foam.dao.index.PersistedIndex.java Source code

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Here is the source code for foam.dao.index.PersistedIndex.java

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/**
 * @license
 * Copyright 2017 The FOAM Authors. All Rights Reserved.
 *     http://www.apache.org/licenses/LICENSE-2.0
 */

package foam.dao.index;

import java.io.*;
import org.apache.commons.io.IOUtils;

public class PersistedIndex extends ProxyIndex implements Closeable {
    protected final File file_;
    protected FileInputStream fis_;
    protected FileOutputStream fos_;

    protected ByteArrayOutputStream bos_ = new ByteArrayOutputStream();

    public PersistedIndex(String filename, Index index) throws IOException {
        this.file_ = new File(filename).getAbsoluteFile();
        if (!file_.exists()) {
            if (!this.file_.createNewFile()) {
                throw new IOException("Unable to create file: " + filename);
            }
        }
        this.fis_ = new FileInputStream(this.file_);
        this.fos_ = new FileOutputStream(this.file_);
        setDelegate(index);
    }

    @Override
    public Object wrap(Object state) {
        synchronized (file_) {
            try {
                long position = fos_.getChannel().position();
                ObjectOutputStream oos = new ObjectOutputStream(bos_);
                oos.writeObject(state);
                oos.flush();

                bos_.writeTo(fos_);
                bos_.flush();
                bos_.reset();

                return position;
            } catch (Throwable t) {
                throw new RuntimeException(t);
            }
        }
    }

    @Override
    public Object unwrap(Object state) {
        synchronized (file_) {
            try {
                long position = (long) state;
                fis_.getChannel().position(position);
                ObjectInputStream iis = new ObjectInputStream(fis_);
                return iis.readObject();
            } catch (Throwable t) {
                throw new RuntimeException(t);
            }
        }
    }

    @Override
    public void close() throws IOException {
        IOUtils.closeQuietly(bos_);
        IOUtils.closeQuietly(fos_);
        IOUtils.closeQuietly(fis_);
    }
}