From e68b6c970e6b248df84a454d4f535316eed4e887 Mon Sep 17 00:00:00 2001
From: Taylor Brandstetter <deadbeef@webrtc.org>
Date: Thu, 5 Oct 2017 09:13:55 -0700
Subject: [PATCH] Adding back sigslot::repeater.

This time, with variadic template args, and unit tests!

NOPRESUBMIT=True

Bug: None
Change-Id: I2669cf5b24ab511eef8c01866748c1424b04abe1
Reviewed-on: https://webrtc-review.googlesource.com/4300
Commit-Queue: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20171}
---
 rtc_base/BUILD.gn            |  1 +
 rtc_base/sigslot_unittest.cc | 35 +++++++++++++++++++++-
 rtc_base/sigslotrepeater.h   | 56 ++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+), 1 deletion(-)
 create mode 100644 rtc_base/sigslotrepeater.h

diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 8c3000e0d0..8d93870931 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -554,6 +554,7 @@ rtc_static_library("rtc_base_generic") {
     "signalthread.h",
     "sigslot.cc",
     "sigslot.h",
+    "sigslotrepeater.h",
     "socket.h",
     "socketadapters.cc",
     "socketadapters.h",
diff --git a/rtc_base/sigslot_unittest.cc b/rtc_base/sigslot_unittest.cc
index b5cab9366c..e60d301323 100644
--- a/rtc_base/sigslot_unittest.cc
+++ b/rtc_base/sigslot_unittest.cc
@@ -9,8 +9,8 @@
  */
 
 #include "rtc_base/sigslot.h"
-
 #include "rtc_base/gunit.h"
+#include "rtc_base/sigslotrepeater.h"
 
 // This function, when passed a has_slots or signalx, will break the build if
 // its threading requirement is not single threaded
@@ -355,3 +355,36 @@ TEST(SigslotTest, CallDisconnectAllWhileSignalFiring) {
   EXPECT_EQ(1, receiver1.signal_count());
   EXPECT_EQ(0, receiver2.signal_count());
 }
+
+// Basic test that a sigslot repeater works.
+TEST(SigslotRepeaterTest, RepeatsSignalsAfterRepeatCalled) {
+  sigslot::signal<> signal;
+  sigslot::repeater<> repeater;
+  repeater.repeat(signal);
+  // Note that receiver is connected to the repeater, not directly to the
+  // source signal.
+  SigslotReceiver<> receiver;
+  receiver.Connect(&repeater);
+  // The repeater should repeat the signal, causing the receiver to see it.
+  signal();
+  EXPECT_EQ(1, receiver.signal_count());
+  // Repeat another signal for good measure.
+  signal();
+  EXPECT_EQ(2, receiver.signal_count());
+}
+
+// After calling "stop", a repeater should stop repeating signals.
+TEST(SigslotRepeaterTest, StopsRepeatingSignalsAfterStopCalled) {
+  // Same setup as above test.
+  sigslot::signal<> signal;
+  sigslot::repeater<> repeater;
+  repeater.repeat(signal);
+  SigslotReceiver<> receiver;
+  receiver.Connect(&repeater);
+  signal();
+  ASSERT_EQ(1, receiver.signal_count());
+  // Now call stop. The next signal should NOT propagate to the receiver.
+  repeater.stop(signal);
+  signal();
+  EXPECT_EQ(1, receiver.signal_count());
+}
diff --git a/rtc_base/sigslotrepeater.h b/rtc_base/sigslotrepeater.h
new file mode 100644
index 0000000000..ca4485457e
--- /dev/null
+++ b/rtc_base/sigslotrepeater.h
@@ -0,0 +1,56 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef RTC_BASE_SIGSLOTREPEATER_H__
+#define RTC_BASE_SIGSLOTREPEATER_H__
+
+// repeaters are both signals and slots, which are designed as intermediate
+// pass-throughs for signals and slots which don't know about each other (for
+// modularity or encapsulation).  This eliminates the need to declare a signal
+// handler whose sole purpose is to fire another signal.  The repeater connects
+// to the originating signal using the 'repeat' method.  When the repeated
+// signal fires, the repeater will also fire.
+//
+// TODO(deadbeef): Actually use this, after we decide on some style points on
+// using signals, so it doesn't get deleted again.
+
+#include "rtc_base/sigslot.h"
+
+namespace sigslot {
+
+template <class mt_policy, typename... Args>
+class repeater_with_thread_policy
+    : public signal_with_thread_policy<mt_policy, Args...>,
+      public has_slots<mt_policy> {
+ private:
+  // These typedefs are just to make the code below more readable. Code using
+  // repeaters shouldn't need to reference these types directly.
+  typedef signal_with_thread_policy<mt_policy, Args...> base_type;
+  typedef repeater_with_thread_policy<mt_policy, Args...> this_type;
+
+ public:
+  repeater_with_thread_policy() {}
+  repeater_with_thread_policy(const this_type& s) : base_type(s) {}
+
+  void reemit(Args... args) { base_type::emit(args...); }
+  void repeat(base_type& s) { s.connect(this, &this_type::reemit); }
+  void stop(base_type& s) { s.disconnect(this); }
+};
+
+// Alias with default thread policy. Needed because both default arguments
+// and variadic template arguments must go at the end of the list, so we
+// can't have both at once.
+template <typename... Args>
+using repeater =
+    repeater_with_thread_policy<SIGSLOT_DEFAULT_MT_POLICY, Args...>;
+
+}  // namespace sigslot
+
+#endif  // RTC_BASE_SIGSLOTREPEATER_H__