src/common/Ref.h

/*
 * Copyright (c) 2014 - 2020 Christian Schoenebeck
 *
 * http://www.linuxsampler.org
 *
 * This file is part of LinuxSampler and released under the same terms.
 * See README file for details.
 */

#ifndef LS_REF_H
#define LS_REF_H

#include "global.h"

#include <set>
#include <stdio.h>
#if __cplusplus >= 201103L && !CONFIG_NO_CPP11STL
# include <type_traits> // for std::enable_if and std::is_same
#endif

// You may enable this while developing or at least when you encounter any kind
// of crashes or other misbehaviors in conjunction with Ref class guarded code.
// Enabling the following macro will add a bunch of sanity checks for easing
// debugging of such issues, however it comes with the cost that everything will
// be much slower.
#define LS_REF_ASSERT_MODE 0

// Enable this for VERY verbose debug messages for debugging deep issues with
// Ref class.
#define LS_REF_VERBOSE_DEBUG_MSG 0

#if LS_REF_ASSERT_MODE
# warning LS_REF_ASSERT_MODE is enabled which will decrease runtime efficiency!
# include <assert.h>
#endif

// Whether the Ref<> class shall be thread safe. Performance penalty should not
// be measurable in practice due to non blocking, lock-free atomic add, sub and
// CAS instructions being used, so this is recommended and enabled by default.
#ifndef LS_REF_ATOMIC
# define LS_REF_ATOMIC 1
#endif

//NOTE: We are using our own atomic implementation instead of std::atomic of the
// C++ STL, because our atomic implementation is lock-free and wait-free. The
// C++ standard just recommends, but does not guarantee lock-free implementation
// (state of the C++20 standard as of 2020-04-27):
// https://en.cppreference.com/w/cpp/atomic/atomic/is_lock_free
#if LS_REF_ATOMIC
# include "atomic.h"
# include <stdatomic.h>
# if __STDC_NO_ATOMICS__
#  undef LS_REF_ATOMIC
#  warning Ref<> class will not be thread safe, since compiler does not support C11 atomics!
# endif
#else
# warning Ref<> class will not be thread safe (feature explicitly disabled)!
#endif

#if LS_REF_ASSERT_MODE && LS_REF_ATOMIC
# include "Mutex.h"
#endif

namespace LinuxSampler {

    template<typename T, typename T_BASE> class Ref;

    #if LS_REF_ASSERT_MODE
    extern std::set<void*> _allRefPtrs;
    #endif
    #if LS_REF_ASSERT_MODE && LS_REF_ATOMIC
    extern Mutex _allRefPtrsMutex;
    #endif

    /**
     * Exists just for implementation detail purpose, you cannot use it
     * directly. Use its derived template class Ref instead.
     *
     * @see Ref
     */
    template<typename T_BASE>
    class RefBase {
    public:
        template<typename T_BASE1>
        class _RefCounter {
        public:
            _RefCounter(T_BASE1* p, int refs, bool released) :
                #if LS_REF_ATOMIC
                references(ATOMIC_INIT(refs)),
                #else
                references(refs),
                #endif
                ptr(p)
            {
                #if LS_REF_ATOMIC
                atomic_store(&zombi, released);
                #endif
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p: new counter (refs=%d)\n", ptr,
                    #if LS_REF_ATOMIC
                       atomic_read(&references)
                    #else
                       references
                    #endif
                );
                #endif
                #if LS_REF_ASSERT_MODE
                assert(p);
                assert(refs > 0);
                assert(!released);
                {
                    #if LS_REF_ATOMIC
                    LockGuard lock(_allRefPtrsMutex);
                    #endif
                    assert(!_allRefPtrs.count(p));
                    _allRefPtrs.insert(p);
                }
                #endif
            }

            virtual ~_RefCounter() {
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p: counter destructor (refs=%d)\n", ptr,
                    #if LS_REF_ATOMIC
                       atomic_read(&references)
                    #else
                       references
                    #endif
                );
                #endif
                fflush(stdout);
            }

            void retain() {
                #if LS_REF_ATOMIC
                atomic_inc(&references);
                #else
                references++;
                #endif
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p: retain (refs=%d)\n", ptr,
                    #if LS_REF_ATOMIC
                       atomic_read(&references)
                    #else
                       references
                    #endif
                );
                #endif
            }

