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_ARG_H
11 #define _LIBCPP___FORMAT_FORMAT_ARG_H
12 
13 #include <__assert>
14 #include <__concepts/arithmetic.h>
15 #include <__config>
16 #include <__format/concepts.h>
17 #include <__format/format_fwd.h>
18 #include <__format/format_parse_context.h>
19 #include <__functional/invoke.h>
20 #include <__memory/addressof.h>
21 #include <__type_traits/conditional.h>
22 #include <__utility/forward.h>
23 #include <__utility/move.h>
24 #include <__utility/unreachable.h>
25 #include <__variant/monostate.h>
26 #include <cstdint>
27 #include <string_view>
28 
29 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
30 #  pragma GCC system_header
31 #endif
32 
33 _LIBCPP_BEGIN_NAMESPACE_STD
34 
35 #if _LIBCPP_STD_VER >= 20
36 
37 namespace __format {
38 /// The type stored in @ref basic_format_arg.
39 ///
40 /// @note The 128-bit types are unconditionally in the list to avoid the values
41 /// of the enums to depend on the availability of 128-bit integers.
42 ///
43 /// @note The value is stored as a 5-bit value in the __packed_arg_t_bits. This
44 /// limits the maximum number of elements to 32.
45 /// When modifying update the test
46 /// test/libcxx/utilities/format/format.arguments/format.arg/arg_t.compile.pass.cpp
47 /// It could be packed in 4-bits but that means a new type directly becomes an
48 /// ABI break. The packed type is 64-bit so this reduces the maximum number of
49 /// packed elements from 16 to 12.
50 ///
51 /// @note Some members of this enum are an extension. These extensions need
52 /// special behaviour in visit_format_arg. There they need to be wrapped in a
53 /// handle to satisfy the user observable behaviour. The internal function
54 /// __visit_format_arg doesn't do this wrapping. So in the format functions
55 /// this function is used to avoid unneeded overhead.
56 enum class _LIBCPP_ENUM_VIS __arg_t : uint8_t {
57   __none,
58   __boolean,
59   __char_type,
60   __int,
61   __long_long,
62   __i128, // extension
63   __unsigned,
64   __unsigned_long_long,
65   __u128, // extension
66   __float,
67   __double,
68   __long_double,
69   __const_char_type_ptr,
70   __string_view,
71   __ptr,
72   __handle
73 };
74 
75 inline constexpr unsigned __packed_arg_t_bits = 5;
76 inline constexpr uint8_t __packed_arg_t_mask = 0x1f;
77 
78 inline constexpr unsigned __packed_types_storage_bits = 64;
79 inline constexpr unsigned __packed_types_max = __packed_types_storage_bits / __packed_arg_t_bits;
80 
81 _LIBCPP_HIDE_FROM_ABI
82 constexpr bool __use_packed_format_arg_store(size_t __size) { return __size <= __packed_types_max; }
83 
84 _LIBCPP_HIDE_FROM_ABI
85 constexpr __arg_t __get_packed_type(uint64_t __types, size_t __id) {
86   _LIBCPP_ASSERT_UNCATEGORIZED(__id <= __packed_types_max, "");
87 
88   if (__id > 0)
89     __types >>= __id * __packed_arg_t_bits;
90 
91   return static_cast<__format::__arg_t>(__types & __packed_arg_t_mask);
92 }
93 
94 } // namespace __format
95 
96 // This function is not user obervable, so it can directly use the non-standard
97 // types of the "variant". See __arg_t for more details.
