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.Coprocessor1;
  import mars.mips.hardware.InvalidRegisterAccessException;
  import mars.mips.hardware.RegisterFile;
  import mars.simulator.Exceptions;
  
  /*
   * 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 input data.
   */
  
  public class SyscallInputDialogDouble extends AbstractSyscall {
  
  	/**
  	 * Build an instance of the syscall with its default service number and name.
  	 */
  	public SyscallInputDialogDouble() {
  		super(53, "InputDialogDouble");
  	}
  
  	/**
  	 * System call to input data.
  	 */
  	@Override
  	public void simulate(final ProgramStatement statement) throws ProcessingException {
  		// Input arguments: $a0 = address of null-terminated string that is the message to user
  		// Outputs:
  		//    $f0 and $f1 contains value of double read. $f1 contains high order word of the double.
  		//    $a1 contains status value
  		//       0: valid input data, correctly parsed
  		//       -1: input data cannot be correctly parsed
  		//       -2: Cancel was chosen
  		//       -3: OK was chosen but no data had been input into field
  
  		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);
  		}
  
  		// Values returned by Java's InputDialog:
  		// A null return value means that "Cancel" was chosen rather than OK.
  		// An empty string returned (that is, inputValue.length() of zero)
  		// means that OK was chosen but no string was input.
  		String inputValue = null;
  		inputValue = JOptionPane.showInputDialog(message);
  
  		try {
  			Coprocessor1.setRegisterPairToDouble(0, 0.0);  // set $f0 to zero
  			if (inputValue == null)  // Cancel was chosen
  			{
  				RegisterFile.updateRegister(5, -2);  // set $a1 to -2 flag
  			} else if (inputValue.length() == 0)  // OK was chosen but there was no input
  			{
  				RegisterFile.updateRegister(5, -3);  // set $a1 to -3 flag
  			} else {
  				final double doubleValue = Double.parseDouble(inputValue);
  
  				// Successful parse of valid input data
  				Coprocessor1.setRegisterPairToDouble(0, doubleValue);  // set $f0 to input data
  				RegisterFile.updateRegister(5, 0);  // set $a1 to valid flag
  
  			}
  
  		} // end try block
  
  		catch (final InvalidRegisterAccessException e)   // register ID error in this method
  		{
  			RegisterFile.updateRegister(5, -1);  // set $a1 to -1 flag
  			throw new ProcessingException(statement, "invalid int reg. access during double input (syscall "
  					+ getNumber() + ")", Exceptions.SYSCALL_EXCEPTION);
  		}
  
  		catch (final NumberFormatException e)    // Unsuccessful parse of input data
  		{
  			RegisterFile.updateRegister(5, -1);  // set $a1 to -1 flag
  			/*  Don't throw exception because returning a status flag
  			throw new ProcessingException(statement,
  			   "invalid float input (syscall "+this.getNumber()+")",
  				          Exceptions.SYSCALL_EXCEPTION);
  			*/
  		}
  
  	}
  
  }
  