From 7a319156c10fbd41d79534fea38e86c9f8403672 Mon Sep 17 00:00:00 2001
From: Gyu-Ho Lee <gyuhox@gmail.com>
Date: Wed, 28 Sep 2016 07:19:16 -0700
Subject: [PATCH] wal: set writer offset for PageWriter

---
 wal/encoder.go     |  4 ++--
 wal/record_test.go |  2 +-
 wal/wal.go         | 17 ++++++++++++-----
 wal/wal_test.go    |  4 ++--
 4 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/wal/encoder.go b/wal/encoder.go
index edbd1785ab8f..6b26bf972692 100644
--- a/wal/encoder.go
+++ b/wal/encoder.go
@@ -39,9 +39,9 @@ type encoder struct {
 	uint64buf []byte
 }
 
-func newEncoder(w io.Writer, prevCrc uint32) *encoder {
+func newEncoder(w io.Writer, offset int, prevCrc uint32) *encoder {
 	return &encoder{
-		bw:  ioutil.NewPageWriter(w, walPageBytes),
+		bw:  ioutil.NewPageWriter(w, offset, walPageBytes),
 		crc: crc.New(prevCrc, crcTable),
 		// 1MB buffer
 		buf:       make([]byte, 1024*1024),
diff --git a/wal/record_test.go b/wal/record_test.go
index ddbc37d869e5..2a6904a81fce 100644
--- a/wal/record_test.go
+++ b/wal/record_test.go
@@ -69,7 +69,7 @@ func TestWriteRecord(t *testing.T) {
 	typ := int64(0xABCD)
 	d := []byte("Hello world!")
 	buf := new(bytes.Buffer)
-	e := newEncoder(buf, 0)
+	e := newEncoder(buf, 0, 0)
 	e.encode(&walpb.Record{Type: typ, Data: d})
 	e.flush()
 	decoder := newDecoder(ioutil.NopCloser(buf))
diff --git a/wal/wal.go b/wal/wal.go
index 0bd85c166123..92e70adef323 100644
--- a/wal/wal.go
+++ b/wal/wal.go
@@ -112,7 +112,9 @@ func Create(dirpath string, metadata []byte) (*WAL, error) {
 	if err != nil {
 		return nil, err
 	}
-	if _, err = f.Seek(0, os.SEEK_END); err != nil {
+	var offset int64
+	offset, err = f.Seek(0, os.SEEK_END)
+	if err != nil {
 		return nil, err
 	}
 	if err = fileutil.Preallocate(f.File, SegmentSizeBytes, true); err != nil {
@@ -122,7 +124,7 @@ func Create(dirpath string, metadata []byte) (*WAL, error) {
 	w := &WAL{
 		dir:      dirpath,
 		metadata: metadata,
-		encoder:  newEncoder(f, 0),
+		encoder:  newEncoder(f, int(offset), 0),
 	}
 	w.locks = append(w.locks, f)
 	if err = w.saveCrc(0); err != nil {
@@ -342,8 +344,13 @@ func (w *WAL) ReadAll() (metadata []byte, state raftpb.HardState, ents []raftpb.
 	w.metadata = metadata
 
 	if w.tail() != nil {
+		var offset int64
+		offset, err = w.tail().Seek(0, os.SEEK_CUR)
+		if err != nil {
+			return
+		}
 		// create encoder (chain crc with the decoder), enable appending
-		w.encoder = newEncoder(w.tail(), w.decoder.lastCRC())
+		w.encoder = newEncoder(w.tail(), int(offset), w.decoder.lastCRC())
 	}
 	w.decoder = nil
 
@@ -377,7 +384,7 @@ func (w *WAL) cut() error {
 	// update writer and save the previous crc
 	w.locks = append(w.locks, newTail)
 	prevCrc := w.encoder.crc.Sum32()
-	w.encoder = newEncoder(w.tail(), prevCrc)
+	w.encoder = newEncoder(w.tail(), int(off), prevCrc)
 	if err = w.saveCrc(prevCrc); err != nil {
 		return err
 	}
@@ -416,7 +423,7 @@ func (w *WAL) cut() error {
 	w.locks[len(w.locks)-1] = newTail
 
 	prevCrc = w.encoder.crc.Sum32()
-	w.encoder = newEncoder(w.tail(), prevCrc)
+	w.encoder = newEncoder(w.tail(), int(off), prevCrc)
 
 	plog.Infof("segmented wal file %v is created", fpath)
 	return nil
diff --git a/wal/wal_test.go b/wal/wal_test.go
index 6fc6f782ea59..a762ee255c60 100644
--- a/wal/wal_test.go
+++ b/wal/wal_test.go
@@ -61,7 +61,7 @@ func TestNew(t *testing.T) {
 	}
 
 	var wb bytes.Buffer
-	e := newEncoder(&wb, 0)
+	e := newEncoder(&wb, 0, 0)
 	err = e.encode(&walpb.Record{Type: crcType, Crc: 0})
 	if err != nil {
 		t.Fatalf("err = %v, want nil", err)
@@ -528,7 +528,7 @@ func TestSaveEmpty(t *testing.T) {
 	var buf bytes.Buffer
 	var est raftpb.HardState
 	w := WAL{
-		encoder: newEncoder(&buf, 0),
+		encoder: newEncoder(&buf, 0, 0),
 	}
 	if err := w.saveState(&est); err != nil {
 		t.Errorf("err = %v, want nil", err)