include/wx/meta/movable.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/meta/movable.h
   3 // Purpose:     Test if a type is movable using memmove() etc.
   4 // Author:      Vaclav Slavik
   5 // Created:     2008-01-21
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2008 Vaclav Slavik
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_META_MOVABLE_H_
  12 #define _WX_META_MOVABLE_H_
  13
  14 #include "wx/defs.h"
  15 #include "wx/string.h" // for wxIsMovable<wxString> specialization
  16
  17 // Helper to decide if an object of type T is "movable", i.e. if it can be
  18 // copied to another memory location using memmove() or realloc() C functions.
  19 // C++ only gurantees that POD types (including primitive types) are
  20 // movable.
  21 template<typename T>
  22 struct wxIsMovable
  23 {
  24     // NB: enum, because VC6 can't handle "static const bool value = true;"
  25     enum { value = false };
  26 };
  27
  28 // Macro to add wxIsMovable<T> specialization for given type that marks it
  29 // as movable:
  30 #define WX_DECLARE_TYPE_MOVABLE(type)                       \
  31     template<> struct wxIsMovable<type>                     \
  32     {                                                       \
  33         enum { value = true };                              \
  34     };
  35
  36 WX_DECLARE_TYPE_MOVABLE(bool)
  37 WX_DECLARE_TYPE_MOVABLE(unsigned char)
  38 WX_DECLARE_TYPE_MOVABLE(signed char)
  39 WX_DECLARE_TYPE_MOVABLE(unsigned int)
  40 WX_DECLARE_TYPE_MOVABLE(signed int)
  41 WX_DECLARE_TYPE_MOVABLE(unsigned short int)
  42 WX_DECLARE_TYPE_MOVABLE(signed short int)
  43 WX_DECLARE_TYPE_MOVABLE(signed long int)
  44 WX_DECLARE_TYPE_MOVABLE(unsigned long int)
  45 WX_DECLARE_TYPE_MOVABLE(float)
  46 WX_DECLARE_TYPE_MOVABLE(double)
  47 WX_DECLARE_TYPE_MOVABLE(long double)
  48 #if wxWCHAR_T_IS_REAL_TYPE
  49 WX_DECLARE_TYPE_MOVABLE(wchar_t)
  50 #endif
  51 #ifdef wxLongLong_t
  52 WX_DECLARE_TYPE_MOVABLE(wxLongLong_t)
  53 WX_DECLARE_TYPE_MOVABLE(wxULongLong_t)
  54 #endif
  55
  56 // Visual C++ 6.0 can't compile partial template specializations and as this is
  57 // only an optimization, we can live with pointers not being recognized as
  58 // movable types under VC6
  59 #if !defined(__VISUALC__) || wxCHECK_VISUALC_VERSION(7)
  60
  61 // pointers are movable:
  62 template<typename T>
  63 struct wxIsMovable<T*>
  64 {
  65     enum { value = true };
  66 };
  67 template<typename T>
  68 struct wxIsMovable<const T*>
  69 {
  70     enum { value = true };
  71 };
  72
  73 #endif // !VC++ < 7
  74
  75 // Our implementation of wxString is written in such way that it's safe to move
  76 // it around. OTOH, we don't know anything about std::string.
  77 // (NB: we don't put this into string.h and choose to include wx/string.h from
  78 // here instead so that rarely-used wxIsMovable<T> code isn't included by
  79 // everything)
  80 #if !wxUSE_STL
  81 WX_DECLARE_TYPE_MOVABLE(wxString)
  82 #endif
  83
  84
  85 #endif // _WX_META_MOVABLE_H_