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/*
* 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.
*/
package com.google.common.hash;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.AtomicLongMap;
import junit.framework.TestCase;
import java.util.Collections;
import java.util.List;
import java.util.Random;
/**
* Unit tests for functions of {@code Hashing} that don't have their own tests.
*/
public class HashingTest extends TestCase {
public void testPadToLong() {
assertEquals(0x1111111111111111L, Hashing.padToLong(HashCodes.fromLong(0x1111111111111111L)));
assertEquals(0x9999999999999999L, Hashing.padToLong(HashCodes.fromLong(0x9999999999999999L)));
assertEquals(0x0000000011111111L, Hashing.padToLong(HashCodes.fromInt(0x11111111)));
assertEquals(0x0000000099999999L, Hashing.padToLong(HashCodes.fromInt(0x99999999)));
}
public void testConsistentHash_correctness() {
long[] interestingValues = { -1, 0, 1, 2, Long.MAX_VALUE, Long.MIN_VALUE };
for (long h : interestingValues) {
checkConsistentHashCorrectness(h);
}
Random r = new Random(7);
for (int i = 0; i < 20; i++) {
checkConsistentHashCorrectness(r.nextLong());
}
}
private void checkConsistentHashCorrectness(long hashCode) {
int last = 0;
for (int shards = 1; shards <= 100000; shards++) {
int b = Hashing.consistentHash(hashCode, shards);
if (b != last) {
assertEquals(shards - 1, b);
last = b;
}
}
}
public void testConsistentHash_probabilities() {
AtomicLongMap<Integer> map = AtomicLongMap.create();
Random r = new Random(9);
for (int i = 0; i < ITERS; i++) {
countRemaps(r.nextLong(), map);
}
for (int shard = 2; shard <= MAX_SHARDS; shard++) {
// Rough: don't exceed 1.2x the expected number of remaps by more than 20
assertTrue(map.get(shard) <= 1.2 * ITERS / shard + 20);
}
}
private void countRemaps(long h, AtomicLongMap<Integer> map) {
int last = 0;
for (int shards = 2; shards <= MAX_SHARDS; shards++) {
int chosen = Hashing.consistentHash(h, shards);
if (chosen != last) {
map.incrementAndGet(shards);
last = chosen;
}
}
}
private static final int ITERS = 10000;
private static final int MAX_SHARDS = 500;
public void testConsistentHash_outOfRange() {
try {
Hashing.consistentHash(5L, 0);
fail();
} catch (IllegalArgumentException expected) {
}
}
public void testConsistentHash_ofHashCode() {
checkSameResult(HashCodes.fromLong(1), 1);
checkSameResult(HashCodes.fromLong(0x9999999999999999L), 0x9999999999999999L);
checkSameResult(HashCodes.fromInt(0x99999999), 0x0000000099999999L);
}
public void checkSameResult(HashCode hashCode, long equivLong) {
assertEquals(Hashing.consistentHash(equivLong, 5555), Hashing.consistentHash(hashCode, 5555));
}
public void testCombineOrdered_null() {
try {
Hashing.combineOrdered(null);
fail();
} catch (NullPointerException expected) {
}
}
public void testCombineOrdered_empty() {
try {
Hashing.combineOrdered(Collections.<HashCode>emptySet());
fail();
} catch (IllegalArgumentException expected) {
}
}
public void testCombineOrdered_differentBitLengths() {
try {
Hashing.combineOrdered(ImmutableList.of(HashCodes.fromInt(32), HashCodes.fromLong(32L)));
fail();
} catch (IllegalArgumentException expected) {
}
}
public void testCombineOrdered() {
HashCode hash31 = HashCodes.fromInt(31);
HashCode hash32 = HashCodes.fromInt(32);
assertEquals(hash32, Hashing.combineOrdered(ImmutableList.of(hash32)));
assertEquals(HashCodes.fromBytes(new byte[] { (byte) 0x80, 0, 0, 0 }),
Hashing.combineOrdered(ImmutableList.of(hash32, hash32)));
assertEquals(HashCodes.fromBytes(new byte[] { (byte) 0xa0, 0, 0, 0 }),
Hashing.combineOrdered(ImmutableList.of(hash32, hash32, hash32)));
assertFalse(
Hashing.combineOrdered(ImmutableList.of(hash31, hash32)).equals(
Hashing.combineOrdered(ImmutableList.of(hash32, hash31))));
}
public void testCombineOrdered_randomHashCodes() {
Random random = new Random(7);
List<HashCode> hashCodes = Lists.newArrayList();
for (int i = 0; i < 10; i++) {
hashCodes.add(HashCodes.fromLong(random.nextLong()));
}
HashCode hashCode1 = Hashing.combineOrdered(hashCodes);
Collections.shuffle(hashCodes, random);
HashCode hashCode2 = Hashing.combineOrdered(hashCodes);
assertFalse(hashCode1.equals(hashCode2));
}
public void testCombineUnordered_null() {
try {
Hashing.combineUnordered(null);
fail();
} catch (NullPointerException expected) {
}
}
public void testCombineUnordered_empty() {
try {
Hashing.combineUnordered(Collections.<HashCode>emptySet());
fail();
} catch (IllegalArgumentException expected) {
}
}
public void testCombineUnordered_differentBitLengths() {
try {
Hashing.combineUnordered(ImmutableList.of(HashCodes.fromInt(32), HashCodes.fromLong(32L)));
fail();
} catch (IllegalArgumentException expected) {
}
}
public void testCombineUnordered() {
HashCode hash31 = HashCodes.fromInt(31);
HashCode hash32 = HashCodes.fromInt(32);
assertEquals(hash32, Hashing.combineUnordered(ImmutableList.of(hash32)));
assertEquals(HashCodes.fromInt(64), Hashing.combineUnordered(ImmutableList.of(hash32, hash32)));
assertEquals(HashCodes.fromInt(96),
Hashing.combineUnordered(ImmutableList.of(hash32, hash32, hash32)));
assertEquals(
Hashing.combineUnordered(ImmutableList.of(hash31, hash32)),
Hashing.combineUnordered(ImmutableList.of(hash32, hash31)));
}
public void testCombineUnordered_randomHashCodes() {
Random random = new Random();
List<HashCode> hashCodes = Lists.newArrayList();
for (int i = 0; i < 10; i++) {
hashCodes.add(HashCodes.fromLong(random.nextLong()));
}
HashCode hashCode1 = Hashing.combineUnordered(hashCodes);
Collections.shuffle(hashCodes);
HashCode hashCode2 = Hashing.combineUnordered(hashCodes);
assertEquals(hashCode1, hashCode2);
}
}
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