org.apache.hudi.common.util.hash.Hash Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* 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
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* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.hudi.common.util.hash;
import org.apache.hudi.common.bloom.InternalBloomFilter;
/**
* This class represents a common API for hashing functions used by
* {@link InternalBloomFilter}.
*
* The code in class is ported from {@link org.apache.hadoop.util.hash.Hash} in Apache Hadoop.
*/
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;
}
}
/**
* 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;
}
}
/**
* 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 length, and
* the provided seed value
*
* @param bytes input bytes
* @param length length of the valid bytes to consider
* @param initval seed value
* @return hash value
*/
public abstract int hash(byte[] bytes, int length, int initval);
}