| $$ This is a pump file for generating file templates. Pump is a python |
| $$ script that is part of the Google Test suite of utilities. Description |
| $$ can be found here: |
| $$ |
| $$ http://code.google.com/p/googletest/wiki/PumpManual |
| $$ |
| |
| $$ |
| $$ MAX_ARITY controls the number of arguments that Bind() supports. |
| $$ The amount of code, and more importantly, the number of template types |
| $$ generated by pump grows at O(MAX_ARITY^2). |
| $$ |
| $$ We tried going to 11 and found it imposed an extra 10 penalty on windows |
| $$ cycle times compared to our original baseline of 6. |
| $$ |
| $$ Currently 7 is chosen as a compromise between supporting a convenient |
| $$ number of arguments and keeping compile times low. At 7, we have 115 |
| $$ templates being generated by pump. |
| $$ |
| $$ Be careful when adjusting this number. If people find a need to bind |
| $$ a larger number of arguments, consider refactoring the function to use |
| $$ a param struct instead of raising the MAX_ARITY. |
| $$ |
| $$ See http://crbug.com/98542 for more context. |
| $$ |
| $var MAX_ARITY = 7 |
| |
| // 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 COMPILE_ASSERT asserts 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 { |
| |
| $range ARITY 0..MAX_ARITY |
| $for ARITY [[ |
| $range ARG 1..ARITY |
| |
| template <typename Functor[[]] |
| $if ARITY > 0 [[, ]] $for ARG , [[typename P$(ARG)]]> |
| base::Callback< |
| typename internal::BindState< |
| typename internal::FunctorTraits<Functor>::RunnableType, |
| typename internal::FunctorTraits<Functor>::RunType, |
| void($for ARG , [[typename internal::CallbackParamTraits<P$(ARG)>::StorageType]])> |
| ::UnboundRunType> |
| Bind(Functor functor |
| $if ARITY > 0 [[, ]] $for ARG , [[const P$(ARG)& p$(ARG)]]) { |
| // Typedefs for how to store and run the functor. |
| typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType; |
| typedef typename internal::FunctorTraits<Functor>::RunType RunType; |
| |
| $if ARITY > 0 [[ |
| |
| // Use RunnableType::RunType instead of RunType above because our |
| // checks should below for bound references need to know what the actual |
| // functor is going to interpret the argument as. |
| typedef internal::FunctionTraits<typename RunnableType::RunType> |
| BoundFunctorTraits; |
| |
| // Do not allow binding a non-const reference parameter. Non-const reference |
| // parameters are disallowed by the Google style guide. Also, binding a |
| // non-const reference parameter can make for subtle bugs because the |
| // invoked function will receive a reference to the stored copy of the |
| // argument and not the original. |
| COMPILE_ASSERT( |
| !($for ARG || [[ |
| is_non_const_reference<typename BoundFunctorTraits::A$(ARG)Type>::value ]]), |
| do_not_bind_functions_with_nonconst_ref); |
| |
| ]] |
| |
| |
| $for ARG [[ |
| |
| |
| $if ARG == 1 [[ |
| // For methods, we need to be careful for parameter 1. We do not require |
| // a scoped_refptr because BindState<> itself takes care of AddRef() for |
| // methods. We also disallow binding of an array as the method's target |
| // object. |
| COMPILE_ASSERT( |
| internal::HasIsMethodTag<RunnableType>::value || |
| !internal::NeedsScopedRefptrButGetsRawPtr<P$(ARG)>::value, |
| p$(ARG)_is_refcounted_type_and_needs_scoped_refptr); |
| COMPILE_ASSERT(!internal::HasIsMethodTag<RunnableType>::value || |
| !is_array<P$(ARG)>::value, |
| first_bound_argument_to_method_cannot_be_array); |
| ]] $else [[ |
| COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P$(ARG)>::value, |
| p$(ARG)_is_refcounted_type_and_needs_scoped_refptr); |
| ]] $$ $if ARG |
| |
| ]] $$ $for ARG |
| |
| typedef internal::BindState<RunnableType, RunType, [[]] |
| void($for ARG , [[typename internal::CallbackParamTraits<P$(ARG)>::StorageType]])> [[]] |
| BindState; |
| |
| |
| return Callback<typename BindState::UnboundRunType>( |
| new BindState(internal::MakeRunnable(functor)[[]] |
| $if ARITY > 0 [[, ]] $for ARG , [[p$(ARG)]])); |
| } |
| |
| ]] $$ for ARITY |
| |
| } // namespace base |
| |
| #endif // BASE_BIND_H_ |