include/tools/weakbase.h

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  19 #ifndef INCLUDED_TOOLS_WEAKBASE_H
  20 #define INCLUDED_TOOLS_WEAKBASE_H
  21
  22 #include <sal/types.h>
  23 #include <rtl/ref.hxx>
  24 #include <tools/toolsdllapi.h>
  25
  26 /** the template classes in this header are helper to implement weak references
  27     to implementation objects that are not refcounted.
  28
  29     THIS IS NOT THREADSAFE
  30
  31     Use this only to have 'safe' pointers to implementation objects that you
  32     don't own but that you reference with a pointer.
  33
  34     Example:
  35
  36     class ImplClass : public tools::WeakBase< ImplClass >
  37     {
  38         ~ImplClass() { clearWeek(); } // not needed but safer, see method description
  39         ...
  40     };
  41
  42     class UserClass
  43     {
  44         tools::WeakReference< ImplClass > mxWeakRef;
  45
  46         UserClass( ImplClass* pObject ) : mxWeakRef( pObject ) {}
  47
  48         DoSomething()
  49         {
  50             if( mxWeakRef.is() )
  51                 mxWeakRef->DoSomethingMore();
  52         }
  53     };
  54 */
  55 namespace tools
  56 {
  57 class WeakBase;
  58
  59 /** private connection helper, do not use directly */
  60 struct WeakConnection
  61 {
  62     sal_Int32   mnRefCount;
  63     WeakBase*   mpReference;
  64
  65     WeakConnection() : mnRefCount( 0 ), mpReference( nullptr ) {};
  66     WeakConnection( WeakBase* pReference ) : mnRefCount( 0 ), mpReference( pReference ) {};
  67     void acquire() { mnRefCount++; }
  68     void release() { mnRefCount--; if( mnRefCount == 0 ) delete this; }
  69 };
  70
  71 /** template implementation to hold a weak reference to an instance of type reference_type */
  72 template <class reference_type>
  73 class SAL_WARN_UNUSED WeakReference
  74 {
  75 public:
  76     /** constructs an empty reference */
  77     inline WeakReference();
  78
  79     /** constructs a reference with a pointer to a class derived from WeakBase */
  80     inline WeakReference( reference_type* pReference );
  81
  82     /** constructs a reference from another reference */
  83     inline WeakReference( const WeakReference< reference_type >& rWeakRef );
  84
  85     /** move a reference from another reference */
  86     inline WeakReference( WeakReference< reference_type >&& rWeakRef );
  87
  88     /** returns true if the reference object is not null and still alive */
  89     inline bool is() const;
  90
  91     /** returns true if the reference object is not null and still alive */
  92     operator bool() const { return is(); }
  93
  94     /** returns the pointer to the reference object or null */
  95     inline reference_type * get() const;
  96
  97     /** sets this reference to the given object or null */
  98     inline void reset( reference_type* pReference );
  99
 100     /** resets this reference to null */
 101     inline void reset();
 102
 103     /** returns the pointer to the reference object or null */
 104     inline reference_type * operator->() const;
 105
 106     /** returns a ref to the reference object */
 107     inline reference_type& operator*() const;
 108
 109     /** returns true if this instance references pReferenceObject */
 110     inline bool operator== (const reference_type * pReferenceObject) const;
 111
 112     /** returns true if this instance and the given weakref reference the same object */
 113     inline bool operator== (const WeakReference<reference_type> & handle) const;
 114
 115     /** only needed for using this class with stl containers */
 116     inline bool operator!= (const WeakReference<reference_type> & handle) const;
 117
 118     /** only needed for using this class with stl containers */
 119     inline bool operator< (const WeakReference<reference_type> & handle) const;
 120
 121     /** only needed for using this class with stl containers */
 122     inline bool operator> (const WeakReference<reference_type> & handle) const;
 123
 124     /** the assignment operator */
 125     inline WeakReference<reference_type>& operator= (const WeakReference<reference_type> & handle);
 126
 127     /** the move assignment operator */
 128     inline WeakReference<reference_type>& operator= (WeakReference<reference_type> && handle);
 129
 130 private:
 131     rtl::Reference<WeakConnection> mpWeakConnection;
 132 };
 133
 134 /** derive your implementation classes from this class if you want them to support weak references */
 135 class TOOLS_DLLPUBLIC WeakBase
 136 {
 137     template<typename T> friend class WeakReference;
 138
 139 public:
 140     WeakBase() {}
 141     virtual ~WeakBase();
 142     /** clears the reference pointer in all living weak references for this instance.
 143         Further created weak references will also be invalid.
 144         You should call this method in the d'tor of your derived classes for an early
 145         invalidate of all living weak references while your object is already inside
 146         it d'tor.
 147     */
 148     inline void clearWeak();
 149
 150 private:
 151     inline WeakConnection* getWeakConnection();
 152     rtl::Reference<WeakConnection> mpWeakConnection;
 153 };
 154
 155 }
 156
 157 #endif
 158
 159 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */