Chris@101: /* Copyright 2006-2014 Joaquin M Lopez Munoz.
Chris@16:  * Distributed under the Boost Software License, Version 1.0.
Chris@16:  * (See accompanying file LICENSE_1_0.txt or copy at
Chris@16:  * http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  *
Chris@16:  * See http://www.boost.org/libs/flyweight for library home page.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_FLYWEIGHT_KEY_VALUE_HPP
Chris@16: #define BOOST_FLYWEIGHT_KEY_VALUE_HPP
Chris@16: 
Chris@101: #if defined(_MSC_VER)
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@101: #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
Chris@101: #include <boost/detail/workaround.hpp>
Chris@101: #include <boost/flyweight/detail/perfect_fwd.hpp>
Chris@16: #include <boost/flyweight/detail/value_tag.hpp>
Chris@16: #include <boost/flyweight/key_value_fwd.hpp>
Chris@16: #include <boost/mpl/assert.hpp>
Chris@16: #include <boost/type_traits/aligned_storage.hpp>
Chris@16: #include <boost/type_traits/alignment_of.hpp> 
Chris@16: #include <boost/type_traits/is_same.hpp>
Chris@16: #include <new>
Chris@16: 
Chris@16: /* key-value policy: flywewight lookup is based on Key, which also serves
Chris@16:  * to construct Value only when needed (new factory entry). key_value is
Chris@16:  * used to avoid the construction of temporary values when such construction
Chris@16:  * is expensive.
Chris@16:  * Optionally, KeyFromValue extracts the key from a value, which
Chris@16:  * is needed in expressions like this:
Chris@16:  *
Chris@16:  *  typedef flyweight<key_value<Key,Value> > fw_t;
Chris@16:  *  fw_t  fw;
Chris@16:  *  Value v;
Chris@16:  *  fw=v; // no key explicitly given
Chris@16:  *
Chris@16:  * If no KeyFromValue is provided, this latter expression fails to compile.
Chris@16:  */
Chris@16: 
Chris@16: namespace boost{
Chris@16: 
Chris@16: namespace flyweights{
Chris@16: 
Chris@16: namespace detail{
Chris@16: 
Chris@16: template<typename Key,typename Value,typename KeyFromValue>
Chris@16: struct optimized_key_value:value_marker
Chris@16: {
Chris@16:   typedef Key   key_type;
Chris@16:   typedef Value value_type;
Chris@16: 
Chris@16:   class rep_type
Chris@16:   {
Chris@16:   public:
Chris@16:     /* template ctors */
Chris@16: 
Chris@101: #define BOOST_FLYWEIGHT_PERFECT_FWD_CTR_BODY(args)       \
Chris@101:   :value_ptr(0)                                          \
Chris@101: {                                                        \
Chris@101:   new(spc_ptr())key_type(BOOST_FLYWEIGHT_FORWARD(args)); \
Chris@16: }
Chris@16: 
Chris@101:   BOOST_FLYWEIGHT_PERFECT_FWD(
Chris@101:     explicit rep_type,
Chris@101:     BOOST_FLYWEIGHT_PERFECT_FWD_CTR_BODY)
Chris@101: 
Chris@101: #undef BOOST_FLYWEIGHT_PERFECT_FWD_CTR_BODY
Chris@16: 
Chris@16:     rep_type(const rep_type& x):value_ptr(x.value_ptr)
Chris@16:     {
Chris@16:       if(!x.value_ptr)new(key_ptr())key_type(*x.key_ptr());
Chris@16:     }
Chris@16: 
Chris@101:     rep_type(const value_type& x):value_ptr(&x){}
Chris@101: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@101:     rep_type(rep_type&& x):value_ptr(x.value_ptr)
Chris@101:     {
Chris@101:       if(!x.value_ptr)new(key_ptr())key_type(std::move(*x.key_ptr()));
Chris@101:     }
Chris@101: 
Chris@101:     rep_type(value_type&& x):value_ptr(&x){}
Chris@101: #endif
Chris@101: 
Chris@16:     ~rep_type()
Chris@16:     {
Chris@16:       if(!value_ptr)       key_ptr()->~key_type();
Chris@16:       else if(value_cted())value_ptr->~value_type();
Chris@16:     }
Chris@16: 
Chris@16:     operator const key_type&()const
Chris@16:     {
Chris@16:       if(value_ptr)return key_from_value(*value_ptr);
Chris@16:       else         return *key_ptr();
Chris@16:     }
Chris@16: 
Chris@16:     operator const value_type&()const
Chris@16:     {
Chris@16:       /* This is always called after construct_value() or copy_value(),
Chris@16:        * so we access spc directly rather than through value_ptr to
Chris@16:        * save us an indirection.
