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/*
 * 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
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(); } }





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