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.dht;
  
  import java.math.BigInteger;
  import java.nio.ByteBuffer;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Random;
  import java.util.function.Function;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.primitives.Longs;
  
  import accord.primitives.Ranges;
  import org.apache.cassandra.db.CachedHashDecoratedKey;
  import org.apache.cassandra.db.DecoratedKey;
  import org.apache.cassandra.db.marshal.AbstractType;
  import org.apache.cassandra.db.marshal.LongType;
  import org.apache.cassandra.utils.ByteBufferUtil;
  import org.apache.cassandra.utils.FBUtilities;
  import org.apache.cassandra.utils.ObjectSizes;
  import org.apache.cassandra.utils.Pair;
  import org.apache.cassandra.utils.bytecomparable.ByteComparable;
  import org.apache.cassandra.utils.bytecomparable.ByteSource;
  import org.apache.cassandra.utils.bytecomparable.ByteSourceInverse;
  import org.apache.cassandra.utils.memory.HeapCloner;
  
  /**
   * Special ordered partitioner for the TCM snapshots table, sorting in reverse. Keys are longs (epoch), and tokens
   * become Long.MAX_VALUE - key. Keys are required to be >= 0.
   */
  public class ReversedLongLocalPartitioner implements IPartitioner
  {
      public static ReversedLongLocalPartitioner instance = new ReversedLongLocalPartitioner();
      private static final ReversedLongLocalToken MIN_TOKEN = new ReversedLongLocalToken(Long.MIN_VALUE);
      private static final long HEAP_SIZE = ObjectSizes.measure(MIN_TOKEN);
  
      private ReversedLongLocalPartitioner() {}
  
      public DecoratedKey decorateKey(ByteBuffer key)
      {
          return new CachedHashDecoratedKey(getToken(key), key); // CachedHashDecoratedKey is used for bloom filter hash calculation
      }
  
      public Token midpoint(Token ltoken, Token rtoken)
      {
          // the symbolic MINIMUM token should act as ZERO: the empty bit array
          BigInteger left = ltoken.equals(MIN_TOKEN) ? BigInteger.ZERO : BigInteger.valueOf(ltoken.getLongValue());
          BigInteger right = rtoken.equals(MIN_TOKEN) ? BigInteger.ZERO : BigInteger.valueOf(rtoken.getLongValue());
          Pair<BigInteger, Boolean> midpair = FBUtilities.midpoint(left, right, 63);
          // discard the remainder
          return new ReversedLongLocalToken(midpair.left.longValue());
      }
  
      public Token split(Token left, Token right, double ratioToLeft)
      {
          throw new UnsupportedOperationException();
      }
  
      public Token getMinimumToken()
      {
          return MIN_TOKEN;
      }
  
      public Token getToken(ByteBuffer key)
      {
          if (!key.hasRemaining())
              return MIN_TOKEN;
          long longKey = ByteBufferUtil.toLong(HeapCloner.instance.clone(key));
          assert longKey >= 0 : "ReversedLocalLongToken only supports non-negative keys, not " + longKey;
          return new ReversedLongLocalToken(Long.MAX_VALUE - longKey);
      }
  
      public Token getRandomToken()
      {
          throw new UnsupportedOperationException();
      }
  
      public Token getRandomToken(Random random)
      {
          throw new UnsupportedOperationException();
      }
  
      public Token.TokenFactory getTokenFactory()
      {
          return tokenFactory;
      }
  
      private final Token.TokenFactory tokenFactory = new Token.TokenFactory()
      {
          public Token fromComparableBytes(ByteSource.Peekable comparableBytes, ByteComparable.Version version)
          {
              long tokenData = ByteSourceInverse.getSignedLong(comparableBytes);
              return new ReversedLongLocalToken(tokenData);
          }
  
          public void skipComparableBytes(ByteSource.Peekable comparableBytes, ByteComparable.Version version, IPartitioner partitioner)
          {
              ByteSourceInverse.skipBytes(comparableBytes, Long.BYTES);
          }
  
          public ByteBuffer toByteArray(Token token)
          {
              ReversedLongLocalToken longToken = (ReversedLongLocalToken) token;
              return ByteBufferUtil.bytes(longToken.token);
          }
  
          public Token fromByteArray(ByteBuffer bytes)
          {
              return new ReversedLongLocalToken(ByteBufferUtil.toLong(bytes));
          }
  
          public String toString(Token token)
          {
              return token.toString();
          }
  
          public void validate(String token)
          {
              LongType.instance.validate(LongType.instance.fromString(token));
          }
  
          public Token fromString(String string)
          {
              return new ReversedLongLocalToken(Long.parseLong(string));
          }
      };
  
      public boolean preservesOrder()
      {
          return true;
      }
  
      public Map<Token, Float> describeOwnership(List<Token> sortedTokens)
      {
          return Collections.singletonMap(getMinimumToken(), 1.0F);
      }
  
      public AbstractType<?> getTokenValidator()
      {
          return LongType.instance;
      }
  
      public AbstractType<?> partitionOrdering()
      {
          return LongType.instance;
      }
  
      @Override
      public Function<Ranges, AccordSplitter> accordSplitter()
      {
          throw new UnsupportedOperationException("Accord is not supported by " + getClass().getName());
      }
  
      @VisibleForTesting
      public static class ReversedLongLocalToken extends Token
      {
          private final long token;
  
          public ReversedLongLocalToken(long token)
          {
              this.token = token;
          }
  
          @Override
          public IPartitioner getPartitioner()
          {
              return ReversedLongLocalPartitioner.instance;
          }
  
          @Override
          public long getHeapSize()
          {
              return HEAP_SIZE;
          }
  
          @Override
          public Object getTokenValue()
          {
              return token;
          }
  
          @Override
          public int tokenHash()
          {
              return Long.hashCode(token);
          }
  
          @Override
          public long getLongValue()
          {
              return token;
          }
  
          @Override
          public ByteSource asComparableBytes(ByteComparable.Version version)
          {
              return ByteSource.of(token);
          }
  
          @Override
          public double size(Token next)
          {
              throw new UnsupportedOperationException(String.format("Token type %s does not support token allocation.",
                                                                    getClass().getSimpleName()));
          }
  
          @Override
          public Token nextValidToken()
          {
              throw new UnsupportedOperationException(String.format("Token type %s does not support token allocation.",
                                                                    getClass().getSimpleName()));
          }
  
          @Override
          public Token decreaseSlightly()
          {
              throw new UnsupportedOperationException(String.format("Token type %s does not support token allocation.",
                                                                    getClass().getSimpleName()));
          }
  
          @Override
          public int compareTo(Token o)
          {
              return Long.compare(token, ((ReversedLongLocalToken)o).token);
          }
  
          @Override
          public String toString()
          {
              return String.valueOf(token);
          }
  
          @Override
          public boolean equals(Object o)
          {
              if (this == o) return true;
              if (!(o instanceof ReversedLongLocalToken)) return false;
              ReversedLongLocalToken that = (ReversedLongLocalToken) o;
              return token == that.token;
          }
  
          @Override
          public int hashCode()
          {
              return Longs.hashCode(token);
          }
      }
  }
  