libcxx/include/__format/format_parse_context.h

   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
  34   constexpr explicit basic_format_parse_context(basic_string_view<_CharT> __fmt,
  35                                                 size_t __num_args = 0) noexcept
  36       : __begin_(__fmt.begin()),
  37         __end_(__fmt.end()),
  38         __indexing_(__unknown),
  39         __next_arg_id_(0),
  40         __num_args_(__num_args) {}
  41
  42   basic_format_parse_context(const basic_format_parse_context&) = delete;
  43   basic_format_parse_context&
  44   operator=(const basic_format_parse_context&) = delete;
  45
  46   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator begin() const noexcept {
  47     return __begin_;
  48   }
  49   _LIBCPP_HIDE_FROM_ABI constexpr const_iterator end() const noexcept {
  50     return __end_;
  51   }
  52   _LIBCPP_HIDE_FROM_ABI constexpr void advance_to(const_iterator __it) {
  53     __begin_ = __it;
  54   }
  55
  56   _LIBCPP_HIDE_FROM_ABI constexpr size_t next_arg_id() {
  57     if (__indexing_ == __manual)
  58       std::__throw_format_error("Using automatic argument numbering in manual argument numbering mode");
  59
  60     if (__indexing_ == __unknown)
  61       __indexing_ = __automatic;
  62
  63     // Throws an exception to make the expression a non core constant
  64     // expression as required by:
  65     // [format.parse.ctx]/8
  66     //   Remarks: Let cur-arg-id be the value of next_arg_id_ prior to this
  67     //   call. Call expressions where cur-arg-id >= num_args_ is true are not
  68     //   core constant expressions (7.7 [expr.const]).
  69     // Note: the Throws clause [format.parse.ctx]/9 doesn't specify the
  70     // behavior when id >= num_args_.
  71     if (is_constant_evaluated() && __next_arg_id_ >= __num_args_)
  72       std::__throw_format_error("Argument index outside the valid range");
  73
  74     return __next_arg_id_++;
  75   }
  76   _LIBCPP_HIDE_FROM_ABI constexpr void check_arg_id(size_t __id) {
  77     if (__indexing_ == __automatic)
  78       std::__throw_format_error("Using manual argument numbering in automatic argument numbering mode");
  79
  80     if (__indexing_ == __unknown)
  81       __indexing_ = __manual;
  82
  83     // Throws an exception to make the expression a non core constant
  84     // expression as required by:
  85     // [format.parse.ctx]/11
  86     //   Remarks: Call expressions where id >= num_args_ are not core constant
  87     //   expressions ([expr.const]).
  88     // Note: the Throws clause [format.parse.ctx]/10 doesn't specify the
  89     // behavior when id >= num_args_.
  90     if (is_constant_evaluated() && __id >= __num_args_)
  91       std::__throw_format_error("Argument index outside the valid range");
  92   }
  93
  94 private:
  95   iterator __begin_;
  96   iterator __end_;
  97   enum _Indexing { __unknown, __manual, __automatic };
  98   _Indexing __indexing_;
  99   size_t __next_arg_id_;
 100   size_t __num_args_;
 101 };
 102 _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(basic_format_parse_context);
 103
 104 using format_parse_context = basic_format_parse_context<char>;
 105 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 106 using wformat_parse_context = basic_format_parse_context<wchar_t>;
 107 #endif
 108
 109 #endif //_LIBCPP_STD_VER >= 20
 110
 111 _LIBCPP_END_NAMESPACE_STD
 112
 113 #endif // _LIBCPP___FORMAT_FORMAT_PARSE_CONTEXT_H