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.io.IOException;
  import java.math.BigDecimal;
  import java.math.BigInteger;
  import java.nio.ByteBuffer;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  import java.util.Random;
  import java.util.concurrent.ThreadLocalRandom;
  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.DecoratedKey;
  import org.apache.cassandra.db.PreHashedDecoratedKey;
  import org.apache.cassandra.db.TypeSizes;
  import org.apache.cassandra.db.marshal.AbstractType;
  import org.apache.cassandra.db.marshal.LongType;
  import org.apache.cassandra.db.marshal.PartitionerDefinedOrder;
  import org.apache.cassandra.db.marshal.ValueAccessor;
  import org.apache.cassandra.exceptions.ConfigurationException;
  import org.apache.cassandra.io.util.DataInputPlus;
  import org.apache.cassandra.io.util.DataOutputPlus;
  import org.apache.cassandra.utils.ByteBufferUtil;
  import org.apache.cassandra.utils.MurmurHash;
  import org.apache.cassandra.utils.ObjectSizes;
  import org.apache.cassandra.utils.bytecomparable.ByteComparable;
  import org.apache.cassandra.utils.bytecomparable.ByteSource;
  import org.apache.cassandra.utils.bytecomparable.ByteSourceInverse;
  
  /**
   * This class generates a BigIntegerToken using a Murmur3 hash.
   */
  public class Murmur3Partitioner implements IPartitioner
  {
      public static final LongToken MINIMUM = new LongToken(Long.MIN_VALUE);
      public static final long MAXIMUM = Long.MAX_VALUE;
      private static final int MAXIMUM_TOKEN_SIZE = TypeSizes.sizeof(MAXIMUM);
  
      private static final int HEAP_SIZE = (int) ObjectSizes.measureDeep(MINIMUM);
  
      public static final Murmur3Partitioner instance = new Murmur3Partitioner();
      public static final PartitionerDefinedOrder partitionOrdering = new PartitionerDefinedOrder(instance);
  
      private final Splitter splitter = new Splitter(this)
      {
          final BigInteger MAX = BigInteger.valueOf(Long.MAX_VALUE), MIN = BigInteger.valueOf(Long.MIN_VALUE);
  
          public Token tokenForValue(BigInteger value)
          {
              return new LongToken(value.longValue());
          }
  
          public BigInteger valueForToken(Token token)
          {
              return BigInteger.valueOf(((LongToken) token).token);
          }
  
          @Override
          BigInteger minimumValue()
          {
              return MIN;
          }
  
          @Override
          BigInteger maximumValue()
          {
              return MAX;
          }
      };
  
      protected Murmur3Partitioner() {}
  
      public DecoratedKey decorateKey(ByteBuffer key)
      {
          long[] hash = getHash(key);
          return new PreHashedDecoratedKey(getToken(key, hash), key, hash[0], hash[1]);
      }
  
      public Token midpoint(Token lToken, Token rToken)
      {
          // using BigInteger to avoid long overflow in intermediate operations
          BigInteger l = BigInteger.valueOf(((LongToken) lToken).token),
                     r = BigInteger.valueOf(((LongToken) rToken).token),
                     midpoint;
  
          if (l.compareTo(r) < 0)
          {
              BigInteger sum = l.add(r);
              midpoint = sum.shiftRight(1);
          }
          else // wrapping case
          {
              BigInteger max = BigInteger.valueOf(MAXIMUM);
              BigInteger min = BigInteger.valueOf(MINIMUM.token);
              // length of range we're bisecting is (R - min) + (max - L)
              // so we add that to L giving
              // L + ((R - min) + (max - L) / 2) = (L + R + max - min) / 2
              midpoint = (max.subtract(min).add(l).add(r)).shiftRight(1);
              if (midpoint.compareTo(max) > 0)
                  midpoint = min.add(midpoint.subtract(max));
          }
  
