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 // This macro declares something called "value" inside a class declaration.
  18 //
  19 // It has to be used because VC6 doesn't handle initialization of the static
  20 // variables in the class declaration itself while BCC5.82 doesn't understand
  21 // enums (it compiles the template fine but can't use it later)
  22 #if defined(__VISUALC__) && !wxCHECK_VISUALC_VERSION(7)
  23     #define wxDEFINE_TEMPLATE_BOOL_VALUE(val) enum { value = val }
  24 #else
  25     #define wxDEFINE_TEMPLATE_BOOL_VALUE(val) static const bool value = val
  26 #endif
  27
  28 // Helper to decide if an object of type T is "movable", i.e. if it can be
  29 // copied to another memory location using memmove() or realloc() C functions.
  30 // C++ only gurantees that POD types (including primitive types) are
  31 // movable.
  32 template<typename T>
  33 struct wxIsMovable
  34 {
  35     wxDEFINE_TEMPLATE_BOOL_VALUE(false);
  36 };
  37
  38 // Macro to add wxIsMovable<T> specialization for given type that marks it
  39 // as movable:
  40 #define WX_DECLARE_TYPE_MOVABLE(type)                       \
  41     template<> struct wxIsMovable<type>                     \
  42     {                                                       \
  43         wxDEFINE_TEMPLATE_BOOL_VALUE(true);                 \
  44     };
  45
  46 WX_DECLARE_TYPE_MOVABLE(bool)
  47 WX_DECLARE_TYPE_MOVABLE(unsigned char)
  48 WX_DECLARE_TYPE_MOVABLE(signed char)
  49 WX_DECLARE_TYPE_MOVABLE(unsigned int)
  50 WX_DECLARE_TYPE_MOVABLE(signed int)
  51 WX_DECLARE_TYPE_MOVABLE(unsigned short int)
  52 WX_DECLARE_TYPE_MOVABLE(signed short int)
  53 WX_DECLARE_TYPE_MOVABLE(signed long int)
  54 WX_DECLARE_TYPE_MOVABLE(unsigned long int)
  55 WX_DECLARE_TYPE_MOVABLE(float)
  56 WX_DECLARE_TYPE_MOVABLE(double)
  57 WX_DECLARE_TYPE_MOVABLE(long double)
  58 #if wxWCHAR_T_IS_REAL_TYPE
  59 WX_DECLARE_TYPE_MOVABLE(wchar_t)
  60 #endif
  61 #ifdef wxLongLong_t
  62 WX_DECLARE_TYPE_MOVABLE(wxLongLong_t)
  63 WX_DECLARE_TYPE_MOVABLE(wxULongLong_t)
  64 #endif
  65
  66 // Visual C++ 6.0 can't compile partial template specializations and as this is
  67 // only an optimization, we can live with pointers not being recognized as
  68 // movable types under VC6
  69 #if !defined(__VISUALC__) || wxCHECK_VISUALC_VERSION(7)
  70
  71 // pointers are movable:
  72 template<typename T>
  73 struct wxIsMovable<T*>
  74 {
  75     static const bool value = true;
  76 };
  77
  78 template<typename T>
  79 struct wxIsMovable<const T*>
  80 {
  81     static const bool value = true;
  82 };
  83
  84 #endif // !VC++ < 7
  85
  86 // Our implementation of wxString is written in such way that it's safe to move
  87 // it around (unless position cache is used which unfortunately breaks this).
  88 // OTOH, we don't know anything about std::string.
  89 // (NB: we don't put this into string.h and choose to include wx/string.h from
  90 // here instead so that rarely-used wxIsMovable<T> code isn't included by
  91 // everything)
  92 #if !wxUSE_STL && !wxUSE_STRING_POS_CACHE
  93 WX_DECLARE_TYPE_MOVABLE(wxString)
  94 #endif
  95
  96 #endif // _WX_META_MOVABLE_H_