rtc::Bind: Capture method objects as scoped_refptr if they are ref counted

webrtc/base/bind.h

 // This file was GENERATED by command:
 //     pump.py bind.h.pump
 // DO NOT EDIT BY HAND!!!
 
 /*
  *  Copyright 2012 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.
  */
 
 // To generate bind.h from bind.h.pump, execute:
 // /home/build/google3/third_party/gtest/scripts/pump.py bind.h.pump
 
 // Bind() is an overloaded function that converts method calls into function
-// objects (aka functors). It captures any arguments to the method by value
-// when Bind is called, producing a stateful, nullary function object. Care
-// should be taken about the lifetime of objects captured by Bind(); the
-// returned functor knows nothing about the lifetime of the method's object or
-// any arguments passed by pointer, and calling the functor with a destroyed
-// object will surely do bad things.
+// objects (aka functors). The method object is captured as a scoped_refptr<> if
+// possible, and as a raw pointer otherwise. Any arguments to the method are
+// captured by value. The return value of Bind is a stateful, nullary function
+// object. Care should be taken about the lifetime of objects captured by
+// Bind(); the returned functor knows nothing about the lifetime of a non
+// ref-counted method object or any arguments passed by pointer, and calling the
+// functor with a destroyed object will surely do bad things.
 //
 // Example usage:
 //   struct Foo {
 //     int Test1() { return 42; }
 //     int Test2() const { return 52; }
 //     int Test3(int x) { return x*x; }
 //     float Test4(int x, float y) { return x + y; }
 //   };
 //
 //   int main() {
 //     Foo foo;
 //     cout << rtc::Bind(&Foo::Test1, &foo)() << endl;
 //     cout << rtc::Bind(&Foo::Test2, &foo)() << endl;
 //     cout << rtc::Bind(&Foo::Test3, &foo, 3)() << endl;
 //     cout << rtc::Bind(&Foo::Test4, &foo, 7, 8.5f)() << endl;
 //   }
+//
+// Example usage of ref counted objects:
+//   struct Bar {
+//     int AddRef();
+//     int Release();
+//
+//     void Test() {}
+//     void BindThis() {
+//       // The functor passed to AsyncInvoke() will keep this object alive.
+//       invoker.AsyncInvoke(rtc::Bind(&Bar::Test, this));
+//     }
+//   };
+//
+//   int main() {
+//     rtc::scoped_refptr<Bar> bar = new rtc::RefCountedObject<Bar>();
+//     auto functor = rtc::Bind(&Bar::Test, bar);
+//     bar = nullptr;
+//     // The functor stores an internal scoped_refptr<Bar>, so this is safe.
+//     functor();
+//   }
+//
 
 #ifndef WEBRTC_BASE_BIND_H_
 #define WEBRTC_BASE_BIND_H_
 
+#include "webrtc/base/scoped_ref_ptr.h"
+
 #define NONAME
 
 namespace rtc {
 namespace detail {
 // This is needed because the template parameters in Bind can't be resolved
 // if they're used both as parameters of the function pointer type and as
 // parameters to Bind itself: the function pointer parameters are exact
 // matches to the function prototype, but the parameters to bind have
 // references stripped. This trick allows the compiler to dictate the Bind
 // parameter types rather than deduce them.
 template <class T> struct identity { typedef T type; };
+
+// IsRefCounted<T>::value will be true for types that can be used in
+// rtc::scoped_refptr<T>, i.e. types that implements nullary functions AddRef()
+// and Release(), regardless of their return types. AddRef() and Release() can
+// be defined in T or any superclass of T.
+template <typename T>
+class IsRefCounted {
+  // This is a complex implementation detail done with SFINAE.
+
+  // Define types such that sizeof(Yes) != sizeof(No).
+  struct Yes { char dummy[1]; };
+  struct No { char dummy[2]; };
+  // Define two overloaded template functions with return types of different
+  // size. This way, we can use sizeof() on the return type to determine which
+  // function the compiler would have chosen. One function will be preferred
+  // over the other if it is possible to create it without compiler errors,
+  // otherwise the compiler will simply remove it, and default to the less
+  // preferred function.
+  template <typename R>
+  static Yes test(R* r, decltype(r->AddRef(), r->Release(), 42));
+  template <typename C> static No test(...);
+
+public:
+  // Trick the compiler to tell if it's possible to call AddRef() and Release().
+  static const bool value = sizeof(test<T>((T*)nullptr, 42)) == sizeof(Yes);
+};
+
+// TernaryTypeOperator is a helper class to select a type based on a static bool
+// value.
+template <bool condition, typename IfTrueT, typename IfFalseT>
+struct TernaryTypeOperator {};
+
+template <typename IfTrueT, typename IfFalseT>
+struct TernaryTypeOperator<true, IfTrueT, IfFalseT> {
+  typedef IfTrueT type;
+};
+
+template <typename IfTrueT, typename IfFalseT>
+struct TernaryTypeOperator<false, IfTrueT, IfFalseT> {
+  typedef IfFalseT type;
+};
+
+// PointerType<T>::type will be scoped_refptr<T> for ref counted types, and T*
+// otherwise.
+template <class T>
+struct PointerType {
+  typedef typename TernaryTypeOperator<IsRefCounted<T>::value,
+                                       scoped_refptr<T>,
+                                       T*>::type type;
+};
+
 }  // namespace detail
 