            void release() {
                #if LS_REF_ATOMIC
                bool zero = atomic_dec_and_test(&references);
                # if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p: release (zero=%d)\n", ptr, zero);
                # endif
                if (!zero) return;
                bool expect = false;
                bool release = atomic_compare_exchange_strong(&zombi, &expect, true);
                if (release) deletePtr();
                #else
                if (!references) return;
                references--;
                # if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p: release (refs=%d)\n", ptr, references);
                # endif
                if (!references) deletePtr();
                #endif // LS_REF_ATOMIC
            }
        //protected:
            void deletePtr() {
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("RefCounter %p: deletePtr() (refs=%d)\n", ptr,
                    #if LS_REF_ATOMIC
                       atomic_read(&references)
                    #else
                       references
                    #endif
                );
                #endif
                #if LS_REF_ASSERT_MODE
                # if LS_REF_ATOMIC
                assert(!atomic_read(&references));
                # else
                assert(!references);
                # endif
                {
                    #if LS_REF_ATOMIC
                    LockGuard lock(_allRefPtrsMutex);
                    #endif
                    _allRefPtrs.erase(ptr);
                }
                #endif
                delete ptr;
                delete this;
            }

            #if LS_REF_ATOMIC
            atomic_t references;
            atomic_bool zombi; ///< @c false if not released yet, @c true once @c ptr was released
            #else
            int references;
            #endif
            T_BASE1* ptr;
            //friend class ... todo
        };
        typedef _RefCounter<T_BASE> RefCounter;

        virtual ~RefBase() {
            if (refCounter) refCounter->release();
            refCounter = NULL;
        }

    //protected:
        RefCounter* refCounter;
        //friend class Ref<T_BASE, T_BASE>;

    protected:
        RefBase() : refCounter(NULL) {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("(RefBase empty ctor)\n");
            #endif
        }
/*
        RefBase(RefCounter* rc) {
            refCounter = rc;
        }

        RefBase(const RefBase& r) {
            refCounter = r.refCounter;
            if (refCounter) refCounter->retain();
        }
*/
    };

    /**
     * Replicates a std::shared_ptr template class. Originally this class was
     * introduced to avoid a build requirement of having a C++11 compliant
     * compiler (std::shared_ptr was not part of the C++03 standard). This class
     * had been preserved though due to some advantages over the STL
     * implementation, most notably: unlike std::shared_ptr from the STL, this
     * Ref<> class provides thread safety by using a (guaranteed) lock-free and
     * wait-free implementation, which is relevant for real-time applications.
     *
     * In contrast to the STL implementation though this implementation here
     * also supports copying references of derived, different types (in a type
     * safe manner). You can achieve that by providing a second template
     * argument (which is optional), for declaring a common subtype. For example
     * the following code would not compile:
     * @code
     * void example(UILabel* pLabel) {
     *     Ref<UILabel> lbl = pLabel;
     *     Ref<UIWidget> w = lbl; // compile error, incompatible Ref types
     *     w->resize(16,300);
     * }
     * @endcode
     * Whereas the following would work:
     * @code
     * void example(UILabel* pLabel) {
     *     Ref<UILabel,UIWidget> lbl = pLabel;
     *     Ref<UIWidget> w = lbl; // works (assuming that UILabel is a subclass of UIWidget)
     *     w->resize(16,300);
     * }
     * @endcode
     * Like the STL's std::shared_ptr, this class also emulates raw pointer
     * access and operators. With one addition: if used in the derived common
     * subtype manner as shown above, access to the actual data and boolean
     * operator will also check whether the underlying pointer (of the common
     * subclass) can actually be casted safely to the objects main type (first
     * template argument of this class). For example:
     * @code
     * void example(UILabel* pLabel) { // assuming pLabel is not NULL ...
     *     Ref<UILabel,UIWidget> lbl = pLabel;
     *     Ref<UIDialog,UIWidget> dlg = lbl;
     *     bool b1 = lbl; // will be true (assuming pLabel was not NULL)
     *     bool b2 = dlg; // will be false (assuming that UIDialog is not derived from UILabel)
     *     lbl->setText("foo"); // works
     *     dlg->showModal(); // would crash with -> operator providing a NULL pointer
     * }
     * @endcode
     * Like with std::shared_ptr you must be @b very cautious that you
     * initialize only one Ref class object directly with the same raw pointer.
     * If you forget this fundamental rule somewhere, your code will crash!
     * @code
     * UIWidget* ptr = new UIWidget();
     * Ref<UIWidget> w1 = ptr;
     * Ref<UIWidget> w2 = w1;  // this is OK, copy from a Ref object
     * Ref<UIWidget> w3 = ptr; // illegal! 2nd direct init from same raw pointer. This will crash!
     * @endcode
     * It would be possible to write an implementation of the Ref class that
     * could handle the case above as well without crashing, however it would be
     * too slow for practice. Because it would require a global lookup table
     * maintaining all memory pointers which are currently already guarded by
     * this class. Plus it would need an expensive synchronization to prevent
     * concurrent access on that global lookup table.
     */
    template<typename T, typename T_BASE = T>
    class Ref : public RefBase<T_BASE> {
    public:
        typedef RefBase<T_BASE> RefBaseT;
        typedef typename RefBase<T_BASE>::RefCounter RefCounter;
        
