boost/iterator/iterator_facade.hpp
// (C) Copyright David Abrahams 2002. // (C) Copyright Jeremy Siek 2002. // (C) Copyright Thomas Witt 2002. // Permission to copy, use, modify, // sell and distribute this software is granted provided this // copyright notice appears in all copies. This software is provided // "as is" without express or implied warranty, and with no claim as // to its suitability for any purpose. #ifndef BOOST_ITERATOR_FACADE_23022003THW_HPP #define BOOST_ITERATOR_FACADE_23022003THW_HPP #include <boost/static_assert.hpp> #include <boost/iterator.hpp> #include <boost/iterator/interoperable.hpp> #include <boost/iterator/iterator_traits.hpp> #include <boost/iterator/detail/facade_iterator_category.hpp> #include <boost/iterator/detail/enable_if.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/type_traits/add_const.hpp> #include <boost/type_traits/add_pointer.hpp> #include <boost/type_traits/remove_const.hpp> #include <boost/type_traits/is_convertible.hpp> #include <boost/type_traits/is_pod.hpp> #include <boost/mpl/apply_if.hpp> #include <boost/mpl/or.hpp> #include <boost/mpl/and.hpp> #include <boost/mpl/always.hpp> #include <boost/mpl/apply.hpp> #if BOOST_WORKAROUND(BOOST_MSVC, == 1200) # include <boost/mpl/if.hpp> #endif #include <boost/iterator/detail/config_def.hpp> // this goes last namespace boost { // This forward declaration is required for the friend declaration // in iterator_core_access template <class I, class V, class TC, class R, class D> class iterator_facade; namespace detail { // A binary metafunction class that always returns bool. VC6 // ICEs on mpl::always<bool>, probably because of the default // parameters. struct always_bool2 { template <class T, class U> struct apply { typedef bool type; }; }; // // enable if for use in operator implementation. // template < class Facade1 , class Facade2 , class Return > struct enable_if_interoperable : ::boost::iterators::enable_if< mpl::or_< is_convertible<Facade1, Facade2> , is_convertible<Facade2, Facade1> > , Return > { }; // // Generates associated types for an iterator_facade with the // given parameters. // template < class ValueParam , class CategoryOrTraversal , class Reference , class Difference > struct iterator_facade_types { typedef typename facade_iterator_category< CategoryOrTraversal, ValueParam, Reference >::type iterator_category; typedef typename remove_const<ValueParam>::type value_type; typedef typename mpl::apply_if< detail::iterator_writability_disabled<ValueParam,Reference> , add_pointer<typename add_const<value_type>::type> , add_pointer<value_type> >::type pointer; # if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) \ && (BOOST_WORKAROUND(_STLPORT_VERSION, BOOST_TESTED_AT(0x452)) \ || BOOST_WORKAROUND(BOOST_DINKUMWARE_STDLIB, BOOST_TESTED_AT(310))) \ || BOOST_WORKAROUND(BOOST_RWSTD_VER, BOOST_TESTED_AT(0x20101)) \ || BOOST_WORKAROUND(BOOST_DINKUMWARE_STDLIB, <= 310) // To interoperate with some broken library/compiler // combinations, user-defined iterators must be derived from // std::iterator. It is possible to implement a standard // library for broken compilers without this limitation. # define BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE 1 typedef iterator<iterator_category, value_type, Difference, pointer, Reference> base; # endif }; // operator->() needs special support for input iterators to strictly meet the // standard's requirements. If *i is not a reference type, we must still // produce a (constant) lvalue to which a pointer can be formed. We do that by // returning an instantiation of this special proxy class template. template <class T> struct operator_arrow_proxy { operator_arrow_proxy(T const* px) : m_value(*px) {} const T* operator->() const { return &m_value; } // This function is needed for MWCW and BCC, which won't call operator-> // again automatically per 13.3.1.2 para 8 operator const T*() const { return &m_value; } T m_value; }; // A metafunction that gets the result type for operator->. Also // has a static function make() which builds the result from a // Reference template <class Value, class Reference, class Pointer> struct operator_arrow_result { // CWPro8.3 won't accept "operator_arrow_result::type", and we // need that type below, so metafunction forwarding would be a // losing proposition here. typedef typename mpl::if_< is_reference<Reference> , Pointer , operator_arrow_proxy<Value> >::type type; static type make(Reference x) { return type(&x); } }; # if BOOST_WORKAROUND(BOOST_MSVC, <= 1200) // Deal with ETI template<> struct operator_arrow_result<int, int, int> { typedef int type; }; # endif // // Iterator is actually an iterator_facade, so we do not have to // go through iterator_traits to access the traits. // template <class Iterator> class operator_brackets_proxy { typedef typename Iterator::reference reference; typedef typename Iterator::value_type value_type; public: operator_brackets_proxy(Iterator const& iter) : m_iter(iter) {} operator reference() const { return *m_iter; } operator_brackets_proxy& operator=(value_type const& val) { *m_iter = val; return *this; } private: Iterator m_iter; }; template <class Value, class Reference> struct use_operator_brackets_proxy : mpl::and_< // Really we want an is_copy_constructible trait here, // but is_POD will have to suffice in the meantime. boost::is_POD<Value> , iterator_writability_disabled<Value,Reference> > {}; template <class Iterator, class Value, class Reference> struct operator_brackets_result { typedef typename mpl::if_< use_operator_brackets_proxy<Value,Reference> , Value , operator_brackets_proxy<Iterator> >::type type; }; template <class Iterator> operator_brackets_proxy<Iterator> make_operator_brackets_result(Iterator const& iter, mpl::false_) { return operator_brackets_proxy<Iterator>(iter); } template <class Iterator> typename Iterator::value_type make_operator_brackets_result(Iterator const& iter, mpl::true_) { return *iter; } struct choose_difference_type { template <class I1, class I2> struct apply : # ifdef BOOST_NO_ONE_WAY_ITERATOR_INTEROP iterator_difference<I1> # elif BOOST_WORKAROUND(BOOST_MSVC, == 1200) mpl::if_< is_convertible<I2,I1> , typename I1::difference_type , typename I2::difference_type > # else mpl::apply_if< is_convertible<I2,I1> , iterator_difference<I1> , iterator_difference<I2> > # endif {}; }; } // namespace detail // Macros which describe the declarations of binary operators # ifdef BOOST_NO_STRICT_ITERATOR_INTEROPERABILITY # define BOOST_ITERATOR_FACADE_INTEROP_HEAD(prefix, op, result_type) \ template < \ class Derived1, class V1, class TC1, class R1, class D1 \ , class Derived2, class V2, class TC2, class R2, class D2 \ > \ prefix typename mpl::apply2<result_type,Derived1,Derived2>::type \ operator op( \ iterator_facade<Derived1, V1, TC1, R1, D1> const& lhs \ , iterator_facade<Derived2, V2, TC2, R2, D2> const& rhs) # else # define BOOST_ITERATOR_FACADE_INTEROP_HEAD(prefix, op, result_type) \ template < \ class Derived1, class V1, class TC1, class R1, class D1 \ , class Derived2, class V2, class TC2, class R2, class D2 \ > \ prefix typename detail::enable_if_interoperable< \ Derived1, Derived2 \ , typename mpl::apply2<result_type,Derived1,Derived2>::type \ >::type \ operator op( \ iterator_facade<Derived1, V1, TC1, R1, D1> const& lhs \ , iterator_facade<Derived2, V2, TC2, R2, D2> const& rhs) # endif # define BOOST_ITERATOR_FACADE_PLUS_HEAD(prefix,args) \ template <class Derived, class V, class TC, class R, class D> \ prefix Derived operator+ args // // Helper class for granting access to the iterator core interface. // // The simple core interface is used by iterator_facade. The core // interface of a user/library defined iterator type should not be made public // so that it does not clutter the public interface. Instead iterator_core_access // should be made friend so that iterator_facade can access the core // interface through iterator_core_access. // class iterator_core_access { # if defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) \ || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551)) // Tasteless as this may seem, making all members public allows member templates // to work in the absence of member template friends. public: # else template <class I, class V, class TC, class R, class D> friend class iterator_facade; # define BOOST_ITERATOR_FACADE_RELATION(op) \ BOOST_ITERATOR_FACADE_INTEROP_HEAD(friend,op, detail::always_bool2); BOOST_ITERATOR_FACADE_RELATION(==) BOOST_ITERATOR_FACADE_RELATION(!