238 lines
5.7 KiB
Go
238 lines
5.7 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package lzw
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import (
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"bytes"
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"fmt"
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"internal/testenv"
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"io"
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"math"
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"os"
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"runtime"
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"testing"
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)
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var filenames = []string{
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"../testdata/gettysburg.txt",
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"../testdata/e.txt",
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"../testdata/pi.txt",
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}
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// testFile tests that compressing and then decompressing the given file with
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// the given options yields equivalent bytes to the original file.
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func testFile(t *testing.T, fn string, order Order, litWidth int) {
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// Read the file, as golden output.
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golden, err := os.Open(fn)
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if err != nil {
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t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
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return
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}
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defer golden.Close()
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// Read the file again, and push it through a pipe that compresses at the write end, and decompresses at the read end.
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raw, err := os.Open(fn)
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if err != nil {
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t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err)
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return
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}
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piper, pipew := io.Pipe()
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defer piper.Close()
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go func() {
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defer raw.Close()
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defer pipew.Close()
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lzww := NewWriter(pipew, order, litWidth)
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defer lzww.Close()
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var b [4096]byte
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for {
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n, err0 := raw.Read(b[:])
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if err0 != nil && err0 != io.EOF {
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t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
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return
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}
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_, err1 := lzww.Write(b[:n])
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if err1 != nil {
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t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
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return
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}
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if err0 == io.EOF {
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break
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}
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}
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}()
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lzwr := NewReader(piper, order, litWidth)
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defer lzwr.Close()
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// Compare the two.
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b0, err0 := io.ReadAll(golden)
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b1, err1 := io.ReadAll(lzwr)
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if err0 != nil {
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t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
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return
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}
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if err1 != nil {
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t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
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return
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}
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if len(b1) != len(b0) {
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t.Errorf("%s (order=%d litWidth=%d): length mismatch %d != %d", fn, order, litWidth, len(b1), len(b0))
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return
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}
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for i := 0; i < len(b0); i++ {
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if b1[i] != b0[i] {
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t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x != 0x%02x\n", fn, order, litWidth, i, b1[i], b0[i])
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return
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}
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}
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}
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func TestWriter(t *testing.T) {
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for _, filename := range filenames {
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for _, order := range [...]Order{LSB, MSB} {
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// The test data "2.71828 etcetera" is ASCII text requiring at least 6 bits.
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for litWidth := 6; litWidth <= 8; litWidth++ {
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if filename == "../testdata/gettysburg.txt" && litWidth == 6 {
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continue
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}
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testFile(t, filename, order, litWidth)
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}
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}
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if testing.Short() && testenv.Builder() == "" {
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break
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}
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}
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}
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func TestWriterReset(t *testing.T) {
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for _, order := range [...]Order{LSB, MSB} {
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t.Run(fmt.Sprintf("Order %d", order), func(t *testing.T) {
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for litWidth := 6; litWidth <= 8; litWidth++ {
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t.Run(fmt.Sprintf("LitWidth %d", litWidth), func(t *testing.T) {
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var data []byte
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if litWidth == 6 {
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data = []byte{1, 2, 3}
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} else {
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data = []byte(`lorem ipsum dolor sit amet`)
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}
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var buf bytes.Buffer
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w := NewWriter(&buf, order, litWidth)
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if _, err := w.Write(data); err != nil {
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t.Errorf("write: %v: %v", string(data), err)
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}
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if err := w.Close(); err != nil {
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t.Errorf("close: %v", err)
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}
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b1 := buf.Bytes()
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buf.Reset()
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w.(*Writer).Reset(&buf, order, litWidth)
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if _, err := w.Write(data); err != nil {
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t.Errorf("write: %v: %v", string(data), err)
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}
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if err := w.Close(); err != nil {
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t.Errorf("close: %v", err)
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}
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b2 := buf.Bytes()
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if !bytes.Equal(b1, b2) {
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t.Errorf("bytes written were not same")
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}
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})
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}
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})
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}
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}
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func TestWriterReturnValues(t *testing.T) {
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w := NewWriter(io.Discard, LSB, 8)
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n, err := w.Write([]byte("asdf"))
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if n != 4 || err != nil {
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t.Errorf("got %d, %v, want 4, nil", n, err)
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}
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}
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func TestSmallLitWidth(t *testing.T) {
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w := NewWriter(io.Discard, LSB, 2)
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if _, err := w.Write([]byte{0x03}); err != nil {
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t.Fatalf("write a byte < 1<<2: %v", err)
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}
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if _, err := w.Write([]byte{0x04}); err == nil {
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t.Fatal("write a byte >= 1<<2: got nil error, want non-nil")
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}
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}
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func TestStartsWithClearCode(t *testing.T) {
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// A literal width of 7 bits means that the code width starts at 8 bits,
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// which makes it easier to visually inspect the output (provided that the
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// output is short so codes don't get longer). Each byte is a code:
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// - ASCII bytes are literal codes,
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// - 0x80 is the clear code,
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// - 0x81 is the end code.
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// - 0x82 and above are copy codes (unused in this test case).
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for _, empty := range []bool{false, true} {
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var buf bytes.Buffer
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w := NewWriter(&buf, LSB, 7)
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if !empty {
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w.Write([]byte("Hi"))
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}
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w.Close()
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got := buf.String()
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want := "\x80\x81"
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if !empty {
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want = "\x80Hi\x81"
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}
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if got != want {
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t.Errorf("empty=%t: got %q, want %q", empty, got, want)
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}
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}
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}
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func BenchmarkEncoder(b *testing.B) {
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buf, err := os.ReadFile("../testdata/e.txt")
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if err != nil {
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b.Fatal(err)
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}
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if len(buf) == 0 {
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b.Fatalf("test file has no data")
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}
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for e := 4; e <= 6; e++ {
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n := int(math.Pow10(e))
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buf0 := buf
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buf1 := make([]byte, n)
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for i := 0; i < n; i += len(buf0) {
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if len(buf0) > n-i {
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buf0 = buf0[:n-i]
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}
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copy(buf1[i:], buf0)
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}
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buf0 = nil
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runtime.GC()
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b.Run(fmt.Sprint("1e", e), func(b *testing.B) {
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b.SetBytes(int64(n))
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for i := 0; i < b.N; i++ {
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w := NewWriter(io.Discard, LSB, 8)
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w.Write(buf1)
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w.Close()
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}
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})
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b.Run(fmt.Sprint("1e-Reuse", e), func(b *testing.B) {
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b.SetBytes(int64(n))
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w := NewWriter(io.Discard, LSB, 8)
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for i := 0; i < b.N; i++ {
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w.Write(buf1)
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w.Close()
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w.(*Writer).Reset(io.Discard, LSB, 8)
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}
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})
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}
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}
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