LoopController.h

/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <chrono>
#include <functional>

#include <folly/io/async/HHWheelTimer-fwd.h>

namespace folly {
namespace fibers {

class Fiber;
class FiberManager;

class LoopController {
 public:
  using Clock = std::chrono::steady_clock;
  using TimePoint = std::chrono::time_point<Clock>;

  virtual ~LoopController() {}

  /**
   * Called by FiberManager to associate itself with the LoopController.
   */
  virtual void setFiberManager(FiberManager*) = 0;

  /**
   * Called by FiberManager to schedule the loop function run
   * at some point in the future.
   */
  virtual void schedule() = 0;

  /**
   * Run FiberManager loopUntilNoReadyImpl(). May have additional logic specific
   * to a LoopController.
   */
  virtual void runLoop() = 0;

  /**
   * Run FiberManager runEagerFiberImpl(fiber). May have additional logic
   * specific to a LoopController.
   */
  virtual void runEagerFiber(Fiber*) = 0;

  /**
   * Same as schedule(), but safe to call from any thread.
   */
  virtual void scheduleThreadSafe() = 0;

  /**
   * Used by FiberManager to schedule some function to be run at some time.
   * May return null, but only if called outside of runLoop() call (e.g. if
   * Executor backing the timer is already destroyed).
   */
  virtual HHWheelTimer* timer() = 0;

  /**
   * Should return true only if is the same thread that is (if called from
   * within runLoop()) or will be calling runLoop() or a thread that is
   * syncronized with the thread that will be calling runLoop() (i.e. the
   * currently executing "task" has to be completed before runLoop() is called).
   */
  virtual bool isInLoopThread() = 0;
};
} // namespace fibers
} // namespace folly