1 // Copyright (c) 2014 OPEN CASCADE SAS
3 // This file is part of Open CASCADE Technology software library.
5 // This library is free software; you can redistribute it and/or modify it under
6 // the terms of the GNU Lesser General Public License version 2.1 as published
7 // by the Free Software Foundation, with special exception defined in the file
8 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
9 // distribution for complete text of the license and disclaimer of any warranty.
11 // Alternatively, this file may be used under the terms of Open CASCADE
12 // commercial license or contractual agreement.
14 #ifndef _Standard_Handle_HeaderFile
15 #define _Standard_Handle_HeaderFile
17 #include <Standard_Address.hxx>
18 #include <Standard_Stream.hxx>
19 #include <Standard_Transient.hxx>
21 #include <type_traits>
23 class Standard_Transient;
25 namespace opencascade {
27 //! Trait yielding true if class T1 is base of T2 but not the same
28 template <class T1, class T2, class Dummy = void>
29 struct is_base_but_not_same : std::is_base_of <T1, T2> {};
31 //! Explicit specialization of is_base_of trait to workaround the
32 //! requirement of type to be complete when T1 and T2 are the same.
33 template <class T1, class T2>
34 struct is_base_but_not_same <T1, T2, typename std::enable_if <std::is_same <T1, T2>::value>::type> : std::false_type {};
36 //! Intrusive smart pointer for use with Standard_Transient class and its descendants.
38 //! This class is similar to boost::intrusive_ptr<>, with additional
39 //! feature historically supported by Handles in OCCT:
40 //! it has type conversion to const reference to handle to the base types,
41 //! which allows it to be passed by reference
42 //! in functions accepting reference to handle to base class.
44 //! These casts (potentially unsafe) can be disabled by defining macro
45 //! OCCT_HANDLE_NOCAST; if it is defined, generalized copy constructor
46 //! and assignment operators are defined allowing to initialize handle
47 //! of base type from handle to derived type.
52 //! STL-compliant typedef of contained type
53 typedef T element_type;
58 handle () : entity(0) {}
60 //! Constructor from pointer to new object
61 handle (const T *thePtr) : entity(const_cast<T*>(thePtr))
67 handle (const handle& theHandle) : entity(theHandle.entity)
73 handle (handle&& theHandle) : entity(theHandle.entity)
84 //! Nullify the handle
90 //! Check for being null
91 bool IsNull() const { return entity == 0; }
93 //! Reset by new pointer
94 void reset (T* thePtr)
99 //! Assignment operator
100 handle& operator= (const handle& theHandle)
102 Assign (theHandle.entity);
106 //! Assignment to pointer
107 handle& operator= (const T* thePtr)
109 Assign (const_cast<T*>(thePtr));
114 handle& operator= (handle&& theHandle)
116 std::swap (this->entity, theHandle.entity);
120 //! STL-like cast to pointer to referred object (note non-const).
121 //! @sa std::shared_ptr::get()
122 T* get() const { return static_cast<T*>(this->entity); }
124 //! Member access operator (note non-const)
125 T* operator-> () const { return static_cast<T*>(this->entity); }
127 //! Dereferencing operator (note non-const)
128 T& operator* () const { return *get(); }
130 //! Check for equality
132 bool operator== (const handle<T2>& theHandle) const
134 return get() == theHandle.get();
137 //! Check for equality
139 bool operator== (const T2 *thePtr) const
141 return get() == thePtr;
144 //! Check for equality
146 friend bool operator== (const T2 *left, const handle& right)
148 return left == right.get();
151 //! Check for inequality
153 bool operator!= (const handle<T2>& theHandle) const
155 return get() != theHandle.get();
158 //! Check for inequality
160 bool operator!= (const T2 *thePtr) const
162 return get() != thePtr;
165 //! Check for inequality
167 friend bool operator!= (const T2 *left, const handle& right)
169 return left != right.get();
172 //! Compare operator for possible use in std::map<> etc.
