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 is intended for low-level template classes and functions
26 namespace opencascade {
28 //! Namespace opencascade::std includes templates from C++11 std namespace used by
29 //! OCCT classes. These definitions are imported from std namespace, plus (on older
30 //! compilers) from std::tr1, or implemented by custom code where neither std
31 //! not std::tr1 provide necessary definitions.
34 // import all available standard stuff from std namespace
35 using namespace ::std;
37 // for old MSVC compiler, some standard templates are defined in std::tr1 namespace,
38 // and some missing ones are implemented here
39 #if(defined(_MSC_VER) && (_MSC_VER < 1600))
40 using namespace ::std::tr1;
42 // C++11 template class enable_if
43 template<bool Test, class Type = void>
45 {// type is undefined for assumed !_Test
49 struct enable_if<true, _Type>
50 {// type is _Type for _Test
54 template<bool Condition, typename TypeTrue, typename TypeFalse>
57 typedef TypeTrue type;
60 template<typename TypeTrue, typename TypeFalse>
61 struct conditional<false, TypeTrue, TypeFalse>
63 typedef TypeFalse type;
68 } // namespace opencascade::std
70 //! Trait yielding true if class T1 is base of T2 but not the same
71 template <class T1, class T2, class Dummy = void>
72 struct is_base_but_not_same : opencascade::std::is_base_of <T1, T2> {};
74 //! Explicit specialization of is_base_of trait to workaround the
75 //! requirement of type to be complete when T1 and T2 are the same.
76 template <class T1, class T2>
77 struct is_base_but_not_same <T1, T2, typename opencascade::std::enable_if <opencascade::std::is_same <T1, T2>::value>::type> : opencascade::std::false_type {};
79 //! Intrusive smart pointer for use with Standard_Transient class and its descendants.
81 //! This class is similar to boost::intrusive_ptr<>. The reference counter
82 //! is part of the base class (Standard_Transient), thus creation of a handle
83 //! does not require allocation of additional memory for the counter.
84 //! All handles to the same object share the common counter; object is deleted
85 //! when the last handle pointing on it is destroyed. It is safe to create a new
86 //! handle from plain C pointer to the object already pointed by another handle.
87 //! The same object can be referenced by handles of different types (as soon as
88 //! they are compatible with the object type).
90 //! Handle has type cast operator to const reference to handle to the base
91 //! types, which allows it to be passed by reference in functions accepting
92 //! reference to handle to base class, without copying.
94 //! By default, the type cast operator is provided also for non-const reference.
95 //! These casts (potentially unsafe) can be disabled by defining macro
96 //! OCCT_HANDLE_NOCAST; if it is defined, generalized copy constructor
97 //! and assignment operators are defined allowing to initialize handle
98 //! of base type from handle to derived type.
100 //! Weak pointers are not supported.
105 //! STL-compliant typedef of contained type
106 typedef T element_type;
110 //! Empty constructor
111 handle () : entity(0) {}
113 //! Constructor from pointer to new object
114 handle (const T *thePtr) : entity(const_cast<T*>(thePtr))
120 handle (const handle& theHandle) : entity(theHandle.entity)
125 #if(defined(_MSC_VER) && (_MSC_VER < 1600))
128 handle (handle&& theHandle) : entity(theHandle.entity)
130 theHandle.entity = 0;
140 //! Nullify the handle
146 //! Check for being null
147 bool IsNull() const { return entity == 0; }
149 //! Reset by new pointer
150 void reset (T* thePtr)
155 //! Assignment operator
156 handle& operator= (const handle& theHandle)
158 Assign (theHandle.entity);
162 //! Assignment to pointer
163 handle& operator= (const T* thePtr)
165 Assign (const_cast<T*>(thePtr));
169 #if(defined(_MSC_VER) && (_MSC_VER < 1600))
172 handle& operator= (handle&& theHandle)
174 std::swap (this->entity, theHandle.entity);
179 //! STL-like cast to pointer to referred object (note non-const).
180 //! @sa std::shared_ptr::get()
181 T* get() const { return static_cast<T*>(this->entity); }
183 //! Member access operator (note non-const)
184 T* operator-> () const { return static_cast<T*>(this->entity); }
186 //! Dereferencing operator (note non-const)
187 T& operator* () const { return *get(); }
189 //! Check for equality
191 bool operator== (const handle<T2>& theHandle) const
193 return get() == theHandle.get();
196 //! Check for equality
198 bool operator== (const T2 *thePtr) const
200 return get() == thePtr;
203 //! Check for equality
205 friend bool operator== (const T2 *left, const handle& right)
207 return left == right.get();
210 //! Check for inequality
212 bool operator!= (const handle<T2>& theHandle) const
214 return get() != theHandle.get();
217 //! Check for inequality
219 bool operator!= (const T2 *thePtr) const
221 return get() != thePtr;
224 //! Check for inequality
226 friend bool operator!= (const T2 *left, const handle& right)
228 return left != right.get();
231 //! Compare operator for possible use in std::map<> etc.
