interface/wx/scopeguard.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        scopeguard.h
   3 // Purpose:     interface of global functions
   4 // Author:      wxWidgets team
   5 // Licence:     wxWindows licence
   6 /////////////////////////////////////////////////////////////////////////////
   7
   8 /**
   9     @class wxScopeGuard
  10
  11     Scope guard is an object which allows executing an action on scope exit.
  12
  13     The objects of this class must be constructed using wxMakeGuard() function.
  14
  15     @nolibrary
  16     @category{misc}
  17  */
  18 class wxScopeGuard
  19 {
  20 public:
  21     /**
  22         Call this method to dismiss the execution of the action on scope exit.
  23
  24         A typical example:
  25         @code
  26             Update1();
  27
  28             // ensure that changes done so far are rolled back if the next
  29             // operation throws
  30             wxScopeGuard guard = wxMakeGuard(RollBack);
  31             Update2();
  32
  33             // it didn't throw so commit the changes, i.e. avoid rolling back
  34             guard.Dismiss();
  35         @endcode
  36      */
  37     void Dismiss();
  38 };
  39
  40 /** @addtogroup group_funcmacro_misc */
  41 //@{
  42 /**
  43     Returns a scope guard object which will call the specified function with
  44     the given parameters on scope exit.
  45
  46     This function is overloaded to take several parameters up to some
  47     implementation-defined (but relatively low) limit.
  48
  49     The @a func should be a functor taking parameters of the types P1, ..., PN,
  50     i.e. the expression @c func(p1, ..., pN) should be valid.
  51  */
  52 template <typename F, typename P1, ..., typename PN>
  53 wxScopeGuard wxMakeGuard(F func, P1 p1, ..., PN pN);
  54
  55 //@}
  56
  57 /** @addtogroup group_funcmacro_misc */
  58 //@{
  59 /**
  60     Ensure that the global @a function with a few (up to some
  61     implementation-defined limit) is executed on scope exit, whether due to a
  62     normal function return or because an exception has been thrown.
  63
  64     A typical example of its usage:
  65
  66     @code
  67     void *buf = malloc(size);
  68     wxON_BLOCK_EXIT1(free, buf);
  69     @endcode
  70
  71     Please see the original article by Andrei Alexandrescu and Petru Marginean
  72     published in December 2000 issue of C/C++ Users Journal for more details.
  73
  74     @see wxON_BLOCK_EXIT_OBJ0()
  75
  76     @header{wx/scopeguard.h}
  77 */
  78 #define wxON_BLOCK_EXIT(function, ...)
  79 #define wxON_BLOCK_EXIT0(function)
  80 #define wxON_BLOCK_EXIT1(function, p1)
  81 #define wxON_BLOCK_EXIT2(function, p1, p2)
  82 #define wxON_BLOCK_EXIT3(function, p1, p2, p3)
  83 //@}
  84
  85 /** @addtogroup group_funcmacro_misc */
  86 //@{
  87 /**
  88     This family of macros is similar to wxON_BLOCK_EXIT(), but calls a method
  89     of the given object instead of a free function.
  90
  91     @header{wx/scopeguard.h}
  92 */
  93 #define wxON_BLOCK_EXIT_OBJ(object, method, ...)
  94 #define wxON_BLOCK_EXIT_OBJ0(object, method)
  95 #define wxON_BLOCK_EXIT_OBJ1(object, method, p1)
  96 #define wxON_BLOCK_EXIT_OBJ2(object, method, p1, p2)
  97 #define wxON_BLOCK_EXIT_OBJ3(object, method, p1, p2, p3)
  98 //@}
  99
 100 /** @addtogroup group_funcmacro_misc */
 101 //@{
 102 /**
 103     This family of macros is similar to wxON_BLOCK_OBJ(), but calls a method
 104     of @c this object instead of a method of the specified object.
 105
 106     @header{wx/scopeguard.h}
 107 */
 108 #define wxON_BLOCK_EXIT_THIS(method, ...)
 109 #define wxON_BLOCK_EXIT_THIS0(method)
 110 #define wxON_BLOCK_EXIT_THIS1(method, p1)
 111 #define wxON_BLOCK_EXIT_THIS2(method, p1, p2)
 112 #define wxON_BLOCK_EXIT_THIS3(method, p1, p2, p3)
 113 //@}
 114
 115 /** @addtogroup group_funcmacro_misc */
 116 //@{
 117 /**
 118     This macro sets a variable to the specified value on scope exit.
 119
 120     Example of usage:
 121     @code
 122     void foo()
 123     {
 124         bool isDoingSomething = true;
 125         {
 126             wxON_BLOCK_EXIT_SET(isDoingSomething, false);
 127             ... do something ...
 128         }
 129         ... isDoingSomething is false now ...
 130     }
 131     @endcode
 132
 133     Notice that @a value is copied, i.e. stored by value, so it can be a
 134     temporary object returned by a function call, for example.
 135
 136     @see wxON_BLOCK_EXIT_OBJ0(), wxON_BLOCK_EXIT_NULL()
 137
 138     @header{wx/scopeguard.h}
 139 */
 140 #define wxON_BLOCK_EXIT_SET(var, value)
 141
 142 /**
 143     This macro sets the pointer passed to it as argument to NULL on scope exit.
 144
 145     It must be used instead of wxON_BLOCK_EXIT_SET() when the value being set
 146     is @c NULL.
 147
 148     @header{wx/scopeguard.h}
 149  */
 150 #define wxON_BLOCK_EXIT_NULL(ptr)
 151
 152 //@}
 153