ceph/src/boost/boost/poly_collection/detail/segment_split.hpp

   1 /* Copyright 2016-2017 Joaquin M Lopez Munoz.
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * See http://www.boost.org/libs/poly_collection for library home page.
   7  */
   8
   9 #ifndef BOOST_POLY_COLLECTION_DETAIL_SEGMENT_SPLIT_HPP
  10 #define BOOST_POLY_COLLECTION_DETAIL_SEGMENT_SPLIT_HPP
  11
  12 #if defined(_MSC_VER)
  13 #pragma once
  14 #endif
  15
  16 #include <boost/iterator/iterator_facade.hpp>
  17 #include <boost/poly_collection/detail/iterator_traits.hpp>
  18 #include <typeinfo>
  19 #include <utility>
  20
  21 namespace boost{
  22
  23 namespace poly_collection{
  24
  25 namespace detail{
  26
  27 /* breakdown of an iterator range into local_base_iterator segments */
  28
  29 template<typename PolyCollectionIterator>
  30 class segment_splitter
  31 {
  32   using traits=iterator_traits<PolyCollectionIterator>;
  33   using local_base_iterator=typename traits::local_base_iterator;
  34   using base_segment_info_iterator=typename traits::base_segment_info_iterator;
  35
  36 public:
  37   struct info
  38   {
  39     const std::type_info& type_info()const noexcept{return *pinfo_;}
  40     local_base_iterator   begin()const noexcept{return begin_;}
  41     local_base_iterator   end()const noexcept{return end_;}
  42
  43     const std::type_info* pinfo_;
  44     local_base_iterator   begin_,end_;
  45   };
  46
  47   struct iterator:iterator_facade<iterator,info,std::input_iterator_tag,info>
  48   {
  49     iterator()=default;
  50
  51   private:
  52     friend class segment_splitter;
  53     friend class boost::iterator_core_access;
  54
  55     iterator(
  56       base_segment_info_iterator it,
  57       const PolyCollectionIterator& first,const PolyCollectionIterator& last):
  58       it{it},pfirst{&first},plast{&last}{}
  59     iterator(
  60       const PolyCollectionIterator& first,const PolyCollectionIterator& last):
  61       it{traits::base_segment_info_iterator_from(first)},
  62       pfirst{&first},plast{&last}
  63       {}
  64
  65     info dereference()const noexcept
  66     {
  67       return {
  68         &it->type_info(),
  69         it==traits::base_segment_info_iterator_from(*pfirst)?
  70           traits::local_base_iterator_from(*pfirst):it->begin(),
  71         it==traits::base_segment_info_iterator_from(*plast)?
  72           traits::local_base_iterator_from(*plast):it->end()
  73       };
  74     }
  75
  76     bool equal(const iterator& x)const noexcept{return it==x.it;}
  77     void increment()noexcept{++it;}
  78
  79     base_segment_info_iterator    it;
  80     const PolyCollectionIterator* pfirst;
  81     const PolyCollectionIterator* plast;
  82   };
  83
  84   segment_splitter(
  85     const PolyCollectionIterator& first,const PolyCollectionIterator& last):
  86     pfirst{&first},plast{&last}{}
  87
  88   iterator begin()const noexcept{return {*pfirst,*plast};}
  89
  90   iterator end()const noexcept
  91   {
  92     auto slast=traits::base_segment_info_iterator_from(*plast);
  93     if(slast!=traits::end_base_segment_info_iterator_from(*plast))++slast;
  94     return {slast,*plast,*plast};
  95   }
  96
  97 private:
  98   const PolyCollectionIterator* pfirst;
  99   const PolyCollectionIterator* plast;
 100 };
 101
 102 template<typename PolyCollectionIterator>
 103 segment_splitter<PolyCollectionIterator>
 104 segment_split(
 105   const PolyCollectionIterator& first,const PolyCollectionIterator& last)
 106 {
 107   return {first,last};
 108 }
 109
 110 #if 1
 111 /* equivalent to for(auto i:segment_split(first,last))f(i) */
 112
 113 template<typename PolyCollectionIterator,typename F>
 114 void for_each_segment(
 115   const PolyCollectionIterator& first,const PolyCollectionIterator& last,F&& f)
 116 {
 117   using traits=iterator_traits<PolyCollectionIterator>;
 118   using info=typename segment_splitter<PolyCollectionIterator>::info;
 119
 120   auto sfirst=traits::base_segment_info_iterator_from(first),
 121        slast=traits::base_segment_info_iterator_from(last),
 122        send=traits::end_base_segment_info_iterator_from(last);
 123   auto lbfirst=traits::local_base_iterator_from(first),
 124        lblast=traits::local_base_iterator_from(last);
 125
 126   if(sfirst!=slast){
 127     for(;;){
 128       f(info{&sfirst->type_info(),lbfirst,sfirst->end()});
 129       ++sfirst;
 130       if(sfirst==slast)break;
 131       lbfirst=sfirst->begin();
 132     }
 133     if(sfirst!=send)f(info{&sfirst->type_info(),sfirst->begin(),lblast});
 134   }
 135   else if(sfirst!=send){
 136     f(info{&sfirst->type_info(),lbfirst,lblast});
 137   }
 138 }
 139 #else
 140 template<typename PolyCollectionIterator,typename F>
 141 void for_each_segment(
 142   const PolyCollectionIterator& first,const PolyCollectionIterator& last,F&& f)
 143 {
 144   for(auto i:segment_split(first,last))f(i);
 145 }
 146 #endif
 147
 148 } /* namespace poly_collection::detail */
 149
 150 } /* namespace poly_collection */
 151
 152 } /* namespace boost */
 153
 154 #endif