/*

 * $Id$

 *

 * Copyright (C) 2003-2009 JNode.org

 *

 * This library is free software; you can redistribute it and/or modify it

 * under the terms of the GNU Lesser General Public License as published

 * by the Free Software Foundation; either version 2.1 of the License, or

 * (at your option) any later version.

 *

 * This library 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 Lesser General Public 

 * License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this library; If not, write to the Free Software Foundation, Inc., 

 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

package org.jnode.vm;

import org.jnode.annotation.MagicPermission;

import org.jnode.vm.classmgr.VmCompiledCode;

import org.jnode.vm.classmgr.VmMethod;

import org.vmmagic.unboxed.Address;

@MagicPermission

final class VmStackFrameEnumerator {

    /**

     * Stack frame reader

     */

    private final VmStackReader reader;

    /**

     * Address of current stack frame

     */

    private Address framePtr;

    /**

     * Index in address map of current stack frame method (deals with inlined methods)

     */

    private int codeIndex;

    /**

     * Compiled code for the current frame

     */

    private VmCompiledCode cc;

    /**

     * Initialize this instance.

     *

     * @param reader

     * @param framePtr

     * @param instrPtr

     */

    public VmStackFrameEnumerator(VmStackReader reader, Address framePtr, Address instrPtr) {

        this.reader = reader;

        reset(framePtr, instrPtr);

    }

    /**

     * Initialize this instance.

     * Set the enumerator to enumerate the stack of the current thread.

     *

     * @param reader

     */

    public VmStackFrameEnumerator(VmStackReader reader) {

        this.reader = reader;

        final Address curFrame = VmMagic.getCurrentFrame();

        reset(reader.getPrevious(curFrame), reader.getReturnAddress(curFrame));

    }

    /**

     * Reset the enumerator to the given pointers.

     *

     * @param framePtr

     * @param instrPtr

     */

    public final void reset(Address framePtr, Address instrPtr) {

        this.framePtr = framePtr;

        initializeCodeIndex(instrPtr);

    }

    /**

     * Is the current frameptr valid.

     *

     * @return

     */

    public final boolean isValid() {

        return reader.isValid(framePtr);

    }

    /**

     * Move to the next stack position.

     */

    public final void next() {

        if (reader.isValid(framePtr)) {

            if (cc != null) {

                final int newIndex = cc.getAddressMap().getCallSiteIndex(codeIndex);

                if (newIndex >= 0) {

                    codeIndex = newIndex;

                    return;

                }

            }

            final Address nextIP = reader.getReturnAddress(framePtr).add(-1);

            this.framePtr = reader.getPrevious(framePtr);

            initializeCodeIndex(nextIP);

        }

    }

    /**

     * Gets the method at the current stack position.

     *

     * @return

     */

    public final VmMethod getMethod() {

        VmMethod m = null;

        if (cc != null) {

            m = cc.getAddressMap().getMethodAtIndex(codeIndex);

        }

        if (m == null) {

            m = cc.getMethod();

        }

        if (m == null) {

            m = reader.getMethod(framePtr);

        }

        return m;

    }

    /**

     * Gets the method at the current stack position.

     *

     * @return

     */

    public final int getProgramCounter() {

        if (cc != null) {

            return cc.getAddressMap().getProgramCounterAtIndex(codeIndex);

        } else {

            return -1;

        }

    }

    /**

     * Gets the line number at the current stack position.

     *

     * @return

     */

    public final int getLineNumber() {

        return getMethod().getBytecode().getLineNr(getProgramCounter());

    }

    private void initializeCodeIndex(Address instrPtr) {

        cc = reader.getCompiledCode(framePtr);

        if (cc != null) {

            codeIndex = cc.getAddressMapIndex(instrPtr);

        } else {

            codeIndex = -1;

        }

    }

}