com.google.common.hash.HashingInputStream Maven / Gradle / Ivy
/*
* Copyright (C) 2013 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 com.google.common.annotations.Beta;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* An {@link InputStream} that maintains a hash of the data read from it.
*
* @author Qian Huang
* @since 16.0
*/
@Beta
@ElementTypesAreNonnullByDefault
public final class HashingInputStream extends FilterInputStream {
private final Hasher hasher;
/**
* Creates an input stream that hashes using the given {@link HashFunction} and delegates all data
* read from it to the underlying {@link InputStream}.
*
* The {@link InputStream} should not be read from before or after the hand-off.
*/
public HashingInputStream(HashFunction hashFunction, InputStream in) {
super(checkNotNull(in));
this.hasher = checkNotNull(hashFunction.newHasher());
}
/**
* Reads the next byte of data from the underlying input stream and updates the hasher with the
* byte read.
*/
@Override
@CanIgnoreReturnValue
public int read() throws IOException {
int b = in.read();
if (b != -1) {
hasher.putByte((byte) b);
}
return b;
}
/**
* Reads the specified bytes of data from the underlying input stream and updates the hasher with
* the bytes read.
*/
@Override
@CanIgnoreReturnValue
public int read(byte[] bytes, int off, int len) throws IOException {
int numOfBytesRead = in.read(bytes, off, len);
if (numOfBytesRead != -1) {
hasher.putBytes(bytes, off, numOfBytesRead);
}
return numOfBytesRead;
}
/**
* mark() is not supported for HashingInputStream
*
* @return {@code false} always
*/
@Override
public boolean markSupported() {
return false;
}
/** mark() is not supported for HashingInputStream */
@Override
public void mark(int readlimit) {}
/**
* reset() is not supported for HashingInputStream.
*
* @throws IOException this operation is not supported
*/
@Override
public void reset() throws IOException {
throw new IOException("reset not supported");
}
/**
* Returns the {@link HashCode} based on the data read from this stream. The result is unspecified
* if this method is called more than once on the same instance.
*/
public HashCode hash() {
return hasher.hash();
}
}