ControlUnit.java

//  ControlUnit.java

import java.io.*;

//  Class ControlUnit
//  -------------------------------------------------------------------
/**
  *   Application that reads instructions from a text file and displays
  *   the control word for each one.
  */
  public class ControlUnit
  {

  //  generateControlWord()
  //  -----------------------------------------------------------------
  /**
    *   Decodes a 32-bit instruction and returns the control word for
    *   it.
    */
    public static ControlWord generateControlWord(long instruction)
    {
      //  Decode the instruction
      int opcode  =   (int)((instruction & 0x0FC000000) >> 26);
      int rs      =   (int)((instruction & 0x003E00000) >> 21);
      int rt      =   (int)((instruction & 0x0001F0000) >> 16);
      int rd      =   (int)((instruction & 0x00000F800) >> 11);
      int shamt   =   (int)((instruction & 0x0000007C0) >>  6);
      int func    =   (int)(instruction & 0x00000003F);
      int immediate = (int)(instruction & 0x0000FFFF);
      int address   = (int)(instruction & 0x03FFFFFF);
      
      //  Get the control word and return it.
      return new ControlWord(opcode, rs, rt, rd, shamt, func, immediate,
          address);
    }

  //  main()
  //  -----------------------------------------------------------------
  /**
    *   For each file named on the command line, read instructions from
    *   the file, and print the control word for executing each one.
    *   Lines in the file are structured with the hexadecimal
    *   representation of the instruction, whitespace, and the assembly
    *   language represenation of the same instruction, suitable for
    *   printing.
    */
    public static void main(String[] args) throws IOException,
                                            NumberFormatException
    {
      //  Loop over the file names specified as command line arguments.
      for (int arg = 0; arg < args.length; arg++ )
      {
        //  Set up to read text lines from a file
        BufferedReader br = new BufferedReader(
          new FileReader( args[arg] ) );
        System.out.println("\nFile: " + args[arg] );
        String  lineBuf;
        
        //  Read and process all lines in the file
        while ( (lineBuf = br.readLine()) != null )
        {
          //  Extract the hex representation of the instruction
          lineBuf.trim();
          System.out.println(lineBuf);
          int firstSpace = lineBuf.indexOf(" ");
          lineBuf = lineBuf.substring(0, firstSpace);
          Long LongVal = Long.decode(lineBuf);
          long instruction = LongVal.longValue();
          
          //  Get the control word for the instruction and print it.
          ControlWord cw = ControlUnit.generateControlWord(instruction);
          System.out.println( "  " + cw );
        }
      }
      System.exit(0);
    }
  }