        Ref() : RefBaseT() {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref empty ctor Ref:%p\n", this);
            #endif
        }

        #if __cplusplus >= 201103L && !CONFIG_NO_CPP11STL
        template<std::enable_if<!std::is_same<T_BASE, T>::value>* = NULL> // prevent compiler error if T == T_Base (due to method signature duplicate)
        #endif
        Ref(const T_BASE* p) : RefBaseT() {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref base ptr ctor Ref:%p <- p:%p\n", this, p);
            #endif
            RefBaseT::refCounter = p ? new RefCounter((T_BASE*)p, 1, false) : NULL;
        }

        Ref(const T* p) : RefBaseT() {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref main ptr ctor Ref:%p <- p:%p\n", this, p);
            #endif
            RefBaseT::refCounter = p ? new RefCounter((T*)p, 1, false) : NULL;
        }

        Ref(const RefBaseT& r) : RefBaseT() {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref base ref ctor Ref:%p <- Ref:%p\n", this, &r);
            #endif
            RefBaseT::refCounter = r.refCounter;
            if (RefBaseT::refCounter)
                RefBaseT::refCounter->retain();
        }

        Ref(const Ref& r) : RefBaseT() {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref main ref ctor Ref:%p <- Ref:%p\n", this, &r);
            #endif
            RefBaseT::refCounter = r.refCounter;
            if (RefBaseT::refCounter)
                RefBaseT::refCounter->retain();
        }

        inline T* operator->() {
            return dynamic_cast<T*>( RefBaseT::refCounter->ptr );
        }

        inline const T* operator->() const {
            return dynamic_cast<const T*>( RefBaseT::refCounter->ptr );
        }

        inline T& operator*() {
            return *dynamic_cast<T*>( RefBaseT::refCounter->ptr );
        }

        inline const T& operator*() const {
            return *dynamic_cast<const T*>( RefBaseT::refCounter->ptr );
        }

        inline bool operator==(const RefBaseT& other) const {
            return RefBaseT::refCounter == other.refCounter;
        }

        inline bool operator!=(const RefBaseT& other) const {
            return RefBaseT::refCounter != other.refCounter;
        }

        inline operator bool() const {
            return RefBaseT::refCounter && RefBaseT::refCounter->ptr &&
                   dynamic_cast<const T*>( RefBaseT::refCounter->ptr );
        }

        inline bool operator!() const {
            return !( RefBaseT::refCounter && RefBaseT::refCounter->ptr &&
                      dynamic_cast<const T*>( RefBaseT::refCounter->ptr ) );
        }

/*
        inline operator RefBaseT&() {
            return *this;
        }
        
        inline operator const RefBaseT&() const {
            return *this;
        }
*/
        inline bool isEquivalent(const RefBaseT& other) const {
            if (static_cast<const RefBaseT*>(this) == &other)
                return true;
            return (RefBaseT::refCounter == other.refCounter);
        }

        inline bool isEquivalent(const T_BASE* const other) const {
            if (!other) return !RefBaseT::refCounter;
            if (!RefBaseT::refCounter) return false;
            return other == RefBaseT::refCounter->ptr;
        }

        Ref<T,T_BASE>& operator=(const RefBaseT& other) {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref base ref assignment Ref:%p <- Ref:%p\n", this, &other);
            #endif
            if (isEquivalent(other)) {
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p WRN: equivalent ref assignment ignored.\n", this);
                #endif
                return *this;
            }
            if (RefBaseT::refCounter) {
                RefBaseT::refCounter->release();
                RefBaseT::refCounter = NULL;
            }
            RefBaseT::refCounter = other.refCounter;
            if (RefBaseT::refCounter)
                RefBaseT::refCounter->retain();
            return *this;
        }

