ceph/src/boost/libs/spirit/repository/example/qi/flush_multi_pass.cpp

   1 //  Copyright (c) 2001-2010 Hartmut Kaiser
   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 //  The purpose of this example is to demonstrate a simple use case for the
   7 //  flush_multi_pass parser.
   8
   9 #include <iostream>
  10 #include <fstream>
  11 #include <string>
  12
  13 //[qi_flush_multi_pass_includes
  14 #include <boost/spirit/include/qi.hpp>
  15 #include <boost/spirit/repository/include/qi_flush_multi_pass.hpp>
  16 //]
  17
  18 //[qi_flush_multi_pass_namespace
  19 namespace spirit = boost::spirit;
  20 using boost::spirit::repository::flush_multi_pass;
  21 //]
  22
  23 namespace client
  24 {
  25     //[qi_flush_multi_pass_clear_buffer
  26     template <typename Iterator, typename Skipper>
  27     struct preprocessor : spirit::qi::grammar<Iterator, Skipper>
  28     {
  29         // This is a simplified preprocessor grammar recognizing
  30         //
  31         //   #define MACRONAME something
  32         //   #undef MACRONAME
  33         //
  34         // Its sole purpose is to show an example how to use the
  35         // flush_multi_pass parser. At the end of each line no backtracking can
  36         // occur anymore so that it's safe to clear all internal buffers in the
  37         // multi_pass.
  38         preprocessor() : preprocessor::base_type(file)
  39         {
  40             using spirit::ascii::char_;
  41             using spirit::qi::eol;
  42             using spirit::qi::lit;
  43
  44             file =
  45                 *line
  46                 ;
  47
  48             line =  ( command |  *(char_ - eol) )
  49                 >>  eol
  50                 >>  flush_multi_pass
  51                 ;
  52
  53             command =
  54                     "#define" >> *lit(' ') >> *(char_ - ' ') >> *lit(' ') >> *(char_ - eol)
  55                 |   "#undef"  >> *lit(' ') >> *(char_ - eol)
  56                 ;
  57         }
  58
  59         spirit::qi::rule<Iterator, Skipper> file, line, command;
  60     };
  61     //]
  62 }
  63
  64 template <typename Iterator, typename Skipper>
  65 bool parse(Iterator& first, Iterator end, Skipper const& skipper)
  66 {
  67     client::preprocessor<Iterator, Skipper> g;
  68     return boost::spirit::qi::phrase_parse(first, end, g, skipper);
  69 }
  70
  71 int main()
  72 {
  73     namespace spirit = boost::spirit;
  74     using spirit::ascii::char_;
  75     using spirit::qi::eol;
  76
  77     std::ifstream in("flush_multi_pass.txt");    // we get our input from this file
  78     if (!in.is_open()) {
  79         std::cout << "Could not open input file: 'flush_multi_pass.txt'" << std::endl;
  80         return -1;
  81     }
  82
  83     typedef std::istreambuf_iterator<char> base_iterator_type;
  84     spirit::multi_pass<base_iterator_type> first =
  85         spirit::make_default_multi_pass(base_iterator_type(in));
  86     spirit::multi_pass<base_iterator_type> end =
  87         spirit::make_default_multi_pass(base_iterator_type());
  88
  89     bool result = parse(first, end, '#' >> *(char_ - eol) >> eol);
  90     if (!result) {
  91         std::cout << "Failed parsing input file!" << std::endl;
  92         return -2;
  93     }
  94
  95     std::cout << "Successfully parsed input file!" << std::endl;
  96     return 0;
  97 }
  98