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