ceph/src/boost/boost/outcome/detail/coroutine_support.ipp

   1 /* Tells C++ coroutines about Outcome's result
   2 (C) 2019-2020 Niall Douglas <http://www.nedproductions.biz/> (12 commits)
   3 File Created: Oct 2019
   4
   5
   6 Boost Software License - Version 1.0 - August 17th, 2003
   7
   8 Permission is hereby granted, free of charge, to any person or organization
   9 obtaining a copy of the software and accompanying documentation covered by
  10 this license (the "Software") to use, reproduce, display, distribute,
  11 execute, and transmit the Software, and to prepare derivative works of the
  12 Software, and to permit third-parties to whom the Software is furnished to
  13 do so, all subject to the following:
  14
  15 The copyright notices in the Software and this entire statement, including
  16 the above license grant, this restriction and the following disclaimer,
  17 must be included in all copies of the Software, in whole or in part, and
  18 all derivative works of the Software, unless such copies or derivative
  19 works are solely in the form of machine-executable object code generated by
  20 a source language processor.
  21
  22 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  23 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  24 FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
  25 SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
  26 FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
  27 ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  28 DEALINGS IN THE SOFTWARE.
  29 */
  30
  31 #ifndef BOOST_OUTCOME_COROUTINE_SUPPORT_NAMESPACE_BEGIN
  32 #error This header must only be included by outcome/coroutine_support.hpp or outcome/experimental/coroutine_support.hpp
  33 #endif
  34
  35 #ifndef BOOST_OUTCOME_DETAIL_COROUTINE_SUPPORT_HPP
  36 #define BOOST_OUTCOME_DETAIL_COROUTINE_SUPPORT_HPP
  37
  38 #include <atomic>
  39 #include <cassert>
  40
  41 #if __cpp_coroutines
  42 #if __has_include(<coroutine>)
  43 #include <coroutine>
  44 BOOST_OUTCOME_V2_NAMESPACE_BEGIN
  45 namespace awaitables
  46 {
  47   template <class Promise = void> using coroutine_handle = std::coroutine_handle<Promise>;
  48   template <class... Args> using coroutine_traits = std::coroutine_traits<Args...>;
  49   using std::suspend_always;
  50   using std::suspend_never;
  51 }  // namespace awaitables
  52 BOOST_OUTCOME_V2_NAMESPACE_END
  53 #define BOOST_OUTCOME_FOUND_COROUTINE_HEADER 1
  54 #elif __has_include(<experimental/coroutine>)
  55 #include <experimental/coroutine>
  56 BOOST_OUTCOME_V2_NAMESPACE_BEGIN
  57 namespace awaitables
  58 {
  59   template <class Promise = void> using coroutine_handle = std::experimental::coroutine_handle<Promise>;
  60   template <class... Args> using coroutine_traits = std::experimental::coroutine_traits<Args...>;
  61   using std::experimental::suspend_always;
  62   using std::experimental::suspend_never;
  63 }  // namespace awaitables
  64 BOOST_OUTCOME_V2_NAMESPACE_END
  65 #define BOOST_OUTCOME_FOUND_COROUTINE_HEADER 1
  66 #endif
  67 #endif
  68
  69 BOOST_OUTCOME_V2_NAMESPACE_EXPORT_BEGIN
  70 namespace awaitables
  71 {
  72   namespace detail
  73   {
  74     struct error_type_not_found
  75     {
  76     };
  77     struct exception_type_not_found
  78     {
  79     };
  80     template <class T> struct type_found
  81     {
  82       using type = T;
  83     };
  84     template <class T, class U = typename T::error_type> constexpr inline type_found<U> extract_error_type(int /*unused*/) { return {}; }
  85     template <class T> constexpr inline type_found<error_type_not_found> extract_error_type(...) { return {}; }
  86     template <class T, class U = typename T::exception_type> constexpr inline type_found<U> extract_exception_type(int /*unused*/) { return {}; }
  87     template <class T> constexpr inline type_found<exception_type_not_found> extract_exception_type(...) { return {}; }
  88
  89     BOOST_OUTCOME_TEMPLATE(class T, class U)
  90     BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(std::is_constructible<U, T>::value))
  91     inline bool try_set_error(T &e, U *result)
  92     {
  93       new(result) U(e);
  94       return true;
  95     }
  96     template <class T> inline bool try_set_error(T & /*unused*/, ...) { return false; }
  97     BOOST_OUTCOME_TEMPLATE(class T, class U)
  98     BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(std::is_constructible<U, T>::value))
  99     inline void set_or_rethrow(T &e, U *result) { new(result) U(e); }
 100     template <class T> inline void set_or_rethrow(T &e, ...) { rethrow_exception(e); }
