Source file
src/hash/maphash/maphash_test.go
1
2
3
4
5 package maphash
6
7 import (
8 "bytes"
9 "fmt"
10 "hash"
11 "testing"
12 )
13
14 func TestUnseededHash(t *testing.T) {
15 m := map[uint64]struct{}{}
16 for i := 0; i < 1000; i++ {
17 h := new(Hash)
18 m[h.Sum64()] = struct{}{}
19 }
20 if len(m) < 900 {
21 t.Errorf("empty hash not sufficiently random: got %d, want 1000", len(m))
22 }
23 }
24
25 func TestSeededHash(t *testing.T) {
26 s := MakeSeed()
27 m := map[uint64]struct{}{}
28 for i := 0; i < 1000; i++ {
29 h := new(Hash)
30 h.SetSeed(s)
31 m[h.Sum64()] = struct{}{}
32 }
33 if len(m) != 1 {
34 t.Errorf("seeded hash is random: got %d, want 1", len(m))
35 }
36 }
37
38 func TestHashGrouping(t *testing.T) {
39 b := bytes.Repeat([]byte("foo"), 100)
40 hh := make([]*Hash, 7)
41 for i := range hh {
42 hh[i] = new(Hash)
43 }
44 for _, h := range hh[1:] {
45 h.SetSeed(hh[0].Seed())
46 }
47 hh[0].Write(b)
48 hh[1].WriteString(string(b))
49
50 writeByte := func(h *Hash, b byte) {
51 err := h.WriteByte(b)
52 if err != nil {
53 t.Fatalf("WriteByte: %v", err)
54 }
55 }
56 writeSingleByte := func(h *Hash, b byte) {
57 _, err := h.Write([]byte{b})
58 if err != nil {
59 t.Fatalf("Write single byte: %v", err)
60 }
61 }
62 writeStringSingleByte := func(h *Hash, b byte) {
63 _, err := h.WriteString(string([]byte{b}))
64 if err != nil {
65 t.Fatalf("WriteString single byte: %v", err)
66 }
67 }
68
69 for i, x := range b {
70 writeByte(hh[2], x)
71 writeSingleByte(hh[3], x)
72 if i == 0 {
73 writeByte(hh[4], x)
74 } else {
75 writeSingleByte(hh[4], x)
76 }
77 writeStringSingleByte(hh[5], x)
78 if i == 0 {
79 writeByte(hh[6], x)
80 } else {
81 writeStringSingleByte(hh[6], x)
82 }
83 }
84
85 sum := hh[0].Sum64()
86 for i, h := range hh {
87 if sum != h.Sum64() {
88 t.Errorf("hash %d not identical to a single Write", i)
89 }
90 }
91
92 if sum1 := Bytes(hh[0].Seed(), b); sum1 != hh[0].Sum64() {
93 t.Errorf("hash using Bytes not identical to a single Write")
94 }
95
96 if sum1 := String(hh[0].Seed(), string(b)); sum1 != hh[0].Sum64() {
97 t.Errorf("hash using String not identical to a single Write")
98 }
99 }
100
101 func TestHashBytesVsString(t *testing.T) {
102 s := "foo"
103 b := []byte(s)
104 h1 := new(Hash)
105 h2 := new(Hash)
106 h2.SetSeed(h1.Seed())
107 n1, err1 := h1.WriteString(s)
108 if n1 != len(s) || err1 != nil {
109 t.Fatalf("WriteString(s) = %d, %v, want %d, nil", n1, err1, len(s))
110 }
111 n2, err2 := h2.Write(b)
112 if n2 != len(b) || err2 != nil {
113 t.Fatalf("Write(b) = %d, %v, want %d, nil", n2, err2, len(b))
114 }
115 if h1.Sum64() != h2.Sum64() {
116 t.Errorf("hash of string and bytes not identical")
117 }
118 }
119
120 func TestHashHighBytes(t *testing.T) {
121
122 const N = 10
123 m := map[uint64]struct{}{}
124 for i := 0; i < N; i++ {
125 h := new(Hash)
126 h.WriteString("foo")
