package duckMachine.architecture;
                         
import java.io.*;

/**
 * The input output unit of the machine. This will not work with jdk-1.0!
 * @author Amr Sabry
 * @version jdk-1.1
 */

public class ioUnit implements ioUnitI {
  /**
   * The dataReader converts bytes to chars using an InputStreamReader 
   * (buffered for efficiency) and then collects the chars and parses 
   * them as ints using a StreamTokenizer.
   */
  private StreamTokenizer dataReader; 

  /**
   * The dataWriter stream is built on top of the byte-oriented stream 
   * by wrapping an OutputStreamWriter that can handle chars, and then 
   * a PrintWriter than can handle strings. The output is buffered 
   * for efficiency and is automatically flushed when a newline is printed.
   */
  private PrintWriter dataWriter;

  public ioUnit () { this(DEFAULT_ISTREAM, DEFAULT_OSTREAM); }
  
  public ioUnit (InputStream i, OutputStream o) {
    Reader charReader = new BufferedReader (new InputStreamReader (i));
    dataReader = new StreamTokenizer (charReader);

    Writer charWriter = new BufferedWriter (new OutputStreamWriter (o));
    boolean automaticFlushAtNewline = true;
    dataWriter = new PrintWriter (charWriter, automaticFlushAtNewline); 
  }
 
  public StreamTokenizer getReader () { return dataReader; }

  public PrintWriter getWriter () { return dataWriter; }

  /**
   * Reads an integer from the input stream. If the next
   * token is a number but not an integer, it is coerced to an int.
   * @exception ioE If the input cannot be parsed as a number or
   * some kind of IO exception occurs.  
   */
  public Word readData () throws ioE {
    try {
      dataReader.nextToken();
      if (dataReader.ttype == dataReader.TT_NUMBER) {
	double d = dataReader.nval; 
	int i = (int)d;             
	return new Data(i);
      }
      else throw new ioE("Illegal input");
    }
    catch (java.io.IOException e) {
      throw new ioE("IO exception occured while reading data\n"
			 + e.toString());
    }
  }

  /**
   * Writes an int and flushes the output stream.
   */
  public void writeData (Word w) { 
    dataWriter.println(w); 
  }

}