| // 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> | |
| base::Callback< | |
| typename internal::BindState< | |
| typename internal::FunctorTraits<Functor>::RunnableType, | |
| typename internal::FunctorTraits<Functor>::RunType, | |
| internal::TypeList<>>::UnboundRunType> | |
| Bind(Functor functor) { | |
| // Typedefs for how to store and run the functor. | |
| typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType; | |
| typedef typename internal::FunctorTraits<Functor>::RunType RunType; | |
| typedef internal::BindState<RunnableType, RunType, | |
| internal::TypeList<>> BindState; | |
| return Callback<typename BindState::UnboundRunType>( | |
| new BindState(internal::MakeRunnable(functor))); | |
| } | |
| template <typename Functor, typename... Args> | |
| base::Callback< | |
| typename internal::BindState< | |
| typename internal::FunctorTraits<Functor>::RunnableType, | |
| typename internal::FunctorTraits<Functor>::RunType, | |
| internal::TypeList< | |
| typename internal::CallbackParamTraits<Args>::StorageType...>> | |
| ::UnboundRunType> | |
| Bind(Functor functor, const Args&... args) { | |
| // Typedefs for how to store and run the functor. | |
| typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType; | |
| typedef typename internal::FunctorTraits<Functor>::RunType RunType; | |
| // Use RunnableType::RunType instead of RunType above because our | |
| // checks should below for bound references need to know what the actual | |
| // functor is going to interpret the argument as. | |
| typedef typename RunnableType::RunType 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::HasNonConstReferenceParam<BoundRunType>::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_refcounted_type_and_needs_scoped_refptr"); | |
| typedef internal::BindState< | |
| RunnableType, RunType, | |
| internal::TypeList< | |
| typename internal::CallbackParamTraits<Args>::StorageType...>> | |
| BindState; | |
| return Callback<typename BindState::UnboundRunType>( | |
| new BindState(internal::MakeRunnable(functor), args...)); | |
| } | |
| } // namespace base | |
| #endif // BASE_BIND_H_ |