[WIP][Base] Use variadic template for Callback and Bind

base/bind_internal.h.pump

-$$ This is a pump file for generating file templates.  Pump is a python
-$$ script that is part of the Google Test suite of utilities.  Description
-$$ can be found here:
-$$
-$$ http://code.google.com/p/googletest/wiki/PumpManual
-$$
-
-$$ See comment for MAX_ARITY in base/bind.h.pump.
-$var MAX_ARITY = 7
-$range ARITY 0..MAX_ARITY
-
-// 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_INTERNAL_H_
-#define BASE_BIND_INTERNAL_H_
-
-#include "base/bind_helpers.h"
-#include "base/callback_internal.h"
-#include "base/memory/raw_scoped_refptr_mismatch_checker.h"
-#include "base/memory/weak_ptr.h"
-#include "base/template_util.h"
-#include "build/build_config.h"
-
-#if defined(OS_WIN)
-#include "base/bind_internal_win.h"
-#endif
-
-namespace base {
-namespace internal {
-
-// See base/callback.h for user documentation.
-//
-//
-// CONCEPTS:
-//  Runnable -- A type (really a type class) that has a single Run() method
-//              and a RunType typedef that corresponds to the type of Run().
-//              A Runnable can declare that it should treated like a method
-//              call by including a typedef named IsMethod.  The value of
-//              this typedef is NOT inspected, only the existence.  When a
-//              Runnable declares itself a method, Bind() will enforce special
-//              refcounting + WeakPtr handling semantics for the first
-//              parameter which is expected to be an object.
-//  Functor -- A copyable type representing something that should be called.
-//             All function pointers, Callback<>, and Runnables are functors
-//             even if the invocation syntax differs.
-//  RunType -- A function type (as opposed to function _pointer_ type) for
-//             a Run() function.  Usually just a convenience typedef.
-//  (Bound)ArgsType -- A function type that is being (ab)used to store the
-//                     types of set of arguments.  The "return" type is always
-//                     void here.  We use this hack so that we do not need
-//                     a new type name for each arity of type. (eg.,
-//                     BindState1, BindState2).  This makes forward
-//                     declarations and friending much much easier.
-//
-// Types:
-//  RunnableAdapter<> -- Wraps the various "function" pointer types into an
-//                       object that adheres to the Runnable interface.
-//                       There are |3*ARITY| RunnableAdapter types.
-//  FunctionTraits<> -- Type traits that unwrap a function signature into a
-//                      a set of easier to use typedefs.  Used mainly for
-//                      compile time asserts.
-//                      There are |ARITY| FunctionTraits types.
-//  ForceVoidReturn<> -- Helper class for translating function signatures to
-//                       equivalent forms with a "void" return type.
-//                    There are |ARITY| ForceVoidReturn types.
-//  FunctorTraits<> -- Type traits used determine the correct RunType and
-//                     RunnableType for a Functor.  This is where function
-//                     signature adapters are applied.
-//                    There are |ARITY| ForceVoidReturn types.
-//  MakeRunnable<> -- Takes a Functor and returns an object in the Runnable
-//                    type class that represents the underlying Functor.
-//                    There are |O(1)| MakeRunnable types.
-//  InvokeHelper<> -- Take a Runnable + arguments and actully invokes it.
-//                    Handle the differing syntaxes needed for WeakPtr<> support,
-//                    and for ignoring return values.  This is separate from
-//                    Invoker to avoid creating multiple version of Invoker<>
-//                    which grows at O(n^2) with the arity.
-//                    There are |k*ARITY| InvokeHelper types.
-//  Invoker<> -- Unwraps the curried parameters and executes the Runnable.
-//               There are |(ARITY^2 + ARITY)/2| Invoketypes.
-//  BindState<> -- Stores the curried parameters, and is the main entry point
-//                 into the Bind() system, doing most of the type resolution.
-//                 There are ARITY BindState types.
-
-// RunnableAdapter<>
-//
-// The RunnableAdapter<> templates provide a uniform interface for invoking
-// a function pointer, method pointer, or const method pointer. The adapter
-// exposes a Run() method with an appropriate signature. Using this wrapper
-// allows for writing code that supports all three pointer types without
-// undue repetition.  Without it, a lot of code would need to be repeated 3
-// times.
-//
-// For method pointers and const method pointers the first argument to Run()
-// is considered to be the received of the method.  This is similar to STL's
-// mem_fun().
-//
-// This class also exposes a RunType typedef that is the function type of the
-// Run() function.
-//
-// If and only if the wrapper contains a method or const method pointer, an
-// IsMethod typedef is exposed.  The existence of this typedef (NOT the value)
-// marks that the wrapper should be considered a method wrapper.
