boost/iterator/distance.hpp

0001 // Copyright (C) 2017 Michel Morin.
0002 //
0003 // Distributed under the Boost Software License, Version 1.0.
0004 // (See accompanying file LICENSE_1_0.txt or copy at
0005 // http://www.boost.org/LICENSE_1_0.txt)
0006
0007 #ifndef BOOST_ITERATOR_DISTANCE_HPP
0008 #define BOOST_ITERATOR_DISTANCE_HPP
0009
0010 #include <boost/config.hpp>
0011 #include <boost/iterator/iterator_categories.hpp>
0012 #include <boost/iterator/iterator_traits.hpp>
0013
0014 namespace boost {
0015 namespace iterators {
0016
0017     namespace detail {
0018         template <typename SinglePassIterator>
0019         inline BOOST_CXX14_CONSTEXPR typename iterator_difference<SinglePassIterator>::type
0020         distance_impl(
0021             SinglePassIterator first
0022           , SinglePassIterator last
0023           , single_pass_traversal_tag
0024         )
0025         {
0026             typename iterator_difference<SinglePassIterator>::type n = 0;
0027             while (first != last) {
0028                 ++first;
0029                 ++n;
0030             }
0031             return n;
0032         }
0033
0034         template <typename RandomAccessIterator>
0035         inline BOOST_CXX14_CONSTEXPR typename iterator_difference<RandomAccessIterator>::type
0036         distance_impl(
0037             RandomAccessIterator first
0038           , RandomAccessIterator last
0039           , random_access_traversal_tag
0040         )
0041         {
0042             return last - first;
0043         }
0044     }
0045
0046     namespace distance_adl_barrier {
0047         template <typename SinglePassIterator>
0048         inline BOOST_CXX14_CONSTEXPR typename iterator_difference<SinglePassIterator>::type
0049         distance(SinglePassIterator first, SinglePassIterator last)
0050         {
0051             return detail::distance_impl(
0052                 first, last, typename iterator_traversal<SinglePassIterator>::type()
0053             );
0054         }
0055     }
0056
0057     using namespace distance_adl_barrier;
0058
0059 } // namespace iterators
0060
0061 using namespace iterators::distance_adl_barrier;
0062
0063 } // namespace boost
0064
0065 #endif