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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // This defines a set of argument wrappers and related factory methods that | 5 // This defines a set of argument wrappers and related factory methods that |
6 // can be used specify the refcounting and reference semantics of arguments | 6 // can be used specify the refcounting and reference semantics of arguments |
7 // that are bound by the Bind() function in base/bind.h. | 7 // that are bound by the Bind() function in base/bind.h. |
8 // | 8 // |
9 // It also defines a set of simple functions and utilities that people want | 9 // It also defines a set of simple functions and utilities that people want |
10 // when using Callback<> and Bind(). | 10 // when using Callback<> and Bind(). |
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233 // substitution if T::TargetFunc exists. Thus GoodCheck<Base>(0) will resolve | 233 // substitution if T::TargetFunc exists. Thus GoodCheck<Base>(0) will resolve |
234 // to the variadic version if T has TargetFunc. If T::TargetFunc does not | 234 // to the variadic version if T has TargetFunc. If T::TargetFunc does not |
235 // exist, then &C::TargetFunc is not ambiguous, and the overload resolution | 235 // exist, then &C::TargetFunc is not ambiguous, and the overload resolution |
236 // will prefer GoodCheck(Helper<&C::TargetFunc>*). | 236 // will prefer GoodCheck(Helper<&C::TargetFunc>*). |
237 // | 237 // |
238 // This method of SFINAE will correctly probe for inherited names, but it cannot | 238 // This method of SFINAE will correctly probe for inherited names, but it cannot |
239 // typecheck those names. It's still a good enough sanity check though. | 239 // typecheck those names. It's still a good enough sanity check though. |
240 // | 240 // |
241 // Works on gcc-4.2, gcc-4.4, and Visual Studio 2008. | 241 // Works on gcc-4.2, gcc-4.4, and Visual Studio 2008. |
242 // | 242 // |
243 // TODO(ajwong): Move to ref_counted.h or template_util.h when we've vetted | |
244 // this works well. | |
245 // | |
246 // TODO(ajwong): Make this check for Release() as well. | |
247 // See http://crbug.com/82038. | |
248 template <typename T> | |
249 class SupportsAddRefAndRelease { | |
250 using Yes = char[1]; | |
251 using No = char[2]; | |
252 | |
253 struct BaseMixin { | |
254 void AddRef(); | |
255 }; | |
256 | |
257 // MSVC warns when you try to use Base if T has a private destructor, the | |
258 // common pattern for refcounted types. It does this even though no attempt to | |
259 // instantiate Base is made. We disable the warning for this definition. | |
260 #if defined(OS_WIN) | |
261 #pragma warning(push) | |
262 #pragma warning(disable:4624) | |
263 #endif | |
264 struct Base : public T, public BaseMixin { | |
265 }; | |
266 #if defined(OS_WIN) | |
267 #pragma warning(pop) | |
268 #endif | |
269 | |
270 template <void(BaseMixin::*)()> struct Helper {}; | |
271 | |
272 template <typename C> | |
273 static No& Check(Helper<&C::AddRef>*); | |
274 | |
275 template <typename > | |
276 static Yes& Check(...); | |
277 | |
278 public: | |
279 enum { value = sizeof(Check<Base>(0)) == sizeof(Yes) }; | |
280 }; | |
281 | |
282 // Helpers to assert that arguments of a recounted type are bound with a | |
283 // scoped_refptr. | |
284 template <bool IsClasstype, typename T> | |
285 struct UnsafeBindtoRefCountedArgHelper : std::false_type { | |
286 }; | |
287 | |
288 template <typename T> | |
289 struct UnsafeBindtoRefCountedArgHelper<true, T> | |
290 : std::integral_constant<bool, SupportsAddRefAndRelease<T>::value> { | |
291 }; | |
292 | |
293 template <typename T> | |
294 struct UnsafeBindtoRefCountedArg : std::false_type { | |
295 }; | |
296 | |
297 template <typename T> | |
298 struct UnsafeBindtoRefCountedArg<T*> | |
299 : UnsafeBindtoRefCountedArgHelper<std::is_class<T>::value, T> { | |
300 }; | |
301 | 243 |
302 template <typename T> | 244 template <typename T> |
303 class HasIsMethodTag { | 245 class HasIsMethodTag { |
304 using Yes = char[1]; | 246 using Yes = char[1]; |
305 using No = char[2]; | 247 using No = char[2]; |
306 | 248 |
307 template <typename U> | 249 template <typename U> |
308 static Yes& Check(typename U::IsMethod*); | 250 static Yes& Check(typename U::IsMethod*); |
309 | 251 |
310 template <typename U> | 252 template <typename U> |
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630 | 572 |
631 template <typename T> | 573 template <typename T> |
632 struct IsWeakReceiver<internal::ConstRefWrapper<T>> : IsWeakReceiver<T> {}; | 574 struct IsWeakReceiver<internal::ConstRefWrapper<T>> : IsWeakReceiver<T> {}; |
633 | 575 |
634 template <typename T> | 576 template <typename T> |
635 struct IsWeakReceiver<WeakPtr<T>> : std::true_type {}; | 577 struct IsWeakReceiver<WeakPtr<T>> : std::true_type {}; |
636 | 578 |
637 } // namespace base | 579 } // namespace base |
638 | 580 |
639 #endif // BASE_BIND_HELPERS_H_ | 581 #endif // BASE_BIND_HELPERS_H_ |
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