        Ref<T,T_BASE>& operator=(const Ref<T,T_BASE>& other) {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref main ref assignment Ref:%p <- Ref:%p\n", this, &other);
            #endif
            if (isEquivalent(other)) {
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p WRN: equivalent ref assignment ignored.\n", this);
                #endif
                return *this;
            }
            if (RefBaseT::refCounter) {
                RefBaseT::refCounter->release();
                RefBaseT::refCounter = NULL;
            }
            RefBaseT::refCounter = other.refCounter;
            if (RefBaseT::refCounter)
                RefBaseT::refCounter->retain();
            return *this;
        }

        Ref<T,T_BASE>& operator=(const T* p) {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref main ptr assignment Ref:%p <- p:%p\n", this, p);
            #endif
            if (isEquivalent(p)) {
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p WRN: equivalent ptr assignment ignored.\n", this);
                #endif
                return *this;
            }
            if (RefBaseT::refCounter) {
                RefBaseT::refCounter->release();
                RefBaseT::refCounter = NULL;
            }
            RefBaseT::refCounter = p ? new RefCounter((T*)p, 1, false) : NULL;
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref main ptr assignment done\n");
            #endif
            return *this;
        }

        #if __cplusplus >= 201103L && !CONFIG_NO_CPP11STL
        template<std::enable_if<!std::is_same<T_BASE, T>::value>* = NULL> // prevent compiler error if T == T_Base (due to method signature duplicate)
        #endif
        Ref<T,T_BASE>& operator=(const T_BASE* p) {
            #if LS_REF_VERBOSE_DEBUG_MSG
            printf("Ref base ptr assignment Ref:%p <- p:%p\n", this, p);
            #endif
            if (isEquivalent(p)) {
                #if LS_REF_VERBOSE_DEBUG_MSG
                printf("Ref %p WRN: equivalent ptr assignment ignored.\n", this);
                #endif
                return *this;
            }
            if (RefBaseT::refCounter) {
                RefBaseT::refCounter->release();
                RefBaseT::refCounter = NULL;
            }
            RefBaseT::refCounter = p ? new RefCounter((T*)p, 1, false) : NULL;
            return *this;
        }
    };

