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 // Copyright:   (c) 2008 Vaclav Slavik
   7 // Licence:     wxWindows licence
   8 /////////////////////////////////////////////////////////////////////////////
   9
  10 #ifndef _WX_META_MOVABLE_H_
  11 #define _WX_META_MOVABLE_H_
  12
  13 #include "wx/meta/pod.h"
  14 #include "wx/string.h" // for wxIsMovable<wxString> specialization
  15
  16 // Helper to decide if an object of type T is "movable", i.e. if it can be
  17 // copied to another memory location using memmove() or realloc() C functions.
  18 // C++ only gurantees that POD types (including primitive types) are
  19 // movable.
  20 template<typename T>
  21 struct wxIsMovable
  22 {
  23     wxDEFINE_TEMPLATE_BOOL_VALUE(wxIsPod<T>::value);
  24 };
  25
  26 // Macro to add wxIsMovable<T> specialization for given type that marks it
  27 // as movable:
  28 #define WX_DECLARE_TYPE_MOVABLE(type)                       \
  29     template<> struct wxIsMovable<type>                     \
  30     {                                                       \
  31         wxDEFINE_TEMPLATE_BOOL_VALUE(true);                 \
  32     };
  33
  34 // Our implementation of wxString is written in such way that it's safe to move
  35 // it around (unless position cache is used which unfortunately breaks this).
  36 // OTOH, we don't know anything about std::string.
  37 // (NB: we don't put this into string.h and choose to include wx/string.h from
  38 // here instead so that rarely-used wxIsMovable<T> code isn't included by
  39 // everything)
  40 #if !wxUSE_STD_STRING && !wxUSE_STRING_POS_CACHE
  41 WX_DECLARE_TYPE_MOVABLE(wxString)
  42 #endif
  43
  44 #endif // _WX_META_MOVABLE_H_