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Diffstat (limited to 'security/sandbox/chromium/base/callback_internal.h')
-rw-r--r-- | security/sandbox/chromium/base/callback_internal.h | 234 |
1 files changed, 0 insertions, 234 deletions
diff --git a/security/sandbox/chromium/base/callback_internal.h b/security/sandbox/chromium/base/callback_internal.h deleted file mode 100644 index d1d8ab8ec..000000000 --- a/security/sandbox/chromium/base/callback_internal.h +++ /dev/null @@ -1,234 +0,0 @@ -// Copyright (c) 2012 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. - -// This file contains utility functions and classes that help the -// implementation, and management of the Callback objects. - -#ifndef BASE_CALLBACK_INTERNAL_H_ -#define BASE_CALLBACK_INTERNAL_H_ - -#include <stddef.h> -#include <memory> -#include <type_traits> - -#include "base/atomic_ref_count.h" -#include "base/base_export.h" -#include "base/macros.h" -#include "base/memory/ref_counted.h" -#include "base/memory/scoped_ptr.h" -#include "base/template_util.h" - -namespace base { -namespace internal { -class CallbackBase; - -// BindStateBase is used to provide an opaque handle that the Callback -// class can use to represent a function object with bound arguments. It -// behaves as an existential type that is used by a corresponding -// DoInvoke function to perform the function execution. This allows -// us to shield the Callback class from the types of the bound argument via -// "type erasure." -// At the base level, the only task is to add reference counting data. Don't use -// RefCountedThreadSafe since it requires the destructor to be a virtual method. -// Creating a vtable for every BindState template instantiation results in a lot -// of bloat. Its only task is to call the destructor which can be done with a -// function pointer. -class BindStateBase { - protected: - explicit BindStateBase(void (*destructor)(BindStateBase*)) - : ref_count_(0), destructor_(destructor) {} - ~BindStateBase() = default; - - private: - friend class scoped_refptr<BindStateBase>; - friend class CallbackBase; - - void AddRef(); - void Release(); - - AtomicRefCount ref_count_; - - // Pointer to a function that will properly destroy |this|. - void (*destructor_)(BindStateBase*); - - DISALLOW_COPY_AND_ASSIGN(BindStateBase); -}; - -// Holds the Callback methods that don't require specialization to reduce -// template bloat. -class BASE_EXPORT CallbackBase { - public: - CallbackBase(const CallbackBase& c); - CallbackBase& operator=(const CallbackBase& c); - - // Returns true if Callback is null (doesn't refer to anything). - bool is_null() const { return bind_state_.get() == NULL; } - - // Returns the Callback into an uninitialized state. - void Reset(); - - protected: - // In C++, it is safe to cast function pointers to function pointers of - // another type. It is not okay to use void*. We create a InvokeFuncStorage - // that that can store our function pointer, and then cast it back to - // the original type on usage. - using InvokeFuncStorage = void(*)(); - - // Returns true if this callback equals |other|. |other| may be null. - bool Equals(const CallbackBase& other) const; - - // Allow initializing of |bind_state_| via the constructor to avoid default - // initialization of the scoped_refptr. We do not also initialize - // |polymorphic_invoke_| here because doing a normal assignment in the - // derived Callback templates makes for much nicer compiler errors. - explicit CallbackBase(BindStateBase* bind_state); - - // Force the destructor to be instantiated inside this translation unit so - // that our subclasses will not get inlined versions. Avoids more template - // bloat. - ~CallbackBase(); - - scoped_refptr<BindStateBase> bind_state_; - InvokeFuncStorage polymorphic_invoke_; -}; - -// A helper template to determine if given type is non-const move-only-type, -// i.e. if a value of the given type should be passed via std::move() in a -// destructive way. Types are considered to be move-only if they have a -// sentinel MoveOnlyTypeForCPP03 member: a class typically gets this from using -// the DISALLOW_COPY_AND_ASSIGN_WITH_MOVE_FOR_BIND macro. -// It would be easy to generalize this trait to all move-only types... but this -// confuses template deduction in VS2013 with certain types such as -// std::unique_ptr. -// TODO(dcheng): Revisit this when Windows switches to VS2015 by default. -template <typename T> struct IsMoveOnlyType { - template <typename U> - static YesType Test(const typename U::MoveOnlyTypeForCPP03*); - - template <typename U> - static NoType Test(...); - - static const bool value = sizeof((Test<T>(0))) == sizeof(YesType) && - !is_const<T>::value; -}; - -// Specialization of IsMoveOnlyType so that std::unique_ptr is still considered -// move-only, even without the sentinel member. -template <typename T> -struct IsMoveOnlyType<std::unique_ptr<T>> : std::true_type {}; - -template <typename> -struct CallbackParamTraitsForMoveOnlyType; - -template <typename> -struct CallbackParamTraitsForNonMoveOnlyType; - -// TODO(tzik): Use a default parameter once MSVS supports variadic templates -// with default values. -// http://connect.microsoft.com/VisualStudio/feedbackdetail/view/957801/compilation-error-with-variadic-templates -// -// This is a typetraits object that's used to take an argument type, and -// extract a suitable type for storing and forwarding arguments. -// -// In particular, it strips off references, and converts arrays to -// pointers for storage; and it avoids accidentally trying to create a -// "reference of a reference" if the argument is a reference type. -// -// This array type becomes an issue for storage because we are passing bound -// parameters by const reference. In this case, we end up passing an actual -// array type in the initializer list which C++ does not allow. This will -// break passing of C-string literals. -template <typename T> -struct CallbackParamTraits - : std::conditional<IsMoveOnlyType<T>::value, - CallbackParamTraitsForMoveOnlyType<T>, - CallbackParamTraitsForNonMoveOnlyType<T>>::type { -}; - -template <typename T> -struct CallbackParamTraitsForNonMoveOnlyType { - using ForwardType = const T&; - using StorageType = T; -}; - -// The Storage should almost be impossible to trigger unless someone manually -// specifies type of the bind parameters. However, in case they do, -// this will guard against us accidentally storing a reference parameter. -// -// The ForwardType should only be used for unbound arguments. -template <typename T> -struct CallbackParamTraitsForNonMoveOnlyType<T&> { - using ForwardType = T&; - using StorageType = T; -}; - -// Note that for array types, we implicitly add a const in the conversion. This -// means that it is not possible to bind array arguments to functions that take -// a non-const pointer. Trying to specialize the template based on a "const -// T[n]" does not seem to match correctly, so we are stuck with this -// restriction. -template <typename T, size_t n> -struct CallbackParamTraitsForNonMoveOnlyType<T[n]> { - using ForwardType = const T*; - using StorageType = const T*; -}; - -// See comment for CallbackParamTraits<T[n]>. -template <typename T> -struct CallbackParamTraitsForNonMoveOnlyType<T[]> { - using ForwardType = const T*; - using StorageType = const T*; -}; - -// Parameter traits for movable-but-not-copyable scopers. -// -// Callback<>/Bind() understands movable-but-not-copyable semantics where -// the type cannot be copied but can still have its state destructively -// transferred (aka. moved) to another instance of the same type by calling a -// helper function. When used with Bind(), this signifies transferal of the -// object's state to the target function. -// -// For these types, the ForwardType must not be a const reference, or a -// reference. A const reference is inappropriate, and would break const -// correctness, because we are implementing a destructive move. A non-const -// reference cannot be used with temporaries which means the result of a -// function or a cast would not be usable with Callback<> or Bind(). -template <typename T> -struct CallbackParamTraitsForMoveOnlyType { - using ForwardType = T; - using StorageType = T; -}; - -// CallbackForward() is a very limited simulation of C++11's std::forward() -// used by the Callback/Bind system for a set of movable-but-not-copyable -// types. It is needed because forwarding a movable-but-not-copyable -// argument to another function requires us to invoke the proper move -// operator to create a rvalue version of the type. The supported types are -// whitelisted below as overloads of the CallbackForward() function. The -// default template compiles out to be a no-op. -// -// In C++11, std::forward would replace all uses of this function. However, it -// is impossible to implement a general std::forward without C++11 due to a lack -// of rvalue references. -// -// In addition to Callback/Bind, this is used by PostTaskAndReplyWithResult to -// simulate std::forward() and forward the result of one Callback as a -// parameter to another callback. This is to support Callbacks that return -// the movable-but-not-copyable types whitelisted above. -template <typename T> -typename std::enable_if<!IsMoveOnlyType<T>::value, T>::type& CallbackForward( - T& t) { - return t; -} - -template <typename T> -typename std::enable_if<IsMoveOnlyType<T>::value, T>::type CallbackForward( - T& t) { - return std::move(t); -} - -} // namespace internal -} // namespace base - -#endif // BASE_CALLBACK_INTERNAL_H_ |