1 files changed, 62 insertions, 0 deletions
diff --git a/libmproxy/script/concurrent.py b/libmproxy/script/concurrent.py
new file mode 100644
index 00000000..bee2d43b
--- /dev/null
+++ b/libmproxy/script/concurrent.py
@@ -0,0 +1,62 @@
+"""
+This module provides a @concurrent decorator primitive to
+offload computations from mitmproxy's main master thread.
+"""
+from __future__ import absolute_import, print_function, division
+import threading
+
+
+class ReplyProxy(object):
+    def __init__(self, original_reply, script_thread):
+        self.original_reply = original_reply
+        self.script_thread = script_thread
+        self._ignore_call = True
+        self.lock = threading.Lock()
+
+    def __call__(self, *args, **kwargs):
+        with self.lock:
+            if self._ignore_call:
+                self.script_thread.start()
+                self._ignore_call = False
+                return
+        self.original_reply(*args, **kwargs)
+
+    def __getattr__(self, k):
+        return getattr(self.original_reply, k)
+
+
+def _handle_concurrent_reply(fn, o, *args, **kwargs):
+    # Make first call to o.reply a no op and start the script thread.
+    # We must not start the script thread before, as this may lead to a nasty race condition
+    # where the script thread replies a different response before the normal reply, which then gets swallowed.
+
+    def run():
+        fn(*args, **kwargs)
+        # If the script did not call .reply(), we have to do it now.
+        reply_proxy()
+
+    script_thread = ScriptThread(target=run)
+
+    reply_proxy = ReplyProxy(o.reply, script_thread)
+    o.reply = reply_proxy
+
+
+class ScriptThread(threading.Thread):
+    name = "ScriptThread"
+
+
+def concurrent(fn):
+    if fn.func_name in (
+            "request",
+            "response",
+            "error",
+            "clientconnect",
+            "serverconnect",
+            "clientdisconnect",
+            "next_layer"):
+        def _concurrent(ctx, obj):
+            _handle_concurrent_reply(fn, obj, ctx, obj)
+
+        return _concurrent
+    raise NotImplementedError(
+        "Concurrent decorator not supported for '%s' method." % fn.func_name)