Support a "is_global" and "is_private" member on Rules. (#130)

* Support a "is_global" and "is_private" member on Rules.

When writing linters it is currently impossible to know (via rule introspection)
if a given rule is private or global. We have banned global rules for our use
case and we have to resort to a janky regex against our rules files to know if
anyone is about to commit a global rule. I figure exposing these two flags via
python will be useful for programatically checking those bits.

I'm not very pleased with the name "is_global" - I wanted to go with just
"global" and "private" but "global" is a reserved keyword and rule.global breaks
the python interpreter. I'm open to changing the member names if you have any
suggestions.

* Decrement reference counts on global and private.

* Update global and private checks after API changes.

tests.py

@@ -1038,6 +1038,18 @@ class TestYara(unittest.TestCase):
 
         yara.set_config(max_strings_per_rule=10000)
 
+    def testGlobalPrivate(self):
+
+        rules = """
+        global rule a { condition: true }
+        private rule b { condition: true }
+        """
+
+        # Have to convert to a list because Rules are not subscriptable, yet...
+        r = list(yara.compile(source=rules))
+        self.assertTrue(r[0].is_global == True)
+        self.assertTrue(r[1].is_private == True)
+
 
 if __name__ == "__main__":
     unittest.main()

yara-python.c

@@ -206,6 +206,8 @@ typedef struct
   PyObject* identifier;
   PyObject* tags;
   PyObject* meta;
+  PyObject* global;
+  PyObject* private;
 } Rule;
 
 static void Rule_dealloc(
@@ -217,6 +219,20 @@ static PyObject* Rule_getattro(
 
 static PyMemberDef Rule_members[] = {
   {
+    "is_global",
+    T_OBJECT_EX,
+    offsetof(Rule, global),
+    READONLY,
+    "Rule is global"
+  },
+  {
+    "is_private",
+    T_OBJECT_EX,
+    offsetof(Rule, private),
+    READONLY,
+    "Rule is private"
+  },
+  {
     "identifier",
     T_OBJECT_EX,
     offsetof(Rule, identifier),
@@ -1240,6 +1256,8 @@ static void Rule_dealloc(
   Py_XDECREF(object->identifier);
   Py_XDECREF(object->tags);
   Py_XDECREF(object->meta);
+  Py_XDECREF(object->global);
+  Py_XDECREF(object->private);
   PyObject_Del(self);
 }
 
@@ -1326,6 +1344,8 @@ static PyObject* Rules_next(
       Py_DECREF(object);
     }
 
+    rule->global = PyBool_FromLong(rules->iter_current_rule->flags & RULE_FLAGS_GLOBAL);
+    rule->private = PyBool_FromLong(rules->iter_current_rule->flags & RULE_FLAGS_PRIVATE);
     rule->identifier = PY_STRING(rules->iter_current_rule->identifier);
     rule->tags = tag_list;
     rule->meta = meta_list;