-
-template <typename Functor>
-class RunnableAdapter;
-
-$for ARITY [[
-$range ARG 1..ARITY
-
-// Function: Arity $(ARITY).
-template <typename R[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename A$(ARG)]]>
-class RunnableAdapter<R(*)($for ARG , [[A$(ARG)]])> {
- public:
-  typedef R (RunType)($for ARG , [[A$(ARG)]]);
-
-  explicit RunnableAdapter(R(*function)($for ARG , [[A$(ARG)]]))
-      : function_(function) {
-  }
-
-  R Run($for ARG , [[typename CallbackParamTraits<A$(ARG)>::ForwardType a$(ARG)]]) {
-    return function_($for ARG , [[CallbackForward(a$(ARG))]]);
-  }
-
- private:
-  R (*function_)($for ARG , [[A$(ARG)]]);
-};
-
-// Method: Arity $(ARITY).
-template <typename R, typename T[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename A$(ARG)]]>
-class RunnableAdapter<R(T::*)($for ARG , [[A$(ARG)]])> {
- public:
-  typedef R (RunType)(T*[[]]
-$if ARITY > 0[[, ]] $for ARG , [[A$(ARG)]]);
-  typedef true_type IsMethod;
-
-  explicit RunnableAdapter(R(T::*method)($for ARG , [[A$(ARG)]]))
-      : method_(method) {
-  }
-
-  R Run(T* object[[]]
-$if ARITY > 0[[, ]]  $for ARG, [[typename CallbackParamTraits<A$(ARG)>::ForwardType a$(ARG)]]) {
-    return (object->*method_)($for ARG , [[CallbackForward(a$(ARG))]]);
-  }
-
- private:
-  R (T::*method_)($for ARG , [[A$(ARG)]]);
-};
-
-// Const Method: Arity $(ARITY).
-template <typename R, typename T[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename A$(ARG)]]>
-class RunnableAdapter<R(T::*)($for ARG , [[A$(ARG)]]) const> {
- public:
-  typedef R (RunType)(const T*[[]]
-$if ARITY > 0[[, ]] $for ARG , [[A$(ARG)]]);
-  typedef true_type IsMethod;
-
-  explicit RunnableAdapter(R(T::*method)($for ARG , [[A$(ARG)]]) const)
-      : method_(method) {
-  }
-
-  R Run(const T* object[[]]
-$if ARITY > 0[[, ]]  $for ARG, [[typename CallbackParamTraits<A$(ARG)>::ForwardType a$(ARG)]]) {
-    return (object->*method_)($for ARG , [[CallbackForward(a$(ARG))]]);
-  }
-
- private:
-  R (T::*method_)($for ARG , [[A$(ARG)]]) const;
-};
-
-]]  $$ for ARITY
-
-
-// FunctionTraits<>
-//
-// Breaks a function signature apart into typedefs for easier introspection.
-template <typename Sig>
-struct FunctionTraits;
-
-$for ARITY [[
-$range ARG 1..ARITY
-
-template <typename R[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename A$(ARG)]]>
-struct FunctionTraits<R($for ARG , [[A$(ARG)]])> {
-  typedef R ReturnType;
-$for ARG [[
-
-  typedef A$(ARG) A$(ARG)Type;
-]]
-
-};
-
-]]
-
-
-// ForceVoidReturn<>
-//
-// Set of templates that support forcing the function return type to void.
-template <typename Sig>
-struct ForceVoidReturn;
-
-$for ARITY [[
-$range ARG 1..ARITY
-
-template <typename R[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename A$(ARG)]]>
-struct ForceVoidReturn<R($for ARG , [[A$(ARG)]])> {
-  typedef void(RunType)($for ARG , [[A$(ARG)]]);
-};
-
-]]  $$ for ARITY
-
-
-// FunctorTraits<>
-//
-// See description at top of file.
-template <typename T>
-struct FunctorTraits {
-  typedef RunnableAdapter<T> RunnableType;
-  typedef typename RunnableType::RunType RunType;
-};
-
-template <typename T>
-struct FunctorTraits<IgnoreResultHelper<T> > {
-  typedef typename FunctorTraits<T>::RunnableType RunnableType;
-  typedef typename ForceVoidReturn<
-      typename RunnableType::RunType>::RunType RunType;
-};
-
-template <typename T>
-struct FunctorTraits<Callback<T> > {
-  typedef Callback<T> RunnableType;
-  typedef typename Callback<T>::RunType RunType;
-};
-
-
-// MakeRunnable<>
-//
-// Converts a passed in functor to a RunnableType using type inference.
