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 speci‐
       fied 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 re‐
       turn 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_con‐
       stant(3)

Version 0.7.0                                    3 Novmeber 2010                              gd_get_constant(3)