content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master.journal.ufs;
  
  import alluxio.conf.Configuration;
  import alluxio.master.journal.JournalFileParser;
  import alluxio.proto.journal.Journal;
  import alluxio.underfs.UnderFileSystem;
  import alluxio.underfs.UnderFileSystemConfiguration;
  import alluxio.util.proto.ProtoUtils;
  
  import com.google.common.base.Preconditions;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URI;
  import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * Implementation of {@link JournalFileParser} that parses a journal file.
   */
  @NotThreadSafe
  public final class UfsJournalFileParser implements JournalFileParser {
    private static final Logger LOG = LoggerFactory.getLogger(UfsJournalFileParser.class);
  
    private final UnderFileSystem mUfs;
    /** Buffer used to read from the file. */
    private byte[] mBuffer = new byte[1024];
  
    /** The input stream to read from the journal file. */
    private InputStream mInputStream;
    /** The location of the journal file. */
    private URI mLocation;
  
    /**
     * Creates a new instance of {@link UfsJournalFileParser}.
     *
     * @param location the journal file location
     */
    public UfsJournalFileParser(URI location) {
      mLocation = Preconditions.checkNotNull(location, "location");
      mUfs = UnderFileSystem.Factory.create(mLocation.toString(),
          UnderFileSystemConfiguration.defaults(Configuration.global()));
    }
  
    @Override
    public void close() throws IOException {
      mInputStream.close();
    }
  
    @Override
    public Journal.JournalEntry next() throws IOException {
      if (mInputStream == null) {
        mInputStream = mUfs.open(mLocation.toString());
      }
  
      int firstByte = mInputStream.read();
      if (firstByte == -1) {
        return null;
      }
      // All journal entries start with their size in bytes written as a varint.
      int size;
      try {
        size = ProtoUtils.readRawVarint32(firstByte, mInputStream);
      } catch (IOException e) {
        LOG.warn("Journal entry was truncated in the size portion.");
        return null;
      }
      if (size > mBuffer.length) {
        mBuffer = new byte[size];
      }
      // Total bytes read so far for journal entry.
      int totalBytesRead = 0;
      while (totalBytesRead < size) {
        // Bytes read in last read request.
        int latestBytesRead = mInputStream.read(mBuffer, totalBytesRead, size - totalBytesRead);
        if (latestBytesRead < 0) {
          break;
        }
        totalBytesRead += latestBytesRead;
      }
      if (totalBytesRead < size) {
        LOG.warn("Journal entry was truncated. Expected to read " + size + " bytes but only got "
            + totalBytesRead);
        return null;
      }
  
      return Journal.JournalEntry.parser().parseFrom(mBuffer, 0, size);
    }
  }
  