context_accessor.hpp

#pragma once
 
USERVER_NAMESPACE_BEGIN
 
namespace engine::impl {
 
class TaskContext;
 
template <typename T>
class FutureWaitStrategy;
 
enum class [[nodiscard]] EarlyWakeup : bool {};
 
class ContextAccessor {
 public:
  virtual bool IsReady() const noexcept = 0;
 
  // Atomically:
  // 1. if not `IsReady`, then store `waiter` somewhere to notify when
  //    `IsReady() == true` is reached, and return `EarlyWakeup{false}`;
  // 2. if `IsReady`, then notify `waiter` immediately via `Wakeup*`,
  //    and return `EarlyWakeup{true}`.
  virtual EarlyWakeup TryAppendWaiter(TaskContext& waiter) = 0;
 
  // Remove `waiter` from the internal wait list if it's still there.
  // You may not sleep in `RemoveWaiter`, unlike in `AfterWait`.
  virtual void RemoveWaiter(TaskContext& waiter) noexcept = 0;
 
  // Wait for some cleanup (e.g. wait for `waiter` to actually remove itself).
  // You may sleep in `AfterWait`.
  virtual void AfterWait() noexcept = 0;
 
  // Precondition: IsReady
  // This method is required for WaitAllChecked to properly function.
  virtual void RethrowErrorResult() const = 0;
 
 protected:
  ContextAccessor();
 
  ~ContextAccessor() = default;
};
 
}  // namespace engine::impl
 
USERVER_NAMESPACE_END