          return new LongToken(midpoint.longValue());
      }
  
      public Token split(Token lToken, Token rToken, double ratioToLeft)
      {
          BigDecimal l = BigDecimal.valueOf(((LongToken) lToken).token),
                     r = BigDecimal.valueOf(((LongToken) rToken).token),
                     ratio = BigDecimal.valueOf(ratioToLeft);
          long newToken;
  
          if (l.compareTo(r) < 0)
          {
              newToken = r.subtract(l).multiply(ratio).add(l).toBigInteger().longValue();
          }
          else
          {
              // wrapping case
              // L + ((R - min) + (max - L)) * pct
              BigDecimal max = BigDecimal.valueOf(MAXIMUM);
              BigDecimal min = BigDecimal.valueOf(MINIMUM.token);
  
              BigInteger token = max.subtract(min).add(r).subtract(l).multiply(ratio).add(l).toBigInteger();
  
              BigInteger maxToken = BigInteger.valueOf(MAXIMUM);
  
              if (token.compareTo(maxToken) <= 0)
              {
                  newToken = token.longValue();
              }
              else
              {
                  // if the value is above maximum
                  BigInteger minToken = BigInteger.valueOf(MINIMUM.token);
                  newToken = minToken.add(token.subtract(maxToken)).longValue();
              }
          }
          return new LongToken(newToken);
      }
  
      public boolean supportsSplitting()
      {
          return true;
      }
  
      public LongToken getMinimumToken()
      {
          return MINIMUM;
      }
  
      public static class LongToken extends Token
      {
          static final long serialVersionUID = -5833580143318243006L;
  
          public final long token;
  
          public LongToken(long token)
          {
              this.token = token;
          }
  
          public String toString()
          {
              return Long.toString(token);
          }
  
          public boolean equals(Object obj)
          {
              if (this == obj)
                  return true;
              if (obj == null || this.getClass() != obj.getClass())
                  return false;
  
              return token == (((LongToken)obj).token);
          }
  
          public int hashCode()
          {
              return Longs.hashCode(token);
          }
  
          public int compareTo(Token o)
          {
              return Long.compare(token, ((LongToken) o).token);
          }
  
          @Override
          public ByteSource asComparableBytes(ByteComparable.Version version)
          {
              return ByteSource.of(token);
          }
  
          @Override
          public IPartitioner getPartitioner()
          {
              return instance;
          }
  
          @Override
          public long getHeapSize()
          {
              return HEAP_SIZE;
          }
  
          @Override
          public Object getTokenValue()
          {
              return token;
          }
  
          @Override
          public long getLongValue()
          {
              return token;
          }
  
          @Override
          public int tokenHash()
          {
              return Long.hashCode(token);
          }
  
          @Override
          public TokenFactory tokenFactory()
          {
              return tokenFactory;
          }
  
          @Override
          public double size(Token next)
          {
              LongToken n = (LongToken) next;
              long v = n.token - token;  // Overflow acceptable and desired.
              double d = Math.scalb((double) v, -Long.SIZE); // Scale so that the full range is 1.
              return d > 0.0 ? d : (d + 1.0); // Adjust for signed long, also making sure t.size(t) == 1.
          }
  
          @Override
          public LongToken nextValidToken()
          {
              // CASSANDRA-17109 Added the below checks, but paxos tests were not updated, rather than fix
              // the paxos tests, disabling the checks for now.  The current paxos tests bias twards MIN but
              // not for MAX, which makes the test very flaky as when MAX is generated the test fails...
              // TODO (required): this check breaks a bunch of tests, but should be re-enabled
  //            if (token == MAXIMUM)
  //                throw new IllegalArgumentException("Cannot increase above MAXIMUM");
  
              return new LongToken(token + 1);
          }
  
          public LongToken decreaseSlightly()
          {
              // CASSANDRA-17109 Added the below checks, but paxos tests were not updated, rather than fix
              // the paxos tests, disabling the checks for now
  //            if (equals(MINIMUM))
  //                throw new IllegalArgumentException("Cannot decrease below MINIMUM");
  
              return new LongToken(token - 1);
          }
  
          public static ByteBuffer keyForToken(long token)
          {
              return keyForToken(new LongToken(token));
          }
  