} // namespace LinuxSampler

#endif // LS_REF_H
1	schoenebeck	2581	/*
2	schoenebeck	3767	* Copyright (c) 2014 - 2020 Christian Schoenebeck
3	schoenebeck	2581	*
4			* http://www.linuxsampler.org
5			*
6			* This file is part of LinuxSampler and released under the same terms.
7			* See README file for details.
8			*/
9
10			#ifndef LS_REF_H
11			#define LS_REF_H
12
13	schoenebeck	3768	#include "global.h"
14
15	schoenebeck	2581	#include <set>
16			#include <stdio.h>
17	schoenebeck	3767	#if __cplusplus >= 201103L && !CONFIG_NO_CPP11STL
18			# include <type_traits> // for std::enable_if and std::is_same
19			#endif
20	schoenebeck	2581
21			// You may enable this while developing or at least when you encounter any kind
22			// of crashes or other misbehaviors in conjunction with Ref class guarded code.
23			// Enabling the following macro will add a bunch of sanity checks for easing
24			// debugging of such issues, however it comes with the cost that everything will
25			// be much slower.
26	schoenebeck	2619	#define LS_REF_ASSERT_MODE 0
27	schoenebeck	2581
28	schoenebeck	3768	// Enable this for VERY verbose debug messages for debugging deep issues with
29	schoenebeck	2581	// Ref class.
30			#define LS_REF_VERBOSE_DEBUG_MSG 0
31
32			#if LS_REF_ASSERT_MODE
33	schoenebeck	3768	# warning LS_REF_ASSERT_MODE is enabled which will decrease runtime efficiency!
34	schoenebeck	2581	# include <assert.h>
35			#endif
36
37	schoenebeck	3768	// Whether the Ref<> class shall be thread safe. Performance penalty should not
38			// be measurable in practice due to non blocking, lock-free atomic add, sub and
39			// CAS instructions being used, so this is recommended and enabled by default.
40			#ifndef LS_REF_ATOMIC
41			# define LS_REF_ATOMIC 1
42			#endif
43
44			//NOTE: We are using our own atomic implementation instead of std::atomic of the
45			// C++ STL, because our atomic implementation is lock-free and wait-free. The
46			// C++ standard just recommends, but does not guarantee lock-free implementation
47			// (state of the C++20 standard as of 2020-04-27):
48			// https://en.cppreference.com/w/cpp/atomic/atomic/is_lock_free
49			#if LS_REF_ATOMIC
50			# include "atomic.h"
51			# include <stdatomic.h>
52			# if __STDC_NO_ATOMICS__
53			# undef LS_REF_ATOMIC
54			# warning Ref<> class will not be thread safe, since compiler does not support C11 atomics!
55			# endif
56			#else
57			# warning Ref<> class will not be thread safe (feature explicitly disabled)!
58			#endif
59
60			#if LS_REF_ASSERT_MODE && LS_REF_ATOMIC
61			# include "Mutex.h"
62			#endif
63
64	schoenebeck	2581	namespace LinuxSampler {
65
66			template<typename T, typename T_BASE> class Ref;
67
68	schoenebeck	3768	#if LS_REF_ASSERT_MODE
69	schoenebeck	2581	extern std::set<void*> _allRefPtrs;
70	schoenebeck	3768	#endif
71			#if LS_REF_ASSERT_MODE && LS_REF_ATOMIC
72			extern Mutex _allRefPtrsMutex;
73			#endif
74	schoenebeck	2581
75			/**
76			* Exists just for implementation detail purpose, you cannot use it
77			* directly. Use its derived template class Ref instead.
78			*
79			* @see Ref
80			*/
81			template<typename T_BASE>
82			class RefBase {
83			public:
84			template<typename T_BASE1>
85			class _RefCounter {
86			public:
87	schoenebeck	3768	_RefCounter(T_BASE1* p, int refs, bool released) :
88			#if LS_REF_ATOMIC
89			references(ATOMIC_INIT(refs)),
90			#else
91			references(refs),
92			#endif
93			ptr(p)
94	schoenebeck	2581	{
95	schoenebeck	3768	#if LS_REF_ATOMIC
96			atomic_store(&zombi, released);
97			#endif
98	schoenebeck	2581	#if LS_REF_VERBOSE_DEBUG_MSG
99	schoenebeck	3768	printf("Ref %p: new counter (refs=%d)\n", ptr,
100			#if LS_REF_ATOMIC
101			atomic_read(&references)
102			#else
103			references
104			#endif
105			);
106	schoenebeck	2581	#endif
107			#if LS_REF_ASSERT_MODE
108			assert(p);
109			assert(refs > 0);
110	schoenebeck	3768	assert(!released);
111			{
112			#if LS_REF_ATOMIC
113			LockGuard lock(_allRefPtrsMutex);
114			#endif
115			assert(!_allRefPtrs.count(p));
116			_allRefPtrs.insert(p);
117			}
118	schoenebeck	2581	#endif
119			}
120
121			virtual ~_RefCounter() {
122			#if LS_REF_VERBOSE_DEBUG_MSG
123	schoenebeck	3768	printf("Ref %p: counter destructor (refs=%d)\n", ptr,
124			#if LS_REF_ATOMIC
