/*

  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

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

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code 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

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

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

  * 2 along with this work; if not, write to the Free Software Foundation,

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

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package org.apidesign.javap;

 public final class StackMapIterator {

     private static final StackMapTableData INITIAL_FRAME =

             new StackMapTableData(-1) {

                 @Override

                 int getStackItemsCount() {

                     return 0;

                 }

                 @Override

                 public String toString() {

                     return "INITIAL(0)";

                 }

             };

     private final StackMapTableData[] stackMapTable;

     private int nextFrameIndex;

     private int lastFrameByteCodeOffset;

     private int byteCodeOffset;

     StackMapIterator(final StackMapTableData[] stackMapTable) {

         this.stackMapTable = (stackMapTable != null)

                                  ? stackMapTable

                                  : new StackMapTableData[0];

         this.lastFrameByteCodeOffset = -1;

         advanceBy(0);

     }

     public String getFrameAsString() {

         return getCurrentFrame().toString();

     }

     public int getFrameIndex() {

         return nextFrameIndex;

     }

     public int getFrameStackItemsCount() {

         return getCurrentFrame().getStackItemsCount();

     }

     public void advanceBy(final int numByteCodes) {

         if (numByteCodes < 0) {

             throw new IllegalStateException("Forward only iterator");

         }

         byteCodeOffset += numByteCodes;

         while ((nextFrameIndex < stackMapTable.length)

                     && ((byteCodeOffset - lastFrameByteCodeOffset)

                             >= (stackMapTable[nextFrameIndex].offsetDelta

                                     + 1))) {

             lastFrameByteCodeOffset +=

                     stackMapTable[nextFrameIndex].offsetDelta + 1;

             ++nextFrameIndex;

         }

     }

     public void advanceTo(final int nextByteCodeOffset) {

         advanceBy(nextByteCodeOffset - byteCodeOffset);

     }

     private StackMapTableData getCurrentFrame() {

         return (nextFrameIndex == 0)

                 ? INITIAL_FRAME

                 : stackMapTable[nextFrameIndex - 1];

     }

 }