 template <class ObjectT, class MethodT, class R>
 class MethodFunctor0 {
  public:
   MethodFunctor0(MethodT method, ObjectT* object)
       : method_(method), object_(object) {}
   R operator()() const {
     return (object_->*method_)(); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
 };
 
 template <class FunctorT, class R>
 class Functor0 {
  public:
   explicit Functor0(const FunctorT& functor)
       : functor_(functor) {}
   R operator()() const {
     return functor_(); }
  private:
@@ skipping 14 matching lines @@
 #define FP_T(x) R (ObjectT::*x)() const
 
 template <class ObjectT, class R>
 MethodFunctor0<const ObjectT, FP_T(NONAME), R>
 Bind(FP_T(method), const ObjectT* object) {
   return MethodFunctor0<const ObjectT, FP_T(NONAME), R>(
       method, object);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)()
+
+template <class ObjectT, class R>
+MethodFunctor0<ObjectT, FP_T(NONAME), R>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object) {
+  return MethodFunctor0<ObjectT, FP_T(NONAME), R>(
+      method, object.get());
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)()
 
 template <class R>
 Functor0<FP_T(NONAME), R>
 Bind(FP_T(function)) {
   return Functor0<FP_T(NONAME), R>(
       function);
 }
 
 #undef FP_T
 
 template <class ObjectT, class MethodT, class R,
           class P1>
 class MethodFunctor1 {
  public:
   MethodFunctor1(MethodT method, ObjectT* object,
                  P1 p1)
       : method_(method), object_(object),
       p1_(p1) {}
   R operator()() const {
     return (object_->*method_)(p1_); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
   P1 p1_;
 };
 
 template <class FunctorT, class R,
           class P1>
 class Functor1 {
  public:
   Functor1(const FunctorT& functor, P1 p1)
       : functor_(functor),
       p1_(p1) {}
@@ skipping 22 matching lines @@
 template <class ObjectT, class R,
           class P1>
 MethodFunctor1<const ObjectT, FP_T(NONAME), R, P1>
 Bind(FP_T(method), const ObjectT* object,
      typename detail::identity<P1>::type p1) {
   return MethodFunctor1<const ObjectT, FP_T(NONAME), R, P1>(
       method, object, p1);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)(P1)
+
+template <class ObjectT, class R,
+          class P1>
+MethodFunctor1<ObjectT, FP_T(NONAME), R, P1>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object,
+     typename detail::identity<P1>::type p1) {
+  return MethodFunctor1<ObjectT, FP_T(NONAME), R, P1>(
+      method, object.get(), p1);
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)(P1)
 
 template <class R,
           class P1>
 Functor1<FP_T(NONAME), R, P1>
 Bind(FP_T(function),
      typename detail::identity<P1>::type p1) {
   return Functor1<FP_T(NONAME), R, P1>(
       function, p1);
 }
 
 #undef FP_T
 
 template <class ObjectT, class MethodT, class R,
           class P1,
           class P2>
 class MethodFunctor2 {
  public:
   MethodFunctor2(MethodT method, ObjectT* object,
                  P1 p1,
                  P2 p2)
       : method_(method), object_(object),
       p1_(p1),
       p2_(p2) {}
   R operator()() const {
     return (object_->*method_)(p1_, p2_); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
   P1 p1_;
   P2 p2_;
 };
 