125			atomic_read(&references)
126			#else
127			references
128			#endif
129			);
130	schoenebeck	2581	#endif
131			fflush(stdout);
132			}
133
134			void retain() {
135	schoenebeck	3768	#if LS_REF_ATOMIC
136			atomic_inc(&references);
137			#else
138	schoenebeck	2581	references++;
139	schoenebeck	3768	#endif
140	schoenebeck	2581	#if LS_REF_VERBOSE_DEBUG_MSG
141	schoenebeck	3768	printf("Ref %p: retain (refs=%d)\n", ptr,
142			#if LS_REF_ATOMIC
143			atomic_read(&references)
144			#else
145			references
146			#endif
147			);
148	schoenebeck	2581	#endif
149			}
150
151			void release() {
152	schoenebeck	3768	#if LS_REF_ATOMIC
153			bool zero = atomic_dec_and_test(&references);
154			# if LS_REF_VERBOSE_DEBUG_MSG
155			printf("Ref %p: release (zero=%d)\n", ptr, zero);
156			# endif
157			if (!zero) return;
158			bool expect = false;
159			bool release = atomic_compare_exchange_strong(&zombi, &expect, true);
160			if (release) deletePtr();
161			#else
162	schoenebeck	2581	if (!references) return;
163			references--;
164	schoenebeck	3768	# if LS_REF_VERBOSE_DEBUG_MSG
165			printf("Ref %p: release (refs=%d)\n", ptr, references);
166			# endif
167	schoenebeck	2581	if (!references) deletePtr();
168	schoenebeck	3768	#endif // LS_REF_ATOMIC
169	schoenebeck	2581	}
170			//protected:
171			void deletePtr() {
172			#if LS_REF_VERBOSE_DEBUG_MSG
173	schoenebeck	3768	printf("RefCounter %p: deletePtr() (refs=%d)\n", ptr,
174			#if LS_REF_ATOMIC
175			atomic_read(&references)
176			#else
177			references
178			#endif
179			);
180	schoenebeck	2581	#endif
181			#if LS_REF_ASSERT_MODE
182	schoenebeck	3768	# if LS_REF_ATOMIC
183			assert(!atomic_read(&references));
184			# else
185	schoenebeck	2581	assert(!references);
186	schoenebeck	3768	# endif
187			{
188			#if LS_REF_ATOMIC
189			LockGuard lock(_allRefPtrsMutex);
190			#endif
191			_allRefPtrs.erase(ptr);
192			}
193	schoenebeck	2581	#endif
194			delete ptr;
195			delete this;
196			}
197
198	schoenebeck	3768	#if LS_REF_ATOMIC
199			atomic_t references;
200			atomic_bool zombi; ///< @c false if not released yet, @c true once @c ptr was released
201			#else
202	schoenebeck	2581	int references;
203	schoenebeck	3768	#endif
204	schoenebeck	2581	T_BASE1* ptr;
205			//friend class ... todo
206			};
207			typedef _RefCounter<T_BASE> RefCounter;
208
209			virtual ~RefBase() {
210			if (refCounter) refCounter->release();
211			refCounter = NULL;
212			}
213
214			//protected:
215			RefCounter* refCounter;
216			//friend class Ref<T_BASE, T_BASE>;
217
218			protected:
219			RefBase() : refCounter(NULL) {
220			#if LS_REF_VERBOSE_DEBUG_MSG
221			printf("(RefBase empty ctor)\n");
222			#endif
223			}
224			/*
225			RefBase(RefCounter* rc) {
226			refCounter = rc;
227			}
228
229			RefBase(const RefBase& r) {
230			refCounter = r.refCounter;
231			if (refCounter) refCounter->retain();
232			}
233			*/
234			};
235
236			/**
237	schoenebeck	3768	* Replicates a std::shared_ptr template class. Originally this class was
238			* introduced to avoid a build requirement of having a C++11 compliant
239			* compiler (std::shared_ptr was not part of the C++03 standard). This class
240			* had been preserved though due to some advantages over the STL
241			* implementation, most notably: unlike std::shared_ptr from the STL, this
242			* Ref<> class provides thread safety by using a (guaranteed) lock-free and
243			* wait-free implementation, which is relevant for real-time applications.
244	schoenebeck	2581	*
245			* In contrast to the STL implementation though this implementation here
246			* also supports copying references of derived, different types (in a type
247			* safe manner). You can achieve that by providing a second template
248			* argument (which is optional), for declaring a common subtype. For example
249			* the following code would not compile:
250			* @code
251			* void example(UILabel* pLabel) {
252			* Ref<UILabel> lbl = pLabel;
253			* Ref<UIWidget> w = lbl; // compile error, incompatible Ref types
254			* w->resize(16,300);
255			* }
256			* @endcode
257			* Whereas the following would work:
258			* @code
259			* void example(UILabel* pLabel) {
260			* Ref<UILabel,UIWidget> lbl = pLabel;
261			* Ref<UIWidget> w = lbl; // works (assuming that UILabel is a subclass of UIWidget)