=) BOOST_ITERATOR_FACADE_RELATION(<) BOOST_ITERATOR_FACADE_RELATION(>) BOOST_ITERATOR_FACADE_RELATION(<=) BOOST_ITERATOR_FACADE_RELATION(>=) # undef BOOST_ITERATOR_FACADE_RELATION BOOST_ITERATOR_FACADE_INTEROP_HEAD( friend, -, detail::choose_difference_type) ; BOOST_ITERATOR_FACADE_PLUS_HEAD( friend , (iterator_facade<Derived, V, TC, R, D> const& , typename Derived::difference_type) ) ; BOOST_ITERATOR_FACADE_PLUS_HEAD( friend , (typename Derived::difference_type , iterator_facade<Derived, V, TC, R, D> const&) ) ; # endif template <class Facade> static typename Facade::reference dereference(Facade const& f) { return f.dereference(); } template <class Facade> static void increment(Facade& f) { f.increment(); } template <class Facade> static void decrement(Facade& f) { f.decrement(); } template <class Facade1, class Facade2> static bool equal(Facade1 const& f1, Facade2 const& f2, mpl::true_) { return f1.equal(f2); } template <class Facade1, class Facade2> static bool equal(Facade1 const& f1, Facade2 const& f2, mpl::false_) { return f2.equal(f1); } template <class Facade> static void advance(Facade& f, typename Facade::difference_type n) { f.advance(n); } template <class Facade1, class Facade2> static typename Facade1::difference_type distance_from( Facade1 const& f1, Facade2 const& f2, mpl::true_) { return -f1.distance_to(f2); } template <class Facade1, class Facade2> static typename Facade2::difference_type distance_from( Facade1 const& f1, Facade2 const& f2, mpl::false_) { return f2.distance_to(f1); } private: // objects of this class are useless iterator_core_access(); //undefined }; // // iterator_facade - use as a public base class for defining new // standard-conforming iterators. // template < class Derived // The derived iterator type being constructed , class Value , class CategoryOrTraversal , class Reference = Value& , class Difference = std::ptrdiff_t > class iterator_facade # ifdef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE : public detail::iterator_facade_types< Value, CategoryOrTraversal, Reference, Difference >::base # undef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE # endif { private: // // Curiously Recurring Template interface. // typedef Derived derived_t; Derived& derived() { return static_cast<Derived&>(*this); } Derived const& derived() const { return static_cast<Derived const&>(*this); } typedef detail::iterator_facade_types< Value, CategoryOrTraversal, Reference, Difference > associated_types; public: typedef typename associated_types::value_type value_type; typedef Reference reference; typedef Difference difference_type; typedef typename associated_types::pointer pointer; typedef typename associated_types::iterator_category iterator_category; reference operator*() const { return iterator_core_access::dereference(this->derived()); } typename detail::operator_arrow_result< value_type , reference , pointer >::type operator->() const { return detail::operator_arrow_result< value_type , reference , pointer >::make(*this->derived()); } typename detail::operator_brackets_result<Derived,Value,Reference>::type operator[](difference_type n) const { typedef detail::use_operator_brackets_proxy<Value,Reference> use_proxy; return detail::make_operator_brackets_result<Derived>( this->derived() + n , use_proxy() ); } Derived& operator++() { iterator_core_access::increment(this->derived()); return this->derived(); } Derived operator++(int) { Derived tmp(this->derived()); ++*this; return tmp; } Derived& operator--() { iterator_core_access::decrement(this->derived()); return this->derived(); } Derived operator--(int) { Derived tmp(this->derived()); --*this; return tmp; } Derived& operator+=(difference_type n) { iterator_core_access::advance(this->derived(), n); return this->derived(); } Derived& operator-=(difference_type n) { iterator_core_access::advance(this->derived(), -n); return this->derived(); } Derived operator-(difference_type x) const { Derived result(this->derived()); return result -= x; } # if BOOST_WORKAROUND(BOOST_MSVC, <= 1200) // There appears to be a bug which trashes the data of classes // derived from iterator_facade when they are assigned unless we // define this assignment operator. This bug is only revealed // (so far) in STLPort debug mode, but it's clearly a codegen // problem so we apply the workaround for all MSVC6. iterator_facade& operator=(iterator_facade const&) { return *this; } # endif }; // // Operator implementation. The library supplied operators // enables the user to provide fully interoperable constant/mutable // iterator types. I.e. the library