154 lines
5.7 KiB
Plaintext
154 lines
5.7 KiB
Plaintext
$$ This is a pump file for generating file templates. Pump is a python
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$$ script that is part of the Google Test suite of utilities. Description
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$$ can be found here:
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$$
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$$ http://code.google.com/p/googletest/wiki/PumpManual
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$$
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$$
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$$ MAX_ARITY controls the number of arguments that Bind() supports.
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$$ The amount of code, and more importantly, the number of template types
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$$ generated by pump grows at O(MAX_ARITY^2).
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$$
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$$ We tried going to 11 and found it imposed an extra 10 penalty on windows
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$$ cycle times compared to our original baseline of 6.
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$$
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$$ Currently 7 is chosen as a compromise between supporting a convenient
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$$ number of arguments and keeping compile times low. At 7, we have 115
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$$ templates being generated by pump.
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$$
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$$ Be careful when adjusting this number. If people find a need to bind
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$$ a larger number of arguments, consider refactoring the function to use
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$$ a param struct instead of raising the MAX_ARITY.
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$$
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$$ See http://crbug.com/98542 for more context.
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$$
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$var MAX_ARITY = 7
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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_BIND_H_
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#define BASE_BIND_H_
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#include "base/bind_internal.h"
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#include "base/callback_internal.h"
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// -----------------------------------------------------------------------------
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// Usage documentation
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// -----------------------------------------------------------------------------
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//
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// See base/callback.h for documentation.
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//
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//
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// -----------------------------------------------------------------------------
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// Implementation notes
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// -----------------------------------------------------------------------------
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//
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// If you're reading the implementation, before proceeding further, you should
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// read the top comment of base/bind_internal.h for a definition of common
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// terms and concepts.
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//
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// RETURN TYPES
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//
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// Though Bind()'s result is meant to be stored in a Callback<> type, it
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// cannot actually return the exact type without requiring a large amount
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// of extra template specializations. The problem is that in order to
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// discern the correct specialization of Callback<>, Bind would need to
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// unwrap the function signature to determine the signature's arity, and
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// whether or not it is a method.
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//
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// Each unique combination of (arity, function_type, num_prebound) where
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// function_type is one of {function, method, const_method} would require
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// one specialization. We eventually have to do a similar number of
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// specializations anyways in the implementation (see the Invoker<>,
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// classes). However, it is avoidable in Bind if we return the result
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// via an indirection like we do below.
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//
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// TODO(ajwong): We might be able to avoid this now, but need to test.
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//
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// It is possible to move most of the COMPILE_ASSERT asserts into BindState<>,
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// but it feels a little nicer to have the asserts here so people do not
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// need to crack open bind_internal.h. On the other hand, it makes Bind()
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// harder to read.
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namespace base {
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$range ARITY 0..MAX_ARITY
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$for ARITY [[
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$range ARG 1..ARITY
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template <typename Functor[[]]
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$if ARITY > 0 [[, ]] $for ARG , [[typename P$(ARG)]]>
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base::Callback<
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typename internal::BindState<
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typename internal::FunctorTraits<Functor>::RunnableType,
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typename internal::FunctorTraits<Functor>::RunType,
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void($for ARG , [[typename internal::CallbackParamTraits<P$(ARG)>::StorageType]])>
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::UnboundRunType>
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Bind(Functor functor
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$if ARITY > 0 [[, ]] $for ARG , [[const P$(ARG)& p$(ARG)]]) {
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// Typedefs for how to store and run the functor.
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typedef typename internal::FunctorTraits<Functor>::RunnableType RunnableType;
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typedef typename internal::FunctorTraits<Functor>::RunType RunType;
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// Use RunnableType::RunType instead of RunType above because our
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// checks should below for bound references need to know what the actual
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// functor is going to interpret the argument as.
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typedef internal::FunctionTraits<typename RunnableType::RunType>
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BoundFunctorTraits;
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$if ARITY > 0 [[
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// Do not allow binding a non-const reference parameter. Non-const reference
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// parameters are disallowed by the Google style guide. Also, binding a
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// non-const reference parameter can make for subtle bugs because the
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// invoked function will receive a reference to the stored copy of the
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// argument and not the original.
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COMPILE_ASSERT(
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!($for ARG || [[
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is_non_const_reference<typename BoundFunctorTraits::A$(ARG)Type>::value ]]),
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do_not_bind_functions_with_nonconst_ref);
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]]
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$for ARG [[
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$if ARG == 1 [[
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// For methods, we need to be careful for parameter 1. We do not require
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// a scoped_refptr because BindState<> itself takes care of AddRef() for
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// methods. We also disallow binding of an array as the method's target
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// object.
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COMPILE_ASSERT(
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internal::HasIsMethodTag<RunnableType>::value ||
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!internal::NeedsScopedRefptrButGetsRawPtr<P$(ARG)>::value,
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p$(ARG)_is_refcounted_type_and_needs_scoped_refptr);
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COMPILE_ASSERT(!internal::HasIsMethodTag<RunnableType>::value ||
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!is_array<P$(ARG)>::value,
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first_bound_argument_to_method_cannot_be_array);
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]] $else [[
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COMPILE_ASSERT(!internal::NeedsScopedRefptrButGetsRawPtr<P$(ARG)>::value,
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p$(ARG)_is_refcounted_type_and_needs_scoped_refptr);
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]] $$ $if ARG
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]] $$ $for ARG
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typedef internal::BindState<RunnableType, RunType, [[]]
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void($for ARG , [[typename internal::CallbackParamTraits<P$(ARG)>::StorageType]])> [[]]
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BindState;
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return Callback<typename BindState::UnboundRunType>(
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new BindState(internal::MakeRunnable(functor)[[]]
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$if ARITY > 0 [[, ]] $for ARG , [[p$(ARG)]]));
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}
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]] $$ for ARITY
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} // namespace base
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#endif // BASE_BIND_H_
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