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.index.sai.disk.v1;
  
  import java.io.IOException;
  import java.util.HashMap;
  import java.util.Map;
  import javax.annotation.concurrent.NotThreadSafe;
  
  import org.apache.cassandra.index.sai.disk.format.IndexComponent;
  import org.apache.cassandra.index.sai.disk.format.IndexDescriptor;
  import org.apache.cassandra.index.sai.utils.IndexIdentifier;
  import org.apache.cassandra.index.sai.disk.io.IndexFileUtils;
  import org.apache.lucene.store.ByteArrayDataInput;
  import org.apache.lucene.store.ChecksumIndexInput;
  import org.apache.lucene.store.DataInput;
  import org.apache.lucene.store.IndexInput;
  import org.apache.lucene.util.BytesRef;
  
  @NotThreadSafe
  public class MetadataSource
  {
      private final Map<String, BytesRef> components;
  
      private MetadataSource(Map<String, BytesRef> components)
      {
          this.components = components;
      }
  
      public static MetadataSource loadGroupMetadata(IndexDescriptor indexDescriptor) throws IOException
      {
          return MetadataSource.load(indexDescriptor.openPerSSTableInput(IndexComponent.GROUP_META));
      }
  
      public static MetadataSource loadColumnMetadata(IndexDescriptor indexDescriptor, IndexIdentifier indexIdentifier) throws IOException
      {
          return MetadataSource.load(indexDescriptor.openPerIndexInput(IndexComponent.META, indexIdentifier));
      }
  
      private static MetadataSource load(IndexInput indexInput) throws IOException
      {
          Map<String, BytesRef> components = new HashMap<>();
  
          try (ChecksumIndexInput input = IndexFileUtils.getBufferedChecksumIndexInput(indexInput))
          {
              SAICodecUtils.checkHeader(input);
              final int num = input.readInt();
  
              for (int x = 0; x < num; x++)
              {
                  if (input.length() == input.getFilePointer())
                  {
                      // we should never get here, because we always add footer to the file
                      throw new IllegalStateException("Unexpected EOF in " + input);
                  }
  
                  final String name = input.readString();
                  final int length = input.readInt();
                  final byte[] bytes = new byte[length];
                  input.readBytes(bytes, 0, length);
  
                  components.put(name, new BytesRef(bytes));
              }
  
              SAICodecUtils.checkFooter(input);
          }
  
          return new MetadataSource(components);
      }
  
      public DataInput get(String name)
      {
          BytesRef bytes = components.get(name);
  
          if (bytes == null)
          {
              throw new IllegalArgumentException(String.format("Could not find component '%s'. Available properties are %s.",
                                                               name, components.keySet()));
          }
  
          return new ByteArrayDataInput(bytes.bytes);
      }
  }
  