Chris@16:        */
Chris@16: 
Chris@16:       return *static_cast<value_type*>(spc_ptr());
Chris@16:     }
Chris@16: 
Chris@16:   private:
Chris@16:     friend struct optimized_key_value;
Chris@16: 
Chris@16:     void* spc_ptr()const{return static_cast<void*>(&spc);}
Chris@16:     bool  value_cted()const{return value_ptr==spc_ptr();}
Chris@16: 
Chris@16:     key_type* key_ptr()const
Chris@16:     {
Chris@16:       return static_cast<key_type*>(static_cast<void*>(&spc));
Chris@16:     }
Chris@16: 
Chris@16:     static const key_type& key_from_value(const value_type& x)
Chris@16:     {
Chris@16:       KeyFromValue k;
Chris@16:       return k(x);
Chris@16:     }
Chris@16: 
Chris@16:     void construct_value()const
Chris@16:     {
Chris@16:       if(!value_cted()){
Chris@16:         /* value_ptr must be ==0, oherwise copy_value would have been called */
Chris@16: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@101:         key_type k(std::move(*key_ptr()));
Chris@101: #else
Chris@16:         key_type k(*key_ptr());
Chris@101: #endif
Chris@101: 
Chris@16:         key_ptr()->~key_type();
Chris@16:         value_ptr= /* guarantees key won't be re-dted at ~rep_type if the */
Chris@16:           static_cast<value_type*>(spc_ptr())+1; /* next statement throws */
Chris@16:         value_ptr=new(spc_ptr())value_type(k);
Chris@16:       }
Chris@16:     }
Chris@16: 
Chris@16:     void copy_value()const
Chris@16:     {
Chris@16:       if(!value_cted())value_ptr=new(spc_ptr())value_type(*value_ptr);
Chris@16:     }
Chris@16: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@101:     void move_value()const
Chris@101:     {
Chris@101:       if(!value_cted())value_ptr=
Chris@101:         new(spc_ptr())value_type(std::move(const_cast<value_type&>(*value_ptr)));
Chris@101:     }
Chris@101: #endif
Chris@101: 
Chris@16:     mutable typename boost::aligned_storage<
Chris@16:       (sizeof(key_type)>sizeof(value_type))?
Chris@16:         sizeof(key_type):sizeof(value_type),
Chris@16:       (boost::alignment_of<key_type>::value >
Chris@16:        boost::alignment_of<value_type>::value)?
Chris@16:         boost::alignment_of<key_type>::value:
Chris@16:         boost::alignment_of<value_type>::value
Chris@16:     >::type                                    spc;
Chris@16:     mutable const value_type*                  value_ptr;
Chris@16:   };
Chris@16: 
Chris@16:   static void construct_value(const rep_type& r)
Chris@16:   {
Chris@16:     r.construct_value();
Chris@16:   }
Chris@16: 
Chris@16:   static void copy_value(const rep_type& r)
Chris@16:   {
Chris@16:     r.copy_value();
Chris@16:   }
Chris@101: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@101:   static void move_value(const rep_type& r)
Chris@101:   {
Chris@101:     r.move_value();
Chris@101:   }
Chris@101: #endif
Chris@16: };
Chris@16: 
Chris@16: template<typename Key,typename Value>
Chris@16: struct regular_key_value:value_marker
Chris@16: {
Chris@16:   typedef Key   key_type;
Chris@16:   typedef Value value_type;
Chris@16: 
Chris@16:   class rep_type
Chris@16:   {
Chris@16:   public:
Chris@16:     /* template ctors */
Chris@16: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)&&\
Chris@101:     !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)&&\
Chris@101:     BOOST_WORKAROUND(__GNUC__,<=4)&&(__GNUC__<4||__GNUC_MINOR__<=4)
Chris@16: 
Chris@101: /* GCC 4.4.2 (and probably prior) bug: the default ctor generated by the
Chris@101:  * variadic temmplate ctor below fails to value-initialize key.
