Chris@16: // (C) Copyright David Abrahams 2002.
Chris@16: // (C) Copyright Jeremy Siek    2002.
Chris@16: // (C) Copyright Thomas Witt    2002.
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: #ifndef BOOST_ITERATOR_ADAPTOR_23022003THW_HPP
Chris@16: #define BOOST_ITERATOR_ADAPTOR_23022003THW_HPP
Chris@16: 
Chris@16: #include <boost/static_assert.hpp>
Chris@16: #include <boost/iterator.hpp>
Chris@16: #include <boost/detail/iterator.hpp>
Chris@16: 
Chris@16: #include <boost/iterator/iterator_categories.hpp>
Chris@16: #include <boost/iterator/iterator_facade.hpp>
Chris@16: #include <boost/iterator/detail/enable_if.hpp>
Chris@16: 
Chris@16: #include <boost/mpl/and.hpp>
Chris@16: #include <boost/mpl/not.hpp>
Chris@16: #include <boost/mpl/or.hpp>
Chris@16: 
Chris@16: #include <boost/type_traits/is_same.hpp>
Chris@16: #include <boost/type_traits/is_convertible.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
Chris@16: # include <boost/type_traits/remove_reference.hpp>
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/type_traits/add_reference.hpp>
Chris@16: #include <boost/iterator/detail/config_def.hpp>
Chris@16: 
Chris@16: #include <boost/iterator/iterator_traits.hpp>
Chris@16: 
Chris@101: namespace boost {
Chris@101: namespace iterators {
Chris@101: 
Chris@16:   // Used as a default template argument internally, merely to
Chris@16:   // indicate "use the default", this can also be passed by users
Chris@16:   // explicitly in order to specify that the default should be used.
Chris@16:   struct use_default;
Chris@101: 
Chris@101: } // namespace iterators
Chris@101: 
Chris@101: using iterators::use_default;
Chris@101: 
Chris@101: // the incompleteness of use_default causes massive problems for
Chris@101: // is_convertible (naturally).  This workaround is fortunately not
Chris@101: // needed for vc6/vc7.
Chris@101: template<class To>
Chris@101: struct is_convertible<use_default,To>
Chris@101:   : mpl::false_ {};
Chris@101: 
Chris@101: namespace iterators {
Chris@101: 
Chris@16:   namespace detail
Chris@16:   {
Chris@16: 
Chris@101:     //
Chris@16:     // Result type used in enable_if_convertible meta function.
Chris@101:     // This can be an incomplete type, as only pointers to
Chris@16:     // enable_if_convertible< ... >::type are used.
Chris@16:     // We could have used void for this, but conversion to
Chris@16:     // void* is just to easy.
Chris@16:     //
Chris@16:     struct enable_type;
Chris@16:   }
Chris@16: 
Chris@16: 
Chris@16:   //
Chris@16:   // enable_if for use in adapted iterators constructors.
Chris@16:   //
Chris@16:   // In order to provide interoperability between adapted constant and
Chris@16:   // mutable iterators, adapted iterators will usually provide templated
Chris@16:   // conversion constructors of the following form
Chris@16:   //
Chris@16:   // template <class BaseIterator>
Chris@16:   // class adapted_iterator :
Chris@16:   //   public iterator_adaptor< adapted_iterator<Iterator>, Iterator >
Chris@16:   // {
Chris@16:   // public:
Chris@101:   //
Chris@16:   //   ...
Chris@16:   //
Chris@16:   //   template <class OtherIterator>
Chris@16:   //   adapted_iterator(
Chris@16:   //       OtherIterator const& it
Chris@16:   //     , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0);
Chris@16:   //
Chris@16:   //   ...
Chris@16:   // };
Chris@16:   //
Chris@16:   // enable_if_convertible is used to remove those overloads from the overload
Chris@16:   // set that cannot be instantiated. For all practical purposes only overloads
Chris@16:   // for constant/mutable interaction will remain. This has the advantage that
Chris@16:   // meta functions like boost::is_convertible do not return false positives,
Chris@16:   // as they can only look at the signature of the conversion constructor
Chris@16:   // and not at the actual instantiation.
Chris@16:   //
Chris@16:   // enable_if_interoperable can be safely used in user code. It falls back to
Chris@101:   // always enabled for compilers that don't support enable_if or is_convertible.
Chris@101:   // There is no need for compiler specific workarounds in user code.
Chris@16:   //
Chris@16:   // The operators implementation relies on boost::is_convertible not returning
Chris@16:   // false positives for user/library defined iterator types. See comments
Chris@16:   // on operator implementation for consequences.
Chris@16:   //
Chris@101: #  if defined(BOOST_NO_IS_CONVERTIBLE) || defined(BOOST_NO_SFINAE)
Chris@101: 
Chris@16:   template <class From, class To>
Chris@16:   struct enable_if_convertible
Chris@16:   {
Chris@101:       typedef boost::iterators::detail::enable_type type;
Chris@16:   };
Chris@101: 
Chris@101: #  elif BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292))
Chris@101: 
Chris@16:   // For some reason vc7.1 needs us to "cut off" instantiation
Chris@16:   // of is_convertible in a few cases.