233 bool operator< (const handle<T2>& theHandle) const
235 return get() < theHandle.get();
238 //! Down casting operator from handle to base type
240 static typename opencascade::std::enable_if<is_base_but_not_same<T2, T>::value, handle>::type
241 DownCast (const handle<T2>& theObject)
243 return handle (dynamic_cast<T*>(const_cast<T2*>(theObject.get())));
246 //! Down casting operator from pointer to base type
248 static typename opencascade::std::enable_if<is_base_but_not_same<T2, T>::value, handle>::type
249 DownCast (const T2* thePtr)
251 return handle (dynamic_cast<T*>(const_cast<T2*>(thePtr)));
254 //! For compatibility, define down casting operator from non-base type, as deprecated
256 Standard_DEPRECATED("down-casting from object of the same or unrelated type is meaningless")
257 static handle DownCast (const handle<T2>& theObject, typename opencascade::std::enable_if<!is_base_but_not_same<T2, T>::value, void*>::type = 0)
259 return handle (dynamic_cast<T*>(const_cast<T2*>(theObject.get())));
262 //! For compatibility, define down casting operator from non-base type, as deprecated
264 Standard_DEPRECATED("down-casting from object of the same or unrelated type is meaningless")
265 static handle DownCast (const T2* thePtr, typename opencascade::std::enable_if<!is_base_but_not_same<T2, T>::value, void*>::type = 0)
267 return handle (dynamic_cast<T*>(const_cast<T2*>(thePtr)));
270 #if (defined(__clang__)) || (defined(__INTEL_COMPILER) && __INTEL_COMPILER >= 1300) || \
271 (defined(_MSC_VER) && _MSC_VER >= 1800) || \
272 (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)))
274 //! Conversion to bool for use in conditional expressions
275 explicit operator bool () const
277 return entity != nullptr;
280 #else /* fallback version for compilers not supporting explicit conversion operators (VC10, VC11, GCC below 4.5) */
282 //! Conversion to bool-compatible type for use in conditional expressions
283 operator Standard_Transient* handle::* () const
285 return entity ? &handle::entity : 0;
290 // Support of conversions to handle of base type:
291 // - copy and move constructors and assignment operators if OCCT_HANDLE_NOCAST is defined
292 // - operators of upcast to const reference to base type otherwise
293 #if (defined(__clang__)) || (defined(__INTEL_COMPILER) && __INTEL_COMPILER >= 1206) || \
294 (defined(_MSC_VER) && _MSC_VER >= 1800) || \
295 (defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
297 #ifdef OCCT_HANDLE_NOCAST
299 //! Generalized copy constructor.
300 //! Constructs handle holding entity of base type (T) from the one which holds entity of derived type (T2).
301 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
302 handle (const handle<T2>& theHandle) :
303 entity(theHandle.entity)
308 //! Generalized move constructor
309 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
310 handle (handle<T2>&& theHandle)
311 : entity(theHandle.entity)
313 theHandle.entity = 0;
316 //! Generalized assignment operator
317 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
318 handle operator = (const handle<T2>& theHandle)
320 Assign (theHandle.entity);
324 //! Generalized move operator
325 template <class T2, typename = typename std::enable_if <is_base_but_not_same <T, T2>::value>::type>
326 handle& operator= (handle<T2>&& theHandle)
328 std::swap (this->entity, theHandle.entity);
334 //! Upcast to const reference to base type.
335 template <class T2, typename = typename std::enable_if<is_base_but_not_same<T2, T>::value>::type>
336 operator const handle<T2>& () const
338 return reinterpret_cast<const handle<T2>&>(*this);
341 //! Upcast to non-const reference to base type.
342 //! NB: this cast can be dangerous, but required for legacy code; see #26377
343 template <class T2, typename = typename std::enable_if<is_base_but_not_same<T2, T>::value>::type>
344 operator handle<T2>& ()
346 return reinterpret_cast<handle<T2>&>(*this);
349 #endif /* OCCT_HANDLE_NOCAST */
351 #else /* fallback version for compilers not supporting default arguments of function templates (VC10, VC11, GCC below 4.3) */
353 #ifdef OCCT_HANDLE_NOCAST
355 //! Generalized copy constructor.
356 //! Constructs handle holding entity of base type (T) from the one which holds entity of derived type (T2).
