1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
|
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package lzw
import (
"bytes"
"fmt"
"internal/testenv"
"io"
"math"
"os"
"runtime"
"testing"
)
var filenames = []string{
"../testdata/gettysburg.txt",
"../testdata/e.txt",
"../testdata/pi.txt",
}
// testFile tests that compressing and then decompressing the given file with
// the given options yields equivalent bytes to the original file.
func testFile(t *testing.T, fn string, order Order, litWidth int) {
// Read the file, as golden output.
golden, err := os.Open(fn)
if err != nil {
t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
return
}
defer golden.Close()
// Read the file again, and push it through a pipe that compresses at the write end, and decompresses at the read end.
raw, err := os.Open(fn)
if err != nil {
t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
return
}
piper, pipew := io.Pipe()
defer piper.Close()
go func() {
defer raw.Close()
defer pipew.Close()
lzww := NewWriter(pipew, order, litWidth)
defer lzww.Close()
var b [4096]byte
for {
n, err0 := raw.Read(b[:])
if err0 != nil && err0 != io.EOF {
t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
return
}
_, err1 := lzww.Write(b[:n])
if err1 != nil {
t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
return
}
if err0 == io.EOF {
break
}
}
}()
lzwr := NewReader(piper, order, litWidth)
defer lzwr.Close()
// Compare the two.
b0, err0 := io.ReadAll(golden)
b1, err1 := io.ReadAll(lzwr)
if err0 != nil {
t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
return
}
if err1 != nil {
t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
return
}
if len(b1) != len(b0) {
t.Errorf("%s (order=%d litWidth=%d): length mismatch %d != %d", fn, order, litWidth, len(b1), len(b0))
return
}
for i := 0; i < len(b0); i++ {
if b1[i] != b0[i] {
t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x != 0x%02x\n", fn, order, litWidth, i, b1[i], b0[i])
return
}
}
}
func TestWriter(t *testing.T) {
for _, filename := range filenames {
for _, order := range [...]Order{LSB, MSB} {
// The test data "2.71828 etcetera" is ASCII text requiring at least 6 bits.
for litWidth := 6; litWidth <= 8; litWidth++ {
if filename == "../testdata/gettysburg.txt" && litWidth == 6 {
continue
}
testFile(t, filename, order, litWidth)
}
}
if testing.Short() && testenv.Builder() == "" {
break
}
}
}
func TestWriterReset(t *testing.T) {
for _, order := range [...]Order{LSB, MSB} {
t.Run(fmt.Sprintf("Order %d", order), func(t *testing.T) {
for litWidth := 6; litWidth <= 8; litWidth++ {
t.Run(fmt.Sprintf("LitWidth %d", litWidth), func(t *testing.T) {
var data []byte
if litWidth == 6 {
data = []byte{1, 2, 3}
} else {
data = []byte(`lorem ipsum dolor sit amet`)
}
var buf bytes.Buffer
w := NewWriter(&buf, order, litWidth)
if _, err := w.Write(data); err != nil {
t.Errorf("write: %v: %v", string(data), err)
}
if err := w.Close(); err != nil {
t.Errorf("close: %v", err)
}
b1 := buf.Bytes()
buf.Reset()
w.(*Writer).Reset(&buf, order, litWidth)
if _, err := w.Write(data); err != nil {
t.Errorf("write: %v: %v", string(data), err)
}
if err := w.Close(); err != nil {
t.Errorf("close: %v", err)
}
b2 := buf.Bytes()
if !bytes.Equal(b1, b2) {
t.Errorf("bytes written were not same")
}
})
}
})
}
}
func TestWriterReturnValues(t *testing.T) {
w := NewWriter(io.Discard, LSB, 8)
n, err := w.Write([]byte("asdf"))
if n != 4 || err != nil {
t.Errorf("got %d, %v, want 4, nil", n, err)
}
}
func TestSmallLitWidth(t *testing.T) {
w := NewWriter(io.Discard, LSB, 2)
if _, err := w.Write([]byte{0x03}); err != nil {
t.Fatalf("write a byte < 1<<2: %v", err)
}
if _, err := w.Write([]byte{0x04}); err == nil {
t.Fatal("write a byte >= 1<<2: got nil error, want non-nil")
}
}
func TestStartsWithClearCode(t *testing.T) {
// A literal width of 7 bits means that the code width starts at 8 bits,
// which makes it easier to visually inspect the output (provided that the
// output is short so codes don't get longer). Each byte is a code:
// - ASCII bytes are literal codes,
// - 0x80 is the clear code,
// - 0x81 is the end code.
// - 0x82 and above are copy codes (unused in this test case).
for _, empty := range []bool{false, true} {
var buf bytes.Buffer
w := NewWriter(&buf, LSB, 7)
if !empty {
w.Write([]byte("Hi"))
}
w.Close()
got := buf.String()
want := "\x80\x81"
if !empty {
want = "\x80Hi\x81"
}
if got != want {
t.Errorf("empty=%t: got %q, want %q", empty, got, want)
}
}
}
func BenchmarkEncoder(b *testing.B) {
buf, err := os.ReadFile("../testdata/e.txt")
if err != nil {
b.Fatal(err)
}
if len(buf) == 0 {
b.Fatalf("test file has no data")
}
for e := 4; e <= 6; e++ {
n := int(math.Pow10(e))
buf0 := buf
buf1 := make([]byte, n)
for i := 0; i < n; i += len(buf0) {
if len(buf0) > n-i {
buf0 = buf0[:n-i]
}
copy(buf1[i:], buf0)
}
buf0 = nil
runtime.GC()
b.Run(fmt.Sprint("1e", e), func(b *testing.B) {
b.SetBytes(int64(n))
for i := 0; i < b.N; i++ {
w := NewWriter(io.Discard, LSB, 8)
w.Write(buf1)
w.Close()
}
})
b.Run(fmt.Sprint("1e-Reuse", e), func(b *testing.B) {
b.SetBytes(int64(n))
w := NewWriter(io.Discard, LSB, 8)
for i := 0; i < b.N; i++ {
w.Write(buf1)
w.Close()
w.(*Writer).Reset(io.Discard, LSB, 8)
}
})
}
}
|
