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// 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 (
"fmt"
"internal/testenv"
"io"
"io/ioutil"
"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 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 := ioutil.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()
}
})
}
}
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