[857] | 1 | /*=============================================================================
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| 2 | Copyright (c) 2001-2003 Joel de Guzman
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| 3 | http://spirit.sourceforge.net/
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| 4 |
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| 5 | Use, modification and distribution is subject to the Boost Software
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| 6 | License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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| 7 | http://www.boost.org/LICENSE_1_0.txt)
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| 8 | =============================================================================*/
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| 9 | #ifndef BOOST_SPIRIT_EXCEPTIONS_HPP
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| 10 | #define BOOST_SPIRIT_EXCEPTIONS_HPP
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| 11 |
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| 12 | #include <boost/config.hpp>
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| 13 | #include <boost/throw_exception.hpp>
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| 14 | #include <boost/spirit/core/parser.hpp>
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| 15 | #include <boost/spirit/core/composite/composite.hpp>
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| 16 | #include <exception>
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| 17 |
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| 18 | namespace boost { namespace spirit {
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| 19 |
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| 20 | ///////////////////////////////////////////////////////////////////////////
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| 21 | //
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| 22 | // parser_error_base class
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| 23 | //
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| 24 | // This is the base class of parser_error (see below). This may be
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| 25 | // used to catch any type of parser error.
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| 26 | //
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| 27 | // This exception shouldn't propagate outside the parser. However to
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| 28 | // avoid quirks of many platforms/implementations which fall outside
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| 29 | // the C++ standard, we derive parser_error_base from std::exception
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| 30 | // to allow a single catch handler to catch all exceptions.
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| 31 | //
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| 32 | ///////////////////////////////////////////////////////////////////////////
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| 33 | class parser_error_base : public std::exception
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| 34 | {
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| 35 | protected:
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| 36 |
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| 37 | parser_error_base() {}
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| 38 | virtual ~parser_error_base() throw() {}
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| 39 |
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| 40 | public:
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| 41 |
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| 42 | parser_error_base(parser_error_base const& rhs)
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| 43 | : std::exception(rhs) {}
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| 44 | parser_error_base& operator=(parser_error_base const&)
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| 45 | {
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| 46 | return *this;
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| 47 | }
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| 48 | };
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| 49 |
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| 50 | ///////////////////////////////////////////////////////////////////////////
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| 51 | //
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| 52 | // parser_error class
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| 53 | //
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| 54 | // Generic parser exception class. This is the base class for all
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| 55 | // parser exceptions. The exception holds the iterator position
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| 56 | // where the error was encountered in its member variable "where".
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| 57 | // The parser_error also holds information regarding the error
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| 58 | // (error descriptor) in its member variable "descriptor".
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| 59 | //
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| 60 | // The throw_ function creates and throws a parser_error given
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| 61 | // an iterator and an error descriptor.
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| 62 | //
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| 63 | ///////////////////////////////////////////////////////////////////////////
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| 64 | template <typename ErrorDescrT, typename IteratorT = char const*>
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| 65 | struct parser_error : public parser_error_base
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| 66 | {
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| 67 | typedef ErrorDescrT error_descr_t;
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| 68 | typedef IteratorT iterator_t;
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| 69 |
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| 70 | parser_error(IteratorT where_, ErrorDescrT descriptor_)
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| 71 | : where(where_), descriptor(descriptor_) {}
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| 72 |
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| 73 | parser_error(parser_error const& rhs)
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| 74 | : parser_error_base(rhs)
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| 75 | , where(rhs.where), descriptor(rhs.descriptor) {}
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| 76 |
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| 77 | parser_error&
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| 78 | operator=(parser_error const& rhs)
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| 79 | {
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| 80 | where = rhs.where;
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| 81 | descriptor = rhs.descriptor;
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| 82 | return *this;
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| 83 | }
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| 84 |
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| 85 | virtual
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| 86 | ~parser_error() throw() {}
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| 87 |
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| 88 | virtual const char*
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| 89 | what() const throw()
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| 90 | {
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| 91 | return "boost::spirit::parser_error";
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| 92 | }
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| 93 |
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| 94 | IteratorT where;
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| 95 | ErrorDescrT descriptor;
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| 96 | };
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| 97 |
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| 98 | //////////////////////////////////
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| 99 | template <typename ErrorDescrT, typename IteratorT>
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| 100 | inline void
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| 101 | throw_(IteratorT where, ErrorDescrT descriptor)
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| 102 | {
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| 103 | boost::throw_exception(
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| 104 | parser_error<ErrorDescrT, IteratorT>(where, descriptor));
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| 105 | }
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| 106 |
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| 107 | ///////////////////////////////////////////////////////////////////////////
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| 108 | //
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| 109 | // assertive_parser class
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| 110 | //
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| 111 | // An assertive_parser class is a parser that throws an exception
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| 112 | // in response to a parsing failure. The assertive_parser throws a
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| 113 | // parser_error exception rather than returning an unsuccessful
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| 114 | // match to signal that the parser failed to match the input.
