Unexport some internal implemtnation details

internal/datafile.go

@@ -0,0 +1,143 @@
+package internal
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/pkg/errors"
+
+	pb "github.com/prologic/bitcask/internal/proto"
+	"github.com/prologic/bitcask/internal/streampb"
+)
+
+const (
+	DefaultDatafileFilename = "%09d.data"
+)
+
+var (
+	ErrReadonly = errors.New("error: read only datafile")
+)
+
+type Datafile struct {
+	sync.RWMutex
+
+	id     int
+	r      *os.File
+	w      *os.File
+	offset int64
+	dec    *streampb.Decoder
+	enc    *streampb.Encoder
+}
+
+func NewDatafile(path string, id int, readonly bool) (*Datafile, error) {
+	var (
+		r   *os.File
+		w   *os.File
+		err error
+	)
+
+	fn := filepath.Join(path, fmt.Sprintf(DefaultDatafileFilename, id))
+
+	if !readonly {
+		w, err = os.OpenFile(fn, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0640)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	r, err = os.Open(fn)
+	if err != nil {
+		return nil, err
+	}
+	stat, err := r.Stat()
+	if err != nil {
+		return nil, errors.Wrap(err, "error calling Stat()")
+	}
+
+	offset := stat.Size()
+
+	dec := streampb.NewDecoder(r)
+	enc := streampb.NewEncoder(w)
+
+	return &Datafile{
+		id:     id,
+		r:      r,
+		w:      w,
+		offset: offset,
+		dec:    dec,
+		enc:    enc,
+	}, nil
+}
+
+func (df *Datafile) FileID() int {
+	return df.id
+}
+
+func (df *Datafile) Name() string {
+	return df.r.Name()
+}
+
+func (df *Datafile) Close() error {
+	if df.w == nil {
+		return df.r.Close()
+	}
+
+	err := df.Sync()
+	if err != nil {
+		return err
+	}
+	return df.w.Close()
+}
+
+func (df *Datafile) Sync() error {
+	if df.w == nil {
+		return nil
+	}
+	return df.w.Sync()
+}
+
+func (df *Datafile) Size() (int64, error) {
+	df.RLock()
+	defer df.RUnlock()
+	return df.offset, nil
+}
+
+func (df *Datafile) Read() (e pb.Entry, err error) {
+	df.Lock()
+	defer df.Unlock()
+
+	return e, df.dec.Decode(&e)
+}
+
+func (df *Datafile) ReadAt(index int64) (e pb.Entry, err error) {
+	df.Lock()
+	defer df.Unlock()
+
+	_, err = df.r.Seek(index, os.SEEK_SET)
+	if err != nil {
+		return
+	}
+
+	return e, df.dec.Decode(&e)
+}
+
+func (df *Datafile) Write(e pb.Entry) (int64, error) {
+	if df.w == nil {
+		return -1, ErrReadonly
+	}
+
+	df.Lock()
+	defer df.Unlock()
+
+	e.Offset = df.offset
+
+	n, err := df.enc.Encode(&e)
+	if err != nil {
+		return -1, err
+	}
+	df.offset += n
+
+	return e.Offset, nil
+}