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Implement zero cost ready continuables for await expressions

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This commit is contained in:
Denis Blank 2018-12-16 03:11:37 +01:00
parent fcf9a76029
commit 7dbc95c4b3
1 changed files with 15 additions and 2 deletions
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17
include/continuable/detail/other/coroutines.hpp
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@ -33,12 +33,12 @@
#define CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED #define CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
#include <cassert> #include <cassert>
#include <tuple>
#include <type_traits> #include <type_traits>
#include <experimental/coroutine> #include <experimental/coroutine>
#include <continuable/continuable-primitives.hpp> #include <continuable/continuable-primitives.hpp>
#include <continuable/continuable-result.hpp> #include <continuable/continuable-result.hpp>
#include <continuable/detail/core/annotation.hpp> #include <continuable/detail/core/annotation.hpp>
#include <continuable/detail/core/base.hpp>
#include <continuable/detail/core/types.hpp> #include <continuable/detail/core/types.hpp>
#include <continuable/detail/features.hpp> #include <continuable/detail/features.hpp>
#include <continuable/detail/utility/traits.hpp> #include <continuable/detail/utility/traits.hpp>
@ -77,17 +77,28 @@ class awaitable {
public: public:
explicit constexpr awaitable(Continuable&& continuable) explicit constexpr awaitable(Continuable&& continuable)
: continuable_(std::move(continuable)) { : continuable_(std::move(continuable)) {
// If the continuable is ready resolve the result from the
// continuable immediatly.
if (base::attorney::is_ready(continuable_)) {
traits::unpack(
[&](auto&&... args) {
resolve(std::forward<decltype(args)>(args)...);
},
base::attorney::query(std::move(continuable_)));
}
} }
/// Since continuables are evaluated lazily we are not /// Since continuables are evaluated lazily we are not
/// capable to say whether the resumption will be instantly. /// capable to say whether the resumption will be instantly.
bool await_ready() const noexcept { bool await_ready() const noexcept {
return false; return !result_.is_empty();
} }
/// Suspend the current context /// Suspend the current context
// TODO Convert this to an r-value function once possible // TODO Convert this to an r-value function once possible
void await_suspend(coroutine_handle<> h) { void await_suspend(coroutine_handle<> h) {
assert(result_.is_empty());
// Forward every result to the current awaitable // Forward every result to the current awaitable
std::move(continuable_) std::move(continuable_)
.next([h, this](auto&&... args) mutable { .next([h, this](auto&&... args) mutable {
@ -116,11 +127,13 @@ private:
/// Resolve the continuation through the result /// Resolve the continuation through the result
template <typename... Args> template <typename... Args>
void resolve(Args&&... args) { void resolve(Args&&... args) {
assert(result_.is_empty());
result_.set_value(std::forward<Args>(args)...); result_.set_value(std::forward<Args>(args)...);
} }
/// Resolve the continuation through an error /// Resolve the continuation through an error
void resolve(exception_arg_t, exception_t exception) { void resolve(exception_arg_t, exception_t exception) {
assert(result_.is_empty());
result_.set_exception(std::move(exception)); result_.set_exception(std::move(exception));
} }
}; };