ceph/src/boost/boost/spirit/repository/home/qi/primitive/advance.hpp

   1 //  Copyright (c) 2011 Aaron Graham
   2 //
   3 //  Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #if !defined(BOOST_SPIRIT_REPOSITORY_QI_ADVANCE_JAN_23_2011_1203PM)
   7 #define BOOST_SPIRIT_REPOSITORY_QI_ADVANCE_JAN_23_2011_1203PM
   8
   9 #include <boost/spirit/home/support/terminal.hpp>
  10 #include <boost/spirit/include/qi_parse.hpp>
  11
  12 ///////////////////////////////////////////////////////////////////////////////
  13 // definition the place holder
  14 namespace boost { namespace spirit { namespace repository { namespace qi
  15 {
  16     BOOST_SPIRIT_TERMINAL_EX(advance)
  17 }}}}
  18
  19 ///////////////////////////////////////////////////////////////////////////////
  20 // implementation the enabler
  21 namespace boost { namespace spirit
  22 {
  23     template <typename A0>
  24     struct use_terminal<qi::domain
  25       , terminal_ex<repository::qi::tag::advance, fusion::vector1<A0> > >
  26       : mpl::or_<is_integral<A0>, is_enum<A0> >
  27     {};
  28
  29     template <>
  30     struct use_lazy_terminal<qi::domain, repository::qi::tag::advance, 1>
  31       : mpl::true_
  32     {};
  33 }}
  34
  35 ///////////////////////////////////////////////////////////////////////////////
  36 // implementation of the parser
  37 namespace boost { namespace spirit { namespace repository { namespace qi
  38 {
  39     template <typename Int>
  40     struct advance_parser
  41       : boost::spirit::qi::primitive_parser< advance_parser<Int> >
  42     {
  43         // Define the attribute type exposed by this parser component
  44         template <typename Context, typename Iterator>
  45         struct attribute
  46         {
  47             typedef boost::spirit::unused_type type;
  48         };
  49
  50         advance_parser(Int dist)
  51           : dist(dist)
  52         {}
  53
  54         // This function is called during the actual parsing process
  55         template <typename Iterator, typename Context
  56             , typename Skipper, typename Attribute>
  57         bool parse(Iterator& first, Iterator const& last
  58             , Context&, Skipper&, Attribute&) const
  59         {
  60             // This series of checks is designed to fail parsing on negative
  61             // values, without generating a "expression always evaluates true"
  62             // warning on unsigned types.
  63             if (dist == Int(0)) return true;
  64             if (dist < Int(1)) return false;
  65
  66             typedef typename std::iterator_traits<Iterator>::iterator_category
  67                 iterator_category;
  68             return advance(first, last, iterator_category());
  69         }
  70
  71         // This function is called during error handling to create
  72         // a human readable string for the error context.
  73         template <typename Context>
  74         boost::spirit::info what(Context&) const
  75         {
  76             return boost::spirit::info("advance");
  77         }
  78
  79     private:
  80         // this is the general implementation used by most iterator categories
  81         template <typename Iterator, typename IteratorCategory>
  82         bool advance(Iterator& first, Iterator const& last
  83             , IteratorCategory) const
  84         {
  85             Int n = dist;
  86             Iterator i = first;
  87             while (n)
  88             {
  89                 if (i == last) return false;
  90                 ++i;
  91                 --n;
  92             }
  93             first = i;
  94             return true;
  95         }
  96
  97         // this is a specialization for random access iterators
  98         template <typename Iterator>
  99         bool advance(Iterator& first, Iterator const& last
 100             , std::random_access_iterator_tag) const
 101         {
 102             Iterator const it = first + dist;
 103             if (it > last) return false;
 104             first = it;
 105             return true;
 106         }
 107
 108         Int const dist;
 109     };
 110 }}}}
 111
 112 ///////////////////////////////////////////////////////////////////////////////
 113 // instantiation of the parser
 114 namespace boost { namespace spirit { namespace qi
 115 {
 116     template <typename Modifiers, typename A0>
 117     struct make_primitive<
 118           terminal_ex<repository::qi::tag::advance, fusion::vector1<A0> >
 119         , Modifiers>
 120     {
 121         typedef repository::qi::advance_parser<A0> result_type;
 122
 123         template <typename Terminal>
 124         result_type operator()(Terminal const& term, unused_type) const
 125         {
 126             return result_type(fusion::at_c<0>(term.args));
 127         }
 128     };
 129 }}}
 130
 131 #endif