| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com) | ||
| 3 | // | ||
| 4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | ||
| 5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | ||
| 6 | // | ||
| 7 | // Official repository: https://github.com/boostorg/url | ||
| 8 | // | ||
| 9 | |||
| 10 | #ifndef BOOST_URL_GRAMMAR_OPTIONAL_RULE_HPP | ||
| 11 | #define BOOST_URL_GRAMMAR_OPTIONAL_RULE_HPP | ||
| 12 | |||
| 13 | #include <boost/url/detail/config.hpp> | ||
| 14 | #include <boost/url/optional.hpp> | ||
| 15 | #include <boost/url/error_types.hpp> | ||
| 16 | #include <boost/url/grammar/type_traits.hpp> | ||
| 17 | #include <boost/core/empty_value.hpp> | ||
| 18 | #include <boost/assert.hpp> | ||
| 19 | |||
| 20 | namespace boost { | ||
| 21 | namespace urls { | ||
| 22 | namespace grammar { | ||
| 23 | |||
| 24 | namespace implementation_defined { | ||
| 25 | template<class Rule> | ||
| 26 | struct optional_rule_t | ||
| 27 | : private empty_value<Rule> | ||
| 28 | { | ||
| 29 | using value_type = boost::optional< | ||
| 30 | typename Rule::value_type>; | ||
| 31 | |||
| 32 | system::result<value_type> | ||
| 33 | parse( | ||
| 34 | char const*& it, | ||
| 35 | char const* end) const; | ||
| 36 | |||
| 37 | constexpr | ||
| 38 | 2031 | optional_rule_t( | |
| 39 | Rule const& r) noexcept | ||
| 40 | : empty_value<Rule>( | ||
| 41 | empty_init, | ||
| 42 | 2031 | r) | |
| 43 | { | ||
| 44 | 2031 | } | |
| 45 | }; | ||
| 46 | } // implementation_defined | ||
| 47 | |||
| 48 | /** Match a rule, or the empty string | ||
| 49 | |||
| 50 | Optional BNF elements are denoted with | ||
| 51 | square brackets. If the specified rule | ||
| 52 | returns any error it is treated as if | ||
| 53 | the rule did not match. | ||
| 54 | |||
| 55 | @par Value Type | ||
| 56 | @code | ||
| 57 | using value_type = optional< typename Rule::value_type >; | ||
| 58 | @endcode | ||
| 59 | |||
| 60 | @par Example | ||
| 61 | Rules are used with the function @ref grammar::parse. | ||
| 62 | @code | ||
| 63 | system::result< optional< core::string_view > > rv = parse( "", optional_rule( token_rule( alpha_chars ) ) ); | ||
| 64 | @endcode | ||
| 65 | |||
| 66 | @par BNF | ||
| 67 | @code | ||
| 68 | optional = [ rule ] | ||
| 69 | @endcode | ||
| 70 | |||
| 71 | @par Specification | ||
| 72 | @li <a href="https://datatracker.ietf.org/doc/html/rfc5234#section-3.8" | ||
| 73 | >3.8. Optional Sequence (rfc5234)</a> | ||
| 74 | |||
| 75 | @param r The rule to match | ||
| 76 | @return The adapted rule | ||
| 77 | |||
| 78 | @see | ||
| 79 | @ref alpha_chars, | ||
| 80 | @ref parse, | ||
| 81 | @ref optional, | ||
| 82 | @ref token_rule. | ||
| 83 | */ | ||
| 84 | template<BOOST_URL_CONSTRAINT(Rule) R> | ||
| 85 | auto | ||
| 86 | constexpr | ||
| 87 | 1967 | optional_rule( | |
| 88 | R const& r) -> | ||
| 89 | implementation_defined::optional_rule_t<R> | ||
| 90 | { | ||
| 91 | BOOST_STATIC_ASSERT(grammar::is_rule<R>::value); | ||
| 92 | 1967 | return { r }; | |
| 93 | } | ||
| 94 | |||
| 95 | } // grammar | ||
| 96 | } // urls | ||
| 97 | } // boost | ||
| 98 | |||
| 99 | #include <boost/url/grammar/impl/optional_rule.hpp> | ||
| 100 | |||
| 101 | #endif | ||
| 102 |