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     !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)
34 
35 template <class _CharT>
36 class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT basic_format_parse_context {
37 public:
38   using char_type = _CharT;
39   using const_iterator = typename basic_string_view<_CharT>::const_iterator;
40   using iterator = const_iterator;
41 
42   _LIBCPP_HIDE_FROM_ABI
43   constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
44                                                 size_t __num_args = 0) noexcept
45       : __begin_(__fmt.begin()),
46         __end_(__fmt.end()),
47         __indexing_(__unknown),
48         __next_arg_id_(0),
49         __num_args_(__num_args) {}
50 
51   basic_format_parse_context(const basic_format_parse_context&) = delete;
52   basic_format_parse_context&
53   operator=(const basic_format_parse_context&) = delete;
54 
55   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
56     return __begin_;
57   }
58   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
59     return __end_;
60   }
61   _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
62     __begin_ = __it;
63   }
64 
65   _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
66     if (__indexing_ == __manual)
67       __throw_format_error("Using automatic argument numbering in manual "
68                            "argument numbering mode");
69 
70     if (__indexing_ == __unknown)
71       __indexing_ = __automatic;
72     return __next_arg_id_++;
73   }
74   _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
75     if (__indexing_ == __automatic)
76       __throw_format_error("Using manual argument numbering in automatic "
77                            "argument numbering mode");
78 
79     if (__indexing_ == __unknown)
80       __indexing_ = __manual;
81 
82     // Throws an exception to make the expression a non core constant
83     // expression as required by:
84     // [format.parse.ctx]/11
85     //   Remarks: Call expressions where id >= num_args_ are not core constant
86     //   expressions ([expr.const]).
87     // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
88     // behavior when id >= num_args_.
89     if (is_constant_evaluated() && __id >= __num_args_)
90       __throw_format_error("Argument index outside the valid range");
91   }
92 
93 private:
94   iterator __begin_;
95   iterator __end_;
96   enum _Indexing { __unknown, __manual, __automatic };
97   _Indexing __indexing_;
98   size_t __next_arg_id_;
99   size_t __num_args_;
100 };
101 
102 using format_parse_context = basic_format_parse_context<char>;
103 using wformat_parse_context = basic_format_parse_context<wchar_t>;
104 
105 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)
106 
107 #endif //_LIBCPP_STD_VER > 17
108 
109 _LIBCPP_END_NAMESPACE_STD
110 
111 _LIBCPP_POP_MACROS
112 
113 #endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H
114