001/*
002 * Copyright (C) 2013 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.hash;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018import static java.util.Objects.requireNonNull;
019
020import com.google.common.annotations.Beta;
021import com.google.common.annotations.J2ktIncompatible;
022import com.google.errorprone.annotations.CanIgnoreReturnValue;
023import java.io.FilterInputStream;
024import java.io.IOException;
025import java.io.InputStream;
026
027/**
028 * An {@link InputStream} that maintains a hash of the data read from it.
029 *
030 * @author Qian Huang
031 * @since 16.0
032 */
033@J2ktIncompatible
034@Beta
035public final class HashingInputStream extends FilterInputStream {
036  private final Hasher hasher;
037
038  /**
039   * Creates an input stream that hashes using the given {@link HashFunction} and delegates all data
040   * read from it to the underlying {@link InputStream}.
041   *
042   * <p>The {@link InputStream} should not be read from before or after the hand-off.
043   */
044  public HashingInputStream(HashFunction hashFunction, InputStream in) {
045    super(checkNotNull(in));
046    this.hasher = checkNotNull(hashFunction.newHasher());
047  }
048
049  private InputStream in() {
050    return requireNonNull(in); // guaranteed safe by the constructor
051  }
052
053  /**
054   * Reads the next byte of data from the underlying input stream and updates the hasher with the
055   * byte read.
056   */
057  @Override
058  @CanIgnoreReturnValue
059  public int read() throws IOException {
060    int b = in().read();
061    if (b != -1) {
062      hasher.putByte((byte) b);
063    }
064    return b;
065  }
066
067  /**
068   * Reads the specified bytes of data from the underlying input stream and updates the hasher with
069   * the bytes read.
070   */
071  @Override
072  @CanIgnoreReturnValue
073  public int read(byte[] bytes, int off, int len) throws IOException {
074    int numOfBytesRead = in().read(bytes, off, len);
075    if (numOfBytesRead != -1) {
076      hasher.putBytes(bytes, off, numOfBytesRead);
077    }
078    return numOfBytesRead;
079  }
080
081  /**
082   * mark() is not supported for HashingInputStream
083   *
084   * @return {@code false} always
085   */
086  @Override
087  public boolean markSupported() {
088    return false;
089  }
090
091  /** mark() is not supported for HashingInputStream */
092  @Override
093  public void mark(int readlimit) {}
094
095  /**
096   * reset() is not supported for HashingInputStream.
097   *
098   * @throws IOException this operation is not supported
099   */
100  @Override
101  public void reset() throws IOException {
102    throw new IOException("reset not supported");
103  }
104
105  /**
106   * Returns the {@link HashCode} based on the data read from this stream. The result is unspecified
107   * if this method is called more than once on the same instance.
108   */
109  public HashCode hash() {
110    return hasher.hash();
111  }
112}