DiskIndexSnapshot.java

package proj.zoie.impl.indexing.internal;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.util.Collection;

import proj.zoie.api.DirectoryManager;
import proj.zoie.api.impl.util.ChannelUtil;
import proj.zoie.impl.indexing.internal.ZoieIndexDeletionPolicy.Snapshot;

/**
 * @author ymatsuda
 *
 */
public class DiskIndexSnapshot {
  private DirectoryManager _dirMgr;
  private IndexSignature _sig;
  private Snapshot _snapshot;

  public DiskIndexSnapshot(DirectoryManager dirMgr, IndexSignature sig, Snapshot snapshot) {
    _dirMgr = dirMgr;
    _sig = sig;
    _snapshot = snapshot;
  }

  public void close() {
    _snapshot.close();
  }

  public DirectoryManager getDirecotryManager() {
    return _dirMgr;
  }

  public long writeTo(WritableByteChannel channel) throws IOException {
    // format:
    // <format_version> <sig_len> <sig_data> { <idx_file_name_len> <idx_file_name> <idx_file_len>
    // <idx_file_data> }...

    long amount = 0;

    // format version
    amount += ChannelUtil.writeInt(channel, 1);

    // index signature
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    _sig.save(baos);
    byte[] sigBytes = baos.toByteArray();

    amount += ChannelUtil.writeLong(channel, (long) sigBytes.length); // data length
    amount += channel.write(ByteBuffer.wrap(sigBytes)); // data

    // index files
    Collection<String> fileNames = _snapshot.getFileNames();
    amount += ChannelUtil.writeInt(channel, fileNames.size()); // number of files
    for (String fileName : fileNames) {
      amount += ChannelUtil.writeString(channel, fileName);
      amount += _dirMgr.transferFromFileToChannel(fileName, channel);
    }
    return amount;
  }

  public static void readSnapshot(ReadableByteChannel channel, DirectoryManager dirMgr)
      throws IOException {
    // format version
    int formatVersion = ChannelUtil.readInt(channel);
    if (formatVersion != 1) {
      throw new IOException("snapshot format version mismatch [" + formatVersion + "]");
    }

    // index signature
    if (!dirMgr.transferFromChannelToFile(channel, DirectoryManager.INDEX_DIRECTORY)) {
      throw new IOException("bad snapshot file");
    }

    // index files
    int numFiles = ChannelUtil.readInt(channel); // number of files
    if (numFiles < 0) {
      throw new IOException("bad snapshot file");
    }
    while (numFiles-- > 0) {
      String fileName = ChannelUtil.readString(channel);
      if (fileName == null) {
        throw new IOException("bad snapshot file");
      }
      if (!dirMgr.transferFromChannelToFile(channel, fileName)) {
        throw new IOException("bad snapshot file");
      }
    }
  }
}