include/wx/scopeguard.h

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/scopeguard.h
   3 // Purpose:     declares wxwxScopeGuard and related macros
   4 // Author:      Vadim Zeitlin
   5 // Modified by:
   6 // Created:     03.07.2003
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) 2003 Vadim Zeitlin <vadim@wxwidgets.org>
   9 // Licence:     wxWindows licence
  10 ///////////////////////////////////////////////////////////////////////////////
  11
  12 /*
  13     Acknowledgements: this header is heavily based on (well, almost the exact
  14     copy of) wxScopeGuard.h by Andrei Alexandrescu and Petru Marginean published
  15     in December 2000 issue of C/C++ Users Journal.
  16  */
  17
  18 #ifndef _WX_SCOPEGUARD_H_
  19 #define _WX_SCOPEGUARD_H_
  20
  21 #include "wx/defs.h"
  22
  23 #include "wx/except.h"
  24
  25 // ----------------------------------------------------------------------------
  26 // helpers
  27 // ----------------------------------------------------------------------------
  28
  29 namespace wxPrivate
  30 {
  31     // in the original implementation this was a member template function of
  32     // ScopeGuardImplBase but gcc 2.8 which is still used for OS/2 doesn't
  33     // support member templates and so we must make it global
  34     template <typename ScopeGuardImpl>
  35     void OnScopeExit(ScopeGuardImpl& guard)
  36     {
  37         if ( !guard.WasDismissed() )
  38         {
  39             // we're called from ScopeGuardImpl dtor and so we must not throw
  40             wxTRY
  41             {
  42                 guard.Execute();
  43             }
  44             wxCATCH_ALL(;) // do nothing, just eat the exception
  45         }
  46     }
  47
  48     // just to avoid the warning about unused variables
  49     template <typename T>
  50     void Use(const T& WXUNUSED(t))
  51     {
  52     }
  53 } // namespace wxPrivate
  54
  55 // ============================================================================
  56 // wxScopeGuard for functions and functors
  57 // ============================================================================
  58
  59 // ----------------------------------------------------------------------------
  60 // wxScopeGuardImplBase: used by wxScopeGuardImpl[0..N] below
  61 // ----------------------------------------------------------------------------
  62
  63 class wxScopeGuardImplBase
  64 {
  65 public:
  66     wxScopeGuardImplBase() : m_wasDismissed(false) { }
  67
  68     void Dismiss() const { m_wasDismissed = true; }
  69
  70     // for OnScopeExit() only we can't make it friend, unfortunately)!
  71     bool WasDismissed() const { return m_wasDismissed; }
  72
  73 protected:
  74     ~wxScopeGuardImplBase() { }
  75
  76     wxScopeGuardImplBase(const wxScopeGuardImplBase& other)
  77         : m_wasDismissed(other.m_wasDismissed)
  78     {
  79         other.Dismiss();
  80     }
  81
  82     // must be mutable for copy ctor to work
  83     mutable bool m_wasDismissed;
  84
  85 private:
  86     wxScopeGuardImplBase& operator=(const wxScopeGuardImplBase&);
  87 };
  88
  89 // ----------------------------------------------------------------------------
  90 // wxScopeGuardImpl0: scope guard for actions without parameters
  91 // ----------------------------------------------------------------------------
  92
  93 template <typename F>
  94 class wxScopeGuardImpl0 : public wxScopeGuardImplBase
  95 {
  96 public:
  97     static wxScopeGuardImpl0<F> MakeGuard(F fun)
  98     {
  99         return wxScopeGuardImpl0<F>(fun);
 100     }
 101
 102     ~wxScopeGuardImpl0() { wxPrivate::OnScopeExit(*this); }
 103
 104     void Execute() { m_fun(); }
 105
 106 protected:
 107     wxScopeGuardImpl0(F fun) : m_fun(fun) { }
 108
 109     F m_fun;
 110
