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) ScopeGuard.h by Andrei Alexandrescu and Petru Marginean published
  15     in December 2000 issue of C/C++ Users Journal.
  16     http://www.cuj.com/documents/cujcexp1812alexandr/
  17  */
  18
  19 #ifndef _WX_SCOPEGUARD_H_
  20 #define _WX_SCOPEGUARD_H_
  21
  22 #include "wx/defs.h"
  23
  24 #include "wx/except.h"
  25
  26 // ----------------------------------------------------------------------------
  27 // helpers
  28 // ----------------------------------------------------------------------------
  29
  30 #ifdef __WATCOMC__
  31
  32 // WATCOM-FIXME: C++ of Open Watcom 1.3 doesn't like OnScopeExit() created
  33 // through template so it must be workarounded with dedicated inlined macro.
  34 // For compatibility with Watcom compilers wxPrivate::OnScopeExit must be
  35 // replaced with wxPrivateOnScopeExit but in user code (for everyone who
  36 // doesn't care about OW compatibility) wxPrivate::OnScopeExit still works.
  37
  38 #define wxPrivateOnScopeExit(guard)          \
  39     {                                        \
  40         if ( !(guard).WasDismissed() )       \
  41         {                                    \
  42             wxTRY                            \
  43             {                                \
  44                 (guard).Execute();           \
  45             }                                \
  46             wxCATCH_ALL(;)                   \
  47         }                                    \
  48     }
  49
  50 #define wxPrivateUse(n) wxUnusedVar(n)
  51
  52 #else
  53
  54 namespace wxPrivate
  55 {
  56     // in the original implementation this was a member template function of
  57     // ScopeGuardImplBase but gcc 2.8 which is still used for OS/2 doesn't
  58     // support member templates and so we must make it global
  59     template <class ScopeGuardImpl>
  60     void OnScopeExit(ScopeGuardImpl& guard)
  61     {
  62         if ( !guard.WasDismissed() )
  63         {
  64             // we're called from ScopeGuardImpl dtor and so we must not throw
  65             wxTRY
  66             {
  67                 guard.Execute();
  68             }
  69             wxCATCH_ALL(;) // do nothing, just eat the exception
  70         }
  71     }
  72
  73     // just to avoid the warning about unused variables
  74     template <class T>
  75     void Use(const T& WXUNUSED(t))
  76     {
  77     }
  78 } // namespace wxPrivate
  79
  80 #define wxPrivateOnScopeExit(n) wxPrivate::OnScopeExit(n)
  81 #define wxPrivateUse(n) wxPrivate::Use(n)
  82
  83 #endif
  84
  85 // ============================================================================
  86 // wxScopeGuard for functions and functors
  87 // ============================================================================
  88
  89 // ----------------------------------------------------------------------------
  90 // wxScopeGuardImplBase: used by wxScopeGuardImpl[0..N] below
  91 // ----------------------------------------------------------------------------
  92
  93 class wxScopeGuardImplBase
  94 {
  95 public:
  96     wxScopeGuardImplBase() : m_wasDismissed(false) { }
  97
  98     wxScopeGuardImplBase(const wxScopeGuardImplBase& other)
  99         : m_wasDismissed(other.m_wasDismissed)
 100     {
 101         other.Dismiss();
 102     }
 103
 104     void Dismiss() const { m_wasDismissed = true; }
 105
 106     // for OnScopeExit() only (we can't make it friend, unfortunately)!
