github.com/sbinet/go@v0.0.0-20160827155028-54d7de7dd62b/src/compress/lzw/reader_test.go (about)

     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  }