xref: /external/smali/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/util/VariableSizeLookaheadIterator.java

/*
 * Copyright 2012, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.jf.dexlib2.dexbacked.util;

import org.jf.dexlib2.dexbacked.DexBackedDexFile;
import org.jf.dexlib2.dexbacked.DexReader;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.Iterator;
import java.util.NoSuchElementException;

public abstract class VariableSizeLookaheadIterator<T> implements Iterator<T> {
    @Nonnull private final DexReader reader;

    private T cachedItem = null;

    protected VariableSizeLookaheadIterator(@Nonnull DexBackedDexFile dexFile, int offset) {
        this.reader = dexFile.readerAt(offset);
        cachedItem = readNextItem(reader);
    }

    /**
     * Reads the next item from reader. If the end of the list has been reached, it should return null.
     *
     * @return The item that was read, or null if the end of the list has been reached.
     */
    @Nullable protected abstract T readNextItem(@Nonnull DexReader reader);

    @Override
    public boolean hasNext() {
        return cachedItem != null;
    }

    @Override
    @Nonnull
    public T next() {
        if (cachedItem == null) {
            throw new NoSuchElementException();
        }
        T ret = cachedItem;
        cachedItem = readNextItem(reader);
        return ret;
    }

    @Override public void remove() { throw new UnsupportedOperationException(); }
}