 111     wxScopeGuardImpl0& operator=(const wxScopeGuardImpl0&);
 112 };
 113
 114 template <typename F>
 115 inline wxScopeGuardImpl0<F> wxMakeGuard(F fun)
 116 {
 117     return wxScopeGuardImpl0<F>::MakeGuard(fun);
 118 }
 119
 120 // ----------------------------------------------------------------------------
 121 // wxScopeGuardImpl1: scope guard for actions with 1 parameter
 122 // ----------------------------------------------------------------------------
 123
 124 template <typename F, typename P1>
 125 class wxScopeGuardImpl1 : public wxScopeGuardImplBase
 126 {
 127 public:
 128     static wxScopeGuardImpl1<F, P1> MakeGuard(F fun, P1 p1)
 129     {
 130         return wxScopeGuardImpl1<F, P1>(fun, p1);
 131     }
 132
 133     ~wxScopeGuardImpl1() { wxPrivate::OnScopeExit(*this); }
 134
 135     void Execute() { m_fun(m_p1); }
 136
 137 protected:
 138     wxScopeGuardImpl1(F fun, P1 p1) : m_fun(fun), m_p1(p1) { }
 139
 140     F m_fun;
 141     const P1 m_p1;
 142
 143     wxScopeGuardImpl1& operator=(const wxScopeGuardImpl1&);
 144 };
 145
 146 template <typename F, typename P1>
 147 inline wxScopeGuardImpl1<F, P1> wxMakeGuard(F fun, P1 p1)
 148 {
 149     return wxScopeGuardImpl1<F, P1>::MakeGuard(fun, p1);
 150 }
 151
 152 // ----------------------------------------------------------------------------
 153 // wxScopeGuardImpl2: scope guard for actions with 2 parameters
 154 // ----------------------------------------------------------------------------
 155
 156 template <typename F, typename P1, typename P2>
 157 class wxScopeGuardImpl2 : public wxScopeGuardImplBase
 158 {
 159 public:
 160     static wxScopeGuardImpl2<F, P1, P2> MakeGuard(F fun, P1 p1, P2 p2)
 161     {
 162         return wxScopeGuardImpl2<F, P1, P2>(fun, p1, p2);
 163     }
 164
 165     ~wxScopeGuardImpl2() { wxPrivate::OnScopeExit(*this); }
 166
 167     void Execute() { m_fun(m_p1, m_p2); }
 168
 169 protected:
 170     wxScopeGuardImpl2(F fun, P1 p1, P2 p2) : m_fun(fun), m_p1(p1), m_p2(p2) { }
 171
 172     F m_fun;
 173     const P1 m_p1;
 174     const P2 m_p2;
 175
 176     wxScopeGuardImpl2& operator=(const wxScopeGuardImpl2&);
 177 };
 178
 179 template <typename F, typename P1, typename P2>
 180 inline wxScopeGuardImpl2<F, P1, P2> wxMakeGuard(F fun, P1 p1, P2 p2)
 181 {
 182     return wxScopeGuardImpl2<F, P1, P2>::MakeGuard(fun, p1, p2);
 183 }
 184
 185 // ============================================================================
 186 // wxScopeGuards for object methods
 187 // ============================================================================
 188
 189 // ----------------------------------------------------------------------------
 190 // wxObjScopeGuardImpl0
 191 // ----------------------------------------------------------------------------
 192
 193 template <class Obj, typename MemFun>
 194 class wxObjScopeGuardImpl0 : public wxScopeGuardImplBase
 195 {
 196 public:
 197     static wxObjScopeGuardImpl0<Obj, MemFun>
 198         MakeObjGuard(Obj& obj, MemFun memFun)
 199     {
 200         return wxObjScopeGuardImpl0<Obj, MemFun>(obj, memFun);
 201     }
 202
 203     ~wxObjScopeGuardImpl0() { wxPrivate::OnScopeExit(*this); }
 204
 205     void Execute() { (m_obj.*m_memfun)(); }
 206
 207 protected:
 208     wxObjScopeGuardImpl0(Obj& obj, MemFun memFun)
 209         : m_obj(obj), m_memfun(memFun) { }
 210
 211     Obj& m_obj;
 212     MemFun m_memfun;
 213 };
 214
 215 template <class Obj, typename MemFun>
 216 inline wxObjScopeGuardImpl0<Obj, MemFun> wxMakeObjGuard(Obj& obj, MemFun memFun)
 217 {
 218     return wxObjScopeGuardImpl0<Obj, MemFun>::MakeObjGuard(obj, memFun);
 219 }
 220
 221 template <class Obj, typename MemFun, typename P1>
 222 class wxObjScopeGuardImpl1 : public wxScopeGuardImplBase
 223 {
 224 public:
 225     static wxObjScopeGuardImpl1<Obj, MemFun, P1>
