libcxx/include/__format/format_args.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_ARGS_H
  11 #define _LIBCPP___FORMAT_FORMAT_ARGS_H
  12
  13 #include <__availability>
  14 #include <__config>
  15 #include <__format/format_arg.h>
  16 #include <__format/format_arg_store.h>
  17 #include <__format/format_fwd.h>
  18 #include <cstddef>
  19 #include <cstdint>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_BEGIN_NAMESPACE_STD
  26
  27 #if _LIBCPP_STD_VER >= 20
  28
  29 template <class _Context>
  30 class _LIBCPP_TEMPLATE_VIS basic_format_args {
  31 public:
  32   basic_format_args() noexcept = default;
  33
  34   template <class... _Args>
  35   _LIBCPP_HIDE_FROM_ABI basic_format_args(const __format_arg_store<_Context, _Args...>& __store) noexcept
  36       : __size_(sizeof...(_Args)) {
  37     if constexpr (sizeof...(_Args) != 0) {
  38       if constexpr (__format::__use_packed_format_arg_store(sizeof...(_Args))) {
  39         __values_ = __store.__storage.__values_;
  40         __types_ = __store.__storage.__types_;
  41       } else
  42         __args_ = __store.__storage.__args_;
  43     }
  44   }
  45
  46   _LIBCPP_HIDE_FROM_ABI
  47   basic_format_arg<_Context> get(size_t __id) const noexcept {
  48     if (__id >= __size_)
  49       return basic_format_arg<_Context>{};
  50
  51     if (__format::__use_packed_format_arg_store(__size_))
  52       return basic_format_arg<_Context>{__format::__get_packed_type(__types_, __id), __values_[__id]};
  53
  54     return __args_[__id];
  55   }
  56
  57   _LIBCPP_HIDE_FROM_ABI size_t __size() const noexcept { return __size_; }
  58
  59 private:
  60   size_t __size_{0};
  61   // [format.args]/5
  62   // [Note 1: Implementations are encouraged to optimize the representation of
  63   // basic_format_args for small number of formatting arguments by storing
  64   // indices of type alternatives separately from values and packing the
  65   // former. - end note]
  66   union {
  67     struct {
  68       const __basic_format_arg_value<_Context>* __values_;
  69       uint64_t __types_;
  70     };
  71     const basic_format_arg<_Context>* __args_;
  72   };
  73 };
  74
  75 template <class _Context, class... _Args>
  76 basic_format_args(__format_arg_store<_Context, _Args...>) -> basic_format_args<_Context>;
  77
  78 #endif //_LIBCPP_STD_VER >= 20
  79
  80 _LIBCPP_END_NAMESPACE_STD
  81
  82 #endif // _LIBCPP___FORMAT_FORMAT_ARGS_H