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 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 
86 private:
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 
96 using format_parse_context = basic_format_parse_context<char>;
97 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
98 using 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
106