Add support for non-ref-counted interface classes (issue #2090)

libcef_dll/ctocpp/ctocpp_scoped.h

@@ -0,0 +1,211 @@
+// 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/base/cef_macros.h"
+#include "include/cef_base.h"
+#include "include/capi/cef_base_capi.h"
+#include "libcef_dll/ptr_util.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:
+  // 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(obj.Pass()));
+  //   // |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);
+
+#if DCHECK_IS_ON()
+  // Simple tracking of allocated objects.
+  static base::AtomicRefCount DebugObjCt;  // NOLINT(runtime/int)
+#endif
+
+ protected:
+  CefCToCppScoped() {
+#if DCHECK_IS_ON()
+    base::AtomicRefCountInc(&DebugObjCt);
+#endif
+  }
+
+  virtual ~CefCToCppScoped() {
+#if DCHECK_IS_ON()
+    base::AtomicRefCountDec(&DebugObjCt);
+#endif
+  }
+
+  // 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;
+
+  DISALLOW_COPY_AND_ASSIGN(CefCToCppScoped);
+};
+
+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) {
+  if (!s)
+    return CefOwnPtr<BaseName>();
+
+  // 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) {
+  if (!c.get())
+    return NULL;
+
+  WrapperStruct* wrapperStruct = GetWrapperStruct(c.get());
+
+  // If the type does not match this object then we need to unwrap as the
+  // derived type.
+  if (wrapperStruct->type_ != kWrapperType)
+    return UnwrapDerivedOwn(wrapperStruct->type_, OWN_PASS(c));
+
+  StructName* orig_struct = wrapperStruct->struct_;
+
+  // We should own the object currently.
+  cef_base_scoped_t* base = reinterpret_cast<cef_base_scoped_t*>(orig_struct);
+  DCHECK(base && base->del);
+
+  // Don't delete the original object when the wrapper is deleted.
+  wrapperStruct->struct_ = NULL;
+
+  // 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) {
+  if (!c)
+    return NULL;
+
+  WrapperStruct* wrapperStruct = GetWrapperStruct(c);
+
+  // If the type does not match this object then we need to unwrap as the
+  // derived type.
+  if (wrapperStruct->type_ != kWrapperType)
+    return UnwrapDerivedRaw(wrapperStruct->type_, c);
+
+  // Return the original structure.
+  return wrapperStruct->struct_;
+}
+
+template <class ClassName, class BaseName, class StructName>
+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.
+  if (base && base->del)
+    base->del(base);
+
+  // 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_