libcxx/include/__functional/bind.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___FUNCTIONAL_BIND_H
  11 #define _LIBCPP___FUNCTIONAL_BIND_H
  12
  13 #include <__config>
  14 #include <__functional/weak_result_type.h>
  15 #include <__fwd/functional.h>
  16 #include <__type_traits/decay.h>
  17 #include <__type_traits/invoke.h>
  18 #include <__type_traits/is_reference_wrapper.h>
  19 #include <__type_traits/is_void.h>
  20 #include <tuple>
  21
  22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  23 #  pragma GCC system_header
  24 #endif
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 template <class _Tp>
  29 struct is_bind_expression
  30     : _If< _IsSame<_Tp, __remove_cvref_t<_Tp> >::value, false_type, is_bind_expression<__remove_cvref_t<_Tp> > > {};
  31
  32 #if _LIBCPP_STD_VER >= 17
  33 template <class _Tp>
  34 inline constexpr bool is_bind_expression_v = is_bind_expression<_Tp>::value;
  35 #endif
  36
  37 template <class _Tp>
  38 struct is_placeholder
  39     : _If< _IsSame<_Tp, __remove_cvref_t<_Tp> >::value,
  40            integral_constant<int, 0>,
  41            is_placeholder<__remove_cvref_t<_Tp> > > {};
  42
  43 #if _LIBCPP_STD_VER >= 17
  44 template <class _Tp>
  45 inline constexpr int is_placeholder_v = is_placeholder<_Tp>::value;
  46 #endif
  47
  48 namespace placeholders {
  49
  50 template <int _Np>
  51 struct __ph {};
  52
  53 // C++17 recommends that we implement placeholders as `inline constexpr`, but allows
  54 // implementing them as `extern <implementation-defined>`. Libc++ implements them as
  55 // `extern const` in all standard modes to avoid an ABI break in C++03: making them
  56 // `inline constexpr` requires removing their definition in the shared library to
  57 // avoid ODR violations, which is an ABI break.
  58 //
  59 // In practice, since placeholders are empty, `extern const` is almost impossible
  60 // to distinguish from `inline constexpr` from a usage stand point.
  61 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<1> _1;
  62 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<2> _2;
  63 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<3> _3;
  64 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<4> _4;
  65 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<5> _5;
  66 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<6> _6;
  67 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<7> _7;
  68 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<8> _8;
  69 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<9> _9;
  70 _LIBCPP_EXPORTED_FROM_ABI extern const __ph<10> _10;
  71
  72 } // namespace placeholders
  73
  74 template <int _Np>
  75 struct is_placeholder<placeholders::__ph<_Np> > : public integral_constant<int, _Np> {};
  76
  77 #ifndef _LIBCPP_CXX03_LANG
  78
  79 template <class _Tp, class _Uj>
  80 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& __mu(reference_wrapper<_Tp> __t, _Uj&) {
  81   return __t.get();
  82 }
  83
  84 template <class _Ti, class... _Uj, size_t... _Indx>
  85 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __invoke_of<_Ti&, _Uj...>::type
  86 __mu_expand(_Ti& __ti, tuple<_Uj...>& __uj, __tuple_indices<_Indx...>) {
  87   return __ti(std::forward<_Uj>(std::get<_Indx>(__uj))...);
  88 }
  89
  90 template <class _Ti, class... _Uj, __enable_if_t<is_bind_expression<_Ti>::value, int> = 0>
  91 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __invoke_of<_Ti&, _Uj...>::type
  92 __mu(_Ti& __ti, tuple<_Uj...>& __uj) {
  93   typedef typename __make_tuple_indices<sizeof...(_Uj)>::type __indices;
  94   return std::__mu_expand(__ti, __uj, __indices());
  95 }
  96
  97 template <bool _IsPh, class _Ti, class _Uj>
  98 struct __mu_return2 {};
  99
 100 template <class _Ti, class _Uj>
 101 struct __mu_return2<true, _Ti, _Uj> {
 102   typedef typename tuple_element<is_placeholder<_Ti>::value - 1, _Uj>::type type;
 103 };
 104
 105 template <class _Ti, class _Uj, __enable_if_t<0 < is_placeholder<_Ti>::value, int> = 0>
 106 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 107 typename __mu_return2<0 < is_placeholder<_Ti>::value, _Ti, _Uj>::type
