97 lines
2.5 KiB
Java
97 lines
2.5 KiB
Java
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/*
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* Copyright (C) 2012 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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package com.google.common.hash;
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import static com.google.common.base.Preconditions.checkArgument;
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import static com.google.common.base.Preconditions.checkNotNull;
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import java.io.Serializable;
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import java.util.zip.Checksum;
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import com.google.common.base.Supplier;
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/**
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* {@link HashFunction} adapter for {@link Checksum} instances.
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*
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* @author Colin Decker
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*/
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final class ChecksumHashFunction extends AbstractStreamingHashFunction implements Serializable {
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private final Supplier<? extends Checksum> checksumSupplier;
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private final int bits;
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private final String toString;
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ChecksumHashFunction(Supplier<? extends Checksum> checksumSupplier, int bits, String toString) {
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this.checksumSupplier = checkNotNull(checksumSupplier);
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checkArgument(bits == 32 || bits == 64, "bits (%s) must be either 32 or 64", bits);
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this.bits = bits;
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this.toString = checkNotNull(toString);
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}
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@Override
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public int bits() {
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return bits;
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}
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@Override
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public Hasher newHasher() {
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return new ChecksumHasher(checksumSupplier.get());
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}
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@Override
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public String toString() {
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return toString;
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}
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/**
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* Hasher that updates a checksum.
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*/
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private final class ChecksumHasher extends AbstractByteHasher {
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private final Checksum checksum;
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private ChecksumHasher(Checksum checksum) {
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this.checksum = checkNotNull(checksum);
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}
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@Override
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protected void update(byte b) {
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checksum.update(b);
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}
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@Override
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protected void update(byte[] bytes, int off, int len) {
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checksum.update(bytes, off, len);
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}
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@Override
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public HashCode hash() {
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long value = checksum.getValue();
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if (bits == 32) {
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/*
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* The long returned from a 32-bit Checksum will have all 0s for its second
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* word, so the cast won't lose any information and is necessary to return a
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* HashCode of the correct size.
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*/
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return HashCode.fromInt((int) value);
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} else {
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return HashCode.fromLong(value);
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}
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}
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}
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private static final long serialVersionUID = 0L;
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}
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