 101     template <class T> class fake_atomic
 102     {
 103       T _v;
 104
 105     public:
 106       constexpr fake_atomic(T v)
 107           : _v(v)
 108       {
 109       }
 110       T load(std::memory_order /*unused*/) { return _v; }
 111       void store(T v, std::memory_order /*unused*/) { _v = v; }
 112     };
 113
 114 #ifdef BOOST_OUTCOME_FOUND_COROUTINE_HEADER
 115     template <class Awaitable, bool suspend_initial, bool use_atomic, bool is_void> struct outcome_promise_type
 116     {
 117       using container_type = typename Awaitable::container_type;
 118       using result_set_type = std::conditional_t<use_atomic, std::atomic<bool>, fake_atomic<bool>>;
 119       union {
 120         BOOST_OUTCOME_V2_NAMESPACE::detail::empty_type _default{};
 121         container_type result;
 122       };
 123       result_set_type result_set{false};
 124       coroutine_handle<> continuation;
 125
 126       outcome_promise_type() {}
 127       outcome_promise_type(const outcome_promise_type &) = delete;
 128       outcome_promise_type(outcome_promise_type &&) = delete;
 129       outcome_promise_type &operator=(const outcome_promise_type &) = delete;
 130       outcome_promise_type &operator=(outcome_promise_type &&) = delete;
 131       ~outcome_promise_type()
 132       {
 133         if(result_set.load(std::memory_order_acquire))
 134         {
 135           result.~container_type();
 136         }
 137       }
 138       auto get_return_object() { return Awaitable{*this}; }
 139       void return_value(container_type &&value)
 140       {
 141         assert(!result_set.load(std::memory_order_acquire));
 142         if(result_set.load(std::memory_order_acquire))
 143         {
 144           result.~container_type();
 145         }
 146         new(&result) container_type(static_cast<container_type &&>(value));
 147         result_set.store(true, std::memory_order_release);
 148       }
 149       void return_value(const container_type &value)
 150       {
 151         assert(!result_set.load(std::memory_order_acquire));
 152         if(result_set.load(std::memory_order_acquire))
 153         {
 154           result.~container_type();
 155         }
 156         new(&result) container_type(value);
 157         result_set.store(true, std::memory_order_release);
 158       }
 159       void unhandled_exception()
 160       {
 161         assert(!result_set.load(std::memory_order_acquire));
 162         if(result_set.load(std::memory_order_acquire))
 163         {
 164           result.~container_type();
 165         }
 166 #ifndef BOOST_NO_EXCEPTIONS
 167         auto e = std::current_exception();
 168         auto ec = detail::error_from_exception(static_cast<decltype(e) &&>(e), {});
 169         // Try to set error code first
 170         if(!detail::error_is_set(ec) || !detail::try_set_error(ec, &result))
 171         {
 172           detail::set_or_rethrow(e, &result);
 173         }
 174 #else
 175         std::terminate();
 176 #endif
 177         result_set.store(true, std::memory_order_release);
 178       }
 179       auto initial_suspend() noexcept
 180       {
 181         struct awaiter
 182         {
 183           bool await_ready() noexcept { return !suspend_initial; }
 184           void await_resume() noexcept {}
 185           void await_suspend(coroutine_handle<> /*unused*/) {}
 186         };
 187         return awaiter{};
 188       }
 189       auto final_suspend()
 190       {
 191         struct awaiter
 192         {
 193           bool await_ready() noexcept { return false; }
 194           void await_resume() noexcept {}
 195           void await_suspend(coroutine_handle<outcome_promise_type> self)
 196           {
 197             if(self.promise().continuation)
 198             {
 199               return self.promise().continuation.resume();
 200             }
 201           }
 202         };
 203         return awaiter{};
 204       }
 205     };
 206     template <class Awaitable, bool suspend_initial, bool use_atomic> struct outcome_promise_type<Awaitable, suspend_initial, use_atomic, true>
 207     {
 208       using container_type = void;
 209       using result_set_type = std::conditional_t<use_atomic, std::atomic<bool>, fake_atomic<bool>>;
 210       result_set_type result_set{false};
 211       coroutine_handle<> continuation;
 212
 213       outcome_promise_type() {}
 214       outcome_promise_type(const outcome_promise_type &) = delete;
 215       outcome_promise_type(outcome_promise_type &&) = delete;
 216       outcome_promise_type &operator=(const outcome_promise_type &) = delete;
