cef/libcef_dll/cpptoc/cpptoc_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_CPPTOC_CPPTOC_SCOPED_H_
#define CEF_LIBCEF_DLL_CPPTOC_CPPTOC_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++ class with a C structure. This is used when the class
// implementation exists on this side of the DLL boundary but will have methods
// called from the other side of the DLL boundary.
template <class ClassName, class BaseName, class StructName>
class CefCppToCScoped : public CefBaseScoped {
public:
CefCppToCScoped(const CefCppToCScoped&) = delete;
CefCppToCScoped& operator=(const CefCppToCScoped&) = delete;
// Create a new wrapper instance and associated structure reference for
// passing an object instance the other side. The wrapper object will be
// deleted when |del| is called on the associated structure. The wrapped
// object will be deleted when the wrapper object is deleted. For example:
//
// void MyMethod(CefOwnPtr<MyType> obj) {
// my_method(MyTypeCppToC::WrapOwn(obj));
// }
//
// void my_method(my_type_t* struct) {
// // Delete the MyTypeCppToC wrapper and the owned MyType object.
// struct->del(struct);
// }
static StructName* WrapOwn(CefOwnPtr<BaseName> c) {
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if (!c) {
return nullptr;
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}
// Wrap our object with the CefCppToC class.
ClassName* wrapper = new ClassName();
wrapper->Initialize(c.release(), true);
// Return the structure pointer that can now be passed to the other side.
return wrapper->GetStruct();
}
// Create a new wrapper instance and associated structure reference for
// passing an object instance to the other side. The wrapper object is owned
// by the caller. The wrapped object is unowned and must outlive the wrapper.
// For example:
//
// void MyMethod(MyType* obj) {
// CefOwnPtr<MyTypeCppToC> MyTypeWrapper = MyTypeCppToC::WrapRaw(obj);
// my_method(MyTypeWrapper->GetStruct());
// // MyTypeWrapper is deleted when MyMethod() goes out of scope.
// }
//
// void my_method(my_type_t* struct) {
// // Access |struct| here but you can't delete it.
// }
static CefOwnPtr<ClassName> WrapRaw(CefRawPtr<BaseName> c) {
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if (!c) {
return CefOwnPtr<ClassName>();
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}
// Wrap our object with the CefCppToC class.
ClassName* wrapper = new ClassName();
wrapper->Initialize(c, false);
// Return the owned wrapper object.
return CefOwnPtr<ClassName>(wrapper);
}
// Retrieve the underlying object instance for a structure reference passed
// back from the other side. The caller takes ownership of the object. For
// example:
//
// void my_method(my_type_t* struct) {
// CefOwnPtr<MyType> MyTypePtr = MyTypeCppToC::UnwrapOwn(struct);
// // |struct| has been deleted and should no longer be accessed.
// }
static CefOwnPtr<BaseName> UnwrapOwn(StructName* s) {
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if (!s) {
return CefOwnPtr<BaseName>();
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}
// Cast our structure to the wrapper structure type.
WrapperStruct* wrapperStruct = GetWrapperStruct(s);
// 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_, s);
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}
// We should own the underlying object currently.
DCHECK(wrapperStruct->wrapper_->owned_);
DCHECK(wrapperStruct->object_);
// We're giving up ownership of the underlying object. Clear the pointer so
// it doesn't get deleted.
BaseName* object = wrapperStruct->object_;
wrapperStruct->object_ = nullptr;
delete wrapperStruct->wrapper_;
// Return the underlying object instance.
return CefOwnPtr<BaseName>(object);
}
// Retrieve the underlying object instance for a structure reference passed
// back from the other side. Ownership does not change. For example:
//
// void my_method(my_type_t* struct) {
// CefRawPtr<MyType> MyTypePtr = MyTypeCppToC::UnwrapRaw(struct);
// // |struct| is still valid.
// }
static CefRawPtr<BaseName> UnwrapRaw(StructName* s) {
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if (!s) {
return nullptr;
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}
// Cast our structure to the wrapper structure type.
WrapperStruct* wrapperStruct = GetWrapperStruct(s);
// 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_, s);
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}
// Return the underlying object instance.
return wrapperStruct->object_;
}
// Retrieve the same side wrapper associated with the structure. Ownership
// does not change.
static ClassName* GetWrapper(StructName* s) {
DCHECK(s);
WrapperStruct* wrapperStruct = GetWrapperStruct(s);
// Verify that the wrapper offset was calculated correctly.
DCHECK_EQ(kWrapperType, wrapperStruct->type_);
return static_cast<ClassName*>(wrapperStruct->wrapper_);
}
// Retrieve the underlying object instance from our own structure reference
// when the reference is passed as the required first parameter of a C API
// function call. Ownership of the object does not change.
static BaseName* Get(StructName* s) {
DCHECK(s);
WrapperStruct* wrapperStruct = GetWrapperStruct(s);
// Verify that the wrapper offset was calculated correctly.
DCHECK_EQ(kWrapperType, wrapperStruct->type_);
return wrapperStruct->object_;
}
// If returning the structure across the DLL boundary you should call
// AddRef() on this CefCppToC object. On the other side of the DLL boundary,
// call UnderlyingRelease() on the wrapping CefCToCpp object.
StructName* GetStruct() { return &wrapper_struct_.struct_; }
protected:
CefCppToCScoped() {
wrapper_struct_.type_ = kWrapperType;
wrapper_struct_.wrapper_ = this;
memset(GetStruct(), 0, sizeof(StructName));
}
virtual ~CefCppToCScoped() {
// Only delete the underlying object if we own it.
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if (owned_ && wrapper_struct_.object_) {
delete wrapper_struct_.object_;
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}
}
private:
// Used to associate this wrapper object, the underlying object instance and
// the structure that will be passed to the other side.
struct WrapperStruct {
CefWrapperType type_;
BaseName* object_;
CefCppToCScoped<ClassName, BaseName, StructName>* wrapper_;
StructName struct_;
};
void Initialize(BaseName* obj, bool owned) {
wrapper_struct_.object_ = obj;
owned_ = owned;
cef_base_scoped_t* base = reinterpret_cast<cef_base_scoped_t*>(GetStruct());
base->size = sizeof(StructName);
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if (owned) {
base->del = struct_del;
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}
}
static WrapperStruct* GetWrapperStruct(StructName* s) {
// 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*>(s) -
(sizeof(WrapperStruct) - sizeof(StructName)));
}
// Unwrap as the derived type.
static CefOwnPtr<BaseName> UnwrapDerivedOwn(CefWrapperType type,
StructName* s);
static CefRawPtr<BaseName> UnwrapDerivedRaw(CefWrapperType type,
StructName* s);
static void CEF_CALLBACK struct_del(cef_base_scoped_t* base) {
DCHECK(base);
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if (!base) {
return;
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}
WrapperStruct* wrapperStruct =
GetWrapperStruct(reinterpret_cast<StructName*>(base));
// Verify that the wrapper offset was calculated correctly.
DCHECK_EQ(kWrapperType, wrapperStruct->type_);
// Should only be deleting wrappers that own the underlying object.
DCHECK(wrapperStruct->wrapper_->owned_);
delete wrapperStruct->wrapper_;
}
WrapperStruct wrapper_struct_;
bool owned_;
static CefWrapperType kWrapperType;
};
#endif // CEF_LIBCEF_DLL_CPPTOC_CPPTOC_SCOPED_H_