174 bool operator< (const handle<T2>& theHandle) const
176 return get() < theHandle.get();
179 //! Down casting operator from handle to base type
181 static typename std::enable_if<is_base_but_not_same<T2, T>::value, handle>::type
182 DownCast (const handle<T2>& theObject)
184 return handle (dynamic_cast<T*>(const_cast<T2*>(theObject.get())));
187 //! Down casting operator from pointer to base type
189 static typename std::enable_if<is_base_but_not_same<T2, T>::value, handle>::type
190 DownCast (const T2* thePtr)
192 return handle (dynamic_cast<T*>(const_cast<T2*>(thePtr)));
195 //! For compatibility, define down casting operator from non-base type, as deprecated
197 Standard_DEPRECATED("down-casting from object of the same or unrelated type is meaningless")
198 static handle DownCast (const handle<T2>& theObject, typename std::enable_if<!is_base_but_not_same<T2, T>::value, void*>::type = 0)
200 return handle (dynamic_cast<T*>(const_cast<T2*>(theObject.get())));
203 //! For compatibility, define down casting operator from non-base type, as deprecated
205 Standard_DEPRECATED("down-casting from object of the same or unrelated type is meaningless")
206 static handle DownCast (const T2* thePtr, typename std::enable_if<!is_base_but_not_same<T2, T>::value, void*>::type = 0)
208 return handle (dynamic_cast<T*>(const_cast<T2*>(thePtr)));
211 #if (defined(__clang__)) || (defined(__INTEL_COMPILER) && __INTEL_COMPILER >= 1300) || \
212 (defined(_MSC_VER) && _MSC_VER >= 1800) || \
213 (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)))
215 //! Conversion to bool for use in conditional expressions
216 explicit operator bool () const
218 return entity != nullptr;
221 #else /* fallback version for compilers not supporting explicit conversion operators (VC10, VC11, GCC below 4.5) */
223 //! Conversion to bool-compatible type for use in conditional expressions
224 operator Standard_Transient* handle::* () const
226 return entity ? &handle::entity : 0;
231 // Support of conversions to handle of base type:
232 // - copy and move constructors and assignment operators if OCCT_HANDLE_NOCAST is defined
233 // - operators of upcast to const reference to base type otherwise
234 #if (defined(__clang__)) || (defined(__INTEL_COMPILER) && __INTEL_COMPILER >= 1206) || \
235 (defined(_MSC_VER) && _MSC_VER >= 1800) || \
236 (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
238 #ifdef OCCT_HANDLE_NOCAST
240 //! Generalized copy constructor.
241 //! Constructs handle holding entity of base type (T) from the one which holds entity of derived type (T2).
242 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
243 handle (const handle<T2>& theHandle) :
244 entity(theHandle.entity)
249 //! Generalized move constructor
250 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
251 handle (handle<T2>&& theHandle)
252 : entity(theHandle.entity)
254 theHandle.entity = 0;
257 //! Generalized assignment operator
258 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
259 handle operator = (const handle<T2>& theHandle)
261 Assign (theHandle.entity);
265 //! Generalized move operator
266 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
267 handle& operator= (handle<T2>&& theHandle)
269 std::swap (this->entity, theHandle.entity);
275 //! Upcast to const reference to base type.
276 template <class T2, typename = typename std::enable_if<is_base_but_not_same<T2, T>::value>::type>
277 operator const handle<T2>& () const
279 return reinterpret_cast<const handle<T2>&>(*this);
282 //! Upcast to non-const reference to base type.
283 //! NB: this cast can be dangerous, but required for legacy code; see #26377
284 template <class T2, typename = typename std::enable_if<is_base_but_not_same<T2, T>::value>::type>
285 operator handle<T2>& ()
287 return reinterpret_cast<handle<T2>&>(*this);
290 #endif /* OCCT_HANDLE_NOCAST */
292 #else /* fallback version for compilers not supporting default arguments of function templates (VC10, VC11, GCC below 4.3) */
294 #ifdef OCCT_HANDLE_NOCAST
296 //! Generalized copy constructor.
297 //! Constructs handle holding entity of base type (T) from the one which holds entity of derived type (T2).
299 handle (const handle<T2>& theHandle, typename std::enable_if <is_base_but_not_same <T, T2>::value>::type* = nullptr) :
300 entity(theHandle.entity)
305 //! Generalized move constructor
307 handle (handle<T2>&& theHandle, typename std::enable_if <is_base_but_not_same <T, T2>::value>::type* = nullptr)
308 : entity(theHandle.entity)
310 theHandle.entity = 0;
313 //! Generalized assignment operator.