 107     bool WasDismissed() const { return m_wasDismissed; }
 108
 109 protected:
 110     ~wxScopeGuardImplBase() { }
 111
 112     // must be mutable for copy ctor to work
 113     mutable bool m_wasDismissed;
 114
 115 private:
 116     wxScopeGuardImplBase& operator=(const wxScopeGuardImplBase&);
 117 };
 118
 119 // wxScopeGuard is just a reference, see the explanation in CUJ article
 120 typedef const wxScopeGuardImplBase& wxScopeGuard;
 121
 122 // ----------------------------------------------------------------------------
 123 // wxScopeGuardImpl0: scope guard for actions without parameters
 124 // ----------------------------------------------------------------------------
 125
 126 template <class F>
 127 class wxScopeGuardImpl0 : public wxScopeGuardImplBase
 128 {
 129 public:
 130     static wxScopeGuardImpl0<F> MakeGuard(F fun)
 131     {
 132         return wxScopeGuardImpl0<F>(fun);
 133     }
 134
 135     ~wxScopeGuardImpl0() { wxPrivateOnScopeExit(*this); }
 136
 137     void Execute() { m_fun(); }
 138
 139 protected:
 140     wxScopeGuardImpl0(F fun) : m_fun(fun) { }
 141
 142     F m_fun;
 143
 144     wxScopeGuardImpl0& operator=(const wxScopeGuardImpl0&);
 145 };
 146
 147 template <class F>
 148 inline wxScopeGuardImpl0<F> wxMakeGuard(F fun)
 149 {
 150     return wxScopeGuardImpl0<F>::MakeGuard(fun);
 151 }
 152
 153 // ----------------------------------------------------------------------------
 154 // wxScopeGuardImpl1: scope guard for actions with 1 parameter
 155 // ----------------------------------------------------------------------------
 156
 157 template <class F, class P1>
 158 class wxScopeGuardImpl1 : public wxScopeGuardImplBase
 159 {
 160 public:
 161     static wxScopeGuardImpl1<F, P1> MakeGuard(F fun, P1 p1)
 162     {
 163         return wxScopeGuardImpl1<F, P1>(fun, p1);
 164     }
 165
 166     ~wxScopeGuardImpl1() { wxPrivateOnScopeExit(* this); }
 167
 168     void Execute() { m_fun(m_p1); }
 169
 170 protected:
 171     wxScopeGuardImpl1(F fun, P1 p1) : m_fun(fun), m_p1(p1) { }
 172
 173     F m_fun;
 174     const P1 m_p1;
 175
 176     wxScopeGuardImpl1& operator=(const wxScopeGuardImpl1&);
 177 };
 178
 179 template <class F, class P1>
 180 inline wxScopeGuardImpl1<F, P1> wxMakeGuard(F fun, P1 p1)
 181 {
 182     return wxScopeGuardImpl1<F, P1>::MakeGuard(fun, p1);
 183 }
 184
 185 // ----------------------------------------------------------------------------
 186 // wxScopeGuardImpl2: scope guard for actions with 2 parameters
 187 // ----------------------------------------------------------------------------
 188
 189 template <class F, class P1, class P2>
 190 class wxScopeGuardImpl2 : public wxScopeGuardImplBase
 191 {
 192 public:
 193     static wxScopeGuardImpl2<F, P1, P2> MakeGuard(F fun, P1 p1, P2 p2)
 194     {
 195         return wxScopeGuardImpl2<F, P1, P2>(fun, p1, p2);
 196     }
 197
 198     ~wxScopeGuardImpl2() { wxPrivateOnScopeExit(*this); }
 199
 200     void Execute() { m_fun(m_p1, m_p2); }
 201
 202 protected:
