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_PUSH_MACROS
22 #include <__undef_macros>
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 #if _LIBCPP_STD_VER > 17
27 
28 // TODO FMT Remove this once we require compilers with proper C++20 support.
29 // If the compiler has no concepts support, the format header will be disabled.
30 // Without concepts support enable_if needs to be used and that too much effort
31 // to support compilers with partial C++20 support.
32 #if !defined(_LIBCPP_HAS_NO_CONCEPTS)
33 
34 template <class _CharT>
35 class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_parse_context {
36 public:
37   using char_type = _CharT;
38   using const_iterator = typename basic_string_view<_CharT>::const_iterator;
39   using iterator = const_iterator;
40 
41   _LIBCPP_HIDE_FROM_ABI
42   constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
43                                                 size_t __num_args = 0) noexcept
44       : __begin_(__fmt.begin()),
45         __end_(__fmt.end()),
46         __indexing_(__unknown),
47         __next_arg_id_(0),
48         __num_args_(__num_args) {}
49 
50   basic_format_parse_context(const basic_format_parse_context&) = delete;
51   basic_format_parse_context&
52   operator=(const basic_format_parse_context&) = delete;
53 
54   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
55     return __begin_;
56   }
57   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
58     return __end_;
59   }
60   _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
61     __begin_ = __it;
62   }
63 
64   _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
65     if (__indexing_ == __manual)
66       __throw_format_error("Using automatic argument numbering in manual "
67                            "argument numbering mode");
68 
69     if (__indexing_ == __unknown)
70       __indexing_ = __automatic;
71     return __next_arg_id_++;
72   }
73   _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
74     if (__indexing_ == __automatic)
75       __throw_format_error("Using manual argument numbering in automatic "
76                            "argument numbering mode");
77 
78     if (__indexing_ == __unknown)
79       __indexing_ = __manual;
80 
81     // Throws an exception to make the expression a non core constant
82     // expression as required by:
83     // [format.parse.ctx]/11
84     //   Remarks: Call expressions where id >= num_args_ are not core constant
85     //   expressions ([expr.const]).
86     // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
87     // behavior when id >= num_args_.
88     if (is_constant_evaluated() && __id >= __num_args_)
89       __throw_format_error("Argument index outside the valid range");
90   }
91 
92 private:
93   iterator __begin_;
94   iterator __end_;
95   enum _Indexing { __unknown, __manual, __automatic };
96   _Indexing __indexing_;
97   size_t __next_arg_id_;
98   size_t __num_args_;
99 };
100 
101 using format_parse_context = basic_format_parse_context<char>;
102 using wformat_parse_context = basic_format_parse_context<wchar_t>;
103 
104 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
105 
106 #endif //_LIBCPP_STD_VER > 17
107 
108 _LIBCPP_END_NAMESPACE_STD
109 
110 _LIBCPP_POP_MACROS
111 
112 #endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
113