com.google.common.hash.ChecksumHashFunction Maven / Gradle / Ivy
/*
* Copyright (C) 2012 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.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.errorprone.annotations.Immutable;
import com.google.j2objc.annotations.J2ObjCIncompatible;
import java.io.Serializable;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.nio.ByteBuffer;
import java.util.zip.Checksum;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* {@link HashFunction} adapter for {@link Checksum} instances.
*
* @author Colin Decker
*/
@Immutable
@ElementTypesAreNonnullByDefault
final class ChecksumHashFunction extends AbstractHashFunction implements Serializable {
private final ImmutableSupplier checksumSupplier;
private final int bits;
private final String toString;
ChecksumHashFunction(
ImmutableSupplier checksumSupplier, int bits, String toString) {
this.checksumSupplier = checkNotNull(checksumSupplier);
checkArgument(bits == 32 || bits == 64, "bits (%s) must be either 32 or 64", bits);
this.bits = bits;
this.toString = checkNotNull(toString);
}
@Override
public int bits() {
return bits;
}
@Override
public Hasher newHasher() {
return new ChecksumHasher(checksumSupplier.get());
}
@Override
public String toString() {
return toString;
}
/** Hasher that updates a checksum. */
private final class ChecksumHasher extends AbstractByteHasher {
private final Checksum checksum;
private ChecksumHasher(Checksum checksum) {
this.checksum = checkNotNull(checksum);
}
@Override
protected void update(byte b) {
checksum.update(b);
}
@Override
protected void update(byte[] bytes, int off, int len) {
checksum.update(bytes, off, len);
}
@Override
@J2ObjCIncompatible
protected void update(ByteBuffer b) {
if (!ChecksumMethodHandles.updateByteBuffer(checksum, b)) {
super.update(b);
}
}
@Override
public HashCode hash() {
long value = checksum.getValue();
if (bits == 32) {
/*
* The long returned from a 32-bit Checksum will have all 0s for its second word, so the
* cast won't lose any information and is necessary to return a HashCode of the correct
* size.
*/
return HashCode.fromInt((int) value);
} else {
return HashCode.fromLong(value);
}
}
}
@J2ObjCIncompatible
@SuppressWarnings("unused")
private static final class ChecksumMethodHandles {
private static final @Nullable MethodHandle UPDATE_BB = updateByteBuffer();
@IgnoreJRERequirement // https://github.com/mojohaus/animal-sniffer/issues/67
static boolean updateByteBuffer(Checksum cs, ByteBuffer bb) {
if (UPDATE_BB != null) {
try {
UPDATE_BB.invokeExact(cs, bb);
} catch (Error t) {
throw t;
} catch (Throwable t) {
throw new AssertionError(t);
}
return true;
} else {
return false;
}
}
private static @Nullable MethodHandle updateByteBuffer() {
try {
Class clazz = Class.forName("java.util.zip.Checksum");
return MethodHandles.lookup()
.findVirtual(clazz, "update", MethodType.methodType(void.class, ByteBuffer.class));
} catch (ClassNotFoundException e) {
throw new AssertionError(e);
} catch (IllegalAccessException e) {
// That API is public.
throw newLinkageError(e);
} catch (NoSuchMethodException e) {
// Only introduced in Java 9.
return null;
}
}
private static LinkageError newLinkageError(Throwable cause) {
return new LinkageError(cause.toString(), cause);
}
}
private static final long serialVersionUID = 0L;
}