Add mask

CHANGELOG

@@ -5,6 +5,7 @@
 	* Dynamic bits
 	* Optional binary contents
 	* Sync all if no state passed as argument
+	* Mask method for client-side state manipulation
 - 0.1.0
 	* Release version bump
 - 0.0.19:

shep/state.py

@@ -92,7 +92,8 @@ class State:
 
 
     # enforces state value within bit limit of instantiation
-    def __check_limit(self, v):
+    def __check_limit(self, v, pure=True):
+        if pure:
             if self.__initial_bits == 0:
                 self.__bits += 1
             self.__limit = (1 << self.__bits) - 1
@@ -197,7 +198,7 @@ class State:
         v = 0
         for a in args:
             a = self.__check_value_cursor(a)
-            v = self.__check_limit(v | a)
+            v = self.__check_limit(v | a, pure=False)
         if self.__is_pure(v):
             raise ValueError('use add to add pure values')
         self.__set(k, v)
@@ -593,3 +594,11 @@ class State:
 
     def register_modify(self, key):
         self.modified_last[key] = datetime.datetime.now().timestamp()
+
+
+    def mask(self, key, states):
+        statemask = self.__limit + 1
+        statemask |= states
+        statemask = ~statemask
+        statemask &= self.__limit
+        return statemask

tests/test_state.py

@@ -216,5 +216,26 @@ class TestState(unittest.TestCase):
         states.alias('baz', states.FOO | states.BAR)
 
 
+
+    def test_mask(self):
+        states = State(3)
+        states.add('foo')
+        states.add('bar')
+        states.add('baz')
+        states.alias('all', states.FOO | states.BAR | states.BAZ)
+        mask = states.mask('xyzzy', states.FOO | states.BAZ)
+        self.assertEqual(mask, states.BAR)
+
+
+    def test_mask_dynamic(self):
+        states = State(0)
+        states.add('foo')
+        states.add('bar')
+        states.add('baz')
+        states.alias('all', states.FOO | states.BAR | states.BAZ)
+        mask = states.mask('xyzzy', states.FOO | states.BAZ)
+        self.assertEqual(mask, states.BAR)
+
+
 if __name__ == '__main__':
     unittest.main()