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_CONTEXT_H 11 #define _LIBCPP___FORMAT_FORMAT_CONTEXT_H 12 13 #include <__availability> 14 #include <__concepts/same_as.h> 15 #include <__config> 16 #include <__format/buffer.h> 17 #include <__format/format_arg.h> 18 #include <__format/format_arg_store.h> 19 #include <__format/format_args.h> 20 #include <__format/format_error.h> 21 #include <__format/format_fwd.h> 22 #include <__iterator/back_insert_iterator.h> 23 #include <__iterator/concepts.h> 24 #include <__memory/addressof.h> 25 #include <__utility/move.h> 26 #include <__variant/monostate.h> 27 #include <cstddef> 28 29 #ifndef _LIBCPP_HAS_NO_LOCALIZATION 30 # include <locale> 31 # include <optional> 32 #endif 33 34 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 35 # pragma GCC system_header 36 #endif 37 38 _LIBCPP_BEGIN_NAMESPACE_STD 39 40 #if _LIBCPP_STD_VER >= 20 41 42 template <class _OutIt, class _CharT> 43 requires output_iterator<_OutIt, const _CharT&> 44 class _LIBCPP_TEMPLATE_VIS basic_format_context; 45 46 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 47 /** 48 * Helper to create a basic_format_context. 49 * 50 * This is needed since the constructor is private. 51 */ 52 template <class _OutIt, class _CharT> 53 _LIBCPP_HIDE_FROM_ABI basic_format_context<_OutIt, _CharT> 54 __format_context_create(_OutIt __out_it, 55 basic_format_args<basic_format_context<_OutIt, _CharT>> __args, 56 optional<std::locale>&& __loc = nullopt) { 57 return std::basic_format_context(std::move(__out_it), __args, std::move(__loc)); 58 } 59 # else 60 template <class _OutIt, class _CharT> 61 _LIBCPP_HIDE_FROM_ABI basic_format_context<_OutIt, _CharT> 62 __format_context_create(_OutIt __out_it, basic_format_args<basic_format_context<_OutIt, _CharT>> __args) { 63 return std::basic_format_context(std::move(__out_it), __args); 64 } 65 # endif 66 67 using format_context = basic_format_context<back_insert_iterator<__format::__output_buffer<char>>, char>; 68 # ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS 69 using wformat_context = basic_format_context< back_insert_iterator<__format::__output_buffer<wchar_t>>, wchar_t>; 70 # endif 71 72 template <class _OutIt, class _CharT> 73 requires output_iterator<_OutIt, const _CharT&> 74 class 75 // clang-format off 76 _LIBCPP_TEMPLATE_VIS 77 _LIBCPP_PREFERRED_NAME(format_context) 78 _LIBCPP_IF_WIDE_CHARACTERS(_LIBCPP_PREFERRED_NAME(wformat_context)) 79 // clang-format on 80 basic_format_context { 81 public: 82 using iterator = _OutIt; 83 using char_type = _CharT; 84 template <class _Tp> 85 using formatter_type = formatter<_Tp, _CharT>; 86 87 _LIBCPP_HIDE_FROM_ABI basic_format_arg<basic_format_context> arg(size_t __id) const noexcept { 88 return __args_.get(__id); 89 } 90 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 91 _LIBCPP_HIDE_FROM_ABI std::locale locale() { 92 if (!__loc_) 93 __loc_ = std::locale{}; 94 return *__loc_; 95 } 96 # endif 97 _LIBCPP_HIDE_FROM_ABI iterator out() { return std::move(__out_it_); } 98 _LIBCPP_HIDE_FROM_ABI void advance_to(iterator __it) { __out_it_ = std::move(__it); } 99 100 private: 101 iterator __out_it_; 102 basic_format_args<basic_format_context> __args_; 103 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 104 105 // The Standard doesn't specify how the locale is stored. 106 // [format.context]/6 107 // std::locale locale(); 108 // Returns: The locale passed to the formatting function if the latter 109 // takes one, and std::locale() otherwise. 110 // This is done by storing the locale of the constructor in this optional. If 111 // locale() is called and the optional has no value the value will be created. 112 // This allows the implementation to lazily create the locale. 113 // TODO FMT Validate whether lazy creation is the best solution. 114 optional<std::locale> __loc_; 115 116 template <class _OtherOutIt, class _OtherCharT> 117 friend _LIBCPP_HIDE_FROM_ABI basic_format_context<_OtherOutIt, _OtherCharT> __format_context_create( 118 _OtherOutIt, basic_format_args<basic_format_context<_OtherOutIt, _OtherCharT>>, optional<std::locale>&&); 119 120 // Note: the Standard doesn't specify the required constructors. 