          /**
           * Reverses murmur3 to find a possible 16 byte key that generates a given token
           */
          @VisibleForTesting
          public static ByteBuffer keyForToken(LongToken token)
          {
              ByteBuffer result = ByteBuffer.allocate(16);
              long[] inv = MurmurHash.inv_hash3_x64_128(new long[]{ token.token, 0L });
              result.putLong(inv[0]).putLong(inv[1]).position(0);
              return result;
          }
      }
  
      /**
       * Generate the token of a key.
       * Note that we need to ensure all generated token are strictly bigger than MINIMUM.
       * In particular we don't want MINIMUM to correspond to any key because the range (MINIMUM, X] doesn't
       * include MINIMUM but we use such range to select all data whose token is smaller than X.
       */
      public LongToken getToken(ByteBuffer key)
      {
          return getToken(key, getHash(key));
      }
  
      private LongToken getToken(ByteBuffer key, long[] hash)
      {
          if (key.remaining() == 0)
              return MINIMUM;
  
          return new LongToken(normalize(hash[0]));
      }
  
      @Override
      public boolean isFixedLength()
      {
          return true;
      }
  
      public int getMaxTokenSize()
      {
          return MAXIMUM_TOKEN_SIZE;
      }
  
      public final boolean accordSupported()
      {
          return true;
      }
  
      @Override
      public final void accordSerialize(Token token, DataOutputPlus out) throws IOException
      {
          out.writeLong(flip(((LongToken)token).token));
      }
  
      @Override
      public final void accordSerialize(Token token, ByteBuffer out)
      {
          out.putLong(flip(((LongToken)token).token));
      }
  
      @Override
      public final Token accordDeserialize(DataInputPlus in, int length) throws IOException
      {
          return new LongToken(flip(in.readLong()));
      }
  
      @Override
      public final Token accordDeserialize(ByteBuffer in, int length)
      {
          return new LongToken(flip(in.getLong()));
      }
  
      @Override
      public final <V> Token accordDeserialize(V src, ValueAccessor<V> accessor, int offset, int length)
      {
          return new LongToken(flip(accessor.getLong(src, offset)));
      }
  
      @Override
      public final int accordSerializedSize(Token token)
      {
          return 8;
      }
  
      @Override
      public final int accordFixedLength()
      {
          return 8;
      }
  
      private static long flip(long value)
      {
          return value ^ 0x8000000000000000L;
      }
  
      private long[] getHash(ByteBuffer key)
      {
          long[] hash = new long[2];
          MurmurHash.hash3_x64_128(key, key.position(), key.remaining(), 0, hash);
          return hash;
      }
  
      public LongToken getRandomToken()
      {
          return getRandomToken(ThreadLocalRandom.current());
      }
  
      public LongToken getRandomToken(Random r)
      {
          return new LongToken(normalize(r.nextLong()));
      }
  
      private long normalize(long v)
      {
          // We exclude the MINIMUM value; see getToken()
          return v == Long.MIN_VALUE ? Long.MAX_VALUE : v;
      }
  
      public boolean preservesOrder()
      {
          return false;
      }
  
      public Map<Token, Float> describeOwnership(List<Token> sortedTokens)
      {
          Map<Token, Float> ownerships = new HashMap<Token, Float>();
          Iterator<Token> i = sortedTokens.iterator();
  