 226         MakeObjGuard(Obj& obj, MemFun memFun, P1 p1)
 227     {
 228         return wxObjScopeGuardImpl1<Obj, MemFun, P1>(obj, memFun, p1);
 229     }
 230
 231     ~wxObjScopeGuardImpl1() { wxPrivate::OnScopeExit(*this); }
 232
 233     void Execute() { (m_obj.*m_memfun)(m_p1); }
 234
 235 protected:
 236     wxObjScopeGuardImpl1(Obj& obj, MemFun memFun, P1 p1)
 237         : m_obj(obj), m_memfun(memFun), m_p1(p1) { }
 238
 239     Obj& m_obj;
 240     MemFun m_memfun;
 241     const P1 m_p1;
 242 };
 243
 244 template <class Obj, typename MemFun, typename P1>
 245 inline wxObjScopeGuardImpl1<Obj, MemFun, P1>
 246 wxMakeObjGuard(Obj& obj, MemFun memFun, P1 p1)
 247 {
 248     return wxObjScopeGuardImpl1<Obj, MemFun, P1>::MakeObjGuard(obj, memFun, p1);
 249 }
 250
 251 template <class Obj, typename MemFun, typename P1, typename P2>
 252 class wxObjScopeGuardImpl2 : public wxScopeGuardImplBase
 253 {
 254 public:
 255     static wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>
 256         MakeObjGuard(Obj& obj, MemFun memFun, P1 p1, P2 p2)
 257     {
 258         return wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>(obj, memFun, p1, p2);
 259     }
 260
 261     ~wxObjScopeGuardImpl2() { wxPrivate::OnScopeExit(*this); }
 262
 263     void Execute() { (m_obj.*m_memfun)(m_p1, m_p2); }
 264
 265 protected:
 266     wxObjScopeGuardImpl2(Obj& obj, MemFun memFun, P1 p1, P2 p2)
 267         : m_obj(obj), m_memfun(memFun), m_p1(p1), m_p2(p2) { }
 268
 269     Obj& m_obj;
 270     MemFun m_memfun;
 271     const P1 m_p1;
 272     const P2 m_p2;
 273 };
 274
 275 template <class Obj, typename MemFun, typename P1, typename P2>
 276 inline wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>
 277 wxMakeObjGuard(Obj& obj, MemFun memFun, P1 p1, P2 p2)
 278 {
 279     return wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>::
 280                                             MakeObjGuard(obj, memFun, p1, p2);
 281 }
 282
 283 // ============================================================================
 284 // public stuff
 285 // ============================================================================
 286
 287 // wxScopeGuard is just a reference, see the explanation in CUJ article
 288 typedef const wxScopeGuardImplBase& wxScopeGuard;
 289
 290 // when an unnamed scope guard is needed, the macros below may be used
 291 //
 292 // NB: the original code has a single (and much nicer) ON_BLOCK_EXIT macro
 293 //     but this results in compiler warnings about unused variables and I
 294 //     didn't find a way to work around this other than by having different
 295 //     macros with different names
 296 #define wxON_BLOCK_EXIT0(f) \
 297     wxScopeGuard wxMAKE_UNIQUE_NAME(scopeGuard) = wxMakeGuard(f); \
 298     wxPrivate::Use(wxMAKE_UNIQUE_NAME(scopeGuard))
 299
 300 #define wxON_BLOCK_EXIT_OBJ0(o, m) \
 301     wxScopeGuard wxMAKE_UNIQUE_NAME(scopeGuard) = wxMakeObjGuard(o, m); \
 302     wxPrivate::Use(wxMAKE_UNIQUE_NAME(scopeGuard))
 303
 304 #define wxON_BLOCK_EXIT1(f, p1) \
 305     wxScopeGuard wxMAKE_UNIQUE_NAME(scopeGuard) = wxMakeGuard(f, p1); \
 306     wxPrivate::Use(wxMAKE_UNIQUE_NAME(scopeGuard))
 307
 308 #define wxON_BLOCK_EXIT_OBJ1(o, m, p1) \
 309     wxScopeGuard wxMAKE_UNIQUE_NAME(scopeGuard) = wxMakeObjGuard(o, m, p1); \
 310     wxPrivate::Use(wxMAKE_UNIQUE_NAME(scopeGuard))
 311
 312 #define wxON_BLOCK_EXIT2(f, p1, p2) \
 313     wxScopeGuard wxMAKE_UNIQUE_NAME(scopeGuard) = wxMakeGuard(f, p1, p2); \
 314     wxPrivate::Use(wxMAKE_UNIQUE_NAME(scopeGuard))
 315
 316 #define wxON_BLOCK_EXIT_OBJ2(o, m, p1, p2) \
 317     wxScopeGuard wxMAKE_UNIQUE_NAME(scopeGuard) = wxMakeObjGuard(o, m, p1, p2); \
 318     wxPrivate::Use(wxMAKE_UNIQUE_NAME(scopeGuard))
 319
 320 #endif // _WX_SCOPEGUARD_H_
 321