cef/libcef_dll/ctocpp/ctocpp_scoped.h

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// Copyright (c) 2017 The Chromium Embedded Framework 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 CEF_LIBCEF_DLL_CTOCPP_CTOCPP_SCOPED_H_
#define CEF_LIBCEF_DLL_CTOCPP_CTOCPP_SCOPED_H_
#pragma once
#include "include/base/cef_logging.h"
#include "include/capi/cef_base_capi.h"
#include "include/cef_base.h"
#include "libcef_dll/wrapper_types.h"
// Wrap a C structure with a C++ class. This is used when the implementation
// exists on the other side of the DLL boundary but will have methods called on
// this side of the DLL boundary.
template <class ClassName, class BaseName, class StructName>
class CefCToCppScoped : public BaseName {
public:
CefCToCppScoped(const CefCToCppScoped&) = delete;
CefCToCppScoped& operator=(const CefCToCppScoped&) = delete;
// Create a new wrapper instance for a structure reference received from the
// other side. The caller owns the CToCpp wrapper instance but not necessarily
// the underling object on the CppToC side (depends if s->del is non-NULL).
// The returned wrapper object can be used as either a scoped argument or to
// pass ownership. For example:
//
// void my_method(my_type1_t* struct1, my_type2_t* struct2) {
// // Passes ownership to MyMethod1().
// MyMethod1(MyType1CToCpp::Wrap(struct1));
//
// // Passes reference to MyMethod2().
// CefOwnPtr<MyType1> obj2 = MyType2CToCpp::Wrap(struct2);
// MyMethod2(obj2.get());
// // |obj2| is deleted when my_method() goes out of scope.
// }
//
// void MyMethod1(CefOwnPtr<MyType1> obj1) {
// // |obj1| is deleted when MyMethod1() goes out of scope.
// }
//
// void MyMethod2(CefRawPtr<MyType2> obj2) {
// }
static CefOwnPtr<BaseName> Wrap(StructName* s);
// Retrieve the underlying structure reference from a wrapper instance for
// return back to the other side. Ownership will be passed back to the other
// side and the wrapper will be deleted. For example:
//
// void MyMethod(CefOwnPtr<MyType> obj) {
// // Ownership of the underlying MyType object is passed to my_method().
// my_method(MyTypeCToCpp::UnwrapOwn(std::move(obj)));
// // |obj| is now NULL.
// }
static StructName* UnwrapOwn(CefOwnPtr<BaseName> c);
// Retrieve the underlying structure reference from a wrapper instance for
// return back to the other side. Ownership does not change. For example:
//
// void MyMethod(CefRawPtr<MyType> obj) {
// // A reference is passed to my_method(). Ownership does not change.
// my_method2(MyTypeCToCpp::UnwrapRaw(obj));
// }
static StructName* UnwrapRaw(CefRawPtr<BaseName> c);
// Override delete operator to properly delete the WrapperStruct.
// ~CefCToCppScoped will be called first followed by this method.
static void operator delete(void* ptr);
protected:
CefCToCppScoped() = default;
virtual ~CefCToCppScoped() = default;
// If returning the structure across the DLL boundary use Unwrap() instead.
StructName* GetStruct() const {
WrapperStruct* wrapperStruct = GetWrapperStruct(this);
// Verify that the wrapper offset was calculated correctly.
DCHECK_EQ(kWrapperType, wrapperStruct->type_);
return wrapperStruct->struct_;
}
private:
// Used to associate this wrapper object and the structure reference received
// from the other side.
struct WrapperStruct;
static WrapperStruct* GetWrapperStruct(const BaseName* obj);
// Unwrap as the derived type.
static StructName* UnwrapDerivedOwn(CefWrapperType type,
CefOwnPtr<BaseName> c);
static StructName* UnwrapDerivedRaw(CefWrapperType type,
CefRawPtr<BaseName> c);
static CefWrapperType kWrapperType;
};
template <class ClassName, class BaseName, class StructName>
struct CefCToCppScoped<ClassName, BaseName, StructName>::WrapperStruct {
CefWrapperType type_;
StructName* struct_;
ClassName wrapper_;
};
template <class ClassName, class BaseName, class StructName>
CefOwnPtr<BaseName> CefCToCppScoped<ClassName, BaseName, StructName>::Wrap(
StructName* s) {
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if (!s) {
return CefOwnPtr<BaseName>();
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}
// Wrap their structure with the CefCToCpp object.
