src/main/java/com/android/apkzlib/zip/utils/CloseableByteSource.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.utils;

import com.google.common.io.ByteSource;

import java.io.Closeable;
import java.io.IOException;

/**
 * Byte source that can be closed. Closing a byte source allows releasing any resources associated
 * with it. This should not be confused with closing streams. For example, {@link ByteTracker} uses
 * {@code CloseableByteSources} to know when the data associated with the byte source can be
 * released.
 */
public abstract class CloseableByteSource extends ByteSource implements Closeable {

    /**
     * Has the source been closed?
     */
    private boolean closed;

    /**
     * Creates a new byte source.
     */
    public CloseableByteSource() {
        closed = false;
    }

    @Override
    public final synchronized void close() throws IOException {
        if (closed) {
            return;
        }

        try {
            innerClose();
        } finally {
            closed = true;
        }
    }

    /**
     * Closes the by source. This method is only invoked once, even if {@link #close()} is
     * called multiple times.
     *
     * @throws IOException failed to close
     */
    protected abstract void innerClose() throws IOException;
}