 108 __mu(_Ti&, _Uj& __uj) {
 109   const size_t __indx = is_placeholder<_Ti>::value - 1;
 110   return std::forward<typename tuple_element<__indx, _Uj>::type>(std::get<__indx>(__uj));
 111 }
 112
 113 template <class _Ti,
 114           class _Uj,
 115           __enable_if_t<!is_bind_expression<_Ti>::value && is_placeholder<_Ti>::value == 0 &&
 116                             !__is_reference_wrapper<_Ti>::value,
 117                         int> = 0>
 118 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Ti& __mu(_Ti& __ti, _Uj&) {
 119   return __ti;
 120 }
 121
 122 template <class _Ti, bool _IsReferenceWrapper, bool _IsBindEx, bool _IsPh, class _TupleUj>
 123 struct __mu_return_impl;
 124
 125 template <bool _Invokable, class _Ti, class... _Uj>
 126 struct __mu_return_invokable // false
 127 {
 128   typedef __nat type;
 129 };
 130
 131 template <class _Ti, class... _Uj>
 132 struct __mu_return_invokable<true, _Ti, _Uj...> {
 133   typedef typename __invoke_of<_Ti&, _Uj...>::type type;
 134 };
 135
 136 template <class _Ti, class... _Uj>
 137 struct __mu_return_impl<_Ti, false, true, false, tuple<_Uj...> >
 138     : public __mu_return_invokable<__invokable<_Ti&, _Uj...>::value, _Ti, _Uj...> {};
 139
 140 template <class _Ti, class _TupleUj>
 141 struct __mu_return_impl<_Ti, false, false, true, _TupleUj> {
 142   typedef typename tuple_element<is_placeholder<_Ti>::value - 1, _TupleUj>::type&& type;
 143 };
 144
 145 template <class _Ti, class _TupleUj>
 146 struct __mu_return_impl<_Ti, true, false, false, _TupleUj> {
 147   typedef typename _Ti::type& type;
 148 };
 149
 150 template <class _Ti, class _TupleUj>
 151 struct __mu_return_impl<_Ti, false, false, false, _TupleUj> {
 152   typedef _Ti& type;
 153 };
 154
 155 template <class _Ti, class _TupleUj>
 156 struct __mu_return
 157     : public __mu_return_impl<
 158           _Ti,
 159           __is_reference_wrapper<_Ti>::value,
 160           is_bind_expression<_Ti>::value,
 161           0 < is_placeholder<_Ti>::value && is_placeholder<_Ti>::value <= tuple_size<_TupleUj>::value,
 162           _TupleUj> {};
 163
 164 template <class _Fp, class _BoundArgs, class _TupleUj>
 165 struct __is_valid_bind_return {
 166   static const bool value = false;
 167 };
 168
 169 template <class _Fp, class... _BoundArgs, class _TupleUj>
 170 struct __is_valid_bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj> {
 171   static const bool value = __invokable<_Fp, typename __mu_return<_BoundArgs, _TupleUj>::type...>::value;
 172 };
 173
 174 template <class _Fp, class... _BoundArgs, class _TupleUj>
 175 struct __is_valid_bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj> {
 176   static const bool value = __invokable<_Fp, typename __mu_return<const _BoundArgs, _TupleUj>::type...>::value;
 177 };
 178
 179 template <class _Fp, class _BoundArgs, class _TupleUj, bool = __is_valid_bind_return<_Fp, _BoundArgs, _TupleUj>::value>
 180 struct __bind_return;
 181
 182 template <class _Fp, class... _BoundArgs, class _TupleUj>
 183 struct __bind_return<_Fp, tuple<_BoundArgs...>, _TupleUj, true> {
 184   typedef typename __invoke_of< _Fp&, typename __mu_return< _BoundArgs, _TupleUj >::type... >::type type;
 185 };
 186
 187 template <class _Fp, class... _BoundArgs, class _TupleUj>
 188 struct __bind_return<_Fp, const tuple<_BoundArgs...>, _TupleUj, true> {
 189   typedef typename __invoke_of< _Fp&, typename __mu_return< const _BoundArgs, _TupleUj >::type... >::type type;
 190 };
 191
 192 template <class _Fp, class _BoundArgs, size_t... _Indx, class _Args>
 193 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __bind_return<_Fp, _BoundArgs, _Args>::type
 194 __apply_functor(_Fp& __f, _BoundArgs& __bound_args, __tuple_indices<_Indx...>, _Args&& __args) {
 195   return std::__invoke(__f, std::__mu(std::get<_Indx>(__bound_args), __args)...);
 196 }
 197
 198 template <class _Fp, class... _BoundArgs>
 199 class __bind : public __weak_result_type<__decay_t<_Fp> > {
 200 protected:
 201   using _Fd = __decay_t<_Fp>;
 202   typedef tuple<__decay_t<_BoundArgs>...> _Td;
 203
 204 private:
