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 * Copyright 2012, Google Inc.
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 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * 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
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 */

package org.jf.dexlib2.dexbacked.util;

import com.google.common.collect.AbstractIterator;
import org.jf.dexlib2.dexbacked.DexBackedDexFile;
import org.jf.dexlib2.dexbacked.DexReader;

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

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

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

    /**
     * Reads the next item from reader. If the end of the list has been reached, it should call endOfData.
     *
     * endOfData has a return value of T, so you can simply {@code return endOfData()}
     *
     * @return The item that was read. If endOfData was called, the return value is ignored.
     */
    @Nullable protected abstract T readNextItem(@Nonnull DexReader reader);

    @Override
    protected T computeNext() {
        return readNextItem(reader);
    }

    public final int getReaderOffset() {
        return reader.getOffset();
    }
}