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Posted to commits@hbase.apache.org by st...@apache.org on 2008/09/23 20:23:48 UTC
svn commit: r698268 - in
/hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util: Hash.java
MurmurHash.java
Author: stack
Date: Tue Sep 23 11:23:48 2008
New Revision: 698268
URL: http://svn.apache.org/viewvc?rev=698268&view=rev
Log:
HBASE-875 Use MurmurHash instead of JenkinsHash
Added:
hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/Hash.java
hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/MurmurHash.java
Added: hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/Hash.java
URL: http://svn.apache.org/viewvc/hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/Hash.java?rev=698268&view=auto
==============================================================================
--- hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/Hash.java (added)
+++ hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/Hash.java Tue Sep 23 11:23:48 2008
@@ -0,0 +1,119 @@
+/**
+ * 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;
+
+import org.apache.hadoop.conf.Configuration;
+
+/**
+ * This class represents a common API for hashing functions.
+ */
+public abstract class Hash {
+ /** Constant to denote invalid hash type. */
+ public static final int INVALID_HASH = -1;
+ /** Constant to denote {@link JenkinsHash}. */
+ public static final int JENKINS_HASH = 0;
+ /** Constant to denote {@link MurmurHash}. */
+ public static final int MURMUR_HASH = 1;
+
+ /**
+ * This utility method converts String representation of hash function name
+ * to a symbolic constant. Currently two function types are supported,
+ * "jenkins" and "murmur".
+ * @param name hash function name
+ * @return one of the predefined constants
+ */
+ public static int parseHashType(String name) {
+ if ("jenkins".equalsIgnoreCase(name)) {
+ return JENKINS_HASH;
+ } else if ("murmur".equalsIgnoreCase(name)) {
+ return MURMUR_HASH;
+ } else {
+ return INVALID_HASH;
+ }
+ }
+
+ /**
+ * This utility method converts the name of the configured
+ * hash type to a symbolic constant.
+ * @param conf configuration
+ * @return one of the predefined constants
+ */
+ public static int getHashType(Configuration conf) {
+ String name = conf.get("hbase.hash.type", "murmur");
+ return parseHashType(name);
+ }
+
+ /**
+ * Get a singleton instance of hash function of a given type.
+ * @param type predefined hash type
+ * @return hash function instance, or null if type is invalid
+ */
+ public static Hash getInstance(int type) {
+ switch(type) {
+ case JENKINS_HASH:
+ return JenkinsHash.getInstance();
+ case MURMUR_HASH:
+ return MurmurHash.getInstance();
+ default:
+ return null;
+ }
+ }
+
+ /**
+ * Get a singleton instance of hash function of a type
+ * defined in the configuration.
+ * @param conf current configuration
+ * @return defined hash type, or null if type is invalid
+ */
+ public static Hash getInstance(Configuration conf) {
+ int type = getHashType(conf);
+ return getInstance(type);
+ }
+
+ /**
+ * Calculate a hash using all bytes from the input argument, and
+ * a seed of -1.
+ * @param bytes input bytes
+ * @return hash value
+ */
+ public int hash(byte[] bytes) {
+ return hash(bytes, bytes.length, -1);
+ }
+
+ /**
+ * Calculate a hash using all bytes from the input argument,
+ * and a provided seed value.
+ * @param bytes input bytes
+ * @param initval seed value
+ * @return hash value
+ */
+ public int hash(byte[] bytes, int initval) {
+ return hash(bytes, bytes.length, initval);
+ }
+
+ /**
+ * Calculate a hash using bytes from 0 to <code>length</code>, and
+ * the provided seed value
+ * @param bytes input bytes
+ * @param length length of the valid bytes to consider
+ * @param initval seed value
+ * @return
+ */
+ public abstract int hash(byte[] bytes, int length, int initval);
+}
Added: hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/MurmurHash.java
URL: http://svn.apache.org/viewvc/hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/MurmurHash.java?rev=698268&view=auto
==============================================================================
--- hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/MurmurHash.java (added)
+++ hadoop/hbase/trunk/src/java/org/apache/hadoop/hbase/util/MurmurHash.java Tue Sep 23 11:23:48 2008
@@ -0,0 +1,83 @@
+/**
+ * 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://murmurhash.googlepages.com/ for more details.
+ *
+ * <p>The C version of MurmurHash 2.0 found at that site was ported
+ * to Java by Andrzej Bialecki (ab at getopt org).</p>
+ */
+public class MurmurHash extends Hash {
+ private static MurmurHash _instance = new MurmurHash();
+
+ public static Hash getInstance() {
+ return _instance;
+ }
+
+ public int hash(byte[] data, int length, int seed) {
+ int m = 0x5bd1e995;
+ int r = 24;
+
+ int h = seed ^ length;
+
+ int len_4 = length >> 2;
+
+ for (int i = 0; i < len_4; i++) {
+ int i_4 = i << 2;
+ int k = data[i_4 + 3];
+ k = k << 8;
+ k = k | (data[i_4 + 2] & 0xff);
+ k = k << 8;
+ k = k | (data[i_4 + 1] & 0xff);
+ k = k << 8;
+ k = k | (data[i_4 + 0] & 0xff);
+ k *= m;
+ k ^= k >>> r;
+ k *= m;
+ h *= m;
+ h ^= k;
+ }
+
+ // avoid calculating modulo
+ int len_m = len_4 << 2;
+ int left = length - len_m;
+
+ if (left != 0) {
+ if (left >= 3) {
+ h ^= (int) data[length - 3] << 16;
+ }
+ if (left >= 2) {
+ h ^= (int) data[length - 2] << 8;
+ }
+ if (left >= 1) {
+ h ^= (int) data[length - 1];
+ }
+
+ h *= m;
+ }
+
+ h ^= h >>> 13;
+ h *= m;
+ h ^= h >>> 15;
+
+ return h;
+ }
+}