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| 115 | //
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| 116 | ///////////////////////////////////////////////////////////////////////////
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| 117 | template <typename ErrorDescrT, typename ParserT>
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| 118 | struct assertive_parser
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| 119 | : public unary<ParserT, parser<assertive_parser<ErrorDescrT, ParserT> > >
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| 120 | {
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| 121 | typedef assertive_parser<ErrorDescrT, ParserT> self_t;
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| 122 | typedef unary<ParserT, parser<self_t> > base_t;
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| 123 | typedef unary_parser_category parser_category_t;
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| 124 |
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| 125 | assertive_parser(ParserT const& parser, ErrorDescrT descriptor)
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| 126 | : base_t(parser), descriptor(descriptor) {}
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| 127 |
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| 128 | template <typename ScannerT>
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| 129 | struct result
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| 130 | {
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| 131 | typedef typename parser_result<ParserT, ScannerT>::type type;
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| 132 | };
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| 133 |
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| 134 | template <typename ScannerT>
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| 135 | typename parser_result<self_t, ScannerT>::type
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| 136 | parse(ScannerT const& scan) const
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| 137 | {
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| 138 | typedef typename parser_result<ParserT, ScannerT>::type result_t;
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| 139 | typedef typename ScannerT::iterator_t iterator_t;
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| 140 |
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| 141 | result_t hit = this->subject().parse(scan);
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| 142 | if (!hit)
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| 143 | {
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| 144 | throw_(scan.first, descriptor);
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| 145 | }
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| 146 | return hit;
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| 147 | }
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| 148 |
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| 149 | ErrorDescrT descriptor;
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| 150 | };
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| 151 |
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| 152 | ///////////////////////////////////////////////////////////////////////////
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| 153 | //
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| 154 | // assertion class
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| 155 | //
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| 156 | // assertive_parsers are never instantiated directly. The assertion
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| 157 | // class is used to indirectly create an assertive_parser object.
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| 158 | // Before declaring the grammar, we declare some assertion objects.
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| 159 | // Examples:
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| 160 | //
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| 161 | // enum Errors
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| 162 | // {
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| 163 | // program_expected, begin_expected, end_expected
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| 164 | // };
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| 165 | //
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| 166 | // assertion<Errors> expect_program(program_expected);
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| 167 | // assertion<Errors> expect_begin(begin_expected);
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| 168 | // assertion<Errors> expect_end(end_expected);
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| 169 | //
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| 170 | // Now, we can use these assertions as wrappers around parsers:
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| 171 | //
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| 172 | // expect_end(str_p("end"))
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| 173 | //
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| 174 | // Take note that although the example uses enums to hold the
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| 175 | // information regarding the error (error desccriptor), we are free
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| 176 | // to use other types such as integers and strings. Enums are
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| 177 | // convenient for error handlers to easily catch since C++ treats
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| 178 | // enums as unique types.
