| 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/core/detail/static_assert.hpp> | ||
| 19 | #include <boost/assert.hpp> | ||
| 20 | |||
| 21 | namespace boost { | ||
| 22 | namespace urls { | ||
| 23 | namespace grammar { | ||
| 24 | |||
| 25 | namespace implementation_defined { | ||
| 26 | template<class Rule> | ||
| 27 | struct optional_rule_t | ||
| 28 | : private empty_value<Rule> | ||
| 29 | { | ||
| 30 | using value_type = boost::optional< | ||
| 31 | typename Rule::value_type>; | ||
| 32 | |||
| 33 | system::result<value_type> | ||
| 34 | parse( | ||
| 35 | char const*& it, | ||
| 36 | char const* end) const; | ||
| 37 | |||
| 38 | constexpr | ||
| 39 | 2048 | optional_rule_t( | |
| 40 | Rule const& r) noexcept | ||
| 41 | : empty_value<Rule>( | ||
| 42 | empty_init, | ||
| 43 | 2048 | r) | |
| 44 | { | ||
| 45 | 2048 | } | |
| 46 | }; | ||
| 47 | } // implementation_defined | ||
| 48 | |||
| 49 | /** Match a rule, or the empty string | ||
| 50 | |||
| 51 | Optional BNF elements are denoted with | ||
| 52 | square brackets. If the specified rule | ||
| 53 | returns any error it is treated as if | ||
| 54 | the rule did not match. | ||
| 55 | |||
| 56 | @par Value Type | ||
| 57 | @code | ||
| 58 | using value_type = optional< typename Rule::value_type >; | ||
| 59 | @endcode | ||
| 60 | |||
| 61 | @par Example | ||
| 62 | Rules are used with the function @ref grammar::parse. | ||
| 63 | @code | ||
| 64 | system::result< optional< core::string_view > > rv = parse( "", optional_rule( token_rule( alpha_chars ) ) ); | ||
| 65 | @endcode | ||
| 66 | |||
| 67 | @par BNF | ||
| 68 | @code | ||
| 69 | optional = [ rule ] | ||
| 70 | @endcode | ||
| 71 | |||
| 72 | @par Specification | ||
| 73 | @li <a href="https://datatracker.ietf.org/doc/html/rfc5234#section-3.8" | ||
| 74 | >3.8. Optional Sequence (rfc5234)</a> | ||
| 75 | |||
| 76 | @param r The rule to match | ||
| 77 | @return The adapted rule | ||
| 78 | |||
| 79 | @see | ||
| 80 | @ref alpha_chars, | ||
| 81 | @ref parse, | ||
| 82 | @ref optional, | ||
| 83 | @ref token_rule. | ||
| 84 | */ | ||
| 85 | template<BOOST_URL_CONSTRAINT(Rule) R> | ||
| 86 | auto | ||
| 87 | constexpr | ||
| 88 | 1984 | optional_rule( | |
| 89 | R const& r) -> | ||
| 90 | implementation_defined::optional_rule_t<R> | ||
| 91 | { | ||
| 92 | BOOST_CORE_STATIC_ASSERT(grammar::is_rule<R>::value); | ||
| 93 | 1984 | return { r }; | |
| 94 | } | ||
| 95 | |||
| 96 | } // grammar | ||
| 97 | } // urls | ||
| 98 | } // boost | ||
| 99 | |||
| 100 | #include <boost/url/grammar/impl/optional_rule.hpp> | ||
| 101 | |||
| 102 | #endif | ||
| 103 |