ceph/src/boost/libs/move/example/doc_move_return.cpp

   1 //////////////////////////////////////////////////////////////////////////////
   2 //
   3 // (C) Copyright Ion Gaztanaga 2014-2014.
   4 // Distributed under the Boost Software License, Version 1.0.
   5 // (See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // See http://www.boost.org/libs/move for documentation.
   9 //
  10 //////////////////////////////////////////////////////////////////////////////
  11
  12 #include <boost/move/detail/config_begin.hpp>
  13
  14 //[move_return_example
  15 #include "movable.hpp"
  16 #include "copymovable.hpp"
  17 #include <boost/move/core.hpp>
  18
  19 template<class Type>
  20 struct factory_functor
  21 {
  22    typedef Type return_type;
  23
  24    Type operator()() const
  25    {  Type t;  return BOOST_MOVE_RET(Type, t);  }
  26 };
  27
  28 struct return_reference
  29 {
  30    typedef non_copy_movable &return_type;
  31
  32    non_copy_movable &operator()() const
  33    {  return ncm; }
  34
  35    static non_copy_movable ncm;
  36 };
  37
  38 non_copy_movable return_reference::ncm;
  39
  40 //A wrapper that locks a mutex while the
  41 //factory creates a new value.
  42 //It must generically move the return value
  43 //if possible both in C++03 and C++11
  44 template <class Factory>
  45 typename Factory::return_type lock_wrapper(Factory f)
  46 {
  47    typedef typename Factory::return_type return_type;
  48    //LOCK();
  49    return_type r = f();
  50    //UNLOCK();
  51
  52    //In C++03: boost::move() if R is not a reference and
  53    //has move emulation enabled. In C++11: just return r.
  54    return BOOST_MOVE_RET(return_type, r);
  55 }
  56
  57 int main()
  58 {
  59    movable m            = lock_wrapper(factory_functor<movable>     ());
  60    copy_movable cm      = lock_wrapper(factory_functor<copy_movable>());
  61    copyable c           = lock_wrapper(factory_functor<copyable>    ());
  62    non_copy_movable &mr = lock_wrapper(return_reference             ());
  63    //<-
  64    (void)m; (void)cm; (void)c; (void)mr;
  65    //->
  66    return 0;
  67 }
  68 //]
  69
  70 #include <boost/move/detail/config_end.hpp>