code: protected boolean isValidString(CobolContext cobolContext, byte[] hostData,
              int start) {
  
          int length = start + getBytesLen();
  
          for (int i = start; i < length; i++) {
              int code = hostData[i] & 0xFF;
              if (code != 0 && code < cobolContext.getHostSpaceCharCode()) {
                  return false;
              }
          }
  
          return true;
      }
docs: Relatively naive implementation that assumes content is either low-value
  or a code point greater or equal to the space character.
  
  @param cobolContext host COBOL configuration parameters
  @param hostData the byte array containing mainframe data
  @param start the start position for the expected type in the byte array
  @return true if the byte array contains a valid string