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.journal;
  
  import javax.annotation.Nullable;
  
  import org.apache.cassandra.utils.Closeable;
  
  /**
   * Mapping of client supplied ids to in-segment offsets
   */
  abstract class Index<K> implements Closeable
  {
      final KeySupport<K> keySupport;
  
      Index(KeySupport<K> keySupport)
      {
          this.keySupport = keySupport;
      }
  
      /**
       * Look up offsets by id. It's possible, due to retries, for a segment
       * to contain the same record with the same id more than once, at
       * different offsets.
       *
       * @return the found offsets into the segment, if any; can be empty
       */
      abstract long[] lookUp(K id);
  
      /**
       * Look up offsets by id. It's possible, due to retries, for a segment
       * to contain the same record with the same id more than once, at
       * different offsets. Return the first offset for provided record id, or -1 if none.
       *
       * @return the first offset into the segment, or -1 is none were found
       */
      abstract long lookUpLast(K id);
  
      abstract long[] lookUpAll(K id);
  
      /**
       * @return the first (smallest) id in the index
       */
      @Nullable
      abstract K firstId();
  
      /**
       * @return the last (largest) id in the index
       */
      @Nullable
      abstract K lastId();
  
      /**
       * @return whether the id falls within lower/upper bounds of the index
       */
      boolean mayContainId(K id)
      {
          K firstId = firstId();
          K lastId = lastId();
  
          return null != firstId && keySupport.compare(id, firstId) >= 0 && (null == lastId || keySupport.compare(id, lastId) <= 0);
      }
  
      /**
       * Helper methods
       */
  
      public static int readOffset(long record)
      {
          return (int) (0xffffffffL & (record >> 32));
      }
  
      public static long writeOffset(long record, int offset)
      {
          record &= 0x00000000ffffffffL; //unset all higher bits
          record |= ((long) offset) << 32;
          return record;
      }
  
      public static int readSize(long record)
      {
          return (int) (0xffffffffL & record);
      }
  
      public static long writeSize(long record, int size)
      {
          record &= 0xffffffff00000000L; // unset all lower bits
          record |= size;
          return record;
      }
  
      public static long composeOffsetAndSize(int offset, int size)
      {
          return writeSize(writeOffset(0, offset), size);
      }
  }
  