262			* w->resize(16,300);
263			* }
264			* @endcode
265			* Like the STL's std::shared_ptr, this class also emulates raw pointer
266			* access and operators. With one addition: if used in the derived common
267			* subtype manner as shown above, access to the actual data and boolean
268			* operator will also check whether the underlying pointer (of the common
269			* subclass) can actually be casted safely to the objects main type (first
270			* template argument of this class). For example:
271			* @code
272			* void example(UILabel* pLabel) { // assuming pLabel is not NULL ...
273			* Ref<UILabel,UIWidget> lbl = pLabel;
274			* Ref<UIDialog,UIWidget> dlg = lbl;
275			* bool b1 = lbl; // will be true (assuming pLabel was not NULL)
276			* bool b2 = dlg; // will be false (assuming that UIDialog is not derived from UILabel)
277			* lbl->setText("foo"); // works
278			* dlg->showModal(); // would crash with -> operator providing a NULL pointer
279			* }
280			* @endcode
281			* Like with std::shared_ptr you must be @b very cautious that you
282			* initialize only one Ref class object directly with the same raw pointer.
283			* If you forget this fundamental rule somewhere, your code will crash!
284			* @code
285			* UIWidget* ptr = new UIWidget();
286			* Ref<UIWidget> w1 = ptr;
287			* Ref<UIWidget> w2 = w1; // this is OK, copy from a Ref object
288			* Ref<UIWidget> w3 = ptr; // illegal! 2nd direct init from same raw pointer. This will crash!
289			* @endcode
290			* It would be possible to write an implementation of the Ref class that
291			* could handle the case above as well without crashing, however it would be
292			* too slow for practice. Because it would require a global lookup table
293			* maintaining all memory pointers which are currently already guarded by
294			* this class. Plus it would need an expensive synchronization to prevent
295			* concurrent access on that global lookup table.
296			*/
297			template<typename T, typename T_BASE = T>
298			class Ref : public RefBase<T_BASE> {
299			public:
300			typedef RefBase<T_BASE> RefBaseT;
301			typedef typename RefBase<T_BASE>::RefCounter RefCounter;
302
303			Ref() : RefBaseT() {
304			#if LS_REF_VERBOSE_DEBUG_MSG
305	schoenebeck	3768	printf("Ref empty ctor Ref:%p\n", this);
306	schoenebeck	2581	#endif
307			}
308
309	schoenebeck	3767	#if __cplusplus >= 201103L && !CONFIG_NO_CPP11STL
310			template<std::enable_if<!std::is_same<T_BASE, T>::value>* = NULL> // prevent compiler error if T == T_Base (due to method signature duplicate)
311			#endif
312	schoenebeck	2581	Ref(const T_BASE* p) : RefBaseT() {
313			#if LS_REF_VERBOSE_DEBUG_MSG
314	schoenebeck	3768	printf("Ref base ptr ctor Ref:%p <- p:%p\n", this, p);
315	schoenebeck	2581	#endif
316	schoenebeck	3768	RefBaseT::refCounter = p ? new RefCounter((T_BASE*)p, 1, false) : NULL;
317	schoenebeck	2581	}
318
319			Ref(const T* p) : RefBaseT() {
320			#if LS_REF_VERBOSE_DEBUG_MSG
321	schoenebeck	3768	printf("Ref main ptr ctor Ref:%p <- p:%p\n", this, p);
322	schoenebeck	2581	#endif
323	schoenebeck	3768	RefBaseT::refCounter = p ? new RefCounter((T*)p, 1, false) : NULL;
324	schoenebeck	2581	}
325
326			Ref(const RefBaseT& r) : RefBaseT() {
327			#if LS_REF_VERBOSE_DEBUG_MSG
328	schoenebeck	3768	printf("Ref base ref ctor Ref:%p <- Ref:%p\n", this, &r);
329	schoenebeck	2581	#endif
330			RefBaseT::refCounter = r.refCounter;
331			if (RefBaseT::refCounter)
332			RefBaseT::refCounter->retain();
333			}
334
335			Ref(const Ref& r) : RefBaseT() {
336			#if LS_REF_VERBOSE_DEBUG_MSG
337	schoenebeck	3768	printf("Ref main ref ctor Ref:%p <- Ref:%p\n", this, &r);
338	schoenebeck	2581	#endif
339			RefBaseT::refCounter = r.refCounter;
340			if (RefBaseT::refCounter)
341			RefBaseT::refCounter->retain();
342			}
343
344			inline T* operator->() {
345			return dynamic_cast<T*>( RefBaseT::refCounter->ptr );
346			}
347
348			inline const T* operator->() const {
349			return dynamic_cast<const T*>( RefBaseT::refCounter->ptr );
350			}
351
352			inline T& operator*() {
353			return dynamic_cast<T>( RefBaseT::refCounter->ptr );
354			}
355
356			inline const T& operator*() const {
357			return dynamic_cast<const T>( RefBaseT::refCounter->ptr );
358			}
359