provides all operators // for all mutable/constant iterator combinations. // // Note though that this kind of interoperability for constant/mutable // iterators is not required by the standard for container iterators. // All the standard asks for is a conversion mutable -> constant. // Most standard library implementations nowadays provide fully interoperable // iterator implementations, but there are still heavily used implementations // that do not provide them. (Actually it's even worse, they do not provide // them for only a few iterators.) // // ?? Maybe a BOOST_ITERATOR_NO_FULL_INTEROPERABILITY macro should // enable the user to turn off mixed type operators // // The library takes care to provide only the right operator overloads. // I.e. // // bool operator==(Iterator, Iterator); // bool operator==(ConstIterator, Iterator); // bool operator==(Iterator, ConstIterator); // bool operator==(ConstIterator, ConstIterator); // // ... // // In order to do so it uses c++ idioms that are not yet widely supported // by current compiler releases. The library is designed to degrade gracefully // in the face of compiler deficiencies. In general compiler // deficiencies result in less strict error checking and more obscure // error messages, functionality is not affected. // // For full operation compiler support for "Substitution Failure Is Not An Error" // (aka. enable_if) and boost::is_convertible is required. // // The following problems occur if support is lacking. // // Pseudo code // // --------------- // AdaptorA<Iterator1> a1; // AdaptorA<Iterator2> a2; // // // This will result in a no such overload error in full operation // // If enable_if or is_convertible is not supported // // The instantiation will fail with an error hopefully indicating that // // there is no operator== for Iterator1, Iterator2 // // The same will happen if no enable_if is used to remove // // false overloads from the templated conversion constructor // // of AdaptorA. // // a1 == a2; // ---------------- // // AdaptorA<Iterator> a; // AdaptorB<Iterator> b; // // // This will result in a no such overload error in full operation // // If enable_if is not supported the static assert used // // in the operator implementation will fail. // // This will accidently work if is_convertible is not supported. // // a == b; // ---------------- // # ifdef BOOST_NO_ONE_WAY_ITERATOR_INTEROP # define BOOST_ITERATOR_CONVERTIBLE(a,b) mpl::true_() # else # define BOOST_ITERATOR_CONVERTIBLE(a,b) is_convertible<a,b>() # endif # define BOOST_ITERATOR_FACADE_INTEROP(op, result_type, return_prefix, base_op) \ BOOST_ITERATOR_FACADE_INTEROP_HEAD(inline, op, result_type) \ { \ /* For those compilers that do not support enable_if */ \ BOOST_STATIC_ASSERT(( \ is_interoperable< Derived1, Derived2 >::value \ )); \ return_prefix iterator_core_access::base_op( \ static_cast<Derived1 const&>(lhs) \ , static_cast<Derived2 const&>(rhs) \ , BOOST_ITERATOR_CONVERTIBLE(Derived2,Derived1) \ ); \ } # define BOOST_ITERATOR_FACADE_RELATION(op, return_prefix, base_op) \ BOOST_ITERATOR_FACADE_INTEROP( \ op \ , detail::always_bool2 \ , return_prefix \ , base_op \ ) BOOST_ITERATOR_FACADE_RELATION(==, return, equal) BOOST_ITERATOR_FACADE_RELATION(!=, return !, equal) BOOST_ITERATOR_FACADE_RELATION(<, return 0 >, distance_from) BOOST_ITERATOR_FACADE_RELATION(>, return 0 <, distance_from) BOOST_ITERATOR_FACADE_RELATION(<=, return 0 >=, distance_from) BOOST_ITERATOR_FACADE_RELATION(>=, return 0 <=, distance_from) # undef BOOST_ITERATOR_FACADE_RELATION // operator- requires an additional part in the static assertion BOOST_ITERATOR_FACADE_INTEROP( - , detail::choose_difference_type , return , distance_from ) # undef BOOST_ITERATOR_FACADE_INTEROP # undef BOOST_ITERATOR_FACADE_INTEROP_HEAD # define BOOST_ITERATOR_FACADE_PLUS(args) \ BOOST_ITERATOR_FACADE_PLUS_HEAD(inline, args) \ { \ Derived tmp(static_cast<Derived const&>(i)); \ return tmp += n; \ } BOOST_ITERATOR_FACADE_PLUS(( iterator_facade<Derived, V, TC, R, D> const& i , typename Derived::difference_type n )) BOOST_ITERATOR_FACADE_PLUS(( typename Derived::difference_type n , iterator_facade<Derived, V, TC, R, D> const& i )) # undef BOOST_ITERATOR_FACADE_PLUS # undef BOOST_ITERATOR_FACADE_PLUS_HEAD } // namespace boost #include <boost/iterator/detail/config_undef.hpp> #endif // BOOST_ITERATOR_FACADE_23022003THW_HPP