145 lines
3.3 KiB
Go
145 lines
3.3 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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"io"
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"io/ioutil"
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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/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 := ioutil.ReadAll(golden)
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b1, err1 := ioutil.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 := range [...]int{6, 7, 8} {
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testFile(t, filename, order, litWidth)
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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(ioutil.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 benchmarkEncoder(b *testing.B, n int) {
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b.StopTimer()
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b.SetBytes(int64(n))
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buf0, err := ioutil.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(buf0) == 0 {
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b.Fatalf("test file has no data")
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}
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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.StartTimer()
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for i := 0; i < b.N; i++ {
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w := NewWriter(ioutil.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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func BenchmarkEncoder1e4(b *testing.B) {
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benchmarkEncoder(b, 1e4)
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}
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func BenchmarkEncoder1e5(b *testing.B) {
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benchmarkEncoder(b, 1e5)
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}
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func BenchmarkEncoder1e6(b *testing.B) {
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benchmarkEncoder(b, 1e6)
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}
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