Chris@16:   template<typename From, typename To>
Chris@16:   struct enable_if_convertible
Chris@16:     : iterators::enable_if<
Chris@16:         mpl::or_<
Chris@16:             is_same<From,To>
Chris@16:           , is_convertible<From, To>
Chris@16:         >
Chris@101:       , boost::iterators::detail::enable_type
Chris@16:     >
Chris@16:   {};
Chris@101: 
Chris@101: #  else
Chris@101: 
Chris@16:   template<typename From, typename To>
Chris@16:   struct enable_if_convertible
Chris@16:     : iterators::enable_if<
Chris@16:           is_convertible<From, To>
Chris@101:         , boost::iterators::detail::enable_type
Chris@16:       >
Chris@16:   {};
Chris@101: 
Chris@16: # endif
Chris@101: 
Chris@16:   //
Chris@16:   // Default template argument handling for iterator_adaptor
Chris@16:   //
Chris@16:   namespace detail
Chris@16:   {
Chris@16:     // If T is use_default, return the result of invoking
Chris@16:     // DefaultNullaryFn, otherwise return T.
Chris@16:     template <class T, class DefaultNullaryFn>
Chris@16:     struct ia_dflt_help
Chris@16:       : mpl::eval_if<
Chris@16:             is_same<T, use_default>
Chris@16:           , DefaultNullaryFn
Chris@16:           , mpl::identity<T>
Chris@16:         >
Chris@16:     {
Chris@16:     };
Chris@16: 
Chris@16:     // A metafunction which computes an iterator_adaptor's base class,
Chris@16:     // a specialization of iterator_facade.
Chris@16:     template <
Chris@16:         class Derived
Chris@16:       , class Base
Chris@16:       , class Value
Chris@16:       , class Traversal
Chris@16:       , class Reference
Chris@16:       , class Difference
Chris@16:     >
Chris@16:     struct iterator_adaptor_base
Chris@16:     {
Chris@16:         typedef iterator_facade<
Chris@16:             Derived
Chris@101: 
Chris@16: # ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
Chris@101:           , typename boost::iterators::detail::ia_dflt_help<
Chris@16:                 Value
Chris@16:               , mpl::eval_if<
Chris@16:                     is_same<Reference,use_default>
Chris@16:                   , iterator_value<Base>
Chris@16:                   , remove_reference<Reference>
Chris@16:                 >
Chris@16:             >::type
Chris@16: # else
Chris@101:           , typename boost::iterators::detail::ia_dflt_help<
Chris@16:                 Value, iterator_value<Base>
Chris@16:             >::type
Chris@16: # endif
Chris@101: 
Chris@101:           , typename boost::iterators::detail::ia_dflt_help<
Chris@16:                 Traversal
Chris@16:               , iterator_traversal<Base>
Chris@16:             >::type
Chris@16: 
Chris@101:           , typename boost::iterators::detail::ia_dflt_help<
Chris@16:                 Reference
Chris@16:               , mpl::eval_if<
Chris@16:                     is_same<Value,use_default>
Chris@16:                   , iterator_reference<Base>
Chris@16:                   , add_reference<Value>
Chris@16:                 >
Chris@16:             >::type
Chris@16: 
Chris@101:           , typename boost::iterators::detail::ia_dflt_help<
Chris@16:                 Difference, iterator_difference<Base>
Chris@16:             >::type
Chris@16:         >
Chris@16:         type;
Chris@16:     };
Chris@101: 
Chris@16:     // workaround for aC++ CR JAGaf33512
Chris@16:     template <class Tr1, class Tr2>
Chris@16:     inline void iterator_adaptor_assert_traversal ()
Chris@16:     {
Chris@16:       BOOST_STATIC_ASSERT((is_convertible<Tr1, Tr2>::value));
Chris@16:     }
Chris@16:   }
Chris@101: 
Chris@16:   //
Chris@16:   // Iterator Adaptor
Chris@16:   //
Chris@16:   // The parameter ordering changed slightly with respect to former
Chris@16:   // versions of iterator_adaptor The idea is that when the user needs
Chris@16:   // to fiddle with the reference type it is highly likely that the
Chris@16:   // iterator category has to be adjusted as well.  Any of the
Chris@16:   // following four template arguments may be ommitted or explicitly
Chris@16:   // replaced by use_default.
Chris@16:   //
Chris@16:   //   Value - if supplied, the value_type of the resulting iterator, unless
Chris@16:   //      const. If const, a conforming compiler strips constness for the
Chris@16:   //      value_type. If not supplied, iterator_traits<Base>::value_type is used
Chris@16:   //
Chris@16:   //   Category - the traversal category of the resulting iterator. If not
Chris@16:   //      supplied, iterator_traversal<Base>::type is used.
Chris@16:   //
Chris@16:   //   Reference - the reference type of the resulting iterator, and in
Chris@16:   //      particular, the result type of operator*(). If not supplied but
Chris@16:   //      Value is supplied, Value& is used. Otherwise
Chris@16:   //      iterator_traits<Base>::reference is used.
