133 lines
3.0 KiB
C++
133 lines
3.0 KiB
C++
//
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// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/url
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//
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#ifndef BOOST_URL_GRAMMAR_VARIANT_RULE_HPP
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#define BOOST_URL_GRAMMAR_VARIANT_RULE_HPP
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#include <boost/url/detail/config.hpp>
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#include <boost/url/error_types.hpp>
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#include <boost/url/variant.hpp>
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#include <boost/url/grammar/detail/tuple.hpp>
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namespace boost {
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namespace urls {
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namespace grammar {
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/** Match one of a set of rules
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Each specified rule is tried in sequence.
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When the first match occurs, the result
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is stored and returned in the variant. If
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no match occurs, an error is returned.
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@par Value Type
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@code
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using value_type = variant< typename Rules::value_type... >;
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@endcode
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@par Example
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Rules are used with the function @ref parse.
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@code
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// request-target = origin-form
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// / absolute-form
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// / authority-form
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// / asterisk-form
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result< variant< url_view, url_view, authority_view, string_view > > rv = grammar::parse(
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"/index.html?width=full",
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variant_rule(
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origin_form_rule,
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absolute_uri_rule,
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authority_rule,
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delim_rule('*') ) );
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@endcode
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@par BNF
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@code
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variant = rule1 / rule2 / rule3...
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@endcode
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@par Specification
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@li <a href="https://datatracker.ietf.org/doc/html/rfc5234#section-3.2"
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>3.2. Alternatives (rfc5234)</a>
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@li <a href="https://datatracker.ietf.org/doc/html/rfc7230#section-5.3"
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>5.3. Request Target (rfc7230)</a>
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@see
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@ref absolute_uri_rule,
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@ref authority_rule,
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@ref delim_rule,
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@ref parse,
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@ref origin_form_rule,
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@ref url_view,
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@ref variant.
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*/
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#ifdef BOOST_URL_DOCS
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template<class... Rules>
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constexpr
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__implementation_defined__
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variant_rule( Rules... rn ) noexcept;
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#else
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template<
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class R0, class... Rn>
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class variant_rule_t
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{
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public:
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using value_type = variant<
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typename R0::value_type,
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typename Rn::value_type...>;
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auto
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parse(
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char const*& it,
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char const* end) const ->
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result<value_type>;
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template<
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class R0_,
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class... Rn_>
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friend
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constexpr
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auto
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variant_rule(
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R0_ const& r0,
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Rn_ const&... rn) noexcept ->
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variant_rule_t<R0_, Rn_...>;
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private:
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constexpr
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variant_rule_t(
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R0 const& r0,
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Rn const&... rn) noexcept
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: rn_(r0, rn...)
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{
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}
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detail::tuple<R0, Rn...> rn_;
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};
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template<
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class R0,
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class... Rn>
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constexpr
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auto
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variant_rule(
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R0 const& r0,
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Rn const&... rn) noexcept ->
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variant_rule_t<R0, Rn...>;
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#endif
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} // grammar
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} // urls
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} // boost
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#include <boost/url/grammar/impl/variant_rule.hpp>
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#endif
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