 205   _Fd __f_;
 206   _Td __bound_args_;
 207
 208   typedef typename __make_tuple_indices<sizeof...(_BoundArgs)>::type __indices;
 209
 210 public:
 211   template <
 212       class _Gp,
 213       class... _BA,
 214       __enable_if_t<is_constructible<_Fd, _Gp>::value && !is_same<__libcpp_remove_reference_t<_Gp>, __bind>::value,
 215                     int> = 0>
 216   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit __bind(_Gp&& __f, _BA&&... __bound_args)
 217       : __f_(std::forward<_Gp>(__f)), __bound_args_(std::forward<_BA>(__bound_args)...) {}
 218
 219   template <class... _Args>
 220   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type
 221   operator()(_Args&&... __args) {
 222     return std::__apply_functor(__f_, __bound_args_, __indices(), tuple<_Args&&...>(std::forward<_Args>(__args)...));
 223   }
 224
 225   template <class... _Args>
 226   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
 227   typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type
 228   operator()(_Args&&... __args) const {
 229     return std::__apply_functor(__f_, __bound_args_, __indices(), tuple<_Args&&...>(std::forward<_Args>(__args)...));
 230   }
 231 };
 232
 233 template <class _Fp, class... _BoundArgs>
 234 struct is_bind_expression<__bind<_Fp, _BoundArgs...> > : public true_type {};
 235
 236 template <class _Rp, class _Fp, class... _BoundArgs>
 237 class __bind_r : public __bind<_Fp, _BoundArgs...> {
 238   typedef __bind<_Fp, _BoundArgs...> base;
 239   typedef typename base::_Fd _Fd;
 240   typedef typename base::_Td _Td;
 241
 242 public:
 243   typedef _Rp result_type;
 244
 245   template <
 246       class _Gp,
 247       class... _BA,
 248       __enable_if_t<is_constructible<_Fd, _Gp>::value && !is_same<__libcpp_remove_reference_t<_Gp>, __bind_r>::value,
 249                     int> = 0>
 250   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit __bind_r(_Gp&& __f, _BA&&... __bound_args)
 251       : base(std::forward<_Gp>(__f), std::forward<_BA>(__bound_args)...) {}
 252
 253   template <
 254       class... _Args,
 255       __enable_if_t<is_convertible<typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type, result_type>::value ||
 256                         is_void<_Rp>::value,
 257                     int> = 0>
 258   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 result_type operator()(_Args&&... __args) {
 259     typedef __invoke_void_return_wrapper<_Rp> _Invoker;
 260     return _Invoker::__call(static_cast<base&>(*this), std::forward<_Args>(__args)...);
 261   }
 262
 263   template <class... _Args,
 264             __enable_if_t<is_convertible<typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type,
 265                                          result_type>::value ||
 266                               is_void<_Rp>::value,
 267                           int> = 0>
 268   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 result_type operator()(_Args&&... __args) const {
 269     typedef __invoke_void_return_wrapper<_Rp> _Invoker;
 270     return _Invoker::__call(static_cast<base const&>(*this), std::forward<_Args>(__args)...);
 271   }
 272 };
 273
 274 template <class _Rp, class _Fp, class... _BoundArgs>
 275 struct is_bind_expression<__bind_r<_Rp, _Fp, _BoundArgs...> > : public true_type {};
 276
 277 template <class _Fp, class... _BoundArgs>
 278 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bind<_Fp, _BoundArgs...>
 279 bind(_Fp&& __f, _BoundArgs&&... __bound_args) {
 280   typedef __bind<_Fp, _BoundArgs...> type;
 281   return type(std::forward<_Fp>(__f), std::forward<_BoundArgs>(__bound_args)...);
 282 }
 283
 284 template <class _Rp, class _Fp, class... _BoundArgs>
 285 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bind_r<_Rp, _Fp, _BoundArgs...>
 286 bind(_Fp&& __f, _BoundArgs&&... __bound_args) {
 287   typedef __bind_r<_Rp, _Fp, _BoundArgs...> type;
 288   return type(std::forward<_Fp>(__f), std::forward<_BoundArgs>(__bound_args)...);
 289 }
 290
 291 #endif // _LIBCPP_CXX03_LANG
 292
 293 _LIBCPP_END_NAMESPACE_STD
 294
 295 #endif // _LIBCPP___FUNCTIONAL_BIND_H