 template <class FunctorT, class R,
           class P1,
           class P2>
 class Functor2 {
  public:
   Functor2(const FunctorT& functor, P1 p1, P2 p2)
@@ skipping 30 matching lines @@
           class P2>
 MethodFunctor2<const ObjectT, FP_T(NONAME), R, P1, P2>
 Bind(FP_T(method), const ObjectT* object,
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2) {
   return MethodFunctor2<const ObjectT, FP_T(NONAME), R, P1, P2>(
       method, object, p1, p2);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)(P1, P2)
+
+template <class ObjectT, class R,
+          class P1,
+          class P2>
+MethodFunctor2<ObjectT, FP_T(NONAME), R, P1, P2>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object,
+     typename detail::identity<P1>::type p1,
+     typename detail::identity<P2>::type p2) {
+  return MethodFunctor2<ObjectT, FP_T(NONAME), R, P1, P2>(
+      method, object.get(), p1, p2);
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)(P1, P2)
 
 template <class R,
           class P1,
           class P2>
 Functor2<FP_T(NONAME), R, P1, P2>
 Bind(FP_T(function),
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2) {
   return Functor2<FP_T(NONAME), R, P1, P2>(
@@ skipping 13 matching lines @@
                  P2 p2,
                  P3 p3)
       : method_(method), object_(object),
       p1_(p1),
       p2_(p2),
       p3_(p3) {}
   R operator()() const {
     return (object_->*method_)(p1_, p2_, p3_); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
   P1 p1_;
   P2 p2_;
   P3 p3_;
 };
 
 template <class FunctorT, class R,
           class P1,
           class P2,
           class P3>
 class Functor3 {
@@ skipping 38 matching lines @@
 MethodFunctor3<const ObjectT, FP_T(NONAME), R, P1, P2, P3>
 Bind(FP_T(method), const ObjectT* object,
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2,
      typename detail::identity<P3>::type p3) {
   return MethodFunctor3<const ObjectT, FP_T(NONAME), R, P1, P2, P3>(
       method, object, p1, p2, p3);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)(P1, P2, P3)
+
+template <class ObjectT, class R,
+          class P1,
+          class P2,
+          class P3>
+MethodFunctor3<ObjectT, FP_T(NONAME), R, P1, P2, P3>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object,
+     typename detail::identity<P1>::type p1,
+     typename detail::identity<P2>::type p2,
+     typename detail::identity<P3>::type p3) {
+  return MethodFunctor3<ObjectT, FP_T(NONAME), R, P1, P2, P3>(
+      method, object.get(), p1, p2, p3);
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)(P1, P2, P3)
 
 template <class R,
           class P1,
           class P2,
           class P3>
 Functor3<FP_T(NONAME), R, P1, P2, P3>
 Bind(FP_T(function),
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2,
@@ skipping 18 matching lines @@
                  P4 p4)
       : method_(method), object_(object),
       p1_(p1),
       p2_(p2),
       p3_(p3),
       p4_(p4) {}
   R operator()() const {
     return (object_->*method_)(p1_, p2_, p3_, p4_); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
   P1 p1_;
   P2 p2_;
   P3 p3_;
   P4 p4_;
 };
 
 template <class FunctorT, class R,
           class P1,
           class P2,
           class P3,
@@ skipping 46 matching lines @@
 Bind(FP_T(method), const ObjectT* object,
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2,
      typename detail::identity<P3>::type p3,
      typename detail::identity<P4>::type p4) {
   return MethodFunctor4<const ObjectT, FP_T(NONAME), R, P1, P2, P3, P4>(
       method, object, p1, p2, p3, p4);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)(P1, P2, P3, P4)
+
+template <class ObjectT, class R,
+          class P1,
+          class P2,
+          class P3,
+          class P4>
+MethodFunctor4<ObjectT, FP_T(NONAME), R, P1, P2, P3, P4>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object,
+     typename detail::identity<P1>::type p1,
+     typename detail::identity<P2>::type p2,
+     typename detail::identity<P3>::type p3,
+     typename detail::identity<P4>::type p4) {
+  return MethodFunctor4<ObjectT, FP_T(NONAME), R, P1, P2, P3, P4>(
+      method, object.get(), p1, p2, p3, p4);
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)(P1, P2, P3, P4)
 
 template <class R,
           class P1,
           class P2,
           class P3,
           class P4>
 Functor4<FP_T(NONAME), R, P1, P2, P3, P4>
 Bind(FP_T(function),
      typename detail::identity<P1>::type p1,
@@ skipping 23 matching lines @@
       : method_(method), object_(object),
       p1_(p1),
       p2_(p2),
       p3_(p3),
       p4_(p4),
       p5_(p5) {}
   R operator()() const {
     return (object_->*method_)(p1_, p2_, p3_, p4_, p5_); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
   P1 p1_;
   P2 p2_;
   P3 p3_;
   P4 p4_;
   P5 p5_;
 };
 
