awaiter.h

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// uvco (c) 2024 Lewin Bormann. See LICENSE for specific terms.
 
#include "uvco/loop/loop.h"
#include <boost/assert.hpp>
 
#include <coroutine>
#include <optional>
 
namespace uvco {
 
template <typename Result> class GenericAwaiter {
public:
  GenericAwaiter() = default;
  GenericAwaiter(const GenericAwaiter &) = delete;
  GenericAwaiter(GenericAwaiter &&) = default;
  GenericAwaiter &operator=(const GenericAwaiter &) = delete;
  GenericAwaiter &operator=(GenericAwaiter &&) = default;
 
  [[nodiscard]] bool await_ready() const { return result_.has_value(); }
 
  void await_suspend(std::coroutine_handle<> handle) {
    BOOST_ASSERT(!handle_);
    handle_ = handle;
  }
 
  Result await_resume() {
    BOOST_ASSERT(result_.has_value());
    return std::move(*result_);
  }
 
  void resume(Result result) {
    result_ = std::move(result);
    if (handle_) {
      std::coroutine_handle<> handle = *handle_;
      handle_.reset();
      Loop::enqueue(handle);
    }
  }
 
private:
  std::optional<Result> result_;
  std::optional<std::coroutine_handle<>> handle_;
};
 
} // namespace uvco