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