| // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_BIND_H_ |
| #define BASE_BIND_H_ |
| |
| #include "base/bind_internal.h" |
| #include "base/callback_internal.h" |
| |
| // ----------------------------------------------------------------------------- |
| // Usage documentation |
| // ----------------------------------------------------------------------------- |
| // |
| // See base/callback.h for documentation. |
| // |
| // |
| // ----------------------------------------------------------------------------- |
| // Implementation notes |
| // ----------------------------------------------------------------------------- |
| // |
| // If you're reading the implementation, before proceeding further, you should |
| // read the top comment of base/bind_internal.h for a definition of common |
| // terms and concepts. |
| // |
| // RETURN TYPES |
| // |
| // Though Bind()'s result is meant to be stored in a Callback<> type, it |
| // cannot actually return the exact type without requiring a large amount |
| // of extra template specializations. The problem is that in order to |
| // discern the correct specialization of Callback<>, Bind would need to |
| // unwrap the function signature to determine the signature's arity, and |
| // whether or not it is a method. |
| // |
| // Each unique combination of (arity, function_type, num_prebound) where |
| // function_type is one of {function, method, const_method} would require |
| // one specialization. We eventually have to do a similar number of |
| // specializations anyways in the implementation (see the Invoker<>, |
| // classes). However, it is avoidable in Bind if we return the result |
| // via an indirection like we do below. |
| // |
| // TODO(ajwong): We might be able to avoid this now, but need to test. |
| // |
| // It is possible to move most of the static_assert into BindState<>, but it |
| // feels a little nicer to have the asserts here so people do not need to crack |
| // open bind_internal.h. On the other hand, it makes Bind() harder to read. |
| |
| namespace base { |
| |
| template <typename Functor, typename... Args> |
| base::Callback< |
| typename internal::BindState< |
| typename internal::FunctorTraits<Functor>::RunnableType, |
| typename internal::FunctorTraits<Functor>::RunType, |
| typename internal::CallbackParamTraits<Args>::StorageType...> |
| ::UnboundRunType> |
| Bind(Functor functor, const Args&... args) { |
| // Type aliases for how to store and run the functor. |
| using RunnableType = typename internal::FunctorTraits<Functor>::RunnableType; |
| using RunType = typename internal::FunctorTraits<Functor>::RunType; |
| |
| // Use RunnableType::RunType instead of RunType above because our |
| // checks below for bound references need to know what the actual |
| // functor is going to interpret the argument as. |
| using BoundRunType = typename RunnableType::RunType; |
| |
| using BoundArgs = |
| internal::TakeTypeListItem<sizeof...(Args), |
| internal::ExtractArgs<BoundRunType>>; |
| |
| // Do not allow binding a non-const reference parameter. Non-const reference |
| // parameters are disallowed by the Google style guide. Also, binding a |
| // non-const reference parameter can make for subtle bugs because the |
| // invoked function will receive a reference to the stored copy of the |
| // argument and not the original. |
| static_assert(!internal::HasNonConstReferenceItem<BoundArgs>::value, |
| "do not bind functions with nonconst ref"); |
| |
| const bool is_method = internal::HasIsMethodTag<RunnableType>::value; |
| |
| // For methods, we need to be careful for parameter 1. We do not require |
| // a scoped_refptr because BindState<> itself takes care of AddRef() for |
| // methods. We also disallow binding of an array as the method's target |
| // object. |
| static_assert(!internal::BindsArrayToFirstArg<is_method, Args...>::value, |
| "first bound argument to method cannot be array"); |
| static_assert( |
| !internal::HasRefCountedParamAsRawPtr<is_method, Args...>::value, |
| "a parameter is a refcounted type and needs scoped_refptr"); |
| |
| using BindState = internal::BindState< |
| RunnableType, RunType, |
| typename internal::CallbackParamTraits<Args>::StorageType...>; |
| |
| return Callback<typename BindState::UnboundRunType>( |
| new BindState(internal::MakeRunnable(functor), args...)); |
| } |
| |
| } // namespace base |
| |
| #endif // BASE_BIND_H_ |