 203     wxScopeGuardImpl2(F fun, P1 p1, P2 p2) : m_fun(fun), m_p1(p1), m_p2(p2) { }
 204
 205     F m_fun;
 206     const P1 m_p1;
 207     const P2 m_p2;
 208
 209     wxScopeGuardImpl2& operator=(const wxScopeGuardImpl2&);
 210 };
 211
 212 template <class F, class P1, class P2>
 213 inline wxScopeGuardImpl2<F, P1, P2> wxMakeGuard(F fun, P1 p1, P2 p2)
 214 {
 215     return wxScopeGuardImpl2<F, P1, P2>::MakeGuard(fun, p1, p2);
 216 }
 217
 218 // ----------------------------------------------------------------------------
 219 // wxScopeGuardImpl3: scope guard for actions with 3 parameters
 220 // ----------------------------------------------------------------------------
 221
 222 template <class F, class P1, class P2, class P3>
 223 class wxScopeGuardImpl3 : public wxScopeGuardImplBase
 224 {
 225 public:
 226     static wxScopeGuardImpl3<F, P1, P2, P3> MakeGuard(F fun, P1 p1, P2 p2, P3 p3)
 227     {
 228         return wxScopeGuardImpl3<F, P1, P2, P3>(fun, p1, p2, p3);
 229     }
 230
 231     ~wxScopeGuardImpl3() { wxPrivateOnScopeExit(*this); }
 232
 233     void Execute() { m_fun(m_p1, m_p2, m_p3); }
 234
 235 protected:
 236     wxScopeGuardImpl3(F fun, P1 p1, P2 p2, P3 p3)
 237         : m_fun(fun), m_p1(p1), m_p2(p2), m_p3(p3) { }
 238
 239     F m_fun;
 240     const P1 m_p1;
 241     const P2 m_p2;
 242     const P3 m_p3;
 243
 244     wxScopeGuardImpl3& operator=(const wxScopeGuardImpl3&);
 245 };
 246
 247 template <class F, class P1, class P2, class P3>
 248 inline wxScopeGuardImpl3<F, P1, P2, P3> wxMakeGuard(F fun, P1 p1, P2 p2, P3 p3)
 249 {
 250     return wxScopeGuardImpl3<F, P1, P2, P3>::MakeGuard(fun, p1, p2, p3);
 251 }
 252
 253 // ============================================================================
 254 // wxScopeGuards for object methods
 255 // ============================================================================
 256
 257 // ----------------------------------------------------------------------------
 258 // wxObjScopeGuardImpl0
 259 // ----------------------------------------------------------------------------
 260
 261 template <class Obj, class MemFun>
 262 class wxObjScopeGuardImpl0 : public wxScopeGuardImplBase
 263 {
 264 public:
 265     static wxObjScopeGuardImpl0<Obj, MemFun>
 266         MakeObjGuard(Obj& obj, MemFun memFun)
 267     {
 268         return wxObjScopeGuardImpl0<Obj, MemFun>(obj, memFun);
 269     }
 270
 271     ~wxObjScopeGuardImpl0() { wxPrivateOnScopeExit(*this); }
 272
 273     void Execute() { (m_obj.*m_memfun)(); }
 274
 275 protected:
 276     wxObjScopeGuardImpl0(Obj& obj, MemFun memFun)
 277         : m_obj(obj), m_memfun(memFun) { }
 278
 279     Obj& m_obj;
 280     MemFun m_memfun;
 281 };
 282
 283 template <class Obj, class MemFun>
 284 inline wxObjScopeGuardImpl0<Obj, MemFun> wxMakeObjGuard(Obj& obj, MemFun memFun)
 285 {
 286     return wxObjScopeGuardImpl0<Obj, MemFun>::MakeObjGuard(obj, memFun);
 287 }
 288
 289 template <class Obj, class MemFun, class P1>
 290 class wxObjScopeGuardImpl1 : public wxScopeGuardImplBase
