content: /*
   * 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.
   */
  
  package org.apache.cassandra.db.streaming;
  
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.io.sstable.Component;
  import org.apache.cassandra.io.sstable.Descriptor;
  import org.apache.cassandra.io.sstable.SSTable;
  import org.apache.cassandra.io.util.File;
  import org.apache.cassandra.io.util.FileUtils;
  
  public class ComponentContext implements AutoCloseable
  {
      private static final Logger logger = LoggerFactory.getLogger(ComponentContext.class);
  
      private final Map<Component, File> hardLinks;
      private final ComponentManifest manifest;
  
      private ComponentContext(Map<Component, File> hardLinks, ComponentManifest manifest)
      {
          this.hardLinks = hardLinks;
          this.manifest = manifest;
      }
  
      public static ComponentContext create(SSTable sstable)
      {
          Descriptor descriptor = sstable.descriptor;
          Map<Component, File> hardLinks = new HashMap<>(1);
  
          for (Component component : descriptor.getFormat().mutableComponents())
          {
              File file = descriptor.fileFor(component);
              if (!file.exists())
                  continue;
  
              File hardlink = descriptor.tmpFileForStreaming(component);
              FileUtils.createHardLink(file, hardlink);
              hardLinks.put(component, hardlink);
          }
  
          return new ComponentContext(hardLinks, ComponentManifest.create(sstable));
      }
  
      public ComponentManifest manifest()
      {
          return manifest;
      }
  
      /**
       * @return file channel to be streamed, either original component or hardlinked component.
       */
      public FileChannel channel(Descriptor descriptor, Component component, long size) throws IOException
      {
          File toTransfer = hardLinks.containsKey(component) ? hardLinks.get(component) : descriptor.fileFor(component);
          @SuppressWarnings("resource") // file channel will be closed by Caller
          FileChannel channel = toTransfer.newReadChannel();
  
          assert size == channel.size() : String.format("Entire sstable streaming expects %s file size to be %s but got %s.",
                                                        component, size, channel.size());
          return channel;
      }
  
      @Override
      public void close()
      {
          Throwable accumulate = null;
          for (File file : hardLinks.values())
              accumulate = FileUtils.deleteWithConfirm(file, accumulate);
  
          hardLinks.clear();
  
          if (accumulate != null)
              logger.warn("Failed to remove hard link files", accumulate);
      }
  }
  