libcxx/include/__cxx03/__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 <__cxx03/__config>
  14 #include <__cxx03/__format/format_error.h>
  15 #include <__cxx03/__type_traits/is_constant_evaluated.h>
  16 #include <__cxx03/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