121 _LIBCPP_HIDE_FROM_ABI explicit basic_format_context( 122 _OutIt __out_it, basic_format_args<basic_format_context> __args, optional<std::locale>&& __loc) 123 : __out_it_(std::move(__out_it)), __args_(__args), __loc_(std::move(__loc)) {} 124 # else 125 template <class _OtherOutIt, class _OtherCharT> 126 friend _LIBCPP_HIDE_FROM_ABI basic_format_context<_OtherOutIt, _OtherCharT> 127 __format_context_create(_OtherOutIt, basic_format_args<basic_format_context<_OtherOutIt, _OtherCharT>>); 128 129 _LIBCPP_HIDE_FROM_ABI explicit basic_format_context(_OutIt __out_it, basic_format_args<basic_format_context> __args) 130 : __out_it_(std::move(__out_it)), __args_(__args) {} 131 # endif 132 }; 133 134 // A specialization for __retarget_buffer 135 // 136 // See __retarget_buffer for the motivation for this specialization. 137 // 138 // This context holds a reference to the instance of the basic_format_context 139 // that is retargeted. It converts a formatting argument when it is requested 140 // during formatting. It is expected that the usage of the arguments is rare so 141 // the lookups are not expected to be used often. An alternative would be to 142 // convert all elements during construction. 143 // 144 // The elements of the retargets context are only used when an underlying 145 // formatter uses a locale specific formatting or an formatting argument is 146 // part for the format spec. For example 147 // format("{:256:{}}", input, 8); 148 // Here the width of an element in input is determined dynamically. 149 // Note when the top-level element has no width the retargeting is not needed. 150 template <class _CharT> 151 class _LIBCPP_TEMPLATE_VIS basic_format_context<typename __format::__retarget_buffer<_CharT>::__iterator, _CharT> { 152 public: 153 using iterator = typename __format::__retarget_buffer<_CharT>::__iterator; 154 using char_type = _CharT; 155 template <class _Tp> 156 using formatter_type = formatter<_Tp, _CharT>; 157 158 template <class _Context> 159 _LIBCPP_HIDE_FROM_ABI explicit basic_format_context(iterator __out_it, _Context& __ctx) 160 : __out_it_(std::move(__out_it)), 161 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 162 __loc_([](void* __c) { return static_cast<_Context*>(__c)->locale(); }), 163 # endif 164 __ctx_(std::addressof(__ctx)), 165 __arg_([](void* __c, size_t __id) { 166 return std::visit_format_arg( 167 [&](auto __arg) -> basic_format_arg<basic_format_context> { 168 if constexpr (same_as<decltype(__arg), monostate>) 169 return {}; 170 else if constexpr (same_as<decltype(__arg), typename basic_format_arg<_Context>::handle>) 171 // At the moment it's not possible for formatting to use a re-targeted handle. 172 // TODO FMT add this when support is needed. 173 std::__throw_format_error("Re-targeting handle not supported"); 174 else 175 return basic_format_arg<basic_format_context>{ 176 __format::__determine_arg_t<basic_format_context, decltype(__arg)>(), 177 __basic_format_arg_value<basic_format_context>(__arg)}; 178 }, 179 static_cast<_Context*>(__c)->arg(__id)); 180 }) { 181 } 182 183 _LIBCPP_HIDE_FROM_ABI basic_format_arg<basic_format_context> arg(size_t __id) const noexcept { 184 return __arg_(__ctx_, __id); 185 } 186 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 187 _LIBCPP_HIDE_FROM_ABI std::locale locale() { return __loc_(__ctx_); } 188 # endif 189 _LIBCPP_HIDE_FROM_ABI iterator out() { return std::move(__out_it_); } 190 _LIBCPP_HIDE_FROM_ABI void advance_to(iterator __it) { __out_it_ = std::move(__it); } 191 192 private: 193 iterator __out_it_; 194 195 # ifndef _LIBCPP_HAS_NO_LOCALIZATION 196 std::locale (*__loc_)(void* __ctx); 197 # endif 198 199 void* __ctx_; 200 basic_format_arg<basic_format_context> (*__arg_)(void* __ctx, size_t __id); 201 }; 202 203 _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(basic_format_context); 204 #endif //_LIBCPP_STD_VER >= 20 205 206 _LIBCPP_END_NAMESPACE_STD 207 208 #endif // _LIBCPP___FORMAT_FORMAT_CONTEXT_H 209