added file checker, completation/size/digest

app/storage/file.go

@@ -38,6 +38,24 @@ func (store *Storage) makeFilesubdir(collection, filename string) string {
 	return filepath.Join(store.basepath, fileSubdir)
 }
 
+func (store *Storage) FileExists(collection, filename string) (bool, int64, error) {
+	var err error
+	var exists bool
+	var size int64
+	filename = store.makeFilepath(collection, filename)
+	stat, err := os.Stat(filename)
+	if os.IsNotExist(err) {
+		err = nil
+		return exists, size, err
+	}
+	if err != nil {
+		return exists, size, err
+	}
+	size = stat.Size()
+	exists = true
+	return exists, size, err
+}
+
 func (store *Storage) GetFileReader(collection, filename string) (io.ReadCloser, error) {
 	var err error
 	var res io.ReadCloser
@@ -51,6 +69,26 @@ func (store *Storage) GetFileReader(collection, filename string) (io.ReadCloser,
 	return res, err
 }
 
+func (store *Storage) GetFileCheksum(collection, filename string) (string, error) {
+	var err error
+	var res string
+
+	filename = store.makeFilepath(collection, filename)
+	file, err := os.OpenFile(filename, os.O_RDONLY, 0)
+	if err != nil {
+		return res, err
+	}
+	defer file.Close()
+
+	hasher := NewHasher()
+	_, err = io.Copy(hasher.Writer(), file)
+	if err != nil {
+		return res, err
+	}
+	res = hasher.Hex()
+	return res, err
+}
+
 func (store *Storage) WriteTempFile(source io.Reader) (string, int64, string, error) {
 	var err error
 	var size int64