315 handle operator = (const handle<T2>& theHandle)
317 std::enable_if <is_base_but_not_same <T, T2>::value, void*>::type aTypeCheckHelperVar;
318 (void)aTypeCheckHelperVar;
319 Assign (theHandle.entity);
323 //! Generalized move operator
325 handle& operator= (handle<T2>&& theHandle)
327 std::enable_if <is_base_but_not_same <T, T2>::value, void*>::type aTypeCheckHelperVar;
328 (void)aTypeCheckHelperVar;
329 std::swap (this->entity, theHandle.entity);
335 //! Upcast to const reference to base type.
336 //! NB: this implementation will cause ambiguity errors on calls to overloaded
337 //! functions accepting handles to different types, since compatibility is
338 //! checked in the cast code rather than ensured by SFINAE (possible with C++11)
340 operator const handle<T2>& () const
342 // error "type is not a member of enable_if" will be generated if T2 is not sub-type of T
343 // (handle is being cast to const& to handle of non-base type)
344 return reinterpret_cast<typename std::enable_if<is_base_but_not_same<T2, T>::value, const handle<T2>&>::type>(*this);
347 //! Upcast to non-const reference to base type.
348 //! NB: this cast can be dangerous, but required for legacy code; see #26377
350 Standard_DEPRECATED("Passing non-const reference to handle of base type in function is unsafe; use variable of exact type")
351 operator handle<T2>& ()
353 // error "type is not a member of enable_if" will be generated if T2 is not sub-type of T
354 // (handle is being cast to const& to handle of non-base type)
355 return reinterpret_cast<typename std::enable_if<is_base_but_not_same<T2, T>::value, handle<T2>&>::type>(*this);
358 #endif /* OCCT_HANDLE_NOCAST */
360 #endif /* compiler switch */
365 void Assign (Standard_Transient *thePtr)
367 if (thePtr == entity)
374 //! Increment reference counter of referred object
378 entity->IncrementRefCounter();
381 //! Decrement reference counter and if 0, destroy referred object
384 if (entity != 0 && entity->DecrementRefCounter() == 0)
389 template <class T2> friend class handle;
392 Standard_Transient* entity;
395 } // namespace opencascade
397 //! Define Handle() macro
398 #define Handle(Class) opencascade::handle<Class>
400 //! Global method HashCode(), for use in hash maps
402 inline Standard_Integer HashCode (const Handle(T)& theHandle, const Standard_Integer theUpper)
404 return ::HashCode (const_cast<Standard_Address>(static_cast<const void*>(theHandle.get())), theUpper);
407 //! For compatibility with previous versions of OCCT, define Handle_Class alias for opencascade::handle<Class>.
408 #if (defined(_MSC_VER) && _MSC_VER >= 1800)
409 //! For Visual Studio 2013+, define Handle_Class as non-template class to allow exporting this type in C++/CLI.
410 #define DEFINE_STANDARD_HANDLECLASS(C1,C2,BC) class C1; class Handle_##C1 : public Handle(C1) \
414 Handle_##C1(Handle(C1)&& theHandle) : Handle(C1)(theHandle) {} \
415 template <class T2, typename = typename std::enable_if <std::is_base_of <C1,T2>::value>::type> \
416 inline Handle_##C1(const opencascade::handle<T2>& theOther) : Handle(C1)(theOther) {} \
417 template <class T2, typename = typename std::enable_if <std::is_base_of <C1,T2>::value>::type> \
418 inline Handle_##C1(const T2* theOther) : Handle(C1)(theOther) {} \
419 template<typename T> inline Handle_##C1& operator=(T theOther) { Handle(C1)::operator=(theOther); return *this; } \
422 //! For other compilers, use simple typedef
423 #define DEFINE_STANDARD_HANDLECLASS(C1,C2,BC) class C1; typedef Handle(C1) Handle_##C1;
426 #define DEFINE_STANDARD_HANDLE(C1,C2) DEFINE_STANDARD_HANDLECLASS(C1,C2,Standard_Transient)
427 #define DEFINE_STANDARD_PHANDLE(C1,C2) DEFINE_STANDARD_HANDLECLASS(C1,C2,Standard_Persistent)