github.com/sean-/go@v0.0.0-20151219100004-97f854cd7bb6/src/compress/lzw/writer_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  	"io"
     9  	"io/ioutil"
    10  	"os"
    11  	"runtime"
    12  	"testing"
    13  )
    14  
    15  var filenames = []string{
    16  	"../testdata/e.txt",
    17  	"../testdata/pi.txt",
    18  }
    19  
    20  // testFile tests that compressing and then decompressing the given file with
    21  // the given options yields equivalent bytes to the original file.
    22  func testFile(t *testing.T, fn string, order Order, litWidth int) {
    23  	// Read the file, as golden output.
    24  	golden, err := os.Open(fn)
    25  	if err != nil {
    26  		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
    27  		return
    28  	}
    29  	defer golden.Close()
    30  
    31  	// Read the file again, and push it through a pipe that compresses at the write end, and decompresses at the read end.
    32  	raw, err := os.Open(fn)
    33  	if err != nil {
    34  		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
    35  		return
    36  	}
    37  
    38  	piper, pipew := io.Pipe()
    39  	defer piper.Close()
    40  	go func() {
    41  		defer raw.Close()
    42  		defer pipew.Close()
    43  		lzww := NewWriter(pipew, order, litWidth)
    44  		defer lzww.Close()
    45  		var b [4096]byte
    46  		for {
    47  			n, err0 := raw.Read(b[:])
    48  			if err0 != nil && err0 != io.EOF {
    49  				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
    50  				return
    51  			}
    52  			_, err1 := lzww.Write(b[:n])
    53  			if err1 != nil {
    54  				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
    55  				return
    56  			}
    57  			if err0 == io.EOF {
    58  				break
    59  			}
    60  		}
    61  	}()
    62  	lzwr := NewReader(piper, order, litWidth)
    63  	defer lzwr.Close()
    64  
    65  	// Compare the two.
    66  	b0, err0 := ioutil.ReadAll(golden)
    67  	b1, err1 := ioutil.ReadAll(lzwr)
    68  	if err0 != nil {
    69  		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
    70  		return
    71  	}
    72  	if err1 != nil {
    73  		t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
    74  		return
    75  	}
    76  	if len(b1) != len(b0) {
    77  		t.Errorf("%s (order=%d litWidth=%d): length mismatch %d != %d", fn, order, litWidth, len(b1), len(b0))
    78  		return
    79  	}
    80  	for i := 0; i < len(b0); i++ {
    81  		if b1[i] != b0[i] {
    82  			t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x != 0x%02x\n", fn, order, litWidth, i, b1[i], b0[i])
    83  			return
    84  		}
    85  	}
    86  }
    87  
    88  func TestWriter(t *testing.T) {
    89  	for _, filename := range filenames {
    90  		for _, order := range [...]Order{LSB, MSB} {
    91  			// The test data "2.71828 etcetera" is ASCII text requiring at least 6 bits.
    92  			for _, litWidth := range [...]int{6, 7, 8} {
    93  				testFile(t, filename, order, litWidth)
    94  			}
    95  		}
    96  	}
    97  }
    98  
    99  func TestWriterReturnValues(t *testing.T) {
   100  	w := NewWriter(ioutil.Discard, LSB, 8)
   101  	n, err := w.Write([]byte("asdf"))
   102  	if n != 4 || err != nil {
   103  		t.Errorf("got %d, %v, want 4, nil", n, err)
   104  	}
   105  }
   106  
   107  func TestSmallLitWidth(t *testing.T) {
   108  	w := NewWriter(ioutil.Discard, LSB, 2)
   109  	if _, err := w.Write([]byte{0x03}); err != nil {
   110  		t.Fatalf("write a byte < 1<<2: %v", err)
   111  	}
   112  	if _, err := w.Write([]byte{0x04}); err == nil {
   113  		t.Fatal("write a byte >= 1<<2: got nil error, want non-nil")
   114  	}
   115  }
   116  
   117  func benchmarkEncoder(b *testing.B, n int) {
   118  	b.StopTimer()
   119  	b.SetBytes(int64(n))
   120  	buf0, err := ioutil.ReadFile("../testdata/e.txt")
   121  	if err != nil {
   122  		b.Fatal(err)
   123  	}
   124  	if len(buf0) == 0 {
   125  		b.Fatalf("test file has no data")
   126  	}
   127  	buf1 := make([]byte, n)
   128  	for i := 0; i < n; i += len(buf0) {
   129  		if len(buf0) > n-i {
   130  			buf0 = buf0[:n-i]
   131  		}
   132  		copy(buf1[i:], buf0)
   133  	}
   134  	buf0 = nil
   135  	runtime.GC()
   136  	b.StartTimer()
   137  	for i := 0; i < b.N; i++ {
   138  		w := NewWriter(ioutil.Discard, LSB, 8)
   139  		w.Write(buf1)
   140  		w.Close()
   141  	}
   142  }
   143  
   144  func BenchmarkEncoder1e4(b *testing.B) {
   145  	benchmarkEncoder(b, 1e4)
   146  }
   147  
   148  func BenchmarkEncoder1e5(b *testing.B) {
   149  	benchmarkEncoder(b, 1e5)
   150  }
   151  
   152  func BenchmarkEncoder1e6(b *testing.B) {
   153  	benchmarkEncoder(b, 1e6)
   154  }