Chris@101:  */
Chris@101: 
Chris@101:     rep_type():key(),value_ptr(0){}
Chris@101: #endif
Chris@101: 
Chris@101: #define BOOST_FLYWEIGHT_PERFECT_FWD_CTR_BODY(args) \
Chris@101:   :key(BOOST_FLYWEIGHT_FORWARD(args)),value_ptr(0){}
Chris@101: 
Chris@101:   BOOST_FLYWEIGHT_PERFECT_FWD(
Chris@101:     explicit rep_type,
Chris@101:     BOOST_FLYWEIGHT_PERFECT_FWD_CTR_BODY)
Chris@101: 
Chris@101: #undef BOOST_FLYWEIGHT_PERFECT_FWD_CTR_BODY
Chris@101: 
Chris@101:     rep_type(const rep_type& x):key(x.key),value_ptr(0){}
Chris@16:     rep_type(const value_type& x):key(no_key_from_value_failure()){}
Chris@16: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@101:     rep_type(rep_type&& x):key(std::move(x.key)),value_ptr(0){}
Chris@101:     rep_type(value_type&& x):key(no_key_from_value_failure()){}
Chris@101: #endif
Chris@16: 
Chris@16:     ~rep_type()
Chris@16:     {
Chris@16:       if(value_ptr)value_ptr->~value_type();
Chris@16:     }
Chris@16: 
Chris@16:     operator const key_type&()const{return key;}
Chris@16: 
Chris@16:     operator const value_type&()const
Chris@16:     {
Chris@16:       /* This is always called after construct_value(),so we access spc
Chris@16:        * directly rather than through value_ptr to save us an indirection.
Chris@16:        */
Chris@16: 
Chris@16:       return *static_cast<value_type*>(spc_ptr());
Chris@16:     }
Chris@16: 
Chris@16:   private:
Chris@16:     friend struct regular_key_value;
Chris@16: 
Chris@16:     void* spc_ptr()const{return static_cast<void*>(&spc);}
Chris@16: 
Chris@16:     struct no_key_from_value_failure
Chris@16:     {
Chris@16:       BOOST_MPL_ASSERT_MSG(
Chris@16:         false,
Chris@16:         NO_KEY_FROM_VALUE_CONVERSION_PROVIDED,
Chris@16:         (key_type,value_type));
Chris@16: 
Chris@16:       operator const key_type&()const;
Chris@16:     };
Chris@16: 
Chris@16:     void construct_value()const
Chris@16:     {
Chris@16:       if(!value_ptr)value_ptr=new(spc_ptr())value_type(key);
Chris@16:     }
Chris@16: 
Chris@16:     key_type                                 key;
Chris@16:     mutable typename boost::aligned_storage<
Chris@16:       sizeof(value_type),
Chris@16:       boost::alignment_of<value_type>::value
Chris@16:     >::type                                  spc;
Chris@16:     mutable const value_type*                value_ptr;
Chris@16:   };
Chris@16: 
Chris@16:   static void construct_value(const rep_type& r)
Chris@16:   {
Chris@16:     r.construct_value();
Chris@16:   }
Chris@16: 
Chris@101:   /* copy_value() and move_value() can't really ever be called, provided to avoid
Chris@101:    * compile errors (it is the no_key_from_value_failure compile error we want to
Chris@101:    * appear in these cases).
Chris@101:    */
Chris@101: 
Chris@16:   static void copy_value(const rep_type&){}
Chris@101: 
Chris@101: #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
Chris@101:   static void move_value(const rep_type&){}
Chris@101: #endif
Chris@16: };
Chris@16: 
Chris@16: } /* namespace flyweights::detail */
Chris@16: 
Chris@16: template<typename Key,typename Value,typename KeyFromValue>
Chris@16: struct key_value:
Chris@16:   mpl::if_<
Chris@16:     is_same<KeyFromValue,no_key_from_value>,
Chris@16:     detail::regular_key_value<Key,Value>,
Chris@16:     detail::optimized_key_value<Key,Value,KeyFromValue>
Chris@16:   >::type
Chris@16: {};
Chris@16: 
Chris@16: } /* namespace flyweights */
Chris@16: 
Chris@16: } /* namespace boost */
Chris@16: 
Chris@16: #endif