returned.

RETURN VALUE

       On  success, gd_get_constant() returns zero.  On error, it returns -1 and sets the dirfile
       error to a non-zero value.  Possible error values are:

       GD_E_BAD_CODE
               The field specified by field_code was not found in the database.

       GD_E_BAD_DIRFILE
               An invalid dirfile was supplied.

       GD_E_BAD_FIELD_TYPE
               The supplied field_code referred to a field of  a  type  other  than  CONST.   The
               caller should use gd_getdata(3), or gd_get_string(3) instead.

       GD_E_BAD_REPR
               The  representation suffix specified in fieldcode, or in one of the field codes it
               uses for input, was invalid.

       GD_E_BAD_TYPE
               An invalid return_type was specified.

       GD_E_INTERNAL_ERROR
               An internal error occurred in the library while trying to perform the task.   This
               indicates a bug in the library.  Please report the incident to the maintainer.

       The dirfile error may be retrieved by calling gd_error(3).  A descriptive error string for
       the last error encountered may be obtained from a call to gd_error_string(3).

SEE ALSO

       dirfile(5),     gd_open(3),     gd_error(3),     gd_error_string(3),     gd_get_carray(3),
       gd_constants(3), gd_put_constant(3)