storage: working on packing and unpacking

tar/storage/entry.go

@@ -0,0 +1,31 @@
+package storage
+
+// Entries is for sorting by Position
+type Entries []Entry
+
+func (e Entries) Len() int           { return len(e) }
+func (e Entries) Swap(i, j int)      { e[i], e[j] = e[j], e[i] }
+func (e Entries) Less(i, j int) bool { return e[i].Position < e[j].Position }
+
+type Type int
+
+const (
+	// FileType represents a file payload from the tar stream.
+	//
+	// This will be used to map to relative paths on disk. Only Size > 0 will get
+	// read into a resulting output stream (due to hardlinks).
+	FileType Type = 1 + iota
+	// SegmentType represents a raw bytes segment from the archive stream. These raw
+	// byte segments consist of the raw headers and various padding.
+	//
+	// It's payload is to be marshalled base64 encoded.
+	SegmentType
+)
+
+type Entry struct {
+	Type     Type   `json:"type"`
+	Name     string `json:"name",omitempty`
+	Size     int64  `json:"size",omitempty`
+	Payload  []byte `json:"payload"` // SegmentType store payload here; FileType store checksum here;
+	Position int    `json:"position"`
+}