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| 179 | //
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| 180 | ///////////////////////////////////////////////////////////////////////////
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| 181 | template <typename ErrorDescrT>
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| 182 | struct assertion
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| 183 | {
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| 184 | assertion(ErrorDescrT descriptor_)
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| 185 | : descriptor(descriptor_) {}
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| 186 |
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| 187 | template <typename ParserT>
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| 188 | assertive_parser<ErrorDescrT, ParserT>
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| 189 | operator()(ParserT const& parser) const
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| 190 | {
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| 191 | return assertive_parser<ErrorDescrT, ParserT>(parser, descriptor);
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| 192 | }
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| 193 |
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| 194 | ErrorDescrT descriptor;
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| 195 | };
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| 196 |
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| 197 | ///////////////////////////////////////////////////////////////////////////
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| 198 | //
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| 199 | // error_status<T>
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| 200 | //
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| 201 | // Where T is an attribute type compatible with the match attribute
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| 202 | // of the fallback_parser's subject (defaults to nil_t). The class
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| 203 | // error_status reports the result of an error handler (see
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| 204 | // fallback_parser). result can be one of:
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| 205 | //
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| 206 | // fail: quit and fail (return a no_match)
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| 207 | // retry: attempt error recovery, possibly moving the scanner
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| 208 | // accept: force success returning a matching length, moving
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| 209 | // the scanner appropriately and returning an attribute
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| 210 | // value
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| 211 | // rethrow: rethrows the error.
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| 212 | //
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| 213 | ///////////////////////////////////////////////////////////////////////////
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| 214 | template <typename T = nil_t>
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| 215 | struct error_status
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| 216 | {
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| 217 | enum result_t { fail, retry, accept, rethrow };
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| 218 |
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| 219 | error_status(
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| 220 | result_t result_ = fail,
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| 221 | std::ptrdiff_t length = -1,
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| 222 | T const& value_ = T())
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| 223 | : result(result_), length(length), value(value_) {}
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| 224 |
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| 225 | result_t result;
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| 226 | std::ptrdiff_t length;
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| 227 | T value;
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| 228 | };
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| 229 |
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| 230 | ///////////////////////////////////////////////////////////////////////////
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| 231 | //
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| 232 | // fallback_parser class
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| 233 | //
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| 234 | // Handles exceptions of type parser_error<ErrorDescrT, IteratorT>
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| 235 | // thrown somewhere inside its embedded ParserT object. The class
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| 236 | // sets up a try block before delegating parsing to its subject.
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| 237 | // When an exception is caught, the catch block then calls the
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| 238 | // HandlerT object. HandlerT may be a function or a functor (with
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| 239 | // an operator() member function) compatible with the interface:
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| 240 | //
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| 241 | // error_status<T>
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| 242 | // handler(ScannerT const& scan, ErrorT error);
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| 243 | //
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| 244 | // Where scan points to the scanner state prior to parsing and error
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| 245 | // is the error that arose (see parser_error). The handler must
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| 246 | // return an error_status<T> object (see above).
