libs/http/include/boost/http/rfc/list_rule.hpp

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1		//
2		// Copyright (c) 2021 Vinnie Falco (vinnie.falco@gmail.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/cppalliance/http
8		//
9
10		#ifndef BOOST_HTTP_RFC_LIST_RULE_HPP
11		#define BOOST_HTTP_RFC_LIST_RULE_HPP
12
13		#include <boost/http/detail/config.hpp>
14		#include <boost/url/grammar/range_rule.hpp>
15		#include <boost/core/empty_value.hpp>
16
17		namespace boost {
18		namespace http {
19
20		namespace implementation_defined {
21		template<class Rule>
22		struct list_rule_t
23		: private empty_value<Rule>
24		{
25		using value_type = grammar::range<
26		typename Rule::value_type>;
27
28		constexpr
29	4531	list_rule_t(
30		Rule const& r,
31		std::size_t n,
32		std::size_t m) noexcept
33		: empty_value<Rule>(
34		empty_init, r)
35	4531	, n_(n)
36	4531	, m_(m)
37		{
38	4531	}
39
40		auto
41		parse(
42		char const*& it,
43		char const* end) const ->
44		system::result<value_type>;
45
46		private:
47		struct first_rule;
48		struct next_rule;
49
50		std::size_t n_;
51		std::size_t m_;
52		};
53		} // implementation_defined
54
55		/** Rule for a comma-delimited list of elements
56
57		This rule defines a list containing
58		at least n and at most m of Element,
59		each separated by at least one comma
60		and optional whitespace.
61
62		@par BNF
63		@code
64		#element => [ 1#element ]
65		1#element => element *( OWS "," OWS element )
66		<n>#<m>element => element <n-1>*<m-1>( OWS "," OWS element )
67		@endcode
68
69		Senders must emit compliant values, but
70		receivers should accept values generated
71		with the legacy production rules:
72
73		@par Legacy BNF
74		@code
75		#element => [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
76
77		1#element => ( "," OWS ) element ( OWS "," [ OWS element ] )
78		@endcode
79
80		@tparam Rule The rule type.
81
82		@param r The rule to use for elements.
83		@param n The minimum number of elements, which may be zero.
84		@param m The maximum number of elements.
85
86		@return A rule that matches the list.
87
88		@par Specification
89		@li <a href="https://datatracker.ietf.org/doc/html/rfc7230#section-7"
90		>5.6.1. Lists (#rule ABNF Extension) (rfc7230)</a>
91		*/
92		template<class Rule>
93		constexpr
94		auto
95	4531	list_rule(
96		Rule const& r,
97		std::size_t n = 0,
98		std::size_t m =
99		std::size_t(-1)) noexcept ->
100		implementation_defined::list_rule_t<Rule>
101		{
102	4531	return implementation_defined::list_rule_t<Rule>(r, n, m);
103		}
104
105		} // http
106		} // boost
107
108		#include <boost/http/rfc/impl/list_rule.hpp>
109
110		#endif
111