85 lines
2.5 KiB
Java
85 lines
2.5 KiB
Java
/*
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* Copyright (C) 2011 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.checkNotNull;
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import java.io.FilterOutputStream;
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import java.io.IOException;
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import java.io.OutputStream;
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import com.google.common.annotations.Beta;
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/**
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* An {@link OutputStream} that maintains a hash of the data written to it.
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*
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* @author Nick Piepmeier
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* @since 16.0
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*/
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@Beta
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public final class HashingOutputStream extends FilterOutputStream {
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private final Hasher hasher;
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/**
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* Creates an output stream that hashes using the given {@link HashFunction},
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* and forwards all data written to it to the underlying {@link OutputStream}.
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*
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* <p>
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* The {@link OutputStream} should not be written to before or after the
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* hand-off.
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*/
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// TODO(user): Evaluate whether it makes sense to always piggyback the
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// computation of a
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// HashCode on an existing OutputStream, compared to creating a separate
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// OutputStream that could
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// be (optionally) be combined with another if needed (with something like
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// MultiplexingOutputStream).
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public HashingOutputStream(HashFunction hashFunction, OutputStream out) {
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super(checkNotNull(out));
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this.hasher = checkNotNull(hashFunction.newHasher());
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}
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@Override
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public void write(int b) throws IOException {
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hasher.putByte((byte) b);
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out.write(b);
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}
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@Override
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public void write(byte[] bytes, int off, int len) throws IOException {
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hasher.putBytes(bytes, off, len);
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out.write(bytes, off, len);
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}
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/**
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* Returns the {@link HashCode} based on the data written to this stream. The
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* result is unspecified if this method is called more than once on the same
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* instance.
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*/
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public HashCode hash() {
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return hasher.hash();
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}
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// Overriding close() because FilterOutputStream's close() method pre-JDK8 has
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// bad behavior:
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// it silently ignores any exception thrown by flush(). Instead, just close the
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// delegate stream.
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// It should flush itself if necessary.
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@Override
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public void close() throws IOException {
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out.close();
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}
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}
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