          // 0-case
          if (!i.hasNext())
              throw new RuntimeException("No nodes present in the cluster. Has this node finished starting up?");
          // 1-case
          if (sortedTokens.size() == 1)
              ownerships.put(i.next(), 1.0F);
          // n-case
          else
          {
              final BigInteger ri = BigInteger.valueOf(MAXIMUM).subtract(BigInteger.valueOf(MINIMUM.token + 1));  //  (used for addition later)
              final BigDecimal r  = new BigDecimal(ri);
              Token start = i.next();BigInteger ti = BigInteger.valueOf(((LongToken)start).token);  // The first token and its value
              Token t; BigInteger tim1 = ti;                                                                // The last token and its value (after loop)
  
              while (i.hasNext())
              {
                  t = i.next(); ti = BigInteger.valueOf(((LongToken) t).token); // The next token and its value
                  float age = new BigDecimal(ti.subtract(tim1).add(ri).mod(ri)).divide(r, 6, BigDecimal.ROUND_HALF_EVEN).floatValue(); // %age = ((T(i) - T(i-1) + R) % R) / R
                  ownerships.put(t, age);                           // save (T(i) -> %age)
                  tim1 = ti;                                        // -> advance loop
              }
  
              // The start token's range extends backward to the last token, which is why both were saved above.
              float x = new BigDecimal(BigInteger.valueOf(((LongToken)start).token).subtract(ti).add(ri).mod(ri)).divide(r, 6, BigDecimal.ROUND_HALF_EVEN).floatValue();
              ownerships.put(start, x);
          }
  
          return ownerships;
      }
  
      public Token.TokenFactory getTokenFactory()
      {
          return tokenFactory;
      }
  
      private static final Token.TokenFactory tokenFactory = new Token.TokenFactory()
      {
          public Token fromComparableBytes(ByteSource.Peekable comparableBytes, ByteComparable.Version version)
          {
              long tokenData = ByteSourceInverse.getSignedLong(comparableBytes);
              return new LongToken(tokenData);
          }
  
          public void skipComparableBytes(ByteSource.Peekable comparableBytes, ByteComparable.Version version, IPartitioner partitioner)
          {
              ByteSourceInverse.skipBytes(comparableBytes, Long.BYTES);
          }
  
          public ByteBuffer toByteArray(Token token)
          {
              LongToken longToken = (LongToken) token;
              return ByteBufferUtil.bytes(longToken.token);
          }
  
          @Override
          public void serialize(Token token, DataOutputPlus out) throws IOException
          {
              out.writeLong(((LongToken) token).token);
          }
  
          @Override
          public Token deserialize(DataInputPlus in, IPartitioner p) throws IOException
          {
              return new LongToken(in.readLong());
          }
  
          @Override
          public void serialize(Token token, ByteBuffer out)
          {
              out.putLong(((LongToken) token).token);
          }
  
          @Override
          public int byteSize(Token token)
          {
              return 8;
          }
  
          public Token fromByteArray(ByteBuffer bytes)
          {
              return new LongToken(ByteBufferUtil.toLong(bytes));
          }
  
          @Override
          public Token fromByteBuffer(ByteBuffer bytes, int position, int length)
          {
              return new LongToken(bytes.getLong(position));
          }
  
          public String toString(Token token)
          {
              return token.toString();
          }
  
          public void validate(String token) throws ConfigurationException
          {
              try
              {
                  fromString(token);
              }
              catch (NumberFormatException e)
              {
                  throw new ConfigurationException(e.getMessage());
              }
          }
  
          public Token fromString(String string)
          {
              try
              {
                  return new LongToken(Long.parseLong(string));
              }
              catch (NumberFormatException e)
              {
                  throw new IllegalArgumentException(String.format("Invalid token for Murmur3Partitioner. Got %s but expected a long value (unsigned 8 bytes integer).", string));
              }
          }
      };
  
      public AbstractType<?> getTokenValidator()
      {
          return LongType.instance;
      }
  
      public Token getMaximumTokenForSplitting()
      {
          return new LongToken(Long.MAX_VALUE);
      }
  
      public AbstractType<?> partitionOrdering()
      {
          return partitionOrdering;
      }
  
      public AbstractType<?> partitionOrdering(AbstractType<?> partitionKeyType)
      {
          return partitionOrdering.withPartitionKeyType(partitionKeyType);
      }
  
      public Optional<Splitter> splitter()
      {
          return Optional.of(splitter);
      }
  
      @Override
      public Function<Ranges, AccordSplitter> accordSplitter()
      {
          return ignore -> splitter;
      }
  }
  