wal: init

wal/wal.go

@@ -0,0 +1,90 @@
+package wal
+
+import (
+	"bufio"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/coreos/etcd/raft"
+)
+
+var (
+	infoType  = int64(1)
+	entryType = int64(2)
+	stateType = int64(3)
+)
+
+type WAL struct {
+	f  *os.File
+	bw *bufio.Writer
+}
+
+func New(path string) (*WAL, error) {
+	f, err := os.Create(path)
+	if err != nil {
+		return nil, err
+	}
+	bw := bufio.NewWriter(f)
+	return &WAL{f, bw}, nil
+}
+
+func (w *WAL) writeInfo(id int64) error {
+	// | 8 bytes | 8 bytes |  8 bytes |
+	// | type    |   len   |   nodeid |
+	o, err := w.f.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return err
+	}
+	if o != 0 || w.bw.Buffered() != 0 {
+		return fmt.Errorf("cannot write info at %d, expect 0", o)
+	}
+	if err := w.writeInt64(infoType); err != nil {
+		return err
+	}
+	if err := w.writeInt64(8); err != nil {
+		return err
+	}
+	return w.writeInt64(id)
+}
+
+func (w *WAL) writeEntry(e *raft.Entry) error {
+	// | 8 bytes | 8 bytes |  variable length |
+	// | type    |   len   |   entry data     |
+	if err := w.writeInt64(entryType); err != nil {
+		return err
+	}
+	b, err := json.Marshal(e)
+	if err != nil {
+		return err
+	}
+	n := len(b)
+	if err := w.writeInt64(int64(n)); err != nil {
+		return err
+	}
+	if _, err := w.bw.Write(b); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (w *WAL) writeState(s *raft.State) error {
+	// | 8 bytes | 8 bytes |  24 bytes |
+	// | type    |   len   |   state   |
+	if err := w.writeInt64(stateType); err != nil {
+		return err
+	}
+	if err := w.writeInt64(24); err != nil {
+		return err
+	}
+	return binary.Write(w.bw, binary.LittleEndian, s)
+}
+
+func (w *WAL) writeInt64(n int64) error {
+	return binary.Write(w.bw, binary.LittleEndian, n)
+}
+
+func (w *WAL) flush() error {
+	return w.bw.Flush()
+}