boost/statechart/result.hpp

   1 #ifndef BOOST_STATECHART_RESULT_HPP_INCLUDED
   2 #define BOOST_STATECHART_RESULT_HPP_INCLUDED
   3 //////////////////////////////////////////////////////////////////////////////
   4 // Copyright 2002-2006 Andreas Huber Doenni
   5 // Distributed under the Boost Software License, Version 1.0. (See accompany-
   6 // ing file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 //////////////////////////////////////////////////////////////////////////////
   8
   9
  10
  11 #include <boost/assert.hpp>
  12
  13
  14
  15 namespace boost
  16 {
  17 namespace statechart
  18 {
  19 namespace detail
  20 {
  21
  22
  23
  24 //////////////////////////////////////////////////////////////////////////////
  25 enum reaction_result
  26 {
  27   no_reaction,
  28   do_forward_event,
  29   do_discard_event,
  30   do_defer_event,
  31   consumed
  32 };
  33
  34 struct result_utility;
  35
  36 //////////////////////////////////////////////////////////////////////////////
  37 class safe_reaction_result
  38 {
  39   public:
  40     //////////////////////////////////////////////////////////////////////////
  41     safe_reaction_result( const safe_reaction_result & other ) :
  42       reactionResult( other.reactionResult )
  43     {
  44       // This assert fails when an attempt is made to make multiple copies of
  45       // a result value. This makes little sense, given the requirement that
  46       // an obtained result value must be returned out of the react function.
  47       BOOST_ASSERT( reactionResult != consumed );
  48       other.reactionResult = consumed;
  49     }
  50
  51     ~safe_reaction_result()
  52     {
  53       // This assert fails when an obtained result value is not returned out
  54       // of the react() function. This can happen if the user accidentally
  55       // makes more than one call to reaction functions inside react() or
  56       // accidentally makes one or more calls to reaction functions outside
  57       // react()
  58       BOOST_ASSERT( reactionResult == consumed );
  59     }
  60
  61   private:
  62     //////////////////////////////////////////////////////////////////////////
  63     safe_reaction_result( reaction_result reactionResult ) :
  64       reactionResult( reactionResult )
  65     {
  66     }
  67
  68     operator reaction_result() const
  69     {
  70       const reaction_result val = reactionResult;
  71       reactionResult = consumed;
  72       return val;
  73     }
  74
  75     safe_reaction_result & operator=( const safe_reaction_result & );
  76
  77     mutable reaction_result reactionResult;
  78
  79     friend struct result_utility;
  80 };
  81
  82
  83
  84 } // namespace detail
  85
  86
  87
  88 #ifdef NDEBUG
  89   typedef detail::reaction_result result;
  90 #else
  91   typedef detail::safe_reaction_result result;
  92 #endif
  93
  94
  95 namespace detail
  96 {
  97
  98
  99
 100 //////////////////////////////////////////////////////////////////////////////
 101 struct result_utility
 102 {
 103   static ::boost::statechart::result make_result( reaction_result value )
 104   {
 105     return value;
 106   }
 107
 108   static reaction_result get_result( ::boost::statechart::result value )
 109   {
 110     return value;
 111   }
 112 };
 113
 114
 115
 116 } // namespace detail
 117 } // namespace statechart
 118 } // namespace boost
 119
 120
 121
 122 #endif