content: package mars.mips.instructions.syscalls;
  
  import javax.swing.JOptionPane;
  
  import mars.Globals;
  import mars.ProcessingException;
  import mars.ProgramStatement;
  import mars.mips.hardware.AddressErrorException;
  import mars.mips.hardware.RegisterFile;
  
  /*
   * Copyright (c) 2003-2008, Pete Sanderson and Kenneth Vollmar
   *
   * Developed by Pete Sanderson (psanderson@otterbein.edu) and Kenneth Vollmar
   * (kenvollmar@missouristate.edu)
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   *
   * (MIT license, http://www.opensource.org/licenses/mit-license.html)
   */
  
  /**
   * Service to display a message to user.
   */
  
  public class SyscallMessageDialog extends AbstractSyscall {
  
  	/**
  	 * Build an instance of the syscall with its default service number and name.
  	 */
  	public SyscallMessageDialog() {
  		super(55, "MessageDialog");
  	}
  
  	/**
  	 * System call to display a message to user.
  	 */
  	@Override
  	public void simulate(final ProgramStatement statement) throws ProcessingException {
  		// Input arguments:
  		//   $a0 = address of null-terminated string that is the message to user
  		//   $a1 = the type of the message to the user, which is one of:
  		//       1: error message
  		//       2: information message
  		//       3: warning message
  		//       4: question message
  		//       other: plain message
  		// Output: none
  
  		String message = new String(); // = "";
  		int byteAddress = RegisterFile.getValue(4);
  		final char ch[] = { ' ' }; // Need an array to convert to String
  		try {
  			ch[0] = (char) Globals.memory.getByte(byteAddress);
  			while (ch[0] != 0) // only uses single location ch[0]
  			{
  				message = message.concat(new String(ch)); // parameter to String constructor is a char[] array
  				byteAddress++;
  				ch[0] = (char) Globals.memory.getByte(byteAddress);
  			}
  		} catch (final AddressErrorException e) {
  			throw new ProcessingException(statement, e);
  		}
  
  		// Display the dialog.
  		int msgType = RegisterFile.getValue(5);
  		if (msgType < 0 || msgType > 3) {
  			msgType = -1; // See values in http://java.sun.com/j2se/1.5.0/docs/api/constant-values.html
  		}
  		JOptionPane.showMessageDialog(null, message, null, msgType);
  
  	}
  
  }
  