Rewrite rtc::Bind using variadic templates.

webrtc/base/bind.h.pump

-/*
- *  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). 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_FROM_HERE,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"
-#include "webrtc/base/template_util.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
-
-$var n = 9
-$range i 0..n
-$for i [[
-$range j 1..i
-
-template <class ObjectT, class MethodT, class R$for j [[,
-          class P$j]]>
-class MethodFunctor$i {
- public:
-  MethodFunctor$i(MethodT method, ObjectT* object$for j [[,
-                 P$j p$j]])
-      : method_(method), object_(object)$for j [[,
-      p$(j)_(p$j)]] {}
-  R operator()() const {
-    return (object_->*method_)($for j , [[p$(j)_]]); }
- private:
-  MethodT method_;
-  typename detail::PointerType<ObjectT>::type object_;$for j [[
-
-  typename rtc::remove_reference<P$j>::type p$(j)_;]]
-
-};
-
-template <class FunctorT, class R$for j [[,
-          class P$j]]>
-class Functor$i {
- public:
-  $if i == 0 [[explicit ]]
-Functor$i(const FunctorT& functor$for j [[, P$j p$j]])
-      : functor_(functor)$for j [[,
-      p$(j)_(p$j)]] {}
-  R operator()() const {
-    return functor_($for j , [[p$(j)_]]); }
- private:
-  FunctorT functor_;$for j [[
-
-  typename rtc::remove_reference<P$j>::type p$(j)_;]]
-
-};
-
-
-#define FP_T(x) R (ObjectT::*x)($for j , [[P$j]])
-
-template <class ObjectT, class R$for j [[,
-          class P$j]]>
-MethodFunctor$i<ObjectT, FP_T(NONAME), R$for j [[, P$j]]>
-Bind(FP_T(method), ObjectT* object$for j [[,
-     typename detail::identity<P$j>::type p$j]]) {
-  return MethodFunctor$i<ObjectT, FP_T(NONAME), R$for j [[, P$j]]>(
-      method, object$for j [[, p$j]]);
-}
-
-#undef FP_T
-#define FP_T(x) R (ObjectT::*x)($for j , [[P$j]]) const
-
-template <class ObjectT, class R$for j [[,
-          class P$j]]>
-MethodFunctor$i<const ObjectT, FP_T(NONAME), R$for j [[, P$j]]>
-Bind(FP_T(method), const ObjectT* object$for j [[,
-     typename detail::identity<P$j>::type p$j]]) {
-  return MethodFunctor$i<const ObjectT, FP_T(NONAME), R$for j [[, P$j]]>(
-      method, object$for j [[, p$j]]);
-}
-
-#undef FP_T
-#define FP_T(x) R (ObjectT::*x)($for j , [[P$j]])
-
-template <class ObjectT, class R$for j [[,
-          class P$j]]>
-MethodFunctor$i<ObjectT, FP_T(NONAME), R$for j [[, P$j]]>
-Bind(FP_T(method), const scoped_refptr<ObjectT>& object$for j [[,
-     typename detail::identity<P$j>::type p$j]]) {
-  return MethodFunctor$i<ObjectT, FP_T(NONAME), R$for j [[, P$j]]>(
-      method, object.get()$for j [[, p$j]]);
-}
-
-#undef FP_T
-#define FP_T(x) R (*x)($for j , [[P$j]])
-
-template <class R$for j [[,
-          class P$j]]>
-Functor$i<FP_T(NONAME), R$for j [[, P$j]]>
-Bind(FP_T(function)$for j [[,
-     typename detail::identity<P$j>::type p$j]]) {
-  return Functor$i<FP_T(NONAME), R$for j [[, P$j]]>(
-      function$for j [[, p$j]]);
-}
-
-#undef FP_T
-
-]]
-
-}  // namespace rtc
-
-#undef NONAME
-
-#endif  // WEBRTC_BASE_BIND_H_