1// Copyright 2011 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package lzw
6
7import (
8	"fmt"
9	"internal/testenv"
10	"io"
11	"math"
12	"os"
13	"runtime"
14	"testing"
15)
16
17var filenames = []string{
18	"../testdata/gettysburg.txt",
19	"../testdata/e.txt",
20	"../testdata/pi.txt",
21}
22
23// testFile tests that compressing and then decompressing the given file with
24// the given options yields equivalent bytes to the original file.
25func testFile(t *testing.T, fn string, order Order, litWidth int) {
26	// Read the file, as golden output.
27	golden, err := os.Open(fn)
28	if err != nil {
29		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
30		return
31	}
32	defer golden.Close()
33
34	// Read the file again, and push it through a pipe that compresses at the write end, and decompresses at the read end.
35	raw, err := os.Open(fn)
36	if err != nil {
37		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
38		return
39	}
40
41	piper, pipew := io.Pipe()
42	defer piper.Close()
43	go func() {
44		defer raw.Close()
45		defer pipew.Close()
46		lzww := NewWriter(pipew, order, litWidth)
47		defer lzww.Close()
48		var b [4096]byte
49		for {
50			n, err0 := raw.Read(b[:])
51			if err0 != nil && err0 != io.EOF {
52				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
53				return
54			}
55			_, err1 := lzww.Write(b[:n])
56			if err1 != nil {
57				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
58				return
59			}
60			if err0 == io.EOF {
61				break
62			}
63		}
64	}()
65	lzwr := NewReader(piper, order, litWidth)
66	defer lzwr.Close()
67
68	// Compare the two.
69	b0, err0 := io.ReadAll(golden)
70	b1, err1 := io.ReadAll(lzwr)
71	if err0 != nil {
72		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
73		return
74	}
75	if err1 != nil {
76		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
77		return
78	}
79	if len(b1) != len(b0) {
80		t.Errorf("%s (order=%d litWidth=%d): length mismatch %d != %d", fn, order, litWidth, len(b1), len(b0))
81		return
82	}
83	for i := 0; i < len(b0); i++ {
84		if b1[i] != b0[i] {
85			t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x != 0x%02x\n", fn, order, litWidth, i, b1[i], b0[i])
86			return
87		}
88	}
89}
90
91func TestWriter(t *testing.T) {
92	for _, filename := range filenames {
93		for _, order := range [...]Order{LSB, MSB} {
94			// The test data "2.71828 etcetera" is ASCII text requiring at least 6 bits.
95			for litWidth := 6; litWidth <= 8; litWidth++ {
96				if filename == "../testdata/gettysburg.txt" && litWidth == 6 {
97					continue
98				}
99				testFile(t, filename, order, litWidth)
100			}
101		}
102		if testing.Short() && testenv.Builder() == "" {
103			break
104		}
105	}
106}
107
108func TestWriterReturnValues(t *testing.T) {
109	w := NewWriter(io.Discard, LSB, 8)
110	n, err := w.Write([]byte("asdf"))
111	if n != 4 || err != nil {
112		t.Errorf("got %d, %v, want 4, nil", n, err)
113	}
114}
115
116func TestSmallLitWidth(t *testing.T) {
117	w := NewWriter(io.Discard, LSB, 2)
118	if _, err := w.Write([]byte{0x03}); err != nil {
119		t.Fatalf("write a byte < 1<<2: %v", err)
120	}
121	if _, err := w.Write([]byte{0x04}); err == nil {
122		t.Fatal("write a byte >= 1<<2: got nil error, want non-nil")
123	}
124}
125
126func BenchmarkEncoder(b *testing.B) {
127	buf, err := os.ReadFile("../testdata/e.txt")
128	if err != nil {
129		b.Fatal(err)
130	}
131	if len(buf) == 0 {
132		b.Fatalf("test file has no data")
133	}
134
135	for e := 4; e <= 6; e++ {
136		n := int(math.Pow10(e))
137		buf0 := buf
138		buf1 := make([]byte, n)
139		for i := 0; i < n; i += len(buf0) {
140			if len(buf0) > n-i {
141				buf0 = buf0[:n-i]
142			}
143			copy(buf1[i:], buf0)
144		}
145		buf0 = nil
146		runtime.GC()
147		b.Run(fmt.Sprint("1e", e), func(b *testing.B) {
148			b.SetBytes(int64(n))
149			for i := 0; i < b.N; i++ {
150				w := NewWriter(io.Discard, LSB, 8)
151				w.Write(buf1)
152				w.Close()
153			}
154		})
155	}
156}
157