dict_decoder_test.go

     1  // Copyright 2016 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 flate
     6  
     7  import (
     8  	"bytes"
     9  	"strings"
    10  	"testing"
    11  )
    12  
    13  func TestDictDecoder(t *testing.T) {
    14  	const (
    15  		abc  = "ABC\n"
    16  		fox  = "The quick brown fox jumped over the lazy dog!\n"
    17  		poem = "The Road Not Taken\nRobert Frost\n" +
    18  			"\n" +
    19  			"Two roads diverged in a yellow wood,\n" +
    20  			"And sorry I could not travel both\n" +
    21  			"And be one traveler, long I stood\n" +
    22  			"And looked down one as far as I could\n" +
    23  			"To where it bent in the undergrowth;\n" +
    24  			"\n" +
    25  			"Then took the other, as just as fair,\n" +
    26  			"And having perhaps the better claim,\n" +
    27  			"Because it was grassy and wanted wear;\n" +
    28  			"Though as for that the passing there\n" +
    29  			"Had worn them really about the same,\n" +
    30  			"\n" +
    31  			"And both that morning equally lay\n" +
    32  			"In leaves no step had trodden black.\n" +
    33  			"Oh, I kept the first for another day!\n" +
    34  			"Yet knowing how way leads on to way,\n" +
    35  			"I doubted if I should ever come back.\n" +
    36  			"\n" +
    37  			"I shall be telling this with a sigh\n" +
    38  			"Somewhere ages and ages hence:\n" +
    39  			"Two roads diverged in a wood, and I-\n" +
    40  			"I took the one less traveled by,\n" +
    41  			"And that has made all the difference.\n"
    42  	)
    43  
    44  	var poemRefs = []struct {
    45  		dist   int // Backward distance (0 if this is an insertion)
    46  		length int // Length of copy or insertion
    47  	}{
    48  		{0, 38}, {33, 3}, {0, 48}, {79, 3}, {0, 11}, {34, 5}, {0, 6}, {23, 7},
    49  		{0, 8}, {50, 3}, {0, 2}, {69, 3}, {34, 5}, {0, 4}, {97, 3}, {0, 4},
    50  		{43, 5}, {0, 6}, {7, 4}, {88, 7}, {0, 12}, {80, 3}, {0, 2}, {141, 4},
    51  		{0, 1}, {196, 3}, {0, 3}, {157, 3}, {0, 6}, {181, 3}, {0, 2}, {23, 3},
    52  		{77, 3}, {28, 5}, {128, 3}, {110, 4}, {70, 3}, {0, 4}, {85, 6}, {0, 2},
    53  		{182, 6}, {0, 4}, {133, 3}, {0, 7}, {47, 5}, {0, 20}, {112, 5}, {0, 1},
    54  		{58, 3}, {0, 8}, {59, 3}, {0, 4}, {173, 3}, {0, 5}, {114, 3}, {0, 4},
    55  		{92, 5}, {0, 2}, {71, 3}, {0, 2}, {76, 5}, {0, 1}, {46, 3}, {96, 4},
    56  		{130, 4}, {0, 3}, {360, 3}, {0, 3}, {178, 5}, {0, 7}, {75, 3}, {0, 3},
    57  		{45, 6}, {0, 6}, {299, 6}, {180, 3}, {70, 6}, {0, 1}, {48, 3}, {66, 4},
    58  		{0, 3}, {47, 5}, {0, 9}, {325, 3}, {0, 1}, {359, 3}, {318, 3}, {0, 2},
    59  		{199, 3}, {0, 1}, {344, 3}, {0, 3}, {248, 3}, {0, 10}, {310, 3}, {0, 3},
    60  		{93, 6}, {0, 3}, {252, 3}, {157, 4}, {0, 2}, {273, 5}, {0, 14}, {99, 4},
    61  		{0, 1}, {464, 4}, {0, 2}, {92, 4}, {495, 3}, {0, 1}, {322, 4}, {16, 4},
    62  		{0, 3}, {402, 3}, {0, 2}, {237, 4}, {0, 2}, {432, 4}, {0, 1}, {483, 5},
    63  		{0, 2}, {294, 4}, {0, 2}, {306, 3}, {113, 5}, {0, 1}, {26, 4}, {164, 3},
    64  		{488, 4}, {0, 1}, {542, 3}, {248, 6}, {0, 5}, {205, 3}, {0, 8}, {48, 3},
    65  		{449, 6}, {0, 2}, {192, 3}, {328, 4}, {9, 5}, {433, 3}, {0, 3}, {622, 25},
    66  		{615, 5}, {46, 5}, {0, 2}, {104, 3}, {475, 10}, {549, 3}, {0, 4}, {597, 8},
    67  		{314, 3}, {0, 1}, {473, 6}, {317, 5}, {0, 1}, {400, 3}, {0, 3}, {109, 3},
    68  		{151, 3}, {48, 4}, {0, 4}, {125, 3}, {108, 3}, {0, 2},
    69  	}
    70  
    71  	var got, want bytes.Buffer
    72  	var dd dictDecoder
    73  	dd.init(1<<11, nil)
    74  
    75  	var writeCopy = func(dist, length int) {
    76  		for length > 0 {
    77  			cnt := dd.tryWriteCopy(dist, length)
    78  			if cnt == 0 {
    79  				cnt = dd.writeCopy(dist, length)
    80  			}
    81  
    82  			length -= cnt
    83  			if dd.availWrite() == 0 {
    84  				got.Write(dd.readFlush())
    85  			}
    86  		}
    87  	}
    88  	var writeString = func(str string) {
    89  		for len(str) > 0 {
    90  			cnt := copy(dd.writeSlice(), str)
    91  			str = str[cnt:]
    92  			dd.writeMark(cnt)
    93  			if dd.availWrite() == 0 {
    94  				got.Write(dd.readFlush())
    95  			}
    96  		}
    97  	}
    98  
    99  	writeString(".")
   100  	want.WriteByte('.')
   101  
   102  	str := poem
   103  	for _, ref := range poemRefs {
   104  		if ref.dist == 0 {
   105  			writeString(str[:ref.length])
   106  		} else {
   107  			writeCopy(ref.dist, ref.length)
   108  		}
   109  		str = str[ref.length:]
   110  	}
   111  	want.WriteString(poem)
   112  
   113  	writeCopy(dd.histSize(), 33)
   114  	want.Write(want.Bytes()[:33])
   115  
   116  	writeString(abc)
   117  	writeCopy(len(abc), 59*len(abc))
   118  	want.WriteString(strings.Repeat(abc, 60))
   119  
   120  	writeString(fox)
   121  	writeCopy(len(fox), 9*len(fox))
   122  	want.WriteString(strings.Repeat(fox, 10))
   123  
   124  	writeString(".")
   125  	writeCopy(1, 9)
   126  	want.WriteString(strings.Repeat(".", 10))
   127  
   128  	writeString(strings.ToUpper(poem))
   129  	writeCopy(len(poem), 7*len(poem))
   130  	want.WriteString(strings.Repeat(strings.ToUpper(poem), 8))
   131  
   132  	writeCopy(dd.histSize(), 10)
   133  	want.Write(want.Bytes()[want.Len()-dd.histSize():][:10])
   134  
   135  	got.Write(dd.readFlush())
   136  	if got.String() != want.String() {
   137  		t.Errorf("final string mismatch:\ngot  %q\nwant %q", got.String(), want.String())
   138  	}
   139  }
   140
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