// Copyright 2011 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 lzw import ( "bytes" "fmt" "internal/testenv" "io" "math" "os" "runtime" "testing" ) var filenames = []string{ "../testdata/gettysburg.txt", "../testdata/e.txt", "../testdata/pi.txt", } // testFile tests that compressing and then decompressing the given file with // the given options yields equivalent bytes to the original file. func testFile(t *testing.T, fn string, order Order, litWidth int) { // Read the file, as golden output. golden, err := os.Open(fn) if err != nil { t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err) return } defer golden.Close() // Read the file again, and push it through a pipe that compresses at the write end, and decompresses at the read end. raw, err := os.Open(fn) if err != nil { t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err) return } piper, pipew := io.Pipe() defer piper.Close() go func() { defer raw.Close() defer pipew.Close() lzww := NewWriter(pipew, order, litWidth) defer lzww.Close() var b [4096]byte for { n, err0 := raw.Read(b[:]) if err0 != nil && err0 != io.EOF { t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0) return } _, err1 := lzww.Write(b[:n]) if err1 != nil { t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1) return } if err0 == io.EOF { break } } }() lzwr := NewReader(piper, order, litWidth) defer lzwr.Close() // Compare the two. b0, err0 := io.ReadAll(golden) b1, err1 := io.ReadAll(lzwr) if err0 != nil { t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0) return } if err1 != nil { t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1) return } if len(b1) != len(b0) { t.Errorf("%s (order=%d litWidth=%d): length mismatch %d != %d", fn, order, litWidth, len(b1), len(b0)) return } for i := 0; i < len(b0); i++ { if b1[i] != b0[i] { t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x != 0x%02x\n", fn, order, litWidth, i, b1[i], b0[i]) return } } } func TestWriter(t *testing.T) { for _, filename := range filenames { for _, order := range [...]Order{LSB, MSB} { // The test data "2.71828 etcetera" is ASCII text requiring at least 6 bits. for litWidth := 6; litWidth <= 8; litWidth++ { if filename == "../testdata/gettysburg.txt" && litWidth == 6 { continue } testFile(t, filename, order, litWidth) } } if testing.Short() && testenv.Builder() == "" { break } } } func TestWriterReset(t *testing.T) { for _, order := range [...]Order{LSB, MSB} { t.Run(fmt.Sprintf("Order %d", order), func(t *testing.T) { for litWidth := 6; litWidth <= 8; litWidth++ { t.Run(fmt.Sprintf("LitWidth %d", litWidth), func(t *testing.T) { var data []byte if litWidth == 6 { data = []byte{1, 2, 3} } else { data = []byte(`lorem ipsum dolor sit amet`) } var buf bytes.Buffer w := NewWriter(&buf, order, litWidth) if _, err := w.Write(data); err != nil { t.Errorf("write: %v: %v", string(data), err) } if err := w.Close(); err != nil { t.Errorf("close: %v", err) } b1 := buf.Bytes() buf.Reset() w.(*Writer).Reset(&buf, order, litWidth) if _, err := w.Write(data); err != nil { t.Errorf("write: %v: %v", string(data), err) } if err := w.Close(); err != nil { t.Errorf("close: %v", err) } b2 := buf.Bytes() if !bytes.Equal(b1, b2) { t.Errorf("bytes written were not same") } }) } }) } } func TestWriterReturnValues(t *testing.T) { w := NewWriter(io.Discard, LSB, 8) n, err := w.Write([]byte("asdf")) if n != 4 || err != nil { t.Errorf("got %d, %v, want 4, nil", n, err) } } func TestSmallLitWidth(t *testing.T) { w := NewWriter(io.Discard, LSB, 2) if _, err := w.Write([]byte{0x03}); err != nil { t.Fatalf("write a byte < 1<<2: %v", err) } if _, err := w.Write([]byte{0x04}); err == nil { t.Fatal("write a byte >= 1<<2: got nil error, want non-nil") } } func BenchmarkEncoder(b *testing.B) { buf, err := os.ReadFile("../testdata/e.txt") if err != nil { b.Fatal(err) } if len(buf) == 0 { b.Fatalf("test file has no data") } for e := 4; e <= 6; e++ { n := int(math.Pow10(e)) buf0 := buf buf1 := make([]byte, n) for i := 0; i < n; i += len(buf0) { if len(buf0) > n-i { buf0 = buf0[:n-i] } copy(buf1[i:], buf0) } buf0 = nil runtime.GC() b.Run(fmt.Sprint("1e", e), func(b *testing.B) { b.SetBytes(int64(n)) for i := 0; i < b.N; i++ { w := NewWriter(io.Discard, LSB, 8) w.Write(buf1) w.Close() } }) b.Run(fmt.Sprint("1e-Reuse", e), func(b *testing.B) { b.SetBytes(int64(n)) w := NewWriter(io.Discard, LSB, 8) for i := 0; i < b.N; i++ { w.Write(buf1) w.Close() w.(*Writer).Reset(io.Discard, LSB, 8) } }) } }