1 files changed, 76 insertions, 0 deletions
diff --git a/weed/pb/volume_info.go b/weed/pb/volume_info.go
new file mode 100644
index 000000000..c4f733f5c
--- /dev/null
+++ b/weed/pb/volume_info.go
@@ -0,0 +1,76 @@
+package pb
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+
+	_ "github.com/chrislusf/seaweedfs/weed/storage/backend/s3_backend"
+	"github.com/chrislusf/seaweedfs/weed/util"
+
+	"github.com/golang/protobuf/jsonpb"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
+)
+
+// MaybeLoadVolumeInfo load the file data as *volume_server_pb.VolumeInfo, the returned volumeInfo will not be nil
+func MaybeLoadVolumeInfo(fileName string) (*volume_server_pb.VolumeInfo, bool, error) {
+
+	volumeInfo := &volume_server_pb.VolumeInfo{}
+
+	glog.V(1).Infof("maybeLoadVolumeInfo checks %s", fileName)
+	if exists, canRead, _, _, _ := util.CheckFile(fileName); !exists || !canRead {
+		if !exists {
+			return volumeInfo, false, nil
+		}
+		if !canRead {
+			glog.Warningf("can not read %s", fileName)
+			return volumeInfo, false, fmt.Errorf("can not read %s", fileName)
+		}
+		return volumeInfo, false, nil
+	}
+
+	glog.V(1).Infof("maybeLoadVolumeInfo reads %s", fileName)
+	tierData, readErr := ioutil.ReadFile(fileName)
+	if readErr != nil {
+		glog.Warningf("fail to read %s : %v", fileName, readErr)
+		return volumeInfo, false, fmt.Errorf("fail to read %s : %v", fileName, readErr)
+	}
+
+	glog.V(1).Infof("maybeLoadVolumeInfo Unmarshal volume info %v", fileName)
+	if err := jsonpb.Unmarshal(bytes.NewReader(tierData), volumeInfo); err != nil {
+		glog.Warningf("unmarshal error: %v", err)
+		return volumeInfo, false, fmt.Errorf("unmarshal error: %v", err)
+	}
+
+	if len(volumeInfo.GetFiles()) == 0 {
+		return volumeInfo, false, nil
+	}
+
+	return volumeInfo, true, nil
+}
+
+func SaveVolumeInfo(fileName string, volumeInfo *volume_server_pb.VolumeInfo) error {
+
+	if exists, _, canWrite, _, _ := util.CheckFile(fileName); exists && !canWrite {
+		return fmt.Errorf("%s not writable", fileName)
+	}
+
+	m := jsonpb.Marshaler{
+		EmitDefaults: true,
+		Indent:       "  ",
+	}
+
+	text, marshalErr := m.MarshalToString(volumeInfo)
+	if marshalErr != nil {
+		return fmt.Errorf("marshal to %s: %v", fileName, marshalErr)
+	}
+
+	writeErr := ioutil.WriteFile(fileName, []byte(text), 0755)
+	if writeErr != nil {
+		return fmt.Errorf("fail to write %s : %v", fileName, writeErr)
+	}
+
+	return nil
+}