1 /*
2 * Copyright (C) 2013 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.hash;
16
17 import static com.google.common.base.Preconditions.checkNotNull;
18
19 import com.google.common.annotations.Beta;
20 import com.google.errorprone.annotations.CanIgnoreReturnValue;
21 import java.io.FilterInputStream;
22 import java.io.IOException;
23 import java.io.InputStream;
24
25 /**
26 * An {@link InputStream} that maintains a hash of the data read from it.
27 *
28 * @author Qian Huang
29 * @since 16.0
30 */
31 @Beta
32 @ElementTypesAreNonnullByDefault
33 public final class HashingInputStream extends FilterInputStream {
34 private final Hasher hasher;
35
36 /**
37 * Creates an input stream that hashes using the given {@link HashFunction} and delegates all data
38 * read from it to the underlying {@link InputStream}.
39 *
40 * <p>The {@link InputStream} should not be read from before or after the hand-off.
41 */
42 public HashingInputStream(HashFunction hashFunction, InputStream in) {
43 super(checkNotNull(in));
44 this.hasher = checkNotNull(hashFunction.newHasher());
45 }
46
47 /**
48 * Reads the next byte of data from the underlying input stream and updates the hasher with the
49 * byte read.
50 */
51 @Override
52 @CanIgnoreReturnValue
53 public int read() throws IOException {
54 int b = in.read();
55 if (b != -1) {
56 hasher.putByte((byte) b);
57 }
58 return b;
59 }
60
61 /**
62 * Reads the specified bytes of data from the underlying input stream and updates the hasher with
63 * the bytes read.
64 */
65 @Override
66 @CanIgnoreReturnValue
67 public int read(byte[] bytes, int off, int len) throws IOException {
68 int numOfBytesRead = in.read(bytes, off, len);
69 if (numOfBytesRead != -1) {
70 hasher.putBytes(bytes, off, numOfBytesRead);
71 }
72 return numOfBytesRead;
73 }
74
75 /**
76 * mark() is not supported for HashingInputStream
77 *
78 * @return {@code false} always
79 */
80 @Override
81 public boolean markSupported() {
82 return false;
83 }
84
85 /** mark() is not supported for HashingInputStream */
86 @Override
87 public void mark(int readlimit) {}
88
89 /**
90 * reset() is not supported for HashingInputStream.
91 *
92 * @throws IOException this operation is not supported
93 */
94 @Override
95 public void reset() throws IOException {
96 throw new IOException("reset not supported");
97 }
98
99 /**
100 * Returns the {@link HashCode} based on the data read from this stream. The result is unspecified
101 * if this method is called more than once on the same instance.
102 */
103 public HashCode hash() {
104 return hasher.hash();
105 }
106 }