Coverage Summary for Class: ChecksumHashFunction (com.google.common.hash)

1 /*
2  * Copyright (C) 2012 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.checkArgument;
18 import static com.google.common.base.Preconditions.checkNotNull;
19 
20 import com.google.errorprone.annotations.Immutable;
21 import java.io.Serializable;
22 import java.util.zip.Checksum;
23 
24 /**
25  * {@link HashFunction} adapter for {@link Checksum} instances.
26  *
27  * @author Colin Decker
28  */
29 @Immutable
30 @ElementTypesAreNonnullByDefault
31 final class ChecksumHashFunction extends AbstractHashFunction implements Serializable {
32   private final ImmutableSupplier<? extends Checksum> checksumSupplier;
33   private final int bits;
34   private final String toString;
35 
36   ChecksumHashFunction(
37       ImmutableSupplier<? extends Checksum> checksumSupplier, int bits, String toString) {
38     this.checksumSupplier = checkNotNull(checksumSupplier);
39     checkArgument(bits == 32 || bits == 64, "bits (%s) must be either 32 or 64", bits);
40     this.bits = bits;
41     this.toString = checkNotNull(toString);
42   }
43 
44   @Override
45   public int bits() {
46     return bits;
47   }
48 
49   @Override
50   public Hasher newHasher() {
51     return new ChecksumHasher(checksumSupplier.get());
52   }
53 
54   @Override
55   public String toString() {
56     return toString;
57   }
58 
59   /** Hasher that updates a checksum. */
60   private final class ChecksumHasher extends AbstractByteHasher {
61     private final Checksum checksum;
62 
63     private ChecksumHasher(Checksum checksum) {
64       this.checksum = checkNotNull(checksum);
65     }
66 
67     @Override
68     protected void update(byte b) {
69       checksum.update(b);
70     }
71 
72     @Override
73     protected void update(byte[] bytes, int off, int len) {
74       checksum.update(bytes, off, len);
75     }
76 
77     @Override
78     public HashCode hash() {
79       long value = checksum.getValue();
80       if (bits == 32) {
81         /*
82          * The long returned from a 32-bit Checksum will have all 0s for its second word, so the
83          * cast won't lose any information and is necessary to return a HashCode of the correct
84          * size.
85          */
86         return HashCode.fromInt((int) value);
87       } else {
88         return HashCode.fromLong(value);
89       }
90     }
91   }
92 
93   private static final long serialVersionUID = 0L;
94 }