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1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
11#define _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
12
13#include <__config>
14#include <__format/format_error.h>
15#include <__type_traits/is_constant_evaluated.h>
16#include <string_view>
17
18#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19# pragma GCC system_header
20#endif
21
22_LIBCPP_BEGIN_NAMESPACE_STD
23
24#if _LIBCPP_STD_VER >= 20
25
26template <class _CharT>
27class basic_format_parse_context {
28public:
29 using char_type = _CharT;
30 using const_iterator = typename basic_string_view<_CharT>::const_iterator;
31 using iterator = const_iterator;
32
33 _LIBCPP_HIDE_FROM_ABI constexpr explicit basic_format_parse_context(
34 basic_string_view<_CharT> __fmt, size_t __num_args = 0) noexcept
35 : __begin_(__fmt.begin()),
36 __end_(__fmt.end()),
37 __indexing_(__unknown),
38 __next_arg_id_(0),
39 __num_args_(__num_args) {}
40
41 basic_format_parse_context(const basic_format_parse_context&) = delete;
42 basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
43
44 _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept { return __begin_; }
45 _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept { return __end_; }
46 _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) { __begin_ = __it; }
47
48 _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
49 if (__indexing_ == __manual)
50 std::__throw_format_error("Using automatic argument numbering in manual argument numbering mode");
51
52 if (__indexing_ == __unknown)
53 __indexing_ = __automatic;
54
55 // Throws an exception to make the expression a non core constant
56 // expression as required by:
57 // [format.parse.ctx]/8
58 // Remarks: Let cur-arg-id be the value of next_arg_id_ prior to this
59 // call. Call expressions where cur-arg-id >= num_args_ is true are not
60 // core constant expressions (7.7 [expr.const]).
61 // Note: the Throws clause [format.parse.ctx]/9 doesn't specify the
62 // behavior when id >= num_args_.
63 if (is_constant_evaluated() && __next_arg_id_ >= __num_args_)
64 std::__throw_format_error("Argument index outside the valid range");
65
66 return __next_arg_id_++;
67 }
68 _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
69 if (__indexing_ == __automatic)
70 std::__throw_format_error("Using manual argument numbering in automatic argument numbering mode");
71
72 if (__indexing_ == __unknown)
73 __indexing_ = __manual;
74
75 // Throws an exception to make the expression a non core constant
76 // expression as required by:
77 // [format.parse.ctx]/11
78 // Remarks: Call expressions where id >= num_args_ are not core constant
79 // expressions ([expr.const]).
80 // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
81 // behavior when id >= num_args_.
82 if (is_constant_evaluated() && __id >= __num_args_)
83 std::__throw_format_error("Argument index outside the valid range");
84 }
85
86private:
87 iterator __begin_;
88 iterator __end_;
89 enum _Indexing { __unknown, __manual, __automatic };
90 _Indexing __indexing_;
91 size_t __next_arg_id_;
92 size_t __num_args_;
93};
94_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(basic_format_parse_context);
95
96using format_parse_context = basic_format_parse_context<char>;
97# if _LIBCPP_HAS_WIDE_CHARACTERS
98using wformat_parse_context = basic_format_parse_context<wchar_t>;
99# endif
100
101#endif // _LIBCPP_STD_VER >= 20
102
103_LIBCPP_END_NAMESPACE_STD
104
105#endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H