1 #pragma once
2 
3 namespace std { namespace experimental { inline namespace coroutines_v1 {
4 
5 template <typename R, typename...> struct coroutine_traits {
6   using promise_type = typename R::promise_type;
7 };
8 
9 template <typename Promise = void> struct coroutine_handle;
10 
11 template <> struct coroutine_handle<void> {
12   static coroutine_handle from_address(void *addr) noexcept {
13     coroutine_handle me;
14     me.ptr = addr;
15     return me;
16   }
17   void operator()() { resume(); }
18   void *address() const noexcept { return ptr; }
19   void resume() const { __builtin_coro_resume(ptr); }
20   void destroy() const { __builtin_coro_destroy(ptr); }
21   bool done() const { return __builtin_coro_done(ptr); }
22   coroutine_handle &operator=(decltype(nullptr)) {
23     ptr = nullptr;
24     return *this;
25   }
26   coroutine_handle(decltype(nullptr)) : ptr(nullptr) {}
27   coroutine_handle() : ptr(nullptr) {}
28 //  void reset() { ptr = nullptr; } // add to P0057?
29   explicit operator bool() const { return ptr; }
30 
31 protected:
32   void *ptr;
33 };
34 
35 template <typename Promise> struct coroutine_handle : coroutine_handle<> {
36   using coroutine_handle<>::operator=;
37 
38   static coroutine_handle from_address(void *addr) noexcept {
39     coroutine_handle me;
40     me.ptr = addr;
41     return me;
42   }
43 
44   Promise &promise() const {
45     return *reinterpret_cast<Promise *>(
46         __builtin_coro_promise(ptr, alignof(Promise), false));
47   }
48   static coroutine_handle from_promise(Promise &promise) {
49     coroutine_handle p;
50     p.ptr = __builtin_coro_promise(&promise, alignof(Promise), true);
51     return p;
52   }
53 };
54 
55   template <typename _PromiseT>
56   bool operator==(coroutine_handle<_PromiseT> const& _Left,
57     coroutine_handle<_PromiseT> const& _Right) noexcept
58   {
59     return _Left.address() == _Right.address();
60   }
61 
62   template <typename _PromiseT>
63   bool operator!=(coroutine_handle<_PromiseT> const& _Left,
64     coroutine_handle<_PromiseT> const& _Right) noexcept
65   {
66     return !(_Left == _Right);
67   }
68 
69 struct suspend_always {
70   bool await_ready() { return false; }
71   void await_suspend(coroutine_handle<>) {}
72   void await_resume() {}
73 };
74 struct suspend_never {
75   bool await_ready() noexcept { return true; }
76   void await_suspend(coroutine_handle<>) noexcept {}
77   void await_resume() noexcept {}
78 };
79 
80 }}}
81