1 files changed, 111 insertions, 0 deletions
diff --git a/src/pkg/compress/lzw/writer_test.go b/src/pkg/compress/lzw/writer_test.go
new file mode 100644
index 000000000..715b974aa
--- /dev/null
+++ b/src/pkg/compress/lzw/writer_test.go
@@ -0,0 +1,111 @@
+// 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 (
+	"io"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+var filenames = []string{
+	"../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, os.O_RDONLY, 0400)
+	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, os.O_RDONLY, 0400)
+	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 != os.EOF {
+				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err0)
+				return
+			}
+			_, err1 := lzww.Write(b[:n])
+			if err1 == os.EPIPE {
+				// Fail, but do not report the error, as some other (presumably reportable) error broke the pipe.
+				return
+			}
+			if err1 != nil {
+				t.Errorf("%s (order=%d litWidth=%d): %v", fn, order, litWidth, err1)
+				return
+			}
+			if err0 == os.EOF {
+				break
+			}
+		}
+	}()
+	lzwr := NewReader(piper, order, litWidth)
+	defer lzwr.Close()
+
+	// Compare the two.
+	b0, err0 := ioutil.ReadAll(golden)
+	b1, err1 := ioutil.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(b0) != len(b1) {
+		t.Errorf("%s (order=%d litWidth=%d): length mismatch %d versus %d", fn, order, litWidth, len(b0), len(b1))
+		return
+	}
+	for i := 0; i < len(b0); i++ {
+		if b0[i] != b1[i] {
+			t.Errorf("%s (order=%d litWidth=%d): mismatch at %d, 0x%02x versus 0x%02x\n", fn, order, litWidth, i, b0[i], b1[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 := range [...]int{6, 7, 8} {
+				testFile(t, filename, order, litWidth)
+			}
+		}
+	}
+}
+
+func BenchmarkEncoder(b *testing.B) {
+	b.StopTimer()
+	buf, _ := ioutil.ReadFile("../testdata/e.txt")
+	b.StartTimer()
+	for i := 0; i < b.N; i++ {
+		w := NewWriter(devNull{}, LSB, 8)
+		w.Write(buf)
+		w.Close()
+	}
+}