-
-template <typename T>
-typename FunctorTraits<T>::RunnableType MakeRunnable(const T& t) {
-  return RunnableAdapter<T>(t);
-}
-
-template <typename T>
-typename FunctorTraits<T>::RunnableType
-MakeRunnable(const IgnoreResultHelper<T>& t) {
-  return MakeRunnable(t.functor_);
-}
-
-template <typename T>
-const typename FunctorTraits<Callback<T> >::RunnableType&
-MakeRunnable(const Callback<T>& t) {
-  DCHECK(!t.is_null());
-  return t;
-}
-
-
-// InvokeHelper<>
-//
-// There are 3 logical InvokeHelper<> specializations: normal, void-return,
-// WeakCalls.
-//
-// The normal type just calls the underlying runnable.
-//
-// We need a InvokeHelper to handle void return types in order to support
-// IgnoreResult().  Normally, if the Runnable's RunType had a void return,
-// the template system would just accept "return functor.Run()" ignoring
-// the fact that a void function is being used with return. This piece of
-// sugar breaks though when the Runnable's RunType is not void.  Thus, we
-// need a partial specialization to change the syntax to drop the "return"
-// from the invocation call.
-//
-// WeakCalls similarly need special syntax that is applied to the first
-// argument to check if they should no-op themselves.
-template <bool IsWeakCall, typename ReturnType, typename Runnable,
-          typename ArgsType>
-struct InvokeHelper;
-
-$for ARITY [[
-$range ARG 1..ARITY
-$range WEAKCALL_ARG 2..ARITY
-
-template <typename ReturnType, typename Runnable[[]]
-$if ARITY > 0 [[,]] $for ARG , [[typename A$(ARG)]]>
-struct InvokeHelper<false, ReturnType, Runnable,
-    void($for ARG , [[A$(ARG)]])>  {
-  static ReturnType MakeItSo(Runnable runnable[[]]
-$if ARITY > 0[[, ]] $for ARG , [[A$(ARG) a$(ARG)]]) {
-    return runnable.Run($for ARG , [[CallbackForward(a$(ARG))]]);
-  }
-};
-
-template <typename Runnable[[]]
-$if ARITY > 0 [[,]] $for ARG , [[typename A$(ARG)]]>
-struct InvokeHelper<false, void, Runnable,
-    void($for ARG , [[A$(ARG)]])>  {
-  static void MakeItSo(Runnable runnable[[]]
-$if ARITY > 0[[, ]] $for ARG , [[A$(ARG) a$(ARG)]]) {
-    runnable.Run($for ARG , [[CallbackForward(a$(ARG))]]);
-  }
-};
-
-$if ARITY > 0 [[
-
-template <typename Runnable[[]], typename BoundWeakPtr
-$if ARITY > 1[[, ]] $for WEAKCALL_ARG , [[typename A$(WEAKCALL_ARG)]]>
-struct InvokeHelper<true, void, Runnable,
-    void(BoundWeakPtr
-$if ARITY > 1[[, ]] $for WEAKCALL_ARG , [[A$(WEAKCALL_ARG)]])>  {
-  static void MakeItSo(Runnable runnable, BoundWeakPtr weak_ptr
-$if ARITY > 1[[, ]] $for WEAKCALL_ARG , [[A$(WEAKCALL_ARG) a$(WEAKCALL_ARG)]]) {
-    if (!weak_ptr.get()) {
-      return;
-    }
-    runnable.Run(weak_ptr.get()
-$if ARITY > 1[[, ]] $for WEAKCALL_ARG , [[CallbackForward(a$(WEAKCALL_ARG))]]);
-  }
-};
-
-]]
-
-]] $$ for ARITY
-
-#if !defined(_MSC_VER)
-
-template <typename ReturnType, typename Runnable, typename ArgsType>
-struct InvokeHelper<true, ReturnType, Runnable, ArgsType> {
-  // WeakCalls are only supported for functions with a void return type.
-  // Otherwise, the function result would be undefined if the the WeakPtr<>
-  // is invalidated.
-  COMPILE_ASSERT(is_void<ReturnType>::value,
-                 weak_ptrs_can_only_bind_to_methods_without_return_values);
-};
-
-#endif
-
-// Invoker<>
-//
-// See description at the top of the file.
-template <int NumBound, typename Storage, typename RunType>
-struct Invoker;
-
-$for ARITY [[
-
-$$ Number of bound arguments.
-$range BOUND 0..ARITY
-$for BOUND [[
-
-$var UNBOUND = ARITY - BOUND
-$range ARG 1..ARITY
-$range BOUND_ARG 1..BOUND
-$range UNBOUND_ARG (ARITY - UNBOUND + 1)..ARITY
-
-// Arity $(ARITY) -> $(UNBOUND).