WrapperStruct* wrapperStruct = new WrapperStruct;
wrapperStruct->type_ = kWrapperType;
wrapperStruct->struct_ = s;
return CefOwnPtr<BaseName>(&wrapperStruct->wrapper_);
}
template <class ClassName, class BaseName, class StructName>
StructName* CefCToCppScoped<ClassName, BaseName, StructName>::UnwrapOwn(
CefOwnPtr<BaseName> c) {
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if (!c.get()) {
return nullptr;
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}
WrapperStruct* wrapperStruct = GetWrapperStruct(c.get());
// If the type does not match this object then we need to unwrap as the
// derived type.
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if (wrapperStruct->type_ != kWrapperType) {
return UnwrapDerivedOwn(wrapperStruct->type_, std::move(c));
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}
StructName* orig_struct = wrapperStruct->struct_;
#if DCHECK_IS_ON()
// We should own the object currently.
cef_base_scoped_t* base = reinterpret_cast<cef_base_scoped_t*>(orig_struct);
DCHECK(base && base->del);
#endif
// Don't delete the original object when the wrapper is deleted.
wrapperStruct->struct_ = nullptr;
// Return the original structure.
return orig_struct;
// The wrapper |c| is deleted when this method goes out of scope.
}
template <class ClassName, class BaseName, class StructName>
StructName* CefCToCppScoped<ClassName, BaseName, StructName>::UnwrapRaw(
CefRawPtr<BaseName> c) {
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if (!c) {
return nullptr;
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}
WrapperStruct* wrapperStruct = GetWrapperStruct(c);
// If the type does not match this object then we need to unwrap as the
// derived type.
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if (wrapperStruct->type_ != kWrapperType) {
return UnwrapDerivedRaw(wrapperStruct->type_, c);
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}
// Return the original structure.
return wrapperStruct->struct_;
}
template <class ClassName, class BaseName, class StructName>
NO_SANITIZE("cfi-icall")
void CefCToCppScoped<ClassName, BaseName, StructName>::operator delete(
void* ptr) {
WrapperStruct* wrapperStruct = GetWrapperStruct(static_cast<BaseName*>(ptr));
// Verify that the wrapper offset was calculated correctly.
DCHECK_EQ(kWrapperType, wrapperStruct->type_);
// May be NULL if UnwrapOwn() was called.
cef_base_scoped_t* base =
reinterpret_cast<cef_base_scoped_t*>(wrapperStruct->struct_);
// If we own the object (base->del != NULL) then notify the other side that
// the object has been deleted.
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if (base && base->del) {
base->del(base);
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}
// Delete the wrapper structure without executing ~CefCToCppScoped() an
// additional time.
::operator delete(wrapperStruct);
}
template <class ClassName, class BaseName, class StructName>
typename CefCToCppScoped<ClassName, BaseName, StructName>::WrapperStruct*
CefCToCppScoped<ClassName, BaseName, StructName>::GetWrapperStruct(
const BaseName* obj) {
// Offset using the WrapperStruct size instead of individual member sizes to
// avoid problems due to platform/compiler differences in structure padding.
return reinterpret_cast<WrapperStruct*>(
reinterpret_cast<char*>(const_cast<BaseName*>(obj)) -
(sizeof(WrapperStruct) - sizeof(ClassName)));
}
#endif // CEF_LIBCEF_DLL_CTOCPP_CTOCPP_SCOPED_H_