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 
26 template <class _CharT>
27 class _LIBCPP_TEMPLATE_VIS basic_format_parse_context {
28 public:
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
34   constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
35                                                 size_t __num_args = 0) noexcept
36       : __begin_(__fmt.begin()),
37         __end_(__fmt.end()),
38         __indexing_(__unknown),
39         __next_arg_id_(0),
40         __num_args_(__num_args) {}
41 
42   basic_format_parse_context(const basic_format_parse_context&) = delete;
43   basic_format_parse_context&
44   operator=(const basic_format_parse_context&) = delete;
45 
46   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
47     return __begin_;
48   }
49   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
50     return __end_;
51   }
52   _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
53     __begin_ = __it;
54   }
55 
56   _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
57     if (__indexing_ == __manual)
58       std::__throw_format_error("Using automatic argument numbering in manual argument numbering mode");
59 
60     if (__indexing_ == __unknown)
61       __indexing_ = __automatic;
62 
63     // Throws an exception to make the expression a non core constant
64     // expression as required by:
65     // [format.parse.ctx]/8
66     //   Remarks: Let cur-arg-id be the value of next_arg_id_ prior to this
67     //   call. Call expressions where cur-arg-id >= num_args_ is true are not
68     //   core constant expressions (7.7 [expr.const]).
69     // Note: the Throws clause [format.parse.ctx]/9 doesn't specify the
70     // behavior when id >= num_args_.
71     if (is_constant_evaluated() && __next_arg_id_ >= __num_args_)
72       std::__throw_format_error("Argument index outside the valid range");
73 
74     return __next_arg_id_++;
75   }
76   _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
77     if (__indexing_ == __automatic)
78       std::__throw_format_error("Using manual argument numbering in automatic argument numbering mode");
79 
80     if (__indexing_ == __unknown)
81       __indexing_ = __manual;
82 
83     // Throws an exception to make the expression a non core constant
84     // expression as required by:
85     // [format.parse.ctx]/11
86     //   Remarks: Call expressions where id >= num_args_ are not core constant
87     //   expressions ([expr.const]).
88     // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
89     // behavior when id >= num_args_.
90     if (is_constant_evaluated() && __id >= __num_args_)
91       std::__throw_format_error("Argument index outside the valid range");
92   }
93 
94 private:
95   iterator __begin_;
96   iterator __end_;
97   enum _Indexing { __unknown, __manual, __automatic };
98   _Indexing __indexing_;
99   size_t __next_arg_id_;
100   size_t __num_args_;
101 };
102 _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(basic_format_parse_context);
103 
104 using format_parse_context = basic_format_parse_context<char>;
105 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
106 using wformat_parse_context = basic_format_parse_context<wchar_t>;
107 #endif
108 
109 #endif //_LIBCPP_STD_VER >= 20
110 
111 _LIBCPP_END_NAMESPACE_STD
112 
113 #endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
114