-template <typename StorageType, typename R[[]]
-$if ARITY > 0 [[,]][[]]
-$for ARG , [[typename X$(ARG)]]>
-struct Invoker<$(BOUND), StorageType, R($for ARG , [[X$(ARG)]])> {
-  typedef R(RunType)(BindStateBase*[[]]
-$if UNBOUND != 0 [[, ]]
-$for UNBOUND_ARG , [[typename CallbackParamTraits<X$(UNBOUND_ARG)>::ForwardType]]);
-
-  typedef R(UnboundRunType)($for UNBOUND_ARG , [[X$(UNBOUND_ARG)]]);
-
-  static R Run(BindStateBase* base[[]]
-$if UNBOUND != 0 [[, ]][[]]
-$for UNBOUND_ARG , [[
-typename CallbackParamTraits<X$(UNBOUND_ARG)>::ForwardType x$(UNBOUND_ARG)
-]][[]]
-) {
-    StorageType* storage = static_cast<StorageType*>(base);
-
-    // Local references to make debugger stepping easier. If in a debugger,
-    // you really want to warp ahead and step through the
-    // InvokeHelper<>::MakeItSo() call below.
-$for BOUND_ARG
-[[
-
-    typedef typename StorageType::Bound$(BOUND_ARG)UnwrapTraits Bound$(BOUND_ARG)UnwrapTraits;
-]]
-
-
-$for BOUND_ARG
-[[
-
-    typename Bound$(BOUND_ARG)UnwrapTraits::ForwardType x$(BOUND_ARG) =
-        Bound$(BOUND_ARG)UnwrapTraits::Unwrap(storage->p$(BOUND_ARG)_);
-]]
-
-    return InvokeHelper<StorageType::IsWeakCall::value, R,
-           typename StorageType::RunnableType,
-           void(
-$for BOUND_ARG , [[
-typename Bound$(BOUND_ARG)UnwrapTraits::ForwardType
-]]
-
-$if UNBOUND > 0 [[$if BOUND > 0 [[, ]]]][[]]
-
-$for UNBOUND_ARG , [[
-typename CallbackParamTraits<X$(UNBOUND_ARG)>::ForwardType x$(UNBOUND_ARG)
-]]
-)>
-               ::MakeItSo(storage->runnable_
-$if ARITY > 0[[, ]] $for ARG , [[CallbackForward(x$(ARG))]]);
-  }
-};
-
-]] $$ for BOUND
-]] $$ for ARITY
-
-
-// BindState<>
-//
-// This stores all the state passed into Bind() and is also where most
-// of the template resolution magic occurs.
-//
-// Runnable is the functor we are binding arguments to.
-// RunType is type of the Run() function that the Invoker<> should use.
-// Normally, this is the same as the RunType of the Runnable, but it can
-// be different if an adapter like IgnoreResult() has been used.
-//
-// BoundArgsType contains the storage type for all the bound arguments by
-// (ab)using a function type.
-template <typename Runnable, typename RunType, typename BoundArgsType>
-struct BindState;
-
-$for ARITY [[
-$range ARG 1..ARITY
-
-template <typename Runnable, typename RunType[[]]
-$if ARITY > 0[[, ]] $for ARG , [[typename P$(ARG)]]>
-struct BindState<Runnable, RunType, void($for ARG , [[P$(ARG)]])> : public BindStateBase {
-  typedef Runnable RunnableType;
-
-$if ARITY > 0 [[
-  typedef IsWeakMethod<HasIsMethodTag<Runnable>::value, P1> IsWeakCall;
-]] $else [[
-  typedef false_type IsWeakCall;
-]]
-
-  typedef Invoker<$(ARITY), BindState, RunType> InvokerType;
-  typedef typename InvokerType::UnboundRunType UnboundRunType;
-
-$if ARITY > 0 [[
-
-  // Convenience typedefs for bound argument types.
-
-$for ARG [[
-  typedef UnwrapTraits<P$(ARG)> Bound$(ARG)UnwrapTraits;
-
-]]  $$ for ARG
-
-
-]]  $$ if ARITY > 0
-
-$$ The extra [[ ]] is needed to massage spacing. Silly pump.py.
-[[  ]]$if ARITY == 0 [[explicit ]]BindState(const Runnable& runnable
-$if ARITY > 0 [[, ]] $for ARG , [[const P$(ARG)& p$(ARG)]])
-      : runnable_(runnable)[[]]
-$if ARITY == 0 [[
- {
-
-]] $else [[
-, $for ARG , [[
-
-        p$(ARG)_(p$(ARG))
-]] {
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::AddRef(p1_);
-
-]]
-  }
-
-  virtual ~BindState() {
-$if ARITY > 0 [[
-    MaybeRefcount<HasIsMethodTag<Runnable>::value, P1>::Release(p1_);
-]]
-  }
-
-  RunnableType runnable_;
-
-$for ARG [[
-  P$(ARG) p$(ARG)_;
-
-]]
-};
-
-]] $$ for ARITY
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_BIND_INTERNAL_H_