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/meta/pod.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     wxDEFINE_TEMPLATE_BOOL_VALUE(wxIsPod<T>::value);
  25 };
  26
  27 // Macro to add wxIsMovable<T> specialization for given type that marks it
  28 // as movable:
  29 #define WX_DECLARE_TYPE_MOVABLE(type)                       \
  30     template<> struct wxIsMovable<type>                     \
  31     {                                                       \
  32         wxDEFINE_TEMPLATE_BOOL_VALUE(true);                 \
  33     };
  34
  35 // Our implementation of wxString is written in such way that it's safe to move
  36 // it around (unless position cache is used which unfortunately breaks this).
  37 // OTOH, we don't know anything about std::string.
  38 // (NB: we don't put this into string.h and choose to include wx/string.h from
  39 // here instead so that rarely-used wxIsMovable<T> code isn't included by
  40 // everything)
  41 #if !wxUSE_STL && !wxUSE_STRING_POS_CACHE
  42 WX_DECLARE_TYPE_MOVABLE(wxString)
  43 #endif
  44
  45 #endif // _WX_META_MOVABLE_H_