--- /dev/null
+// Copyright (c) 2012 Google Inc. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// * Neither the name of Google Inc. nor the name Chromium Embedded
+// Framework nor the names of its contributors may be used to endorse
+// or promote products derived from this software without specific prior
+// written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Do not include this header file directly. Use base/cef_bind.h or
+// base/cef_callback.h instead.
+
+// This file contains utility functions and classes that help the
+// implementation, and management of the Callback objects.
+
+#ifndef CEF_INCLUDE_BASE_INTERNAL_CEF_CALLBACK_INTERNAL_H_
+#define CEF_INCLUDE_BASE_INTERNAL_CEF_CALLBACK_INTERNAL_H_
+
+#include <stddef.h>
+
+#include "include/base/cef_atomic_ref_count.h"
+#include "include/base/cef_macros.h"
+#include "include/base/cef_ref_counted.h"
+#include "include/base/cef_scoped_ptr.h"
+#include "include/base/cef_template_util.h"
+
+template <typename T>
+class ScopedVector;
+
+namespace base {
+namespace cef_internal {
+class CallbackBase;
+
+// 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() {}
+
+ 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 CallbackBase {
+ public:
+ // 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.
+ typedef void(*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 .Pass() in a
+// destructive way.
+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;
+};
+
+// 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, bool is_move_only = IsMoveOnlyType<T>::value>
+struct CallbackParamTraits {
+ typedef const T& ForwardType;
+ typedef T StorageType;
+};
+
+// 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 CallbackParamTraits<T&, false> {
+ typedef T& ForwardType;
+ typedef T StorageType;
+};
+
+// 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 CallbackParamTraits<T[n], false> {
+ typedef const T* ForwardType;
+ typedef const T* StorageType;
+};
+
+// See comment for CallbackParamTraits<T[n]>.
+template <typename T>
+struct CallbackParamTraits<T[], false> {
+ typedef const T* ForwardType;
+ typedef const T* StorageType;
+};
+
+// 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 CallbackParamTraits<T, true> {
+ typedef T ForwardType;
+ typedef T StorageType;
+};
+
+// 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 with 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 enable_if<!IsMoveOnlyType<T>::value, T>::type& CallbackForward(T& t) {
+ return t;
+}
+
+template <typename T>
+typename enable_if<IsMoveOnlyType<T>::value, T>::type CallbackForward(T& t) {
+ return t.Pass();
+}
+
+} // namespace cef_internal
+} // namespace base
+
+#endif // CEF_INCLUDE_BASE_INTERNAL_CEF_CALLBACK_INTERNAL_H_
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