mini_xml_karma.cpp

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/*=============================================================================
    Copyright (c) 2001-2008 Joel de Guzman
    Copyright (c) 2001-2008 Hartmut Kaiser

    Distributed under the Boost Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
///////////////////////////////////////////////////////////////////////////////
//
//  A mini XML-like parser, Karma is used to print out the generated AST
//
//  [ JDG March 25, 2007 ]   spirit2
//  [ HK April 02, 2007  ]   spirit2
//
///////////////////////////////////////////////////////////////////////////////

#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/karma.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/include/phoenix_fusion.hpp>
#include <boost/spirit/include/phoenix_function.hpp>
#include <boost/spirit/include/phoenix_stl.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/variant/recursive_variant.hpp>

#include <iostream>
#include <fstream>
#include <string>
#include <vector>

using namespace boost::spirit;
using namespace boost::spirit::ascii;
using namespace boost::spirit::arg_names;

namespace fusion = boost::fusion;
namespace phoenix = boost::phoenix;

using phoenix::at_c;
using phoenix::push_back;

///////////////////////////////////////////////////////////////////////////////
//  Our mini XML tree representation
///////////////////////////////////////////////////////////////////////////////
struct mini_xml;

typedef
    boost::variant<
        boost::recursive_wrapper<mini_xml>
      , std::string
    >
mini_xml_node;

struct mini_xml
{
    std::string name;                           // tag name
    std::vector<mini_xml_node> children;        // children
};

// We need to tell fusion about our mini_xml struct
// to make it a first-class fusion citizen
BOOST_FUSION_ADAPT_STRUCT(
    mini_xml,
    (std::string, name)
    (std::vector<mini_xml_node>, children)
)

///////////////////////////////////////////////////////////////////////////////
//  Our mini XML grammar definition
///////////////////////////////////////////////////////////////////////////////
template <typename Iterator>
struct mini_xml_parser :
    qi::grammar<Iterator, mini_xml(), space_type>
{
    mini_xml_parser() : mini_xml_parser::base_type(xml)
    {
        text = lexeme[+(char_ - '<')        [_val += _1]];
        node = (xml | text)                 [_val = _1];

        start_tag =
                '<'
            >>  lexeme[+(char_ - '>')       [_val += _1]]
            >>  '>'
        ;

        end_tag =
                "</"
            >>  lit(_r1)
            >>  '>'
        ;

        xml =
                start_tag                   [at_c<0>(_val) = _1]
            >>  *node                       [push_back(at_c<1>(_val), _1)]
            >>  end_tag(at_c<0>(_val))
        ;
    }

    qi::rule<Iterator, mini_xml(), space_type> xml;
    qi::rule<Iterator, mini_xml_node(), space_type> node;
    qi::rule<Iterator, std::string(), space_type> text;
    qi::rule<Iterator, std::string(), space_type> start_tag;
    qi::rule<Iterator, void(std::string), space_type> end_tag;
};

///////////////////////////////////////////////////////////////////////////////
//  A couple of phoenix functions helping to access the elements of the 
//  generated AST
///////////////////////////////////////////////////////////////////////////////
template <typename T>
struct get_element
{
    template <typename T1>
    struct result { typedef T const& type; };

    T const& operator()(mini_xml_node const& node) const
    {
        return boost::get<T>(node);
    }
};

phoenix::function<get_element<std::string> > _string;
phoenix::function<get_element<mini_xml> > _xml;

///////////////////////////////////////////////////////////////////////////////
//  The output grammar defining the format of the generated data
///////////////////////////////////////////////////////////////////////////////
template <typename OutputIterator>
struct mini_xml_generator
  : karma::grammar<OutputIterator, mini_xml()>
{
    mini_xml_generator() : mini_xml_generator::base_type(xml)
    {
        node %= 
                lit[_1 = _string(_r0)] 
            |   xml[_1 = _xml(_r0)]
            ;

        xml =   char_('<') << lit(at_c<0>(_r0)) << '>'
            <<  (*node)[_1 = at_c<1>(_r0)]
            <<  lit("</")  << lit(at_c<0>(_r0)) << '>'
            ;
    }

    karma::rule<OutputIterator, mini_xml()> xml;
    karma::rule<OutputIterator, mini_xml_node()> node;
};

///////////////////////////////////////////////////////////////////////////////
//  Main program
///////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv)
{
    char const* filename;
    if (argc > 1)
    {
        filename = argv[1];
    }
    else
    {
        std::cerr << "Error: No input file provided." << std::endl;
        return 1;
    }

    std::ifstream in(filename, std::ios_base::in);

    if (!in)
    {
        std::cerr << "Error: Could not open input file: "
            << filename << std::endl;
        return 1;
    }

    std::string storage; // We will read the contents here.
    in.unsetf(std::ios::skipws); // No white space skipping!
    std::copy(
        std::istream_iterator<char>(in),
        std::istream_iterator<char>(),
        std::back_inserter(storage));

    typedef mini_xml_parser<std::string::const_iterator> mini_xml_parser;
    mini_xml_parser xmlin;  //  Our grammar definition
    mini_xml ast; // our tree

    std::string::const_iterator iter = storage.begin();
    std::string::const_iterator end = storage.end();
    bool r = qi::phrase_parse(iter, end, xmlin, ast, space);

    if (r && iter == end)
    {
        std::cout << "-------------------------\n";
        std::cout << "Parsing succeeded\n";
        std::cout << "-------------------------\n";

        typedef std::back_insert_iterator<std::string> outiter_type;
        typedef mini_xml_generator<outiter_type> mini_xml_generator;

        mini_xml_generator xmlout;                 //  Our grammar definition

        std::string generated;
        bool r = karma::generate(std::back_inserter(generated), xmlout, ast);

        if (r)
            std::cout << generated << std::endl;
        return 0;
    }
    else
    {
        std::string::const_iterator some = iter+30;
        std::string context(iter, (some>end)?end:some);
        std::cout << "-------------------------\n";
        std::cout << "Parsing failed\n";
        std::cout << "stopped at: \": " << context << "...\"\n";
        std::cout << "-------------------------\n";
        return 1;
    }
}