NAME

       gd_get_carray, gd_get_carray_slice, gd_get_constant — retrieve CONST or CARRAY data from a
       Dirfile database

SYNOPSIS

       #include <getdata.h>

       int gd_get_carray_slice(DIRFILE *dirfile, const char *field_code, unsigned int start,
              size_t len, gd_type_t return_type, void *data_out);

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

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

DESCRIPTION

       The  gd_get_carray_slice() function queries a dirfile(5) database specified by dirfile for
       the CONST or CARRAY scalar field_code, which may contain  a  representation  suffix.   The
       data  in  the  field is converted to the data type specified by return_type, and stored in
       the user-supplied buffer data_out.  The first element of the  field  stored  is  given  by
       start, and the number of elements stored is given by len.

       The  gd_get_carray() function behaves similarly, except it returns the entire field, as if
       gd_get_carray_slice() were called with start equal to zero and  len  equal  to  the  value
       returned  by  gd_array_len(3).   The  gd_get_constant()  function is equivalent to calling
       gd_get_carray_slice() with start equal to zero and len equal to one.

       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 all the requested data of the return type specified.  The number of  elements
       returned   by   gd_get_carray()  may  be  obtained  by  calling  gd_array_len(3).   Unlike
       gd_getdata(3), calling gd_get_carray_slice() never results in a short read; attempting  to
       read past the end of the field will result in an error, and no data will be returned.

       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 field 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_carray(), gd_get_carray_slice(), and gd_get_constant() return zero.  On
       error, they return a negative-valued error code.  Possible error codes are:

       GD_E_ALLOC
               The library was unable to allocate memory.

       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 was not a CONST nor CARRAY.

       GD_E_BAD_TYPE
               An invalid return_type was specified.

       GD_E_BOUNDS
               A request for data beyond the end of the field was made.

       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  error  code  is  also  stored  in  the DIRFILE object and may be retrieved after this
       function returns by calling gd_error(3).  A descriptive error string for the error may  be
       obtained by calling gd_error_string(3).

HISTORY

       The get_constant() function appeared in GetData-0.4.0.

       In  GetData-0.7.0,  this  function was renamed to gd_get_constant().  In this release, the
       gd_get_carray() and gd_get_carray_slice() functions also appeared.

       In GetData-0.10.0, the error return from these functions changed from -1  to  a  negative-
       valued error code.

SEE ALSO

       gd_array_len(3),     gd_carrays(3),     gd_error(3),    gd_error_string(3),    gd_open(3),
       gd_put_carray_slice(3), dirfile(5)