com.google.common.collect.Hashing Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
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/*
* Copyright (C) 2008 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.
*/
package com.google.common.collect;
import com.google.common.annotations.GwtCompatible;
import com.google.common.primitives.Ints;
import javax.annotation.CheckForNull;
/**
* Static methods for implementing hash-based collections.
*
* @author Kevin Bourrillion
* @author Jesse Wilson
* @author Austin Appleby
*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class Hashing {
private Hashing() {}
/*
* These should be ints, but we need to use longs to force GWT to do the multiplications with
* enough precision.
*/
private static final long C1 = 0xcc9e2d51;
private static final long C2 = 0x1b873593;
/*
* This method was rewritten in Java from an intermediate step of the Murmur hash function in
* http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp, which contained the
* following header:
*
* MurmurHash3 was written by Austin Appleby, and is placed in the public domain. The author
* hereby disclaims copyright to this source code.
*/
static int smear(int hashCode) {
return (int) (C2 * Integer.rotateLeft((int) (hashCode * C1), 15));
}
static int smearedHash(@CheckForNull Object o) {
return smear((o == null) ? 0 : o.hashCode());
}
private static final int MAX_TABLE_SIZE = Ints.MAX_POWER_OF_TWO;
static int closedTableSize(int expectedEntries, double loadFactor) {
// Get the recommended table size.
// Round down to the nearest power of 2.
expectedEntries = Math.max(expectedEntries, 2);
int tableSize = Integer.highestOneBit(expectedEntries);
// Check to make sure that we will not exceed the maximum load factor.
if (expectedEntries > (int) (loadFactor * tableSize)) {
tableSize <<= 1;
return (tableSize > 0) ? tableSize : MAX_TABLE_SIZE;
}
return tableSize;
}
static boolean needsResizing(int size, int tableSize, double loadFactor) {
return size > loadFactor * tableSize && tableSize < MAX_TABLE_SIZE;
}
}