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 <string_view>
16 
17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18 #  pragma GCC system_header
19 #endif
20 
21 _LIBCPP_BEGIN_NAMESPACE_STD
22 
23 #if _LIBCPP_STD_VER > 17
24 
25 template <class _CharT>
26 class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_parse_context {
27 public:
28   using char_type = _CharT;
29   using const_iterator = typename basic_string_view<_CharT>::const_iterator;
30   using iterator = const_iterator;
31 
32   _LIBCPP_HIDE_FROM_ABI
33   constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
34                                                 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&
43   operator=(const basic_format_parse_context&) = delete;
44 
45   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
46     return __begin_;
47   }
48   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
49     return __end_;
50   }
51   _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
52     __begin_ = __it;
53   }
54 
55   _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
56     if (__indexing_ == __manual)
57       __throw_format_error("Using automatic argument numbering in manual "
58                            "argument numbering mode");
59 
60     if (__indexing_ == __unknown)
61       __indexing_ = __automatic;
62     return __next_arg_id_++;
63   }
64   _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
65     if (__indexing_ == __automatic)
66       __throw_format_error("Using manual argument numbering in automatic "
67                            "argument numbering mode");
68 
69     if (__indexing_ == __unknown)
70       __indexing_ = __manual;
71 
72     // Throws an exception to make the expression a non core constant
73     // expression as required by:
74     // [format.parse.ctx]/11
75     //   Remarks: Call expressions where id >= num_args_ are not core constant
76     //   expressions ([expr.const]).
77     // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
78     // behavior when id >= num_args_.
79     if (is_constant_evaluated() && __id >= __num_args_)
80       __throw_format_error("Argument index outside the valid range");
81   }
82 
83 private:
84   iterator __begin_;
85   iterator __end_;
86   enum _Indexing { __unknown, __manual, __automatic };
87   _Indexing __indexing_;
88   size_t __next_arg_id_;
89   size_t __num_args_;
90 };
91 
92 using format_parse_context = basic_format_parse_context<char>;
93 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
94 using wformat_parse_context = basic_format_parse_context<wchar_t>;
95 #endif
96 
97 #endif //_LIBCPP_STD_VER > 17
98 
99 _LIBCPP_END_NAMESPACE_STD
100 
101 #endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
102