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