 291 {
 292 public:
 293     static wxObjScopeGuardImpl1<Obj, MemFun, P1>
 294         MakeObjGuard(Obj& obj, MemFun memFun, P1 p1)
 295     {
 296         return wxObjScopeGuardImpl1<Obj, MemFun, P1>(obj, memFun, p1);
 297     }
 298
 299     ~wxObjScopeGuardImpl1() { wxPrivateOnScopeExit(*this); }
 300
 301     void Execute() { (m_obj.*m_memfun)(m_p1); }
 302
 303 protected:
 304     wxObjScopeGuardImpl1(Obj& obj, MemFun memFun, P1 p1)
 305         : m_obj(obj), m_memfun(memFun), m_p1(p1) { }
 306
 307     Obj& m_obj;
 308     MemFun m_memfun;
 309     const P1 m_p1;
 310 };
 311
 312 template <class Obj, class MemFun, class P1>
 313 inline wxObjScopeGuardImpl1<Obj, MemFun, P1>
 314 wxMakeObjGuard(Obj& obj, MemFun memFun, P1 p1)
 315 {
 316     return wxObjScopeGuardImpl1<Obj, MemFun, P1>::MakeObjGuard(obj, memFun, p1);
 317 }
 318
 319 template <class Obj, class MemFun, class P1, class P2>
 320 class wxObjScopeGuardImpl2 : public wxScopeGuardImplBase
 321 {
 322 public:
 323     static wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>
 324         MakeObjGuard(Obj& obj, MemFun memFun, P1 p1, P2 p2)
 325     {
 326         return wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>(obj, memFun, p1, p2);
 327     }
 328
 329     ~wxObjScopeGuardImpl2() { wxPrivateOnScopeExit(*this); }
 330
 331     void Execute() { (m_obj.*m_memfun)(m_p1, m_p2); }
 332
 333 protected:
 334     wxObjScopeGuardImpl2(Obj& obj, MemFun memFun, P1 p1, P2 p2)
 335         : m_obj(obj), m_memfun(memFun), m_p1(p1), m_p2(p2) { }
 336
 337     Obj& m_obj;
 338     MemFun m_memfun;
 339     const P1 m_p1;
 340     const P2 m_p2;
 341 };
 342
 343 template <class Obj, class MemFun, class P1, class P2>
 344 inline wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>
 345 wxMakeObjGuard(Obj& obj, MemFun memFun, P1 p1, P2 p2)
 346 {
 347     return wxObjScopeGuardImpl2<Obj, MemFun, P1, P2>::
 348                                             MakeObjGuard(obj, memFun, p1, p2);
 349 }
 350
 351 template <class Obj, class MemFun, class P1, class P2, class P3>
 352 class wxObjScopeGuardImpl3 : public wxScopeGuardImplBase
 353 {
 354 public:
 355     static wxObjScopeGuardImpl3<Obj, MemFun, P1, P2, P3>
 356         MakeObjGuard(Obj& obj, MemFun memFun, P1 p1, P2 p2, P3 p3)
 357     {
 358         return wxObjScopeGuardImpl3<Obj, MemFun, P1, P2, P3>(obj, memFun, p1, p2, p3);
 359     }
 360
 361     ~wxObjScopeGuardImpl3() { wxPrivateOnScopeExit(*this); }
 362
 363     void Execute() { (m_obj.*m_memfun)(m_p1, m_p2, m_p3); }
 364
 365 protected:
 366     wxObjScopeGuardImpl3(Obj& obj, MemFun memFun, P1 p1, P2 p2, P3 p3)
 367         : m_obj(obj), m_memfun(memFun), m_p1(p1), m_p2(p2), m_p3(p3) { }
 368
 369     Obj& m_obj;
 370     MemFun m_memfun;
 371     const P1 m_p1;
 372     const P2 m_p2;
 373     const P3 m_p3;
 374 };
 375
 376 template <class Obj, class MemFun, class P1, class P2, class P3>
 377 inline wxObjScopeGuardImpl3<Obj, MemFun, P1, P2, P3>
 378 wxMakeObjGuard(Obj& obj, MemFun memFun, P1 p1, P2 p2, P3 p3)
