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Source file src/compress/flate/dict_decoder_test.go

Documentation: compress/flate

  // Copyright 2016 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package flate
  
  import (
  	"bytes"
  	"strings"
  	"testing"
  )
  
  func TestDictDecoder(t *testing.T) {
  	const (
  		abc  = "ABC\n"
  		fox  = "The quick brown fox jumped over the lazy dog!\n"
  		poem = "The Road Not Taken\nRobert Frost\n" +
  			"\n" +
  			"Two roads diverged in a yellow wood,\n" +
  			"And sorry I could not travel both\n" +
  			"And be one traveler, long I stood\n" +
  			"And looked down one as far as I could\n" +
  			"To where it bent in the undergrowth;\n" +
  			"\n" +
  			"Then took the other, as just as fair,\n" +
  			"And having perhaps the better claim,\n" +
  			"Because it was grassy and wanted wear;\n" +
  			"Though as for that the passing there\n" +
  			"Had worn them really about the same,\n" +
  			"\n" +
  			"And both that morning equally lay\n" +
  			"In leaves no step had trodden black.\n" +
  			"Oh, I kept the first for another day!\n" +
  			"Yet knowing how way leads on to way,\n" +
  			"I doubted if I should ever come back.\n" +
  			"\n" +
  			"I shall be telling this with a sigh\n" +
  			"Somewhere ages and ages hence:\n" +
  			"Two roads diverged in a wood, and I-\n" +
  			"I took the one less traveled by,\n" +
  			"And that has made all the difference.\n"
  	)
  
  	var poemRefs = []struct {
  		dist   int // Backward distance (0 if this is an insertion)
  		length int // Length of copy or insertion
  	}{
  		{0, 38}, {33, 3}, {0, 48}, {79, 3}, {0, 11}, {34, 5}, {0, 6}, {23, 7},
  		{0, 8}, {50, 3}, {0, 2}, {69, 3}, {34, 5}, {0, 4}, {97, 3}, {0, 4},
  		{43, 5}, {0, 6}, {7, 4}, {88, 7}, {0, 12}, {80, 3}, {0, 2}, {141, 4},
  		{0, 1}, {196, 3}, {0, 3}, {157, 3}, {0, 6}, {181, 3}, {0, 2}, {23, 3},
  		{77, 3}, {28, 5}, {128, 3}, {110, 4}, {70, 3}, {0, 4}, {85, 6}, {0, 2},
  		{182, 6}, {0, 4}, {133, 3}, {0, 7}, {47, 5}, {0, 20}, {112, 5}, {0, 1},
  		{58, 3}, {0, 8}, {59, 3}, {0, 4}, {173, 3}, {0, 5}, {114, 3}, {0, 4},
  		{92, 5}, {0, 2}, {71, 3}, {0, 2}, {76, 5}, {0, 1}, {46, 3}, {96, 4},
  		{130, 4}, {0, 3}, {360, 3}, {0, 3}, {178, 5}, {0, 7}, {75, 3}, {0, 3},
  		{45, 6}, {0, 6}, {299, 6}, {180, 3}, {70, 6}, {0, 1}, {48, 3}, {66, 4},
  		{0, 3}, {47, 5}, {0, 9}, {325, 3}, {0, 1}, {359, 3}, {318, 3}, {0, 2},
  		{199, 3}, {0, 1}, {344, 3}, {0, 3}, {248, 3}, {0, 10}, {310, 3}, {0, 3},
  		{93, 6}, {0, 3}, {252, 3}, {157, 4}, {0, 2}, {273, 5}, {0, 14}, {99, 4},
  		{0, 1}, {464, 4}, {0, 2}, {92, 4}, {495, 3}, {0, 1}, {322, 4}, {16, 4},
  		{0, 3}, {402, 3}, {0, 2}, {237, 4}, {0, 2}, {432, 4}, {0, 1}, {483, 5},
  		{0, 2}, {294, 4}, {0, 2}, {306, 3}, {113, 5}, {0, 1}, {26, 4}, {164, 3},
  		{488, 4}, {0, 1}, {542, 3}, {248, 6}, {0, 5}, {205, 3}, {0, 8}, {48, 3},
  		{449, 6}, {0, 2}, {192, 3}, {328, 4}, {9, 5}, {433, 3}, {0, 3}, {622, 25},
  		{615, 5}, {46, 5}, {0, 2}, {104, 3}, {475, 10}, {549, 3}, {0, 4}, {597, 8},
  		{314, 3}, {0, 1}, {473, 6}, {317, 5}, {0, 1}, {400, 3}, {0, 3}, {109, 3},
  		{151, 3}, {48, 4}, {0, 4}, {125, 3}, {108, 3}, {0, 2},
  	}
  
  	var got, want bytes.Buffer
  	var dd dictDecoder
  	dd.init(1<<11, nil)
  
  	var writeCopy = func(dist, length int) {
  		for length > 0 {
  			cnt := dd.tryWriteCopy(dist, length)
  			if cnt == 0 {
  				cnt = dd.writeCopy(dist, length)
  			}
  
  			length -= cnt
  			if dd.availWrite() == 0 {
  				got.Write(dd.readFlush())
  			}
  		}
  	}
  	var writeString = func(str string) {
  		for len(str) > 0 {
  			cnt := copy(dd.writeSlice(), str)
  			str = str[cnt:]
  			dd.writeMark(cnt)
  			if dd.availWrite() == 0 {
  				got.Write(dd.readFlush())
  			}
  		}
  	}
  
  	writeString(".")
  	want.WriteByte('.')
  
  	str := poem
  	for _, ref := range poemRefs {
  		if ref.dist == 0 {
  			writeString(str[:ref.length])
  		} else {
  			writeCopy(ref.dist, ref.length)
  		}
  		str = str[ref.length:]
  	}
  	want.WriteString(poem)
  
  	writeCopy(dd.histSize(), 33)
  	want.Write(want.Bytes()[:33])
  
  	writeString(abc)
  	writeCopy(len(abc), 59*len(abc))
  	want.WriteString(strings.Repeat(abc, 60))
  
  	writeString(fox)
  	writeCopy(len(fox), 9*len(fox))
  	want.WriteString(strings.Repeat(fox, 10))
  
  	writeString(".")
  	writeCopy(1, 9)
  	want.WriteString(strings.Repeat(".", 10))
  
  	writeString(strings.ToUpper(poem))
  	writeCopy(len(poem), 7*len(poem))
  	want.WriteString(strings.Repeat(strings.ToUpper(poem), 8))
  
  	writeCopy(dd.histSize(), 10)
  	want.Write(want.Bytes()[want.Len()-dd.histSize():][:10])
  
  	got.Write(dd.readFlush())
  	if got.String() != want.String() {
  		t.Errorf("final string mismatch:\ngot  %q\nwant %q", got.String(), want.String())
  	}
  }
  

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