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.utils;
  
  import java.nio.ByteBuffer;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.cassandra.tcm.ClusterMetadata;
  
  import static org.apache.cassandra.utils.TimeUUID.Generator.nextTimeUUIDAsBytes;
  
  public class CounterId implements Comparable<CounterId>
  {
      public static final int LENGTH = 16; // we assume a fixed length size for all CounterIds
  
      // Lazy holder because this opens the system keyspace and we want to avoid
      // having this triggered during class initialization
      private static class LocalId
      {
          static final LocalCounterIdHolder instance = new LocalCounterIdHolder();
      }
  
      private final ByteBuffer id;
  
      private static LocalCounterIdHolder localId()
      {
          return LocalId.instance;
      }
  
      public static CounterId getLocalId()
      {
          return localId().get();
      }
  
      /**
       * Pack an int in a valid CounterId so that the resulting ids respects the
       * numerical ordering. Used for creating handcrafted but easy to
       * understand contexts in unit tests (see CounterContextTest).
       *
       * Also used to generate a special ID for special-case update contexts (see CounterContext.createUpdate()).
       */
      public static CounterId fromInt(int n)
      {
          long lowBits = 0xC000000000000000L | n;
          return new CounterId(ByteBuffer.allocate(16).putLong(0, 0).putLong(8, lowBits));
      }
  
      /*
       * For performance reasons, this function interns the provided ByteBuffer.
       */
      public static CounterId wrap(ByteBuffer id)
      {
          return new CounterId(id);
      }
  
      public static CounterId wrap(ByteBuffer bb, int offset)
      {
          ByteBuffer dup = bb.duplicate();
          dup.position(offset);
          dup.limit(dup.position() + LENGTH);
          return wrap(dup);
      }
  
      private CounterId(ByteBuffer id)
      {
          if (id.remaining() != LENGTH)
              throw new IllegalArgumentException("A CounterId representation is exactly " + LENGTH + " bytes");
  
          this.id = id;
      }
  
      public static CounterId generate()
      {
          return new CounterId(ByteBuffer.wrap(nextTimeUUIDAsBytes()));
      }
  
      /*
       * For performance reasons, this function returns a reference to the internal ByteBuffer. Clients not modify the
       * result of this function.
       */
      public ByteBuffer bytes()
      {
          return id;
      }
  
      public boolean isLocalId()
      {
          return equals(getLocalId());
      }
  
      public int compareTo(CounterId o)
      {
          return ByteBufferUtil.compareSubArrays(id, id.position(), o.id, o.id.position(), CounterId.LENGTH);
      }
  
      @Override
      public String toString()
      {
          return UUIDGen.getUUID(id).toString();
      }
  
      @Override
      public boolean equals(Object o)
      {
          if (this == o)
              return true;
          if (o == null || getClass() != o.getClass())
              return false;
  
          CounterId otherId = (CounterId)o;
          return id.equals(otherId.id);
      }
  
      @Override
      public int hashCode()
      {
          return id.hashCode();
      }
  
      private static class LocalCounterIdHolder
      {
          private final AtomicReference<CounterId> current;
  
          LocalCounterIdHolder()
          {
              current = new AtomicReference<>(wrap(ByteBufferUtil.bytes(ClusterMetadata.current().myNodeId().toUUID())));
          }
  
          CounterId get()
          {
              return current.get();
          }
      }
  }
  