async_work.h

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// uvco (c) 2024 Lewin Bormann. See LICENSE for specific terms.
 
#include <exception>
#include <functional>
#include <utility>
#include <uv.h>
 
#include "uvco/loop/loop.h"
#include "uvco/promise/promise.h"
 
#include <optional>
#include <uv/unix.h>
#include <variant>
 
namespace uvco {
 
 
Promise<void> innerSubmitWork(const Loop &loop, std::function<void()> work);
 
template <typename R>
  requires std::is_void_v<R> || std::is_move_constructible_v<R>
Promise<R> submitWork(const Loop &loop, std::function<R()> work) {
  std::optional<std::variant<R, std::exception_ptr>> result;
  // Erase return type and use generic submitWork().
  std::function<void()> agnosticWork = [&result, work]() {
    try {
      result = work();
    } catch (...) {
      result = std::current_exception();
    }
  };
  co_await innerSubmitWork(loop, agnosticWork);
  BOOST_ASSERT(result.has_value());
  if (result->index() == 1) {
    std::rethrow_exception(std::get<std::exception_ptr>(*result));
  }
  co_return std::get<R>(std::move(*result));
}
 
template <>
Promise<void> submitWork(const Loop &loop, std::function<void()> work);
 
template <typename T> class ThreadLocalKey {
public:
  ThreadLocalKey() { uv_key_create(&key_); }
  ThreadLocalKey(const ThreadLocalKey &) = default;
  ThreadLocalKey(ThreadLocalKey &&) = default;
  ThreadLocalKey &operator=(const ThreadLocalKey &) = default;
  ThreadLocalKey &operator=(ThreadLocalKey &&) = default;
  ~ThreadLocalKey() = default;
 
  void del() {
    auto *value = uv_key_get(&key_);
    if (value != nullptr) {
      delete static_cast<T *>(value);
      uv_key_set(&key_, nullptr);
    }
  }
 
  T &getOrDefault() {
    auto *value = uv_key_get(&key_);
    if (value == nullptr) {
      value = new T{};
      uv_key_set(&key_, value);
    }
    return *static_cast<T *>(value);
  }
 
  T &get() { return *static_cast<T *>(uv_key_get(&key_)); }
 
  void set(T &&value) { getOrDefault() = std::move(value); }
 
  void setCopy(const T &value) { getOrDefault() = value; }
 
private:
  uv_key_t key_{};
};
 
 
} // namespace uvco