RoutineContext.java

/*
 * $Id: RoutineContext.java 536 2008-02-19 06:03:27Z weiju $
 * 
 * Created on 10/03/2005
 * Copyright 2005-2008 by Wei-ju Wu
 * This file is part of The Z-machine Preservation Project (ZMPP).
 *
 * ZMPP is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ZMPP is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ZMPP.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.zmpp.vm;

/**
 * This class holds information about a subroutine.
 *
 * @author Wei-ju Wu
 * @version 1.0
 */
public class RoutineContext {

    /**
     * Set as return variable value if the call is a call_nx.
     */
    public static final int DISCARD_RESULT = -1;

    /**
     * The start address of the routine's code.
     */
    private int startAddress;

    /**
     * The local variables.
     */
    private short[] locals;

    /**
     * The return address.
     */
    private int returnAddress;

    /**
     * The return variable number to store the return value to.
     */
    private int returnVarNum;

    /**
     * The stack pointer at invocation time.
     */
    private int invocationStackPointer;

    /**
     * The number of arguments.
     */
    private int numArgs;

    /**
     * The return value.
     */
    private short returnValue;

    /**
     * Constructor.
     *
     * @param startAddress the routine's start address
     * @param numLocalVariables the number of local variables
     */
    public RoutineContext(int startAddress, int numLocalVariables) {

        this.startAddress = startAddress;
        locals = new short[numLocalVariables];
    }

    /**
     * Sets the number of arguments.
     *
     * @param numArgs the number of arguments
     */
    public void setNumArguments(final int numArgs) {

        this.numArgs = numArgs;
    }

    /**
     * Returns the number of arguments.
     *
     * @return the number of arguments
     */
    public int getNumArguments() {

        return numArgs;
    }

    /**
     * Returns the number of local variables.
     *
     * @return the number of local variables
     */
    public int getNumLocalVariables() {

        return (locals == null) ? 0 : locals.length;
    }

    /**
     * Sets a value to the specified local variable.
     *
     * @param localNum the local variable number, starting with 0
     * @param value the value
     */
    public void setLocalVariable(final int localNum, final short value) {

        locals[localNum] = value;
    }

    /**
     * Retrieves the value of the specified local variable.
     *
     * @param localNum the local variable number, starting at 0
     * @return the value of the specified variable
     */
    public short getLocalVariable(final int localNum) {

        return locals[localNum];
    }

    /**
     * Returns this routine's start address.
     *
     * @return the start address
     */
    public int getStartAddress() {

        return startAddress;
    }

    /**
     * Returns the routine's return address.
     *
     * @return the routine's return address
     */
    public int getReturnAddress() {

        return returnAddress;
    }

    /**
     * Sets the return address.
     *
     * @param address the return address
     */
    public void setReturnAddress(final int address) {

        this.returnAddress = address;
    }

    /**
     * Returns the routine's return variable number.
     *
     * @return the return variable number or DISCARD_RESULT
     */
    public int getReturnVariable() {

        return returnVarNum;
    }

    /**
     * Sets the routine's return variable number.
     *
     * @param varnum the return variable number or DISCARD_RESULT
     */
    public void setReturnVariable(final int varnum) {

        returnVarNum = varnum;
    }

    /**
     * Returns the stack pointer at invocation time.
     *
     * @return the stack pointer at invocation time
     */
    public int getInvocationStackPointer() {

        return invocationStackPointer;
    }

    /**
     * Sets the stack pointer at invocation time.
     *
     * @param stackpointer the stack pointer at invocation time.
     */
    public void setInvocationStackPointer(final int stackpointer) {

        invocationStackPointer = stackpointer;
    }

    /**
     * Returns the return value.
     *
     * @return the return value
     */
    public short getReturnValue() {

        return returnValue;
    }

    /**
     * Sets the return value.
     *
     * @param value the return value
     */
    public void setReturnValue(final short value) {

        returnValue = value;
    }
}