folly/folly/fibers/FiberManagerInternal.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 <functional>
#include <memory>
#include <queue>
#include <thread>
#include <type_traits>
#include <typeindex>
#include <unordered_set>
#include <vector>

#include <folly/AtomicIntrusiveLinkedList.h>
#include <folly/CPortability.h>
#include <folly/Executor.h>
#include <folly/IntrusiveList.h>
#include <folly/Likely.h>
#include <folly/Portability.h>
#include <folly/Try.h>
#include <folly/functional/Invoke.h>
#include <folly/io/async/HHWheelTimer.h>
#include <folly/io/async/Request.h>

#include <folly/executors/ExecutionObserver.h>
#include <folly/fibers/BoostContextCompatibility.h>
#include <folly/fibers/Fiber.h>
#include <folly/fibers/GuardPageAllocator.h>
#include <folly/fibers/LoopController.h>
#include <folly/fibers/traits.h>

namespace folly {

template <class T>
class Future;

namespace fibers {

class Baton;
class Fiber;

struct TaskOptions;

template <typename T>
class LocalType { … };

class InlineFunctionRunner { … };

/**
 * @class FiberManager
 * @brief Single-threaded task execution engine.
 *
 * FiberManager allows semi-parallel task execution on the same thread. Each
 * task can notify FiberManager that it is blocked on something (via await())
 * call. This will pause execution of this task and it will be resumed only
 * when it is unblocked (via setData()).
 */
class FiberManager : public ::folly::Executor { … };

/**
 * @return      true iff we are running in a fiber's context
 */
inline bool onFiber() { … }

/**
 * Add a new task to be executed.
 *
 * @param func Task functor; must have a signature of `void func()`.
 *             The object will be destroyed once task execution is complete.
 */
template <typename F>
inline void addTask(F&& func) { … }

template <typename F>
inline void addTaskEager(F&& func) { … }

/**
 * Add a new task. When the task is complete, execute finally(Try<Result>&&)
 * on the main context.
 * Task functor is run and destroyed on the fiber context.
 * Finally functor is run and destroyed on the main context.
 *
 * @param func Task functor; must have a signature of `T func()` for some T.
 * @param finally Finally functor; must have a signature of
 *                `void finally(Try<T>&&)` and will be passed
 *                the result of func() (including the exception if occurred).
 */
template <typename F, typename G>
inline void addTaskFinally(F&& func, G&& finally) { … }

template <typename F, typename G>
inline void addTaskFinallyEager(F&& func, G&& finally) { … }

/**
 * Blocks task execution until given promise is fulfilled.
 *
 * Calls function passing in a Promise<T>, which has to be fulfilled.
 *
 * @return data which was used to fulfill the promise.
 */
template <typename F>
typename FirstArgOf<F>::type::value_type inline await_async(F&& func);
#if !defined(_MSC_VER)
template <typename F>
FOLLY_ERASE typename FirstArgOf<F>::type::value_type await(F&& func) { … }
#endif

/**
 * If called from a fiber, immediately switches to the FiberManager's context
 * and runs func(), going back to the Fiber's context after completion.
 * Outside a fiber, just calls func() directly.
 *
 * @return value returned by func().
 */
template <typename F>
invoke_result_t<F> inline runInMainContext(F&& func);

/**
 * Returns a refference to a fiber-local context for given Fiber. Should be
 * always called with the same T for each fiber. Fiber-local context is lazily
 * default-constructed on first request.
 * When new task is scheduled via addTask / addTaskRemote from a fiber its
 * fiber-local context is copied into the new fiber.
 */
template <typename T>
T& local() { … }

inline void yield() { … }
} // namespace fibers
} // namespace folly

#include <folly/fibers/FiberManagerInternal-inl.h>