 379 {
 380     return wxObjScopeGuardImpl3<Obj, MemFun, P1, P2, P3>::
 381                                         MakeObjGuard(obj, memFun, p1, p2, p3);
 382 }
 383
 384 // ----------------------------------------------------------------------------
 385 // wxVariableSetter: use the same technique as for wxScopeGuard to allow
 386 //                   setting a variable to some value on block exit
 387 // ----------------------------------------------------------------------------
 388
 389 namespace wxPrivate
 390 {
 391
 392 // empty class just to be able to define a reference to it
 393 class VariableSetterBase { };
 394
 395 typedef const VariableSetterBase& VariableSetter;
 396
 397 template <typename T, typename U>
 398 class VariableSetterImpl : public VariableSetterBase
 399 {
 400 public:
 401     VariableSetterImpl(T& var, U value)
 402         : m_var(var),
 403           m_value(value)
 404     {
 405     }
 406
 407     ~VariableSetterImpl()
 408     {
 409         m_var = m_value;
 410     }
 411
 412 private:
 413     T& m_var;
 414     const U m_value;
 415
 416     // suppress the warning about assignment operator not being generated
 417     VariableSetterImpl<T, U>& operator=(const VariableSetterImpl<T, U>&);
 418 };
 419
 420 template <typename T>
 421 class VariableNullerImpl : public VariableSetterBase
 422 {
 423 public:
 424     VariableNullerImpl(T& var)
 425         : m_var(var)
 426     {
 427     }
 428
 429     ~VariableNullerImpl()
 430     {
 431         m_var = NULL;
 432     }
 433
 434 private:
 435     T& m_var;
 436
 437     VariableNullerImpl<T>& operator=(const VariableNullerImpl<T>&);
 438 };
 439
 440 } // namespace wxPrivate
 441
 442 template <typename T, typename U>
 443 inline
 444 wxPrivate::VariableSetterImpl<T, U> wxMakeVarSetter(T& var, U value)
 445 {
 446       return wxPrivate::VariableSetterImpl<T, U>(var, value);
 447 }
 448
 449 // calling wxMakeVarSetter(ptr, NULL) doesn't work because U is deduced to be
 450 // "int" and subsequent assignment of "U" to "T *" fails, so provide a special
 451 // function for this special case
 452 template <typename T>
 453 inline
 454 wxPrivate::VariableNullerImpl<T> wxMakeVarNuller(T& var)
 455 {
 456     return wxPrivate::VariableNullerImpl<T>(var);
 457 }
 458
 459 // ============================================================================
 460 // macros for declaring unnamed scoped guards (which can't be dismissed)
 461 // ============================================================================
 462
 463 // NB: the original code has a single (and much nicer) ON_BLOCK_EXIT macro
 464 //     but this results in compiler warnings about unused variables and I
 465 //     didn't find a way to work around this other than by having different
 466 //     macros with different names or using a less natural syntax for passing
 467 //     the arguments (e.g. as Boost preprocessor sequences, which would mean
 468 //     having to write wxON_BLOCK_EXIT(fwrite, (buf)(size)(n)(fp)) instead of