98 template <class _Visitor, class _Context>
99 _LIBCPP_HIDE_FROM_ABI decltype(auto)
100 __visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
101   switch (__arg.__type_) {
102   case __format::__arg_t::__none:
103     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__monostate_);
104   case __format::__arg_t::__boolean:
105     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__boolean_);
106   case __format::__arg_t::__char_type:
107     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__char_type_);
108   case __format::__arg_t::__int:
109     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__int_);
110   case __format::__arg_t::__long_long:
111     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__long_long_);
112   case __format::__arg_t::__i128:
113 #  ifndef _LIBCPP_HAS_NO_INT128
114     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__i128_);
115 #  else
116     __libcpp_unreachable();
117 #  endif
118   case __format::__arg_t::__unsigned:
119     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__unsigned_);
120   case __format::__arg_t::__unsigned_long_long:
121     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__unsigned_long_long_);
122   case __format::__arg_t::__u128:
123 #  ifndef _LIBCPP_HAS_NO_INT128
124     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__u128_);
125 #  else
126     __libcpp_unreachable();
127 #  endif
128   case __format::__arg_t::__float:
129     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__float_);
130   case __format::__arg_t::__double:
131     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__double_);
132   case __format::__arg_t::__long_double:
133     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__long_double_);
134   case __format::__arg_t::__const_char_type_ptr:
135     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__const_char_type_ptr_);
136   case __format::__arg_t::__string_view:
137     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__string_view_);
138   case __format::__arg_t::__ptr:
139     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), __arg.__value_.__ptr_);
140   case __format::__arg_t::__handle:
141     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis),
142                          typename basic_format_arg<_Context>::handle{__arg.__value_.__handle_});
143   }
144 
145   __libcpp_unreachable();
146 }
147 
148 /// Contains the values used in basic_format_arg.
149 ///
150 /// This is a separate type so it's possible to store the values and types in
151 /// separate arrays.
152 template <class _Context>
153 class __basic_format_arg_value {
154   using _CharT = typename _Context::char_type;
155 
156 public:
157   /// Contains the implementation for basic_format_arg::handle.
158   struct __handle {
159     template <class _Tp>
160     _LIBCPP_HIDE_FROM_ABI explicit __handle(_Tp& __v) noexcept
161         : __ptr_(_VSTD::addressof(__v)),
162           __format_([](basic_format_parse_context<_CharT>& __parse_ctx, _Context& __ctx, const void* __ptr) {
163             using _Dp = remove_const_t<_Tp>;
164             using _Qp = conditional_t<__formattable_with<const _Dp, _Context>, const _Dp, _Dp>;
165             static_assert(__formattable_with<_Qp, _Context>, "Mandated by [format.arg]/10");
166 
167             typename _Context::template formatter_type<_Dp> __f;
168             __parse_ctx.advance_to(__f.parse(__parse_ctx));
169             __ctx.advance_to(__f.format(*const_cast<_Qp*>(static_cast<const _Dp*>(__ptr)), __ctx));
170           }) {}
171 
172     const void* __ptr_;
173     void (*__format_)(basic_format_parse_context<_CharT>&, _Context&, const void*);
174   };
175 
176   union {
177     monostate __monostate_;
178     bool __boolean_;
179     _CharT __char_type_;
180     int __int_;
181     unsigned __unsigned_;
182     long long __long_long_;
183     unsigned long long __unsigned_long_long_;
184 #  ifndef _LIBCPP_HAS_NO_INT128
185     __int128_t __i128_;
186     __uint128_t __u128_;
187 #  endif
188     float __float_;
189     double __double_;
190     long double __long_double_;
191     const _CharT* __const_char_type_ptr_;
192     basic_string_view<_CharT> __string_view_;
193     const void* __ptr_;
194     __handle __handle_;
195   };
196 
197   // These constructors contain the exact storage type used. If adjustments are
198   // required, these will be done in __create_format_arg.
