libgo/go/compress/lzw/reader_test.go

   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
   5 package lzw
   6
   7 import (
   8         "bytes"
   9         "fmt"
  10         "io"
  11         "io/ioutil"
  12         "math"
  13         "runtime"
  14         "strconv"
  15         "strings"
  16         "testing"
  17 )
  18
  19 type lzwTest struct {
  20         desc       string
  21         raw        string
  22         compressed string
  23         err        error
  24 }
  25
  26 var lzwTests = []lzwTest{
  27         {
  28                 "empty;LSB;8",
  29                 "",
  30                 "\x01\x01",
  31                 nil,
  32         },
  33         {
  34                 "empty;MSB;8",
  35                 "",
  36                 "\x80\x80",
  37                 nil,
  38         },
  39         {
  40                 "tobe;LSB;7",
  41                 "TOBEORNOTTOBEORTOBEORNOT",
  42                 "\x54\x4f\x42\x45\x4f\x52\x4e\x4f\x54\x82\x84\x86\x8b\x85\x87\x89\x81",
  43                 nil,
  44         },
  45         {
  46                 "tobe;LSB;8",
  47                 "TOBEORNOTTOBEORTOBEORNOT",
  48                 "\x54\x9e\x08\x29\xf2\x44\x8a\x93\x27\x54\x04\x12\x34\xb8\xb0\xe0\xc1\x84\x01\x01",
  49                 nil,
  50         },
  51         {
  52                 "tobe;MSB;7",
  53                 "TOBEORNOTTOBEORTOBEORNOT",
  54                 "\x54\x4f\x42\x45\x4f\x52\x4e\x4f\x54\x82\x84\x86\x8b\x85\x87\x89\x81",
  55                 nil,
  56         },
  57         {
  58                 "tobe;MSB;8",
  59                 "TOBEORNOTTOBEORTOBEORNOT",
  60                 "\x2a\x13\xc8\x44\x52\x79\x48\x9c\x4f\x2a\x40\xa0\x90\x68\x5c\x16\x0f\x09\x80\x80",
  61                 nil,
  62         },
  63         {
  64                 "tobe-truncated;LSB;8",
  65                 "TOBEORNOTTOBEORTOBEORNOT",
  66                 "\x54\x9e\x08\x29\xf2\x44\x8a\x93\x27\x54\x04",
  67                 io.ErrUnexpectedEOF,
  68         },
  69         // This example comes from http://en.wikipedia.org/wiki/Graphics_Interchange_Format.
  70         {
  71                 "gif;LSB;8",
  72                 "\x28\xff\xff\xff\x28\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff",
  73                 "\x00\x51\xfc\x1b\x28\x70\xa0\xc1\x83\x01\x01",
  74                 nil,
  75         },
  76         // This example comes from http://compgroups.net/comp.lang.ruby/Decompressing-LZW-compression-from-PDF-file
  77         {
  78                 "pdf;MSB;8",
  79                 "-----A---B",
  80                 "\x80\x0b\x60\x50\x22\x0c\x0c\x85\x01",
  81                 nil,
  82         },
  83 }
  84
  85 func TestReader(t *testing.T) {
  86         var b bytes.Buffer
  87         for _, tt := range lzwTests {
  88                 d := strings.Split(tt.desc, ";")
  89                 var order Order
  90                 switch d[1] {
  91                 case "LSB":
  92                         order = LSB
  93                 case "MSB":
  94                         order = MSB
  95                 default:
  96                         t.Errorf("%s: bad order %q", tt.desc, d[1])
  97                 }
  98                 litWidth, _ := strconv.Atoi(d[2])
  99                 rc := NewReader(strings.NewReader(tt.compressed), order, litWidth)
 100                 defer rc.Close()
 101                 b.Reset()
 102                 n, err := io.Copy(&b, rc)
 103                 s := b.String()
 104                 if err != nil {
 105                         if err != tt.err {
 106                                 t.Errorf("%s: io.Copy: %v want %v", tt.desc, err, tt.err)
 107                         }
 108                         if err == io.ErrUnexpectedEOF {
 109                                 // Even if the input is truncated, we should still return the
 110                                 // partial decoded result.
 111                                 if n == 0 || !strings.HasPrefix(tt.raw, s) {
 112                                         t.Errorf("got %d bytes (%q), want a non-empty prefix of %q", n, s, tt.raw)
 113                                 }
 114                         }
 115                         continue
 116                 }
 117                 if s != tt.raw {
 118                         t.Errorf("%s: got %d-byte %q want %d-byte %q", tt.desc, n, s, len(tt.raw), tt.raw)
 119                 }
 120         }
 121 }
 122
 123 func BenchmarkDecoder(b *testing.B) {
 124         buf, err := ioutil.ReadFile("../testdata/e.txt")
 125         if err != nil {
 126                 b.Fatal(err)
 127         }
 128         if len(buf) == 0 {
 129                 b.Fatalf("test file has no data")
 130         }
 131
 132         for e := 4; e <= 6; e++ {
 133                 n := int(math.Pow10(e))
 134                 b.Run(fmt.Sprint("1e", e), func(b *testing.B) {
 135                         b.StopTimer()
 136                         b.SetBytes(int64(n))
 137                         buf0 := buf
 138                         compressed := new(bytes.Buffer)
 139                         w := NewWriter(compressed, LSB, 8)
 140                         for i := 0; i < n; i += len(buf0) {
 141                                 if len(buf0) > n-i {
 142                                         buf0 = buf0[:n-i]
 143                                 }
 144                                 w.Write(buf0)
 145                         }
 146                         w.Close()
 147                         buf1 := compressed.Bytes()
 148                         buf0, compressed, w = nil, nil, nil
 149                         runtime.GC()
 150                         b.StartTimer()
 151                         for i := 0; i < b.N; i++ {
 152                                 io.Copy(ioutil.Discard, NewReader(bytes.NewReader(buf1), LSB, 8))
 153                         }
 154                 })
 155         }
 156 }