Add Bag.get_bytes to get length in bytes

2 files changed, 13 insertions, 2 deletions

diff --git a/obnamlib/bag.py b/obnamlib/bag.py
index 1a1e2648..cf176b1b 100644
--- a/obnamlib/bag.py
+++ b/obnamlib/bag.py
@@ -24,6 +24,7 @@ class Bag(object):
     def __init__(self):
         self._bag_id = None
         self._blobs = []
+        self._blobs_bytes = 0
 
     def get_id(self):
         return self._bag_id
@@ -35,11 +36,15 @@ class Bag(object):
         if self.get_id() is None:
             raise BagIdNotSetError()
         self._blobs.append(blob)
+        self._blobs_bytes += len(blob)
         return obnamlib.make_object_id(self.get_id(), len(self) - 1)
 
     def __len__(self):
         return len(self._blobs)
 
+    def get_bytes(self):
+        return self._blobs_bytes
+
     def __getitem__(self, index):
         return self._blobs[index]
 
diff --git a/obnamlib/bag_tests.py b/obnamlib/bag_tests.py
index e0b5c4e3..1465fc24 100644
--- a/obnamlib/bag_tests.py
+++ b/obnamlib/bag_tests.py
@@ -36,6 +36,10 @@ class BagTests(unittest.TestCase):
         bag = obnamlib.Bag()
         self.assertEqual(len(bag), 0)
 
+    def test_has_no_bytes_initially(self):
+        bag = obnamlib.Bag()
+        self.assertEqual(bag.get_bytes(), 0)
+
     def test_raises_error_if_appending_blob_without_id_being_set(self):
         bag = obnamlib.Bag()
         self.assertRaises(
@@ -43,11 +47,13 @@ class BagTests(unittest.TestCase):
             bag.append, 'blob')
 
     def test_appends_a_blob(self):
+        blob = 'foo'
         bag = obnamlib.Bag()
         bag.set_id(1)
-        bag.append('foo')
+        bag.append(blob)
         self.assertEqual(len(bag), 1)
-        self.assertEqual(bag[0], 'foo')
+        self.assertEqual(bag.get_bytes(), len(blob))
+        self.assertEqual(bag[0], blob)
 
     def test_appending_returns_object_id(self):
         bag = obnamlib.Bag()