EaglerForge/sources/main/java/com/google/common/hash/ChecksumHashFunction.java

97 lines
2.5 KiB
Java

/*
* 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 java.io.Serializable;
import java.util.zip.Checksum;
import com.google.common.base.Supplier;
/**
* {@link HashFunction} adapter for {@link Checksum} instances.
*
* @author Colin Decker
*/
final class ChecksumHashFunction extends AbstractStreamingHashFunction implements Serializable {
private final Supplier<? extends Checksum> checksumSupplier;
private final int bits;
private final String toString;
ChecksumHashFunction(Supplier<? extends Checksum> 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
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);
}
}
}
private static final long serialVersionUID = 0L;
}