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| 247 | //
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| 248 | ///////////////////////////////////////////////////////////////////////////
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| 249 | namespace impl
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| 250 | {
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| 251 | template <typename RT, typename ParserT, typename ScannerT>
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| 252 | RT fallback_parser_parse(ParserT const& p, ScannerT const& scan);
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| 253 | }
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| 254 |
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| 255 | template <typename ErrorDescrT, typename ParserT, typename HandlerT>
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| 256 | struct fallback_parser
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| 257 | : public unary<ParserT,
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| 258 | parser<fallback_parser<ErrorDescrT, ParserT, HandlerT> > >
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| 259 | {
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| 260 | typedef fallback_parser<ErrorDescrT, ParserT, HandlerT>
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| 261 | self_t;
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| 262 | typedef ErrorDescrT
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| 263 | error_descr_t;
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| 264 | typedef unary<ParserT, parser<self_t> >
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| 265 | base_t;
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| 266 | typedef unary_parser_category
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| 267 | parser_category_t;
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| 268 |
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| 269 | fallback_parser(ParserT const& parser, HandlerT const& handler_)
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| 270 | : base_t(parser), handler(handler_) {}
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| 271 |
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| 272 | template <typename ScannerT>
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| 273 | struct result
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| 274 | {
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| 275 | typedef typename parser_result<ParserT, ScannerT>::type type;
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| 276 | };
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| 277 |
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| 278 | template <typename ScannerT>
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| 279 | typename parser_result<self_t, ScannerT>::type
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| 280 | parse(ScannerT const& scan) const
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| 281 | {
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| 282 | typedef typename parser_result<self_t, ScannerT>::type result_t;
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| 283 | return impl::fallback_parser_parse<result_t>(*this, scan);
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| 284 | }
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| 285 |
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| 286 | HandlerT handler;
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| 287 | };
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| 288 |
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| 289 | ///////////////////////////////////////////////////////////////////////////
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| 290 | //
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| 291 | // guard class
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| 292 | //
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| 293 | // fallback_parser objects are not instantiated directly. The guard
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| 294 | // class is used to indirectly create a fallback_parser object.
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| 295 | // guards are typically predeclared just like assertions (see the
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| 296 | // assertion class above; the example extends the previous example
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| 297 | // introduced in the assertion class above):
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| 298 | //
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| 299 | // guard<Errors> my_guard;
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| 300 | //
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| 301 | // Errors, in this example is the error descriptor type we want to
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| 302 | // detect; This is essentially the ErrorDescrT template parameter
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| 303 | // of the fallback_parser class.
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| 304 | //
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| 305 | // my_guard may now be used in a grammar declaration as:
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| 306 | //
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| 307 | // my_guard(p)[h]
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| 308 | //
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| 309 | // where p is a parser, h is a function or functor compatible with
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| 310 | // fallback_parser's HandlerT (see above).
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| 311 | //
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| 312 | ///////////////////////////////////////////////////////////////////////////
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| 313 | template <typename ErrorDescrT>
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| 314 | struct guard;
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| 315 |
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| 316 | template <typename ErrorDescrT, typename ParserT>
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| 317 | struct guard_gen : public unary<ParserT, nil_t>
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| 318 | {
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| 319 | typedef guard<ErrorDescrT> parser_generator_t;
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| 320 | typedef unary_parser_category parser_category_t;
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| 321 |
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| 322 | guard_gen(ParserT const& p)
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| 323 | : unary<ParserT, nil_t>(p) {}
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| 324 |
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| 325 | template <typename HandlerT>
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| 326 | fallback_parser<ErrorDescrT, ParserT, HandlerT>
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| 327 | operator[](HandlerT const& handler) const
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| 328 | {
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| 329 | return fallback_parser<ErrorDescrT, ParserT, HandlerT>
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| 330 | (this->subject(), handler);
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| 331 | }
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| 332 | };
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| 333 |
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| 334 | template <typename ErrorDescrT>
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| 335 | struct guard
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| 336 | {
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| 337 | template <typename ParserT>
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| 338 | struct result
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| 339 | {
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| 340 | typedef guard_gen<ErrorDescrT, ParserT> type;
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| 341 | };
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| 342 |
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| 343 | template <typename ParserT>
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| 344 | static guard_gen<ErrorDescrT, ParserT>
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| 345 | generate(ParserT const& parser)
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| 346 | {
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| 347 | return guard_gen<ErrorDescrT, ParserT>(parser);
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| 348 | }
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| 349 |
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| 350 | template <typename ParserT>
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| 351 | guard_gen<ErrorDescrT, ParserT>
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| 352 | operator()(ParserT const& parser) const
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| 353 | {
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| 354 | return guard_gen<ErrorDescrT, ParserT>(parser);
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| 355 | }
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| 356 | };
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| 357 |
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| 358 | }} // namespace boost::spirit
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| 359 |
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| 360 | #include <boost/spirit/error_handling/impl/exceptions.ipp>
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| 361 | #endif
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| 362 |
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