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.trie;
  
  import java.io.Closeable;
  import java.io.IOException;
  import javax.annotation.concurrent.NotThreadSafe;
  
  import org.apache.commons.lang3.mutable.MutableLong;
  
  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.IndexOutputWriter;
  import org.apache.cassandra.index.sai.disk.v1.SAICodecUtils;
  import org.apache.cassandra.io.tries.IncrementalDeepTrieWriterPageAware;
  import org.apache.cassandra.io.tries.IncrementalTrieWriter;
  import org.apache.cassandra.utils.bytecomparable.ByteComparable;
  
  /**
   * Writes terms dictionary to disk in a trie format (see {@link IncrementalTrieWriter}).
   * <p>
   * Allows for variable-length keys. Trie values are 64-bit offsets to the posting file, pointing to the beginning of
   * summary block for that postings list.
   */
  @NotThreadSafe
  public class TrieTermsDictionaryWriter implements Closeable
  {
      private final IncrementalTrieWriter<Long> termsDictionaryWriter;
      private final IndexOutputWriter termDictionaryOutput;
      private final long startOffset;
  
      TrieTermsDictionaryWriter(IndexDescriptor indexDescriptor, IndexIdentifier indexIdentifier) throws IOException
      {
          termDictionaryOutput = indexDescriptor.openPerIndexOutput(IndexComponent.TERMS_DATA, indexIdentifier, true);
          startOffset = termDictionaryOutput.getFilePointer();
  
          SAICodecUtils.writeHeader(termDictionaryOutput);
          // we pass the output as SequentialWriter, but we keep IndexOutputWriter around to write footer on flush
          termsDictionaryWriter = new IncrementalDeepTrieWriterPageAware<>(TrieTermsDictionaryReader.trieSerializer, termDictionaryOutput.asSequentialWriter());
      }
  
      public void add(ByteComparable term, long postingListOffset) throws IOException
      {
          termsDictionaryWriter.add(term, postingListOffset);
      }
  
      @Override
      public void close()
      {
          termsDictionaryWriter.close();
          termDictionaryOutput.close();
      }
  
      /**
       * complete trie index and write footer
       *
       * @return the position in the file of the root node.
       */
      public long complete(MutableLong footerPointer) throws IOException
      {
          long root = termsDictionaryWriter.complete();
  
          footerPointer.setValue(termDictionaryOutput.getFilePointer());
          SAICodecUtils.writeFooter(termDictionaryOutput);
          return root;
      }
  
      /**
       * @return current file pointer
       */
      public long getFilePointer()
      {
          return termDictionaryOutput.getFilePointer();
      }
  
      /**
       * @return file pointer where index structure begins
       */
      public long getStartOffset()
      {
          return startOffset;
      }
  }
  