include/boost/url/grammar/optional_rule.hpp
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include/boost/url/grammar/optional_rule.hpp
| Line | Hits | Source Code |
|---|---|---|
| 1 | // | |
| 2 | // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com) | |
| 3 | // Copyright (c) 2022 Alan de Freitas (alandefreitas@gmail.com) | |
| 4 | // | |
| 5 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
| 6 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
| 7 | // | |
| 8 | // Official repository: https://github.com/boostorg/url | |
| 9 | // | |
| 10 | ||
| 11 | #ifndef BOOST_URL_GRAMMAR_OPTIONAL_RULE_HPP | |
| 12 | #define BOOST_URL_GRAMMAR_OPTIONAL_RULE_HPP | |
| 13 | ||
| 14 | #include <boost/url/detail/config.hpp> | |
| 15 | #include <boost/url/optional.hpp> | |
| 16 | #include <boost/url/error_types.hpp> | |
| 17 | #include <boost/url/grammar/type_traits.hpp> | |
| 18 | #include <boost/core/empty_value.hpp> | |
| 19 | #include <boost/core/detail/static_assert.hpp> | |
| 20 | #include <boost/assert.hpp> | |
| 21 | ||
| 22 | namespace boost { | |
| 23 | namespace urls { | |
| 24 | namespace grammar { | |
| 25 | ||
| 26 | namespace implementation_defined { | |
| 27 | template<class Rule> | |
| 28 | struct optional_rule_t | |
| 29 | : private empty_value<Rule> | |
| 30 | { | |
| 31 | using value_type = boost::optional< | |
| 32 | typename Rule::value_type>; | |
| 33 | ||
| 34 | BOOST_URL_CXX14_CONSTEXPR | |
| 35 | system::result<value_type> | |
| 36 | parse( | |
| 37 | char const*& it, | |
| 38 | char const* end) const; | |
| 39 | ||
| 40 | constexpr | |
| 41 | 2137 | optional_rule_t( |
| 42 | Rule const& r) noexcept | |
| 43 | : empty_value<Rule>( | |
| 44 | empty_init, | |
| 45 | 2137 | r) |
| 46 | { | |
| 47 | 2137 | } |
| 48 | }; | |
| 49 | } // implementation_defined | |
| 50 | ||
| 51 | /** Match a rule, or the empty string | |
| 52 | ||
| 53 | Optional BNF elements are denoted with | |
| 54 | square brackets. If the specified rule | |
| 55 | returns any error it is treated as if | |
| 56 | the rule did not match. | |
| 57 | ||
| 58 | @par Value Type | |
| 59 | @code | |
| 60 | using value_type = optional< typename Rule::value_type >; | |
| 61 | @endcode | |
| 62 | ||
| 63 | @par Example | |
| 64 | Rules are used with the function @ref grammar::parse. | |
| 65 | @code | |
| 66 | system::result< optional< core::string_view > > rv = parse( "", optional_rule( token_rule( alpha_chars ) ) ); | |
| 67 | @endcode | |
| 68 | ||
| 69 | @par BNF | |
| 70 | @code | |
| 71 | optional = [ rule ] | |
| 72 | @endcode | |
| 73 | ||
| 74 | @par Specification | |
| 75 | @li <a href="https://datatracker.ietf.org/doc/html/rfc5234#section-3.8" | |
| 76 | >3.8. Optional Sequence (rfc5234)</a> | |
| 77 | ||
| 78 | @param r The rule to match | |
| 79 | @return The adapted rule | |
| 80 | ||
| 81 | @see | |
| 82 | @ref alpha_chars, | |
| 83 | @ref parse, | |
| 84 | @ref optional, | |
| 85 | @ref token_rule. | |
| 86 | */ | |
| 87 | template<BOOST_URL_CONSTRAINT(Rule) R> | |
| 88 | auto | |
| 89 | constexpr | |
| 90 | 2137 | optional_rule( |
| 91 | R const& r) -> | |
| 92 | implementation_defined::optional_rule_t<R> | |
| 93 | { | |
| 94 | BOOST_CORE_STATIC_ASSERT(grammar::is_rule<R>::value); | |
| 95 | 2137 | return { r }; |
| 96 | } | |
| 97 | ||
| 98 | } // grammar | |
| 99 | } // urls | |
| 100 | } // boost | |
| 101 | ||
| 102 | #include <boost/url/grammar/impl/optional_rule.hpp> | |
| 103 | ||
| 104 | #endif | |
| 105 |