358 handle (const handle<T2>& theHandle, typename std::enable_if <is_base_but_not_same <T, T2>::value>::type* = nullptr) :
359 entity(theHandle.entity)
364 #if(defined(_MSC_VER) && (_MSC_VER < 1600))
366 //! Generalized move constructor
368 handle (handle<T2>&& theHandle, typename std::enable_if <is_base_but_not_same <T, T2>::value>::type* = nullptr)
369 : entity(theHandle.entity)
371 theHandle.entity = 0;
375 //! Generalized assignment operator.
377 handle operator = (const handle<T2>& theHandle)
379 std::enable_if <is_base_but_not_same <T, T2>::value, void*>::type aTypeCheckHelperVar;
380 (void)aTypeCheckHelperVar;
381 Assign (theHandle.entity);
385 #if(defined(_MSC_VER) && (_MSC_VER < 1600))
387 //! Generalized move operator
389 handle& operator= (handle<T2>&& theHandle)
391 std::enable_if <is_base_but_not_same <T, T2>::value, void*>::type aTypeCheckHelperVar;
392 (void)aTypeCheckHelperVar;
393 std::swap (this->entity, theHandle.entity);
400 //! Upcast to const reference to base type.
401 //! NB: this implementation will cause ambiguity errors on calls to overloaded
402 //! functions accepting handles to different types, since compatibility is
403 //! checked in the cast code rather than ensured by SFINAE (possible with C++11)
405 operator const handle<T2>& () const
407 // error "type is not a member of enable_if" will be generated if T2 is not sub-type of T
408 // (handle is being cast to const& to handle of non-base type)
409 return reinterpret_cast<typename opencascade::std::enable_if<is_base_but_not_same<T2, T>::value, const handle<T2>&>::type>(*this);
412 //! Upcast to non-const reference to base type.
413 //! NB: this cast can be dangerous, but required for legacy code; see #26377
415 Standard_DEPRECATED("Passing non-const reference to handle of base type in function is unsafe; use variable of exact type")
416 operator handle<T2>& ()
418 // error "type is not a member of enable_if" will be generated if T2 is not sub-type of T
419 // (handle is being cast to const& to handle of non-base type)
420 return reinterpret_cast<typename opencascade::std::enable_if<is_base_but_not_same<T2, T>::value, handle<T2>&>::type>(*this);
423 #endif /* OCCT_HANDLE_NOCAST */
425 #endif /* compiler switch */
430 void Assign (Standard_Transient *thePtr)
432 if (thePtr == entity)
439 //! Increment reference counter of referred object
443 entity->IncrementRefCounter();
446 //! Decrement reference counter and if 0, destroy referred object
449 if (entity != 0 && entity->DecrementRefCounter() == 0)
454 template <class T2> friend class handle;
457 Standard_Transient* entity;
460 } // namespace opencascade
462 //! Define Handle() macro
463 #define Handle(Class) opencascade::handle<Class>
465 //! Global method HashCode(), for use in hash maps
467 inline Standard_Integer HashCode (const Handle(T)& theHandle, const Standard_Integer theUpper)
469 return ::HashCode (const_cast<Standard_Address>(static_cast<const void*>(theHandle.get())), theUpper);
472 //! For compatibility with previous versions of OCCT, define Handle_Class alias for opencascade::handle<Class>.
473 #if (defined(_MSC_VER) && _MSC_VER >= 1800)
474 //! For Visual Studio 2013+, define Handle_Class as non-template class to allow exporting this type in C++/CLI.
475 #define DEFINE_STANDARD_HANDLECLASS(C1,C2,BC) class C1; class Handle_##C1 : public Handle(C1) \
479 Handle_##C1(Handle(C1)&& theHandle) : Handle(C1)(theHandle) {} \
480 template <class T2, typename = typename std::enable_if <std::is_base_of <C1,T2>::value>::type> \
481 inline Handle_##C1(const opencascade::handle<T2>& theOther) : Handle(C1)(theOther) {} \
482 template <class T2, typename = typename std::enable_if <std::is_base_of <C1,T2>::value>::type> \
483 inline Handle_##C1(const T2* theOther) : Handle(C1)(theOther) {} \
484 template<typename T> inline Handle_##C1& operator=(T theOther) { Handle(C1)::operator=(theOther); return *this; } \
487 //! For other compilers, use simple typedef
488 #define DEFINE_STANDARD_HANDLECLASS(C1,C2,BC) class C1; typedef Handle(C1) Handle_##C1;
491 #define DEFINE_STANDARD_HANDLE(C1,C2) DEFINE_STANDARD_HANDLECLASS(C1,C2,Standard_Transient)
492 #define DEFINE_STANDARD_PHANDLE(C1,C2) DEFINE_STANDARD_HANDLECLASS(C1,C2,Standard_Persistent)