AbstractNonStreamingHashFunctionTest.java revision 5cab40b862c21656c2ace19596874eb3ffe1b649 
1/*
2 * Copyright (C) 2011 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.hash;
18
19import com.google.common.collect.ImmutableList;
20import com.google.common.hash.HashTestUtils.RandomHasherAction;
21import com.google.common.jdk5backport.Arrays;
22
23import junit.framework.TestCase;
24
25import junit.framework.TestCase;
26
27import java.io.ByteArrayOutputStream;
28import java.nio.ByteBuffer;
29import java.nio.charset.Charset;
30import java.util.List;
31import java.util.Random;
32
33/**
34 * Tests for AbstractNonStreamingHashFunction.
35 */
36public class AbstractNonStreamingHashFunctionTest extends TestCase {
37  /**
38   * Constructs two trivial HashFunctions (output := input), one streaming and one non-streaming,
39   * and checks that their results are identical, no matter which newHasher version we used.
40   */
41  public void testExhaustive() {
42    List<Hasher> hashers = ImmutableList.of(
43        new StreamingVersion().newHasher(),
44        new StreamingVersion().newHasher(52),
45        new NonStreamingVersion().newHasher(),
46        new NonStreamingVersion().newHasher(123));
47    Random random = new Random(0);
48    for (int i = 0; i < 200; i++) {
49      RandomHasherAction.pickAtRandom(random).performAction(random, hashers);
50    }
51    HashCode[] codes = new HashCode[hashers.size()];
52    for (int i = 0; i < hashers.size(); i++) {
53      codes[i] = hashers.get(i).hash();
54    }
55    for (int i = 1; i < codes.length; i++) {
56      assertEquals(codes[i - 1], codes[i]);
57    }
58  }
59
60  public void testPutStringWithLowSurrogate() {
61    // we pad because the dummy hash function we use to test this, merely copies the input into
62    // the output, so the input must be at least 32 bits, since the output has to be that long
63    assertPutString(new char[] { 'p', HashTestUtils.randomLowSurrogate(new Random()) });
64  }
65
66  public void testPutStringWithHighSurrogate() {
67    // we pad because the dummy hash function we use to test this, merely copies the input into
68    // the output, so the input must be at least 32 bits, since the output has to be that long
69    assertPutString(new char[] { 'p', HashTestUtils.randomHighSurrogate(new Random()) });
70  }
71
72  public void testPutStringWithLowHighSurrogate() {
73    assertPutString(new char[] {
74        HashTestUtils.randomLowSurrogate(new Random()),
75        HashTestUtils.randomHighSurrogate(new Random()) });
76  }
77
78  public void testPutStringWithHighLowSurrogate() {
79    assertPutString(new char[] {
80        HashTestUtils.randomHighSurrogate(new Random()),
81        HashTestUtils.randomLowSurrogate(new Random()) });
82  }
83
84  private static void assertPutString(char[] chars) {
85    Hasher h1 = new NonStreamingVersion().newHasher();
86    Hasher h2 = new NonStreamingVersion().newHasher();
87    String s = new String(chars);
88    // this is the correct implementation of the spec
89    for (int i = 0; i < s.length(); i++) {
90      h1.putChar(s.charAt(i));
91    }
92    h2.putUnencodedChars(s);
93    assertEquals(h1.hash(), h2.hash());
94  }
95
96  static class StreamingVersion extends AbstractStreamingHashFunction {
97    @Override
98    public int bits() {
99      return 32;
100    }
101
102    @Override
103    public Hasher newHasher() {
104      return new AbstractStreamingHasher(4, 4) {
105        final ByteArrayOutputStream out = new ByteArrayOutputStream();
106        @Override
107        HashCode makeHash() {
108          return HashCode.fromBytes(out.toByteArray());
109        }
110
111        @Override
112        protected void process(ByteBuffer bb) {
113          while (bb.hasRemaining()) {
114            out.write(bb.get());
115          }
116        }
117
118        @Override
119        protected void processRemaining(ByteBuffer bb) {
120          while (bb.hasRemaining()) {
121            out.write(bb.get());
122          }
123        }
124      };
125    }
126  }
127
128  static class NonStreamingVersion extends AbstractNonStreamingHashFunction {
129    @Override
130    public int bits() {
131      return 32;
132    }
133
134    @Override
135    public HashCode hashBytes(byte[] input) {
136      return HashCode.fromBytes(input);
137    }
138
139    @Override
140    public HashCode hashBytes(byte[] input, int off, int len) {
141      return HashCode.fromBytes(Arrays.copyOfRange(input, off, off + len));
142    }
143
144    @Override
145    public HashCode hashString(CharSequence input, Charset charset) {
146      throw new UnsupportedOperationException();
147    }
148
149    @Override
150    public HashCode hashLong(long input) {
151      throw new UnsupportedOperationException();
152    }
153
154    @Override
155    public HashCode hashInt(int input) {
156      throw new UnsupportedOperationException();
157    }
158  }
159}
160