初始提交: UE5.3项目基础框架

Plugins/CesiumForUnreal/Source/ThirdParty/include/CesiumAsync/Promise.h

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+#pragma once
+
+#include "Impl/AsyncSystemSchedulers.h"
+#include "Impl/cesium-async++.h"
+
+#include <exception>
+#include <memory>
+
+namespace CesiumAsync {
+
+template <typename T> class Future;
+
+/**
+ * @brief A promise that can be resolved or rejected by an asynchronous task.
+ *
+ * @tparam T The type of the object that the promise will be resolved with.
+ */
+template <typename T> class Promise {
+public:
+  /**
+   * @brief Will be called when the task completed successfully.
+   *
+   * @param value The value that was computed by the asynchronous task.
+   */
+  void resolve(T&& value) const { this->_pEvent->set(std::move(value)); }
+
+  /**
+   * @brief Will be called when the task completed successfully.
+   *
+   * @param value The value that was computed by the asynchronous task.
+   */
+  void resolve(const T& value) const { this->_pEvent->set(value); }
+
+  /**
+   * @brief Will be called when the task failed.
+   *
+   * @param error The error that caused the task to fail.
+   */
+  template <typename TException> void reject(TException error) const {
+    this->_pEvent->set_exception(std::make_exception_ptr(error));
+  }
+
+  /**
+   * @brief Will be called when the task failed.
+   *
+   * @param error The error, captured with `std::current_exception`, that
+   * caused the task to fail.
+   */
+  void reject(const std::exception_ptr& error) const {
+    this->_pEvent->set_exception(error);
+  }
+
+  /**
+   * @brief Gets the Future that resolves or rejects when this Promise is
+   * resolved or rejected.
+   *
+   * This method may only be called once.
+   *
+   * @return The future.
+   */
+  Future<T> getFuture() const {
+    return Future<T>(this->_pSchedulers, this->_pEvent->get_task());
+  }
+
+private:
+  Promise(
+      const std::shared_ptr<CesiumImpl::AsyncSystemSchedulers>& pSchedulers,
+      const std::shared_ptr<async::event_task<T>>& pEvent) noexcept
+      : _pSchedulers(pSchedulers), _pEvent(pEvent) {}
+
+  std::shared_ptr<CesiumImpl::AsyncSystemSchedulers> _pSchedulers;
+  std::shared_ptr<async::event_task<T>> _pEvent;
+
+  friend class AsyncSystem;
+};
+
+/**
+ * @brief Specialization for promises that resolve to no value.
+ */
+template <> class Promise<void> {
+public:
+  /**
+   * @brief Will be called when the task completed successfully.
+   */
+  void resolve() const { this->_pEvent->set(); }
+
+  /**
+   * @brief Will be called when the task failed.
+   *
+   * @param error The error that caused the task to fail.
+   */
+  template <typename TException> void reject(TException error) const {
+    this->_pEvent->set_exception(std::make_exception_ptr(error));
+  }
+
+  /**
+   * @brief Will be called when the task failed.
+   *
+   * @param error The error, captured with `std::current_exception`, that
+   * caused the task to fail.
+   */
+  void reject(const std::exception_ptr& error) const {
+    this->_pEvent->set_exception(error);
+  }
+  /**
+   * @copydoc Promise::getFuture
+   */
+  Future<void> getFuture() const {
+    return Future<void>(this->_pSchedulers, this->_pEvent->get_task());
+  }
+
+private:
+  Promise(
+      const std::shared_ptr<CesiumImpl::AsyncSystemSchedulers>& pSchedulers,
+      const std::shared_ptr<async::event_task<void>>& pEvent) noexcept
+      : _pSchedulers(pSchedulers), _pEvent(pEvent) {}
+
+  std::shared_ptr<CesiumImpl::AsyncSystemSchedulers> _pSchedulers;
+  std::shared_ptr<async::event_task<void>> _pEvent;
+
+  friend class AsyncSystem;
+};
+
+} // namespace CesiumAsync