Merge pull request #313 from JoranHonig/features/search_strategy_bfs

Implement breadth first search

mythril/laser/ethereum/strategy/basic.py

@@ -27,3 +27,28 @@ class DepthFirstSearchStrategy:
         except IndexError:
             raise StopIteration()
 
+
+class BreadthFirstSearchStrategy:
+    """
+    Implements a breadth first search strategy
+    I.E. Execute all states of a "level" before continuing
+    """
+    def __init__(self, work_list, max_depth):
+        self.work_list = work_list
+        self.max_depth = max_depth
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        """ Picks the next state to execute """
+        try:
+            # This strategies assumes that new states are appended at the end of the work_list
+            # By taking the first element we effectively pick the "oldest" states, which amounts to bfs
+            global_state = self.work_list.pop(0)
+            if global_state.mstate.depth >= self.max_depth:
+                return self.__next__()
+            return global_state
+        except IndexError:
+            raise StopIteration()
+