Chris@16:   //
Chris@16:   //   Difference - the difference_type of the resulting iterator. If not
Chris@16:   //      supplied, iterator_traits<Base>::difference_type is used.
Chris@16:   //
Chris@16:   template <
Chris@16:       class Derived
Chris@16:     , class Base
Chris@16:     , class Value        = use_default
Chris@16:     , class Traversal    = use_default
Chris@16:     , class Reference    = use_default
Chris@16:     , class Difference   = use_default
Chris@16:   >
Chris@16:   class iterator_adaptor
Chris@101:     : public boost::iterators::detail::iterator_adaptor_base<
Chris@16:         Derived, Base, Value, Traversal, Reference, Difference
Chris@16:       >::type
Chris@16:   {
Chris@16:       friend class iterator_core_access;
Chris@16: 
Chris@16:    protected:
Chris@101:       typedef typename boost::iterators::detail::iterator_adaptor_base<
Chris@16:           Derived, Base, Value, Traversal, Reference, Difference
Chris@16:       >::type super_t;
Chris@16:    public:
Chris@16:       iterator_adaptor() {}
Chris@16: 
Chris@16:       explicit iterator_adaptor(Base const &iter)
Chris@16:           : m_iterator(iter)
Chris@16:       {
Chris@16:       }
Chris@16: 
Chris@16:       typedef Base base_type;
Chris@16: 
Chris@16:       Base const& base() const
Chris@16:         { return m_iterator; }
Chris@16: 
Chris@16:    protected:
Chris@16:       // for convenience in derived classes
Chris@16:       typedef iterator_adaptor<Derived,Base,Value,Traversal,Reference,Difference> iterator_adaptor_;
Chris@101: 
Chris@16:       //
Chris@16:       // lvalue access to the Base object for Derived
Chris@16:       //
Chris@16:       Base const& base_reference() const
Chris@16:         { return m_iterator; }
Chris@16: 
Chris@16:       Base& base_reference()
Chris@16:         { return m_iterator; }
Chris@16: 
Chris@16:    private:
Chris@16:       //
Chris@16:       // Core iterator interface for iterator_facade.  This is private
Chris@16:       // to prevent temptation for Derived classes to use it, which
Chris@16:       // will often result in an error.  Derived classes should use
Chris@16:       // base_reference(), above, to get direct access to m_iterator.
Chris@101:       //
Chris@16:       typename super_t::reference dereference() const
Chris@16:         { return *m_iterator; }
Chris@16: 
Chris@16:       template <
Chris@16:       class OtherDerived, class OtherIterator, class V, class C, class R, class D
Chris@101:       >
Chris@16:       bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const
Chris@16:       {
Chris@16:         // Maybe readd with same_distance
Chris@16:         //           BOOST_STATIC_ASSERT(
Chris@16:         //               (detail::same_category_and_difference<Derived,OtherDerived>::value)
Chris@16:         //               );
Chris@16:           return m_iterator == x.base();
Chris@16:       }
Chris@16: 
Chris@16:       typedef typename iterator_category_to_traversal<
Chris@16:           typename super_t::iterator_category
Chris@16:       >::type my_traversal;
Chris@16: 
Chris@16: # define BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(cat) \
Chris@101:       boost::iterators::detail::iterator_adaptor_assert_traversal<my_traversal, cat>();
Chris@16: 
Chris@16:       void advance(typename super_t::difference_type n)
Chris@16:       {
Chris@16:           BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)
Chris@16:           m_iterator += n;
Chris@16:       }
Chris@101: 
Chris@16:       void increment() { ++m_iterator; }
Chris@16: 
Chris@101:       void decrement()
Chris@16:       {
Chris@16:           BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(bidirectional_traversal_tag)
Chris@16:            --m_iterator;
Chris@16:       }
Chris@16: 
Chris@16:       template <
Chris@16:           class OtherDerived, class OtherIterator, class V, class C, class R, class D
Chris@101:       >
Chris@16:       typename super_t::difference_type distance_to(
Chris@16:           iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const
Chris@16:       {
Chris@16:           BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)
Chris@16:           // Maybe readd with same_distance
Chris@16:           //           BOOST_STATIC_ASSERT(
Chris@16:           //               (detail::same_category_and_difference<Derived,OtherDerived>::value)
Chris@16:           //               );
Chris@16:           return y.base() - m_iterator;
Chris@16:       }
Chris@16: 
Chris@16: # undef BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL
Chris@101: 
Chris@16:    private: // data members
Chris@16:       Base m_iterator;
Chris@16:   };
Chris@16: 
Chris@101: } // namespace iterators
Chris@101: 
Chris@101: using iterators::iterator_adaptor;
Chris@101: using iterators::enable_if_convertible;
Chris@101: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/iterator/detail/config_undef.hpp>
Chris@16: 
Chris@16: #endif // BOOST_ITERATOR_ADAPTOR_23022003THW_HPP