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.io.sstable.format;
  
  import java.io.IOException;
  import java.nio.file.NoSuchFileException;
  import java.util.Set;
  
  import org.apache.cassandra.io.FSReadError;
  import org.apache.cassandra.io.compress.CompressionMetadata;
  import org.apache.cassandra.io.sstable.Component;
  import org.apache.cassandra.io.sstable.CorruptSSTableException;
  import org.apache.cassandra.io.sstable.Descriptor;
  import org.apache.cassandra.io.sstable.format.SSTableFormat.Components;
  import org.apache.cassandra.io.util.File;
  
  public class CompressionInfoComponent
  {
      public static CompressionMetadata maybeLoad(Descriptor descriptor, Set<Component> components)
      {
          if (components.contains(Components.COMPRESSION_INFO))
              return load(descriptor);
  
          return null;
      }
  
      public static CompressionMetadata loadIfExists(Descriptor descriptor)
      {
          if (descriptor.fileFor(Components.COMPRESSION_INFO).exists())
              return load(descriptor);
  
          return null;
      }
  
      public static CompressionMetadata load(Descriptor descriptor)
      {
          return CompressionMetadata.open(descriptor.fileFor(Components.COMPRESSION_INFO),
                                          descriptor.fileFor(Components.DATA).length(),
                                          descriptor.version.hasMaxCompressedLength());
      }
  
      /**
       * Best-effort checking to verify the expected compression info component exists, according to the TOC file.
       * The verification depends on the existence of TOC file. If absent, the verification is skipped.
       *
       * @param descriptor
       * @param actualComponents actual components listed from the file system.
       * @throws CorruptSSTableException if TOC expects compression info but not found from disk.
       * @throws FSReadError             if unable to read from TOC file.
       */
      public static void verifyCompressionInfoExistenceIfApplicable(Descriptor descriptor, Set<Component> actualComponents) throws CorruptSSTableException, FSReadError
      {
          File tocFile = descriptor.fileFor(Components.TOC);
          if (tocFile.exists())
          {
              try
              {
                  Set<Component> expectedComponents = TOCComponent.loadTOC(descriptor, false);
                  if (expectedComponents.contains(Components.COMPRESSION_INFO) && !actualComponents.contains(Components.COMPRESSION_INFO))
                  {
                      File compressionInfoFile = descriptor.fileFor(Components.COMPRESSION_INFO);
                      throw new CorruptSSTableException(new NoSuchFileException(compressionInfoFile.absolutePath()), compressionInfoFile);
                  }
              }
              catch (IOException e)
              {
                  throw new FSReadError(e, tocFile);
              }
          }
      }
  }
  