Added branch finder

Author: alexirpan

controlflow.py

@@ -0,0 +1,44 @@
+import bdb
+import sys
+
+MAX_LINES = 10000 # maximum lines run across all files
+
+class BranchFinder(bdb.Bdb):
+    def __init__(self):
+        bdb.Bdb.__init__(self)
+        self.branches = []
+        self.prevline = None
+        self.lines_left = MAX_LINES
+
+    def user_line(self, frame):
+        """This function is called when we stop or break at this line."""
+        # This is so awful but it works
+        # Only care about lines in the string executed
+        self.lines_left -= 1
+        if self.lines_left <= 0:
+            self.set_quit()
+        if "<string>" not in str(frame.f_code):
+            return
+        if self.prevline and frame.f_lineno != self.prevline + 1:
+            self.branches.append((self.prevline, frame.f_lineno))
+        self.prevline = frame.f_lineno
+
+    def runscript(self, script_str):
+        self.set_step()
+        try:
+            self.run(script_str)
+        except Exception, e: # catch all exceptions, and reraise them with more web-friendly message
+            # Janky janky way to get exception name. Please don't break?
+            name = str(type(e)).split("'")[1]
+            return "%s raised on line %d: %s" % (name, self.prevline, e)
+        return self.branches
+
+# runs arbitrary code!
+# (please don't break me :( )
+def exec_script_str(script_str):
+    runner = BranchFinder()
+    return runner.runscript(script_str)
+
+if __name__ == '__main__':
+    with open(sys.argv[1]) as f:
+        print exec_script_str(f.read())