 template <class FunctorT, class R,
           class P1,
           class P2,
@@ skipping 54 matching lines @@
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2,
      typename detail::identity<P3>::type p3,
      typename detail::identity<P4>::type p4,
      typename detail::identity<P5>::type p5) {
   return MethodFunctor5<const ObjectT, FP_T(NONAME), R, P1, P2, P3, P4, P5>(
       method, object, p1, p2, p3, p4, p5);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)(P1, P2, P3, P4, P5)
+
+template <class ObjectT, class R,
+          class P1,
+          class P2,
+          class P3,
+          class P4,
+          class P5>
+MethodFunctor5<ObjectT, FP_T(NONAME), R, P1, P2, P3, P4, P5>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object,
+     typename detail::identity<P1>::type p1,
+     typename detail::identity<P2>::type p2,
+     typename detail::identity<P3>::type p3,
+     typename detail::identity<P4>::type p4,
+     typename detail::identity<P5>::type p5) {
+  return MethodFunctor5<ObjectT, FP_T(NONAME), R, P1, P2, P3, P4, P5>(
+      method, object.get(), p1, p2, p3, p4, p5);
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)(P1, P2, P3, P4, P5)
 
 template <class R,
           class P1,
           class P2,
           class P3,
           class P4,
           class P5>
 Functor5<FP_T(NONAME), R, P1, P2, P3, P4, P5>
 Bind(FP_T(function),
@@ skipping 28 matching lines @@
       p1_(p1),
       p2_(p2),
       p3_(p3),
       p4_(p4),
       p5_(p5),
       p6_(p6) {}
   R operator()() const {
     return (object_->*method_)(p1_, p2_, p3_, p4_, p5_, p6_); }
  private:
   MethodT method_;
-  ObjectT* object_;
+  typename detail::PointerType<ObjectT>::type object_;
   P1 p1_;
   P2 p2_;
   P3 p3_;
   P4 p4_;
   P5 p5_;
   P6 p6_;
 };
 
 template <class FunctorT, class R,
           class P1,
@@ skipping 62 matching lines @@
      typename detail::identity<P2>::type p2,
      typename detail::identity<P3>::type p3,
      typename detail::identity<P4>::type p4,
      typename detail::identity<P5>::type p5,
      typename detail::identity<P6>::type p6) {
   return MethodFunctor6<const ObjectT, FP_T(NONAME), R, P1, P2, P3, P4, P5, P6>(
       method, object, p1, p2, p3, p4, p5, p6);
 }
 
 #undef FP_T
+#define FP_T(x) R (ObjectT::*x)(P1, P2, P3, P4, P5, P6)
+
+template <class ObjectT, class R,
+          class P1,
+          class P2,
+          class P3,
+          class P4,
+          class P5,
+          class P6>
+MethodFunctor6<ObjectT, FP_T(NONAME), R, P1, P2, P3, P4, P5, P6>
+Bind(FP_T(method), const scoped_refptr<ObjectT>& object,
+     typename detail::identity<P1>::type p1,
+     typename detail::identity<P2>::type p2,
+     typename detail::identity<P3>::type p3,
+     typename detail::identity<P4>::type p4,
+     typename detail::identity<P5>::type p5,
+     typename detail::identity<P6>::type p6) {
+  return MethodFunctor6<ObjectT, FP_T(NONAME), R, P1, P2, P3, P4, P5, P6>(
+      method, object.get(), p1, p2, p3, p4, p5, p6);
+}
+
+#undef FP_T
 #define FP_T(x) R (*x)(P1, P2, P3, P4, P5, P6)
 
 template <class R,
           class P1,
           class P2,
           class P3,
           class P4,
           class P5,
           class P6>
 Functor6<FP_T(NONAME), R, P1, P2, P3, P4, P5, P6>
 Bind(FP_T(function),
      typename detail::identity<P1>::type p1,
      typename detail::identity<P2>::type p2,
      typename detail::identity<P3>::type p3,
      typename detail::identity<P4>::type p4,
      typename detail::identity<P5>::type p5,
      typename detail::identity<P6>::type p6) {
   return Functor6<FP_T(NONAME), R, P1, P2, P3, P4, P5, P6>(
       function, p1, p2, p3, p4, p5, p6);
 }
 
 #undef FP_T
 
 }  // namespace rtc
 
 #undef NONAME
 
 #endif  // WEBRTC_BASE_BIND_H_