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 #  pragma clang include_instead(<format>)
20 #endif
21 
22 _LIBCPP_BEGIN_NAMESPACE_STD
23 
24 #if _LIBCPP_STD_VER > 17
25 
26 // TODO FMT Remove this once we require compilers with proper C++20 support.
27 // If the compiler has no concepts support, the format header will be disabled.
28 // Without concepts support enable_if needs to be used and that too much effort
29 // to support compilers with partial C++20 support.
30 #if !defined(_LIBCPP_HAS_NO_CONCEPTS)
31 
32 template <class _CharT>
33 class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_parse_context {
34 public:
35   using char_type = _CharT;
36   using const_iterator = typename basic_string_view<_CharT>::const_iterator;
37   using iterator = const_iterator;
38 
39   _LIBCPP_HIDE_FROM_ABI
40   constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
41                                                 size_t __num_args = 0) noexcept
42       : __begin_(__fmt.begin()),
43         __end_(__fmt.end()),
44         __indexing_(__unknown),
45         __next_arg_id_(0),
46         __num_args_(__num_args) {}
47 
48   basic_format_parse_context(const basic_format_parse_context&) = delete;
49   basic_format_parse_context&
50   operator=(const basic_format_parse_context&) = delete;
51 
52   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
53     return __begin_;
54   }
55   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
56     return __end_;
57   }
58   _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
59     __begin_ = __it;
60   }
61 
62   _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
63     if (__indexing_ == __manual)
64       __throw_format_error("Using automatic argument numbering in manual "
65                            "argument numbering mode");
66 
67     if (__indexing_ == __unknown)
68       __indexing_ = __automatic;
69     return __next_arg_id_++;
70   }
71   _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
72     if (__indexing_ == __automatic)
73       __throw_format_error("Using manual argument numbering in automatic "
74                            "argument numbering mode");
75 
76     if (__indexing_ == __unknown)
77       __indexing_ = __manual;
78 
79     // Throws an exception to make the expression a non core constant
80     // expression as required by:
81     // [format.parse.ctx]/11
82     //   Remarks: Call expressions where id >= num_args_ are not core constant
83     //   expressions ([expr.const]).
84     // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
85     // behavior when id >= num_args_.
86     if (is_constant_evaluated() && __id >= __num_args_)
87       __throw_format_error("Argument index outside the valid range");
88   }
89 
90 private:
91   iterator __begin_;
92   iterator __end_;
93   enum _Indexing { __unknown, __manual, __automatic };
94   _Indexing __indexing_;
95   size_t __next_arg_id_;
96   size_t __num_args_;
97 };
98 
99 using format_parse_context = basic_format_parse_context<char>;
100 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
101 using wformat_parse_context = basic_format_parse_context<wchar_t>;
102 #endif
103 
104 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
105 
106 #endif //_LIBCPP_STD_VER > 17
107 
108 _LIBCPP_END_NAMESPACE_STD
109 
110 #endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
111