readCdfUnitNames <- function(filename, units=NULL, verbose=0) {

   # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

   # Validate arguments

   # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

   # Argument 'filename':
   filename <- file.path(dirname(filename), basename(filename));
   if (!file.exists(filename))
     stop("File not found: ", filename);
 
   # Argument 'units':
   if (is.null(units)) {
   } else if (is.numeric(units)) {
     units <- as.integer(units);

     if (any(units < 1))
       stop("Argument 'units' contains non-positive indices.");

   } else {
     stop("Argument 'units' must be numeric or NULL: ", class(units)[1]);
   }
 

   # Argument 'verbose':

   if (length(verbose) != 1)
     stop("Argument 'units' must be a single integer.");
   verbose <- as.integer(verbose);
   if (!is.finite(verbose))
     stop("Argument 'units' must be an integer: ", verbose);
 

   # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

   # Read the CDF file

   # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   # UNSUPPORTED CASE?
   if (!is.null(units) && length(units) == 0L) {
     stop("readCdfUnitNames(..., units=integer(0)) is not supported.")
   }
 

   res <- .Call("R_affx_get_cdf_unit_names", filename, units, verbose,

         PACKAGE="affxparser");

 
   # Sanity check
   if (is.null(res)) {
     stop("Failed to read unit names from CDF file: ", filename);
   }

   res;
 } # readCdfUnitNames()

 ############################################################################
 # HISTORY:

 # 2011-11-18
 # o ROBUSTNESS: Added sanity check that the native code did not return NULL.

 # 2006-03-28
 # o Unit indices are now one-based. /HB
 ############################################################################