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      1 /*
      2  * Copyright 2012, Google Inc.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are
      7  * met:
      8  *
      9  *     * Redistributions of source code must retain the above copyright
     10  * notice, this list of conditions and the following disclaimer.
     11  *     * Redistributions in binary form must reproduce the above
     12  * copyright notice, this list of conditions and the following disclaimer
     13  * in the documentation and/or other materials provided with the
     14  * distribution.
     15  *     * Neither the name of Google Inc. nor the names of its
     16  * contributors may be used to endorse or promote products derived from
     17  * this software without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 package org.jf.dexlib2.dexbacked.util;
     33 
     34 import org.jf.dexlib2.dexbacked.DexBackedDexFile;
     35 import org.jf.dexlib2.dexbacked.DexReader;
     36 
     37 import javax.annotation.Nonnull;
     38 import java.util.ListIterator;
     39 import java.util.NoSuchElementException;
     40 
     41 public abstract class VariableSizeListIterator<T> implements ListIterator<T> {
     42     @Nonnull private DexReader reader;
     43     protected final int size;
     44     private final int startOffset;
     45 
     46     private int index;
     47 
     48     protected VariableSizeListIterator(@Nonnull DexBackedDexFile dexFile, int offset, int size) {
     49         this.reader = dexFile.readerAt(offset);
     50         this.startOffset = offset;
     51         this.size = size;
     52     }
     53 
     54     /**
     55      * Reads the next item from reader.
     56      *
     57      * @param reader The {@code DexReader} to read the next item from
     58      * @param index The index of the item being read. This is guaranteed to be less than {@code size}
     59      * @return The item that was read
     60      */
     61     protected abstract T readNextItem(@Nonnull DexReader reader, int index);
     62 
     63     public int getReaderOffset() {
     64         return reader.getOffset();
     65     }
     66 
     67     @Override
     68     public boolean hasNext() {
     69         return index < size;
     70     }
     71 
     72     @Override
     73     public T next() {
     74         if (index >= size) {
     75             throw new NoSuchElementException();
     76         }
     77         return readNextItem(reader, index++);
     78     }
     79 
     80     @Override
     81     public boolean hasPrevious() {
     82         return index > 0;
     83     }
     84 
     85     @Override
     86     public T previous() {
     87         int targetIndex = index-1;
     88         reader.setOffset(startOffset);
     89         index = 0;
     90         while (index < targetIndex) {
     91             readNextItem(reader, index++);
     92         }
     93         return readNextItem(reader, index++);
     94     }
     95 
     96     @Override
     97     public int nextIndex() {
     98         return index;
     99     }
    100 
    101     @Override
    102     public int previousIndex() {
    103         return index - 1;
    104     }
    105 
    106     @Override public void remove() { throw new UnsupportedOperationException(); }
    107     @Override public void set(T t) { throw new UnsupportedOperationException(); }
    108     @Override public void add(T t) { throw new UnsupportedOperationException(); }
    109 }
    110