199 
200   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value() noexcept : __monostate_() {}
201   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(bool __value) noexcept : __boolean_(__value) {}
202   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(_CharT __value) noexcept : __char_type_(__value) {}
203   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(int __value) noexcept : __int_(__value) {}
204   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(unsigned __value) noexcept : __unsigned_(__value) {}
205   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(long long __value) noexcept : __long_long_(__value) {}
206   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(unsigned long long __value) noexcept
207       : __unsigned_long_long_(__value) {}
208 #  ifndef _LIBCPP_HAS_NO_INT128
209   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(__int128_t __value) noexcept : __i128_(__value) {}
210   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(__uint128_t __value) noexcept : __u128_(__value) {}
211 #  endif
212   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(float __value) noexcept : __float_(__value) {}
213   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(double __value) noexcept : __double_(__value) {}
214   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(long double __value) noexcept : __long_double_(__value) {}
215   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(const _CharT* __value) noexcept : __const_char_type_ptr_(__value) {}
216   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(basic_string_view<_CharT> __value) noexcept
217       : __string_view_(__value) {}
218   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(const void* __value) noexcept : __ptr_(__value) {}
219   _LIBCPP_HIDE_FROM_ABI __basic_format_arg_value(__handle&& __value) noexcept : __handle_(std::move(__value)) {}
220 };
221 
222 template <class _Context>
223 class _LIBCPP_TEMPLATE_VIS basic_format_arg {
224 public:
225   class _LIBCPP_TEMPLATE_VIS handle;
226 
227   _LIBCPP_HIDE_FROM_ABI basic_format_arg() noexcept
228       : __type_{__format::__arg_t::__none} {}
229 
230   _LIBCPP_HIDE_FROM_ABI explicit operator bool() const noexcept {
231     return __type_ != __format::__arg_t::__none;
232   }
233 
234 private:
235   using char_type = typename _Context::char_type;
236 
237   // TODO FMT Implement constrain [format.arg]/4
238   // Constraints: The template specialization
239   //   typename Context::template formatter_type<T>
240   // meets the Formatter requirements ([formatter.requirements]).  The extent
241   // to which an implementation determines that the specialization meets the
242   // Formatter requirements is unspecified, except that as a minimum the
243   // expression
244   //   typename Context::template formatter_type<T>()
245   //    .format(declval<const T&>(), declval<Context&>())
246   // shall be well-formed when treated as an unevaluated operand.
247 
248 public:
249   __basic_format_arg_value<_Context> __value_;
250   __format::__arg_t __type_;
251 
252   _LIBCPP_HIDE_FROM_ABI explicit basic_format_arg(__format::__arg_t __type,
253                                                   __basic_format_arg_value<_Context> __value) noexcept
254       : __value_(__value), __type_(__type) {}
255 };
256 
257 template <class _Context>
258 class _LIBCPP_TEMPLATE_VIS basic_format_arg<_Context>::handle {
259 public:
260   _LIBCPP_HIDE_FROM_ABI
261   void format(basic_format_parse_context<char_type>& __parse_ctx, _Context& __ctx) const {
262     __handle_.__format_(__parse_ctx, __ctx, __handle_.__ptr_);
263   }
264 
265   _LIBCPP_HIDE_FROM_ABI explicit handle(typename __basic_format_arg_value<_Context>::__handle& __handle) noexcept
266       : __handle_(__handle) {}
267 
268 private:
269   typename __basic_format_arg_value<_Context>::__handle& __handle_;
270 };
271 
272 // This function is user facing, so it must wrap the non-standard types of
273 // the "variant" in a handle to stay conforming. See __arg_t for more details.
274 template <class _Visitor, class _Context>
275 _LIBCPP_HIDE_FROM_ABI decltype(auto)
276 visit_format_arg(_Visitor&& __vis, basic_format_arg<_Context> __arg) {
277   switch (__arg.__type_) {
278 #  ifndef _LIBCPP_HAS_NO_INT128
279   case __format::__arg_t::__i128: {
280     typename __basic_format_arg_value<_Context>::__handle __h{__arg.__value_.__i128_};
281     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__h});
282   }
283 
284   case __format::__arg_t::__u128: {
285     typename __basic_format_arg_value<_Context>::__handle __h{__arg.__value_.__u128_};
286     return _VSTD::invoke(_VSTD::forward<_Visitor>(__vis), typename basic_format_arg<_Context>::handle{__h});
287   }
288 #  endif
289   default:
290     return _VSTD::__visit_format_arg(_VSTD::forward<_Visitor>(__vis), __arg);
291   }
292 }
293 
294 #endif //_LIBCPP_STD_VER >= 20
295 
296 _LIBCPP_END_NAMESPACE_STD
297 
298 #endif // _LIBCPP___FORMAT_FORMAT_ARG_H
299