99 lines
2.9 KiB
C++
99 lines
2.9 KiB
C++
// Copyright (c) 2001-2010 Hartmut Kaiser
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// The purpose of this example is to demonstrate a simple use case for the
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// flush_multi_pass parser.
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#include <iostream>
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#include <fstream>
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#include <string>
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//[qi_flush_multi_pass_includes
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#include <boost/spirit/include/qi.hpp>
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#include <boost/spirit/repository/include/qi_flush_multi_pass.hpp>
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//]
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//[qi_flush_multi_pass_namespace
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namespace spirit = boost::spirit;
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using boost::spirit::repository::flush_multi_pass;
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//]
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namespace client
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{
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//[qi_flush_multi_pass_clear_buffer
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template <typename Iterator, typename Skipper>
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struct preprocessor : spirit::qi::grammar<Iterator, Skipper>
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{
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// This is a simplified preprocessor grammar recognizing
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//
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// #define MACRONAME something
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// #undef MACRONAME
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//
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// Its sole purpose is to show an example how to use the
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// flush_multi_pass parser. At the end of each line no backtracking can
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// occur anymore so that it's safe to clear all internal buffers in the
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// multi_pass.
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preprocessor() : preprocessor::base_type(file)
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{
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using spirit::ascii::char_;
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using spirit::qi::eol;
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using spirit::qi::lit;
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file =
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*line
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;
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line = ( command | *(char_ - eol) )
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>> eol
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>> flush_multi_pass
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;
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command =
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"#define" >> *lit(' ') >> *(char_ - ' ') >> *lit(' ') >> *(char_ - eol)
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| "#undef" >> *lit(' ') >> *(char_ - eol)
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;
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}
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spirit::qi::rule<Iterator, Skipper> file, line, command;
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};
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//]
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}
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template <typename Iterator, typename Skipper>
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bool parse(Iterator& first, Iterator end, Skipper const& skipper)
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{
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client::preprocessor<Iterator, Skipper> g;
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return boost::spirit::qi::phrase_parse(first, end, g, skipper);
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}
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int main()
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{
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namespace spirit = boost::spirit;
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using spirit::ascii::char_;
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using spirit::qi::eol;
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std::ifstream in("flush_multi_pass.txt"); // we get our input from this file
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if (!in.is_open()) {
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std::cout << "Could not open input file: 'flush_multi_pass.txt'" << std::endl;
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return -1;
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}
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typedef std::istreambuf_iterator<char> base_iterator_type;
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spirit::multi_pass<base_iterator_type> first =
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spirit::make_default_multi_pass(base_iterator_type(in));
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spirit::multi_pass<base_iterator_type> end =
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spirit::make_default_multi_pass(base_iterator_type());
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bool result = parse(first, end, '#' >> *(char_ - eol) >> eol);
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if (!result) {
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std::cout << "Failed parsing input file!" << std::endl;
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return -2;
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}
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std::cout << "Successfully parsed input file!" << std::endl;
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return 0;
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}
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