src/main/java/com/android/apkzlib/zip/InflaterByteSource.java

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.apkzlib.zip;

import com.android.apkzlib.zip.utils.CloseableByteSource;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.SequenceInputStream;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import javax.annotation.Nonnull;

/**
 * Byte source that inflates another byte source. It assumed the inner byte source has deflated
 * data.
 */
public class InflaterByteSource extends CloseableByteSource {

    /**
     * The stream factory for the deflated data.
     */
    @Nonnull
    private final CloseableByteSource deflatedSource;

    /**
     * Creates a new source.
     * @param byteSource the factory for deflated data
     */
    public InflaterByteSource(@Nonnull CloseableByteSource byteSource) {
        deflatedSource = byteSource;
    }

    @Override
    public InputStream openStream() throws IOException {
        /*
         * The extra byte is a dummy byte required by the inflater. Weirdo.
         * (see the java.util.Inflater documentation). Looks like a hack...
         * "Oh, I need an extra dummy byte to allow for some... err... optimizations..."
         */
        ByteArrayInputStream hackByte = new ByteArrayInputStream(new byte[] { 0 });
        return new InflaterInputStream(new SequenceInputStream(deflatedSource.openStream(),
                hackByte), new Inflater(true));
    }

    @Override
    public void innerClose() throws IOException {
        deflatedSource.close();
    }
}