360			inline bool operator==(const RefBaseT& other) const {
361			return RefBaseT::refCounter == other.refCounter;
362			}
363
364			inline bool operator!=(const RefBaseT& other) const {
365			return RefBaseT::refCounter != other.refCounter;
366			}
367
368			inline operator bool() const {
369			return RefBaseT::refCounter && RefBaseT::refCounter->ptr &&
370			dynamic_cast<const T*>( RefBaseT::refCounter->ptr );
371			}
372
373			inline bool operator!() const {
374			return !( RefBaseT::refCounter && RefBaseT::refCounter->ptr &&
375			dynamic_cast<const T*>( RefBaseT::refCounter->ptr ) );
376			}
377
378			/*
379			inline operator RefBaseT&() {
380			return *this;
381			}
382
383			inline operator const RefBaseT&() const {
384			return *this;
385			}
386			*/
387			inline bool isEquivalent(const RefBaseT& other) const {
388			if (static_cast<const RefBaseT*>(this) == &other)
389			return true;
390			return (RefBaseT::refCounter == other.refCounter);
391			}
392
393			inline bool isEquivalent(const T_BASE* const other) const {
394			if (!other) return !RefBaseT::refCounter;
395			if (!RefBaseT::refCounter) return false;
396			return other == RefBaseT::refCounter->ptr;
397			}
398
399			Ref<T,T_BASE>& operator=(const RefBaseT& other) {
400			#if LS_REF_VERBOSE_DEBUG_MSG
401	schoenebeck	3768	printf("Ref base ref assignment Ref:%p <- Ref:%p\n", this, &other);
402	schoenebeck	2581	#endif
403			if (isEquivalent(other)) {
404			#if LS_REF_VERBOSE_DEBUG_MSG
405	schoenebeck	3768	printf("Ref %p WRN: equivalent ref assignment ignored.\n", this);
406	schoenebeck	2581	#endif
407			return *this;
408			}
409			if (RefBaseT::refCounter) {
410			RefBaseT::refCounter->release();
411			RefBaseT::refCounter = NULL;
412			}
413			RefBaseT::refCounter = other.refCounter;
414			if (RefBaseT::refCounter)
415			RefBaseT::refCounter->retain();
416			return *this;
417			}
418
419			Ref<T,T_BASE>& operator=(const Ref<T,T_BASE>& other) {
420			#if LS_REF_VERBOSE_DEBUG_MSG
421	schoenebeck	3768	printf("Ref main ref assignment Ref:%p <- Ref:%p\n", this, &other);
422	schoenebeck	2581	#endif
423			if (isEquivalent(other)) {
424			#if LS_REF_VERBOSE_DEBUG_MSG
425	schoenebeck	3768	printf("Ref %p WRN: equivalent ref assignment ignored.\n", this);
426	schoenebeck	2581	#endif
427			return *this;
428			}
429			if (RefBaseT::refCounter) {
430			RefBaseT::refCounter->release();
431			RefBaseT::refCounter = NULL;
432			}
433			RefBaseT::refCounter = other.refCounter;
434			if (RefBaseT::refCounter)
435			RefBaseT::refCounter->retain();
436			return *this;
437			}
438
439			Ref<T,T_BASE>& operator=(const T* p) {
440			#if LS_REF_VERBOSE_DEBUG_MSG
441	schoenebeck	3768	printf("Ref main ptr assignment Ref:%p <- p:%p\n", this, p);
442	schoenebeck	2581	#endif
443			if (isEquivalent(p)) {
444			#if LS_REF_VERBOSE_DEBUG_MSG
445	schoenebeck	3768	printf("Ref %p WRN: equivalent ptr assignment ignored.\n", this);
446	schoenebeck	2581	#endif
447			return *this;
448			}
449			if (RefBaseT::refCounter) {
450			RefBaseT::refCounter->release();
451			RefBaseT::refCounter = NULL;
452			}
453	schoenebeck	3768	RefBaseT::refCounter = p ? new RefCounter((T*)p, 1, false) : NULL;
454	schoenebeck	2581	#if LS_REF_VERBOSE_DEBUG_MSG
455			printf("Ref main ptr assignment done\n");
456			#endif
457			return *this;
458			}
459
460	schoenebeck	3767	#if __cplusplus >= 201103L && !CONFIG_NO_CPP11STL
461			template<std::enable_if<!std::is_same<T_BASE, T>::value>* = NULL> // prevent compiler error if T == T_Base (due to method signature duplicate)
462			#endif
463	schoenebeck	2581	Ref<T,T_BASE>& operator=(const T_BASE* p) {
464			#if LS_REF_VERBOSE_DEBUG_MSG
465	schoenebeck	3768	printf("Ref base ptr assignment Ref:%p <- p:%p\n", this, p);
466	schoenebeck	2581	#endif
467			if (isEquivalent(p)) {
468			#if LS_REF_VERBOSE_DEBUG_MSG
469	schoenebeck	3768	printf("Ref %p WRN: equivalent ptr assignment ignored.\n", this);
470	schoenebeck	2581	#endif
471			return *this;
472			}
473			if (RefBaseT::refCounter) {
474			RefBaseT::refCounter->release();
475			RefBaseT::refCounter = NULL;
476			}
477	schoenebeck	3768	RefBaseT::refCounter = p ? new RefCounter((T*)p, 1, false) : NULL;
478	schoenebeck	2581	return *this;
479			}
480			};
481
482			} // namespace LinuxSampler
483
484			#endif // LS_REF_H