VariableSizeLookaheadIterator.java revision 84c1762a62d7fc6638432c6c56e0422aa8cc6939 
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
32package org.jf.dexlib2.dexbacked.util;
33
34import org.jf.dexlib2.dexbacked.DexBackedDexFile;
35import org.jf.dexlib2.dexbacked.DexReader;
36
37import javax.annotation.Nonnull;
38import javax.annotation.Nullable;
39import java.util.Iterator;
40import java.util.NoSuchElementException;
41
42public abstract class VariableSizeLookaheadIterator<T> implements Iterator<T> {
43    @Nonnull private final DexReader reader;
44
45    private T cachedItem = null;
46
47    protected VariableSizeLookaheadIterator(@Nonnull DexBackedDexFile dexFile, int offset) {
48        this.reader = dexFile.readerAt(offset);
49        cachedItem = readNextItem(reader);
50    }
51
52    /**
53     * Reads the next item from reader. If the end of the list has been reached, it should return null.
54     *
55     * @return The item that was read, or null if the end of the list has been reached.
56     */
57    @Nullable protected abstract T readNextItem(@Nonnull DexReader reader);
58
59    @Override
60    public boolean hasNext() {
61        return cachedItem != null;
62    }
63
64    @Override
65    @Nonnull
66    public T next() {
67        if (cachedItem == null) {
68            throw new NoSuchElementException();
69        }
70        T ret = cachedItem;
71        cachedItem = readNextItem(reader);
72        return ret;
73    }
74
75    @Override public void remove() { throw new UnsupportedOperationException(); }
76}
77