rangelib.py: Add parse_raw() method.

parse_raw() parses a string generated by RangeSet.to_string_raw().

>>> RangeSet.parse_raw(RangeSet("0-9").to_string_raw())
<RangeSet("0-9")>

Change-Id: Ia74daa30476d5e9ad73c368f4ecc64c755b734a5

tools/releasetools/rangelib.py

@@ -71,6 +71,19 @@ class RangeSet(object):
     """
     return cls(text)
 
+  @classmethod
+  def parse_raw(cls, text):
+    """Parse a string generated by RangeSet.to_string_raw().
+
+    >>> RangeSet.parse_raw(RangeSet("0-9").to_string_raw())
+    <RangeSet("0-9")>
+    """
+
+    raw = [int(i) for i in text.split(',')]
+    assert raw[0] == len(raw[1:]), "Invalid raw string."
+
+    return cls(data=raw[1:])
+
   def _parse_internal(self, text):
     data = []
     last = -1

tools/releasetools/test_rangelib.py

@@ -123,3 +123,17 @@ class RangeSetTest(unittest.TestCase):
     self.assertTrue(RangeSet(data=[2, 9, 30, 31, 31, 32, 35, 36]).monotonic)
     self.assertTrue(RangeSet(data=[0, 5, 5, 10]).monotonic)
     self.assertFalse(RangeSet(data=[5, 10, 0, 5]).monotonic)
+
+  def test_parse_raw(self):
+    self.assertEqual(
+        RangeSet.parse_raw(RangeSet("0-9").to_string_raw()),
+        RangeSet("0-9"))
+    self.assertEqual(RangeSet.parse_raw(
+        RangeSet("2-10 12").to_string_raw()),
+        RangeSet("2-10 12"))
+    self.assertEqual(
+        RangeSet.parse_raw(RangeSet("11 2-10 12 1 0").to_string_raw()),
+        RangeSet("11 2-10 12 1 0"))
+
+    with self.assertRaises(AssertionError):
+      RangeSet.parse_raw("4,0,10")