 217       outcome_promise_type &operator=(outcome_promise_type &&) = delete;
 218       ~outcome_promise_type() = default;
 219       auto get_return_object() { return Awaitable{*this}; }
 220       void return_void()
 221       {
 222         assert(!result_set.load(std::memory_order_acquire));
 223         result_set.store(true, std::memory_order_release);
 224       }
 225       void unhandled_exception()
 226       {
 227         assert(!result_set.load(std::memory_order_acquire));
 228         std::rethrow_exception(std::current_exception());
 229       }
 230       auto initial_suspend() noexcept
 231       {
 232         struct awaiter
 233         {
 234           bool await_ready() noexcept { return !suspend_initial; }
 235           void await_resume() noexcept {}
 236           void await_suspend(coroutine_handle<> /*unused*/) {}
 237         };
 238         return awaiter{};
 239       }
 240       auto final_suspend()
 241       {
 242         struct awaiter
 243         {
 244           bool await_ready() noexcept { return false; }
 245           void await_resume() noexcept {}
 246           void await_suspend(coroutine_handle<outcome_promise_type> self)
 247           {
 248             if(self.promise().continuation)
 249             {
 250               return self.promise().continuation.resume();
 251             }
 252           }
 253         };
 254         return awaiter{};
 255       }
 256     };
 257     template <class Awaitable, bool suspend_initial, bool use_atomic> constexpr inline auto move_result_from_promise_if_not_void(outcome_promise_type<Awaitable, suspend_initial, use_atomic, false> &p) { return static_cast<typename Awaitable::container_type &&>(p.result); }
 258     template <class Awaitable, bool suspend_initial, bool use_atomic> constexpr inline void move_result_from_promise_if_not_void(outcome_promise_type<Awaitable, suspend_initial, use_atomic, true> & /*unused*/) {}
 259
 260     template <class Cont, bool suspend_initial, bool use_atomic> struct BOOST_OUTCOME_NODISCARD awaitable
 261     {
 262       using container_type = Cont;
 263       using promise_type = outcome_promise_type<awaitable, suspend_initial, use_atomic, std::is_void<container_type>::value>;
 264       coroutine_handle<promise_type> _h;
 265
 266       awaitable(awaitable &&o) noexcept
 267           : _h(static_cast<coroutine_handle<promise_type> &&>(o._h))
 268       {
 269         o._h = nullptr;
 270       }
 271       awaitable(const awaitable &o) = delete;
 272       awaitable &operator=(awaitable &&) = delete;  // as per P1056
 273       awaitable &operator=(const awaitable &) = delete;
 274       ~awaitable()
 275       {
 276         if(_h)
 277         {
 278           _h.destroy();
 279         }
 280       }
 281       explicit awaitable(promise_type &p)
 282           : _h(coroutine_handle<promise_type>::from_promise(p))
 283       {
 284       }
 285       bool await_ready() noexcept { return _h.promise().result_set.load(std::memory_order_acquire); }
 286       container_type await_resume()
 287       {
 288         assert(_h.promise().result_set.load(std::memory_order_acquire));
 289         if(!_h.promise().result_set.load(std::memory_order_acquire))
 290         {
 291           std::terminate();
 292         }
 293         return detail::move_result_from_promise_if_not_void(_h.promise());
 294       }
 295       void await_suspend(coroutine_handle<> cont)
 296       {
 297         _h.promise().continuation = cont;
 298         _h.resume();
 299       }
 300     };
 301 #endif
 302   }  // namespace detail
 303
 304 }  // namespace awaitables
 305
 306 BOOST_OUTCOME_V2_NAMESPACE_END
 307
 308 #endif
 309
 310 #ifdef BOOST_OUTCOME_FOUND_COROUTINE_HEADER
 311 BOOST_OUTCOME_COROUTINE_SUPPORT_NAMESPACE_EXPORT_BEGIN
 312 /*! AWAITING HUGO JSON CONVERSION TOOL
 313 SIGNATURE NOT RECOGNISED
 314 */
 315 template <class T> using eager = BOOST_OUTCOME_V2_NAMESPACE::awaitables::detail::awaitable<T, false, false>;
 316
 317 /*! AWAITING HUGO JSON CONVERSION TOOL
 318 SIGNATURE NOT RECOGNISED
 319 */
 320 template <class T> using atomic_eager = BOOST_OUTCOME_V2_NAMESPACE::awaitables::detail::awaitable<T, false, true>;
 321
 322 /*! AWAITING HUGO JSON CONVERSION TOOL
 323 SIGNATURE NOT RECOGNISED
 324 */
 325 template <class T> using lazy = BOOST_OUTCOME_V2_NAMESPACE::awaitables::detail::awaitable<T, true, false>;
 326
 327 /*! AWAITING HUGO JSON CONVERSION TOOL
 328 SIGNATURE NOT RECOGNISED
 329 */
 330 template <class T> using atomic_lazy = BOOST_OUTCOME_V2_NAMESPACE::awaitables::detail::awaitable<T, true, true>;
 331
 332 BOOST_OUTCOME_COROUTINE_SUPPORT_NAMESPACE_END
 333 #endif