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