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* pOjbect ) : 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 the pointer to the reference object or null */
  92     inline reference_type * get() const;
  93
  94     /** sets this reference to the given object or null */
  95     inline void reset( reference_type* pReference );
  96
  97     /** resets this reference to null */
  98     inline void reset();
  99
 100     /** returns the pointer to the reference object or null */
 101     inline reference_type * operator->() const;
 102
 103     /** returns true if this instance references pReferenceObject */
 104     inline bool operator== (const reference_type * pReferenceObject) const;
 105
 106     /** returns true if this instance and the given weakref reference the same object */
 107     inline bool operator== (const WeakReference<reference_type> & handle) const;
 108
 109     /** only needed for using this class with stl containers */
 110     inline bool operator!= (const WeakReference<reference_type> & handle) const;
 111
 112     /** only needed for using this class with stl containers */
 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     /** the assignment operator */
 119     inline WeakReference<reference_type>& operator= (const WeakReference<reference_type> & handle);
 120
 121     /** the move assignment operator */
 122     inline WeakReference<reference_type>& operator= (WeakReference<reference_type> && handle);
 123
 124 private:
 125     rtl::Reference<WeakConnection> mpWeakConnection;
 126 };
 127
 128 /** derive your implementation classes from this class if you want them to support weak references */
 129 class TOOLS_DLLPUBLIC WeakBase
 130 {
 131     template<typename T> friend class WeakReference;
 132
 133 public:
 134     WeakBase() {}
 135     virtual ~WeakBase();
 136     /** clears the reference pointer in all living weak references for this instance.
 137         Further created weak references will also be invalid.
 138         You should call this method in the d'tor of your derived classes for an early
 139         invalidate of all living weak references while your object is already inside
 140         it d'tor.
 141     */
 142     inline void clearWeak();
 143
 144 private:
 145     inline WeakConnection* getWeakConnection();
 146     rtl::Reference<WeakConnection> mpWeakConnection;
 147 };
 148
 149 }
 150
 151 #endif
 152
 153 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */