HBASE-9631. Add murmur3 hash

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1546894 13f79535-47bb-0310-9956-ffa450edef68

hbase-common/src/main/java/org/apache/hadoop/hbase/util/Hash.java

@@ -35,11 +35,13 @@ public abstract class Hash {
   public static final int JENKINS_HASH = 0;
   /** Constant to denote {@link MurmurHash}. */
   public static final int MURMUR_HASH  = 1;
+  /** Constant to denote {@link MurmurHash3}. */
+  public static final int MURMUR_HASH3 = 2;
 
   /**
    * This utility method converts String representation of hash function name
-   * to a symbolic constant. Currently two function types are supported,
-   * "jenkins" and "murmur".
+   * to a symbolic constant. Currently three function types are supported,
+   * "jenkins", "murmur" and "murmur3".
    * @param name hash function name
    * @return one of the predefined constants
    */
@@ -48,6 +50,8 @@ public abstract class Hash {
       return JENKINS_HASH;
     } else if ("murmur".equalsIgnoreCase(name)) {
       return MURMUR_HASH;
+    } else if ("murmur3".equalsIgnoreCase(name)) {
+      return MURMUR_HASH3;
     } else {
       return INVALID_HASH;
     }
@@ -75,6 +79,8 @@ public abstract class Hash {
       return JenkinsHash.getInstance();
     case MURMUR_HASH:
       return MurmurHash.getInstance();
+    case MURMUR_HASH3:
+      return MurmurHash3.getInstance();
     default:
       return null;
     }

hbase-common/src/main/java/org/apache/hadoop/hbase/util/MurmurHash3.java

@@ -0,0 +1,88 @@
+/**
+ *
+ * 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.hadoop.hbase.util;
+
+/**
+ * This is a very fast, non-cryptographic hash suitable for general hash-based
+ * lookup.  See http://code.google.com/p/smhasher/wiki/MurmurHash3 for details.
+ *
+ * <p>MurmurHash3 is the successor to MurmurHash2. It comes in 3 variants, and
+ * the 32-bit version targets low latency for hash table use.</p>
+ */
+public class MurmurHash3 extends Hash {
+  private static MurmurHash3 _instance = new MurmurHash3();
+
+  public static Hash getInstance() {
+    return _instance;
+  }
+
+  /** Returns the MurmurHash3_x86_32 hash. */
+  @edu.umd.cs.findbugs.annotations.SuppressWarnings("SF")
+  @Override
+  public int hash(byte[] bytes, int offset, int length, int initval) {
+    final int c1 = 0xcc9e2d51;
+    final int c2 = 0x1b873593;
+
+    int h1 = initval;
+    int roundedEnd = offset + (length & 0xfffffffc); // round down to 4 byte block
+
+    for (int i = offset; i < roundedEnd; i += 4) {
+      // little endian load order
+      int k1 = (bytes[i] & 0xff) | ((bytes[i + 1] & 0xff) << 8) | ((bytes[i + 2] & 0xff) << 16)
+          | (bytes[i + 3] << 24);
+      k1 *= c1;
+      k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15);
+      k1 *= c2;
+
+      h1 ^= k1;
+      h1 = (h1 << 13) | (h1 >>> 19); // ROTL32(h1,13);
+      h1 = h1 * 5 + 0xe6546b64;
+    }
+
+    // tail
+    int k1 = 0;
+
+    switch (length & 0x03) {
+    case 3:
+      k1 = (bytes[roundedEnd + 2] & 0xff) << 16;
+      // FindBugs SF_SWITCH_FALLTHROUGH
+    case 2:
+      k1 |= (bytes[roundedEnd + 1] & 0xff) << 8;
+      // FindBugs SF_SWITCH_FALLTHROUGH
+    case 1:
+      k1 |= (bytes[roundedEnd] & 0xff);
+      k1 *= c1;
+      k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15);
+      k1 *= c2;
+      h1 ^= k1;
+    }
+
+    // finalization
+    h1 ^= length;
+
+    // fmix(h1);
+    h1 ^= h1 >>> 16;
+    h1 *= 0x85ebca6b;
+    h1 ^= h1 >>> 13;
+    h1 *= 0xc2b2ae35;
+    h1 ^= h1 >>> 16;
+
+    return h1;
+  }
+}