Chris@16: // (C) Copyright Jeremy Siek 2001.
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: 
Chris@16: #ifndef BOOST_SHADOW_ITERATOR_HPP
Chris@16: #define BOOST_SHADOW_ITERATOR_HPP
Chris@16: 
Chris@16: #include <boost/iterator_adaptors.hpp>
Chris@16: #include <boost/operators.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16:   namespace detail {
Chris@16: 
Chris@16:     template <class A, class B, class D>
Chris@16:     class shadow_proxy
Chris@16:       : boost::operators< shadow_proxy<A,B,D> >
Chris@16:     {
Chris@16:       typedef shadow_proxy self;
Chris@16:     public:
Chris@16:       inline shadow_proxy(A aa, B bb) : a(aa), b(bb) { }
Chris@16:       inline shadow_proxy(const self& x) : a(x.a), b(x.b) { }
Chris@16:       template <class Self>
Chris@16:       inline shadow_proxy(Self x) : a(x.a), b(x.b) { }
Chris@16:       inline self& operator=(const self& x) { a = x.a; b = x.b; return *this; }
Chris@16:       inline self& operator++() { ++a; return *this; }
Chris@16:       inline self& operator--() { --a; return *this; }
Chris@16:       inline self& operator+=(const self& x) { a += x.a; return *this; }
Chris@16:       inline self& operator-=(const self& x) { a -= x.a; return *this; }
Chris@16:       inline self& operator*=(const self& x) { a *= x.a; return *this; }
Chris@16:       inline self& operator/=(const self& x) { a /= x.a; return *this; }
Chris@16:       inline self& operator%=(const self& x) { return *this; } // JGS
Chris@16:       inline self& operator&=(const self& x) { return *this; } // JGS
Chris@16:       inline self& operator|=(const self& x) { return *this; } // JGS
Chris@16:       inline self& operator^=(const self& x) { return *this; } // JGS
Chris@16:       inline friend D operator-(const self& x, const self& y) {
Chris@16:         return x.a - y.a;
Chris@16:       } 
Chris@16:       inline bool operator==(const self& x) const { return a == x.a;  }
Chris@16:       inline bool operator<(const self& x) const { return a < x.a;  }
Chris@16:       //  protected:
Chris@16:       A a;
Chris@16:       B b;
Chris@16:     };
Chris@16: 
Chris@16:     struct shadow_iterator_policies
Chris@16:     {
Chris@16:       template <typename iter_pair>
Chris@16:       void initialize(const iter_pair&) { }
Chris@16: 
Chris@16:       template <typename Iter>
Chris@16:       typename Iter::reference dereference(const Iter& i) const { 
Chris@16:         typedef typename Iter::reference R;
Chris@16:         return R(*i.base().first, *i.base().second); 
Chris@16:       }
Chris@16:       template <typename Iter>
Chris@16:       bool equal(const Iter& p1, const Iter& p2) const { 
Chris@16:         return p1.base().first == p2.base().first;  
Chris@16:       }
Chris@16:       template <typename Iter>
Chris@16:       void increment(Iter& i) { ++i.base().first; ++i.base().second; }
Chris@16: 
Chris@16:       template <typename Iter>
Chris@16:       void decrement(Iter& i) { --i.base().first; --i.base().second; }
Chris@16: 
Chris@16:       template <typename Iter>
Chris@16:       bool less(const Iter& x, const Iter& y) const { 
Chris@16:         return x.base().first < y.base().first;  
Chris@16:       }
Chris@16:       template <typename Iter>
Chris@16:       typename Iter::difference_type
Chris@16:       distance(const Iter& x, const Iter& y) const { 
Chris@16:         return y.base().first - x.base().first; 
Chris@16:       }
Chris@16:       template <typename D, typename Iter>
Chris@16:       void advance(Iter& p, D n) { p.base().first += n; p.base().second += n; }
Chris@16:     };
Chris@16: 
Chris@16:   } // namespace detail
Chris@16: 
Chris@16:   template <typename IterA, typename IterB>
Chris@16:   struct shadow_iterator_generator {
Chris@16:     
Chris@16:     // To use the iterator_adaptor we can't derive from
Chris@16:     // random_access_iterator because we don't have a real reference.
Chris@16:     // However, we want the STL algorithms to treat the shadow
Chris@16:     // iterator like a random access iterator.
Chris@16:     struct shadow_iterator_tag : public std::input_iterator_tag {
Chris@16:       operator std::random_access_iterator_tag() {
Chris@16:         return std::random_access_iterator_tag();
Chris@16:       };
Chris@16:     };
Chris@16:     typedef typename std::iterator_traits<IterA>::value_type Aval;
Chris@16:     typedef typename std::iterator_traits<IterB>::value_type Bval;
Chris@16:     typedef typename std::iterator_traits<IterA>::reference Aref;
Chris@16:     typedef typename std::iterator_traits<IterB>::reference Bref;
Chris@16:     typedef typename std::iterator_traits<IterA>::difference_type D;
Chris@16:     typedef detail::shadow_proxy<Aval,Bval,Aval> V;
Chris@16:     typedef detail::shadow_proxy<Aref,Bref,Aval> R;
Chris@16:     typedef iterator_adaptor< std::pair<IterA, IterB>,
Chris@16:                               detail::shadow_iterator_policies,
Chris@16:                               V, R, V*, shadow_iterator_tag,
Chris@16:                               D> type;
Chris@16:   };
Chris@16: 
Chris@16:   // short cut for creating a shadow iterator
Chris@16:   template <class IterA, class IterB>
Chris@16:   inline typename shadow_iterator_generator<IterA,IterB>::type
Chris@16:   make_shadow_iter(IterA a, IterB b) {
Chris@16:     typedef typename shadow_iterator_generator<IterA,IterB>::type Iter;
Chris@16:     return Iter(std::make_pair(a,b)); 
Chris@16:   }
Chris@16: 
Chris@16:   template <class Cmp>
Chris@16:   struct shadow_cmp {
Chris@16:     inline shadow_cmp(const Cmp& c) : cmp(c) { }
Chris@16:     template <class ShadowProxy1, class ShadowProxy2>
Chris@16:     inline bool operator()(const ShadowProxy1& x, const ShadowProxy2& y) const
Chris@16:     {
Chris@16:       return cmp(x.a, y.a);
Chris@16:     }
Chris@16:     Cmp cmp;
Chris@16:   };
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: namespace std {
Chris@16:   template <class A1, class B1, class D1,
Chris@16:             class A2, class B2, class D2>
Chris@16:   void swap(boost::detail::shadow_proxy<A1&,B1&,D1> x,
Chris@16:             boost::detail::shadow_proxy<A2&,B2&,D2> y)
Chris@16:   {
Chris@16:     std::swap(x.a, y.a);
Chris@16:     std::swap(x.b, y.b);
Chris@16:   }
Chris@16: }
Chris@16: 
Chris@16: #endif // BOOST_SHADOW_ITERATOR_HPP