127 m[h.Sum64()>>32] = struct{}{}
128 }
129 if len(m) < N/2 {
130 t.Errorf("from %d seeds, wanted at least %d different hashes; got %d", N, N/2, len(m))
131 }
132 }
133
134 func TestRepeat(t *testing.T) {
135 h1 := new(Hash)
136 h1.WriteString("testing")
137 sum1 := h1.Sum64()
138
139 h1.Reset()
140 h1.WriteString("testing")
141 sum2 := h1.Sum64()
142
143 if sum1 != sum2 {
144 t.Errorf("different sum after reseting: %#x != %#x", sum1, sum2)
145 }
146
147 h2 := new(Hash)
148 h2.SetSeed(h1.Seed())
149 h2.WriteString("testing")
150 sum3 := h2.Sum64()
151
152 if sum1 != sum3 {
153 t.Errorf("different sum on the same seed: %#x != %#x", sum1, sum3)
154 }
155 }
156
157 func TestSeedFromSum64(t *testing.T) {
158 h1 := new(Hash)
159 h1.WriteString("foo")
160 x := h1.Sum64()
161 h2 := new(Hash)
162 h2.SetSeed(h1.Seed())
163 h2.WriteString("foo")
164 y := h2.Sum64()
165 if x != y {
166 t.Errorf("hashes don't match: want %x, got %x", x, y)
167 }
168 }
169
170 func TestSeedFromSeed(t *testing.T) {
171 h1 := new(Hash)
172 h1.WriteString("foo")
173 _ = h1.Seed()
174 x := h1.Sum64()
175 h2 := new(Hash)
176 h2.SetSeed(h1.Seed())
177 h2.WriteString("foo")
178 y := h2.Sum64()
179 if x != y {
180 t.Errorf("hashes don't match: want %x, got %x", x, y)
181 }
182 }
183
184 func TestSeedFromFlush(t *testing.T) {
185 b := make([]byte, 65)
186 h1 := new(Hash)
187 h1.Write(b)
188 x := h1.Sum64()
189 h2 := new(Hash)
190 h2.SetSeed(h1.Seed())
191 h2.Write(b)
192 y := h2.Sum64()
193 if x != y {
194 t.Errorf("hashes don't match: want %x, got %x", x, y)
195 }
196 }
197
198 func TestSeedFromReset(t *testing.T) {
199 h1 := new(Hash)
200 h1.WriteString("foo")
201 h1.Reset()
202 h1.WriteString("foo")
203 x := h1.Sum64()
204 h2 := new(Hash)
205 h2.SetSeed(h1.Seed())
206 h2.WriteString("foo")
207 y := h2.Sum64()
208 if x != y {
209 t.Errorf("hashes don't match: want %x, got %x", x, y)
210 }
211 }
212
213
214 var _ hash.Hash = &Hash{}
215 var _ hash.Hash64 = &Hash{}
216
217 func benchmarkSize(b *testing.B, size int) {
218 h := &Hash{}
219 buf := make([]byte, size)
220 s := string(buf)
221
222 b.Run("Write", func(b *testing.B) {
223 b.SetBytes(int64(size))
224 for i := 0; i < b.N; i++ {
225 h.Reset()
226 h.Write(buf)
227 h.Sum64()
228 }
229 })
230
231 b.Run("Bytes", func(b *testing.B) {
232 b.SetBytes(int64(size))
233 seed := h.Seed()
234 for i := 0; i < b.N; i++ {
235 Bytes(seed, buf)
236 }
237 })
238
239 b.Run("String", func(b *testing.B) {
240 b.SetBytes(int64(size))
241 seed := h.Seed()
242 for i := 0; i < b.N; i++ {
243 String(seed, s)
244 }
245 })
246 }
247
248 func BenchmarkHash(b *testing.B) {
249 sizes := []int{4, 8, 16, 32, 64, 256, 320, 1024, 4096, 16384}
250 for _, size := range sizes {
251 b.Run(fmt.Sprint("n=", size), func(b *testing.B) {
252 benchmarkSize(b, size)
253 })
254 }
255 }
256
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