 469 //     wxON_BLOCK_EXIT4(fwrite, buf, size, n, fp)).
 470
 471 #define wxGuardName    wxMAKE_UNIQUE_NAME(wxScopeGuard)
 472
 473 #define wxON_BLOCK_EXIT0_IMPL(n, f) \
 474     wxScopeGuard n = wxMakeGuard(f); \
 475     wxPrivateUse(n)
 476 #define wxON_BLOCK_EXIT0(f) \
 477     wxON_BLOCK_EXIT0_IMPL(wxGuardName, f)
 478
 479 #define wxON_BLOCK_EXIT_OBJ0_IMPL(n, o, m) \
 480     wxScopeGuard n = wxMakeObjGuard(o, m); \
 481     wxPrivateUse(n)
 482 #define wxON_BLOCK_EXIT_OBJ0(o, m) \
 483     wxON_BLOCK_EXIT_OBJ0_IMPL(wxGuardName, o, &m)
 484
 485 #define wxON_BLOCK_EXIT_THIS0(m) \
 486     wxON_BLOCK_EXIT_OBJ0(*this, m)
 487
 488
 489 #define wxON_BLOCK_EXIT1_IMPL(n, f, p1) \
 490     wxScopeGuard n = wxMakeGuard(f, p1); \
 491     wxPrivateUse(n)
 492 #define wxON_BLOCK_EXIT1(f, p1) \
 493     wxON_BLOCK_EXIT1_IMPL(wxGuardName, f, p1)
 494
 495 #define wxON_BLOCK_EXIT_OBJ1_IMPL(n, o, m, p1) \
 496     wxScopeGuard n = wxMakeObjGuard(o, m, p1); \
 497     wxPrivateUse(n)
 498 #define wxON_BLOCK_EXIT_OBJ1(o, m, p1) \
 499     wxON_BLOCK_EXIT_OBJ1_IMPL(wxGuardName, o, &m, p1)
 500
 501 #define wxON_BLOCK_EXIT_THIS1(m, p1) \
 502     wxON_BLOCK_EXIT_OBJ1(*this, m, p1)
 503
 504
 505 #define wxON_BLOCK_EXIT2_IMPL(n, f, p1, p2) \
 506     wxScopeGuard n = wxMakeGuard(f, p1, p2); \
 507     wxPrivateUse(n)
 508 #define wxON_BLOCK_EXIT2(f, p1, p2) \
 509     wxON_BLOCK_EXIT2_IMPL(wxGuardName, f, p1, p2)
 510
 511 #define wxON_BLOCK_EXIT_OBJ2_IMPL(n, o, m, p1, p2) \
 512     wxScopeGuard n = wxMakeObjGuard(o, m, p1, p2); \
 513     wxPrivateUse(n)
 514 #define wxON_BLOCK_EXIT_OBJ2(o, m, p1, p2) \
 515     wxON_BLOCK_EXIT_OBJ2_IMPL(wxGuardName, o, &m, p1, p2)
 516
 517 #define wxON_BLOCK_EXIT_THIS2(m, p1, p2) \
 518     wxON_BLOCK_EXIT_OBJ2(*this, m, p1, p2)
 519
 520
 521 #define wxON_BLOCK_EXIT3_IMPL(n, f, p1, p2, p3) \
 522     wxScopeGuard n = wxMakeGuard(f, p1, p2, p3); \
 523     wxPrivateUse(n)
 524 #define wxON_BLOCK_EXIT3(f, p1, p2, p3) \
 525     wxON_BLOCK_EXIT3_IMPL(wxGuardName, f, p1, p2, p3)
 526
 527 #define wxON_BLOCK_EXIT_OBJ3_IMPL(n, o, m, p1, p2, p3) \
 528     wxScopeGuard n = wxMakeObjGuard(o, m, p1, p2, p3); \
 529     wxPrivateUse(n)
 530 #define wxON_BLOCK_EXIT_OBJ3(o, m, p1, p2, p3) \
 531     wxON_BLOCK_EXIT_OBJ3_IMPL(wxGuardName, o, &m, p1, p2, p3)
 532
 533 #define wxON_BLOCK_EXIT_THIS3(m, p1, p2, p3) \
 534     wxON_BLOCK_EXIT_OBJ3(*this, m, p1, p2, p3)
 535
 536
 537 #define wxSetterName wxMAKE_UNIQUE_NAME(wxVarSetter)
 538
 539 #define wxON_BLOCK_EXIT_SET_IMPL(n, var, value) \
 540     wxPrivate::VariableSetter n = wxMakeVarSetter(var, value); \
 541     wxPrivateUse(n)
 542
 543 #define wxON_BLOCK_EXIT_SET(var, value) \
 544     wxON_BLOCK_EXIT_SET_IMPL(wxSetterName, var, value)
 545
 546 #define wxON_BLOCK_EXIT_NULL_IMPL(n, var) \
 547     wxPrivate::VariableSetter n = wxMakeVarNuller(var); \
 548     wxPrivateUse(n)
 549
 550 #define wxON_BLOCK_EXIT_NULL(ptr) \
 551     wxON_BLOCK_EXIT_NULL_IMPL(wxSetterName, ptr)
 552
 553 #endif // _WX_SCOPEGUARD_H_