/*
    * Copyright (C) 2011 The Guava Authors
    *
    * Licensed 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.
   */
  
  /*
   * MurmurHash3 was written by Austin Appleby, and is placed in the public
   * domain. The author hereby disclaims copyright to this source code.
   */
  
  /*
   * Source:
   * http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
   * (Modified to adapt to Guava coding conventions and to use the HashFunction interface)
   */
  
  package com.google.common.hash;
  
  import static com.google.common.primitives.UnsignedBytes.toInt;
  
  import com.google.common.primitives.Chars;
  import com.google.common.primitives.Ints;
  import com.google.common.primitives.Longs;
  
  import java.io.Serializable;
  import java.nio.ByteBuffer;
  
  import javax.annotation.Nullable;
  
  /**
   * See http://smhasher.googlecode.com/svn/trunk/MurmurHash3.cpp
   * MurmurHash3_x86_32
   *
   * @author Austin Appleby
   * @author Dimitris Andreou
   * @author Kurt Alfred Kluever
   */
  final class Murmur3_32HashFunction extends AbstractStreamingHashFunction implements Serializable {
    private static final int C1 = 0xcc9e2d51;
    private static final int C2 = 0x1b873593;
  
    private final int seed;
  
    Murmur3_32HashFunction(int seed) {
      this.seed = seed;
    }
  
    @Override public int bits() {
      return 32;
    }
  
    @Override public Hasher newHasher() {
      return new Murmur3_32Hasher(seed);
    }
  
    @Override
    public String toString() {
      return "Hashing.murmur3_32(" + seed + ")";
    }
  
    @Override
    public boolean equals(@Nullable Object object) {
      if (object instanceof Murmur3_32HashFunction) {
        Murmur3_32HashFunction other = (Murmur3_32HashFunction) object;
        return seed == other.seed;
      }
      return false;
    }
  
    @Override
    public int hashCode() {
      return getClass().hashCode() ^ seed;
    }
  
    @Override public HashCode hashInt(int input) {
      int k1 = mixK1(input);
      int h1 = mixH1(seed, k1);
  
      return fmix(h1, Ints.BYTES);
    }
  
    @Override public HashCode hashLong(long input) {
      int low = (int) input;
      int high = (int) (input >>> 32);
  
      int k1 = mixK1(low);
      int h1 = mixH1(seed, k1);
  
      k1 = mixK1(high);
      h1 = mixH1(h1, k1);
 
     return fmix(h1, Longs.BYTES);
   }
 
   // TODO(user): Maybe implement #hashBytes instead?
   @Override public HashCode hashUnencodedChars(CharSequence input) {
     int h1 = seed;
 
     // step through the CharSequence 2 chars at a time
     for (int i = 1; i < input.length(); i += 2) {
       int k1 = input.charAt(i - 1) | (input.charAt(i) << 16);
       k1 = mixK1(k1);
       h1 = mixH1(h1, k1);
     }
 
     // deal with any remaining characters
     if ((input.length() & 1) == 1) {
       int k1 = input.charAt(input.length() - 1);
       k1 = mixK1(k1);
       h1 ^= k1;
     }
 
     return fmix(h1, Chars.BYTES * input.length());
   }
 
   private static int mixK1(int k1) {
     k1 *= C1;
     k1 = Integer.rotateLeft(k1, 15);
     k1 *= C2;
     return k1;
   }
 
   private static int mixH1(int h1, int k1) {
     h1 ^= k1;
     h1 = Integer.rotateLeft(h1, 13);
     h1 = h1 * 5 + 0xe6546b64;
     return h1;
   }
 
   // Finalization mix - force all bits of a hash block to avalanche
   private static HashCode fmix(int h1, int length) {
     h1 ^= length;
     h1 ^= h1 >>> 16;
     h1 *= 0x85ebca6b;
     h1 ^= h1 >>> 13;
     h1 *= 0xc2b2ae35;
     h1 ^= h1 >>> 16;
     return HashCode.fromInt(h1);
   }
 
   private static final class Murmur3_32Hasher extends AbstractStreamingHasher {
     private static final int CHUNK_SIZE = 4;
     private int h1;
     private int length;
 
     Murmur3_32Hasher(int seed) {
       super(CHUNK_SIZE);
       this.h1 = seed;
       this.length = 0;
     }
 
     @Override protected void process(ByteBuffer bb) {
       int k1 = Murmur3_32HashFunction.mixK1(bb.getInt());
       h1 = Murmur3_32HashFunction.mixH1(h1, k1);
       length += CHUNK_SIZE;
     }
 
     @Override protected void processRemaining(ByteBuffer bb) {
       length += bb.remaining();
       int k1 = 0;
       for (int i = 0; bb.hasRemaining(); i += 8) {
         k1 ^= toInt(bb.get()) << i;
       }
       h1 ^= Murmur3_32HashFunction.mixK1(k1);
     }
 
     @Override public HashCode makeHash() {
       return Murmur3_32HashFunction.fmix(h1, length);
     }
   }
 
   private static final long serialVersionUID = 0L;
 }