/*
* 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 static com.google.common.testing.SerializableTester.reserializeAndAssert;
import com.google.common.collect.ImmutableList;
import junit.framework.TestCase;
import java.util.Arrays;
/**
* Tests for HashCodes, especially making sure that their endianness promises (big-endian)
* are upheld.
*
* @author Dimitris Andreou
*/
public class HashCodesTest extends TestCase {
// note: asInt(), asLong() are in little endian
private static final ImmutableList<ExpectedHashCode> expectedHashCodes = ImmutableList.of(
new ExpectedHashCode(new byte[] {
(byte) 0xef, (byte) 0xcd, (byte) 0xab, (byte) 0x89,
(byte) 0x67, (byte) 0x45, (byte) 0x23, (byte) 0x01},
0x89abcdef, 0x0123456789abcdefL, "efcdab8967452301"),
new ExpectedHashCode(new byte[] {
(byte) 0xef, (byte) 0xcd, (byte) 0xab, (byte) 0x89,
(byte) 0x67, (byte) 0x45, (byte) 0x23, (byte) 0x01, // up to here, same bytes as above
(byte) 0x01, (byte) 0x02, (byte) 0x03, (byte) 0x04,
(byte) 0x05, (byte) 0x06, (byte) 0x07, (byte) 0x08},
0x89abcdef, 0x0123456789abcdefL, // asInt/asLong as above, due to equal eight first bytes
"efcdab89674523010102030405060708"),
new ExpectedHashCode(new byte[] { (byte) 0xdf, (byte) 0x9b, (byte) 0x57, (byte) 0x13 },
0x13579bdf, null, "df9b5713"),
new ExpectedHashCode(new byte[] {
(byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00},
0x0000abcd, null, "cdab0000"),
new ExpectedHashCode(new byte[] {
(byte) 0xef, (byte) 0xcd, (byte) 0xab, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00},
0x00abcdef, 0x0000000000abcdefL, "efcdab0000000000")
);
// expectedHashCodes must contain at least one hash code with 4 bytes
public void testFromInt() {
for (ExpectedHashCode expected : expectedHashCodes) {
if (expected.bytes.length == 4) {
HashCode fromInt = HashCodes.fromInt(expected.asInt);
assertExpectedHashCode(expected, fromInt);
}
}
}
// expectedHashCodes must contain at least one hash code with 8 bytes
public void testFromLong() {
for (ExpectedHashCode expected : expectedHashCodes) {
if (expected.bytes.length == 8) {
HashCode fromLong = HashCodes.fromLong(expected.asLong);
assertExpectedHashCode(expected, fromLong);
}
}
}
public void testFromBytes() {
for (ExpectedHashCode expected : expectedHashCodes) {
HashCode fromBytes = HashCodes.fromBytes(expected.bytes);
assertExpectedHashCode(expected, fromBytes);
}
}
public void testFromBytes_copyOccurs() {
byte[] bytes = new byte[] { (byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00 };
HashCode hashCode = HashCodes.fromBytes(bytes);
int expectedInt = 0x0000abcd;
String expectedToString = "cdab0000";
assertEquals(expectedInt, hashCode.asInt());
assertEquals(expectedToString, hashCode.toString());
bytes[0] = (byte) 0x00;
assertEquals(expectedInt, hashCode.asInt());
assertEquals(expectedToString, hashCode.toString());
}
public void testFromBytesNoCopy_noCopyOccurs() {
byte[] bytes = new byte[] { (byte) 0xcd, (byte) 0xab, (byte) 0x00, (byte) 0x00 };
HashCode hashCode = HashCodes.fromBytesNoCopy(bytes);
assertEquals(0x0000abcd, hashCode.asInt());
assertEquals("cdab0000", hashCode.toString());
bytes[0] = (byte) 0x00;
assertEquals(0x0000ab00, hashCode.asInt());
assertEquals("00ab0000", hashCode.toString());
}
public void testSerialization_IntHashCode() {
reserializeAndAssert(HashCodes.fromInt(42));
}
public void testSerialization_LongHashCode() {
reserializeAndAssert(HashCodes.fromLong(42L));
}
public void testSerialization_BytesHashCode() {
reserializeAndAssert(HashCodes.fromBytes(expectedHashCodes.get(0).bytes));
}
public void testSerialization_BytesHashCode_noCopy() {
reserializeAndAssert(HashCodes.fromBytesNoCopy(expectedHashCodes.get(0).bytes));
}
private void assertExpectedHashCode(ExpectedHashCode expected, HashCode hash) {
assertTrue(Arrays.equals(expected.bytes, hash.asBytes()));
byte[] bb = new byte[hash.bits() / 8];
hash.writeBytesTo(bb, 0, bb.length);
assertTrue(Arrays.equals(expected.bytes, bb));
assertEquals(expected.asInt, hash.asInt());
if (expected.asLong == null) {
try {
hash.asLong();
fail();
} catch (IllegalStateException ok) {}
} else {
assertEquals(expected.asLong.longValue(), hash.asLong());
}
assertEquals(expected.toString, hash.toString());
assertSideEffectFree(hash);
assertReadableBytes(hash);
}
private void assertSideEffectFree(HashCode hash) {
byte[] original = hash.asBytes();
byte[] mutated = hash.asBytes();
mutated[0]++;
assertTrue(Arrays.equals(original, hash.asBytes()));
}
private void assertReadableBytes(HashCode hashCode) {
assertTrue(hashCode.bits() >= 32); // sanity
byte[] hashBytes = hashCode.asBytes();
int totalBytes = hashCode.bits() / 8;
for (int bytes = 0; bytes < totalBytes; bytes++) {
byte[] bb = new byte[bytes];
hashCode.writeBytesTo(bb, 0, bb.length);
assertTrue(Arrays.equals(Arrays.copyOf(hashBytes, bytes), bb));
}
}
private static class ExpectedHashCode {
final byte[] bytes;
final int asInt;
final Long asLong; // null means that asLong should throw an exception
final String toString;
ExpectedHashCode(byte[] bytes, int asInt, Long asLong, String toString) {
this.bytes = bytes;
this.asInt = asInt;
this.asLong = asLong;
this.toString = toString;
}
}
}