Fiber.h

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/*
 * Copyright 2014-present Facebook, Inc.
 *
 * 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 <thread>
#include <typeinfo>

#include <folly/AtomicIntrusiveLinkedList.h>
#include <folly/CPortability.h>
#include <folly/Function.h>
#include <folly/IntrusiveList.h>
#include <folly/Portability.h>
#include <folly/fibers/BoostContextCompatibility.h>
#include <folly/io/async/Request.h>

namespace folly {
namespace fibers {

class Baton;
class FiberManager;

class Fiber {
 public:
  void resume();

  Fiber(const Fiber&) = delete;
  Fiber& operator=(const Fiber&) = delete;

  ~Fiber();

  std::pair<void*, size_t> getStack() const {
    return {fiberStackLimit_, fiberStackSize_};
  }

 private:
  enum State {
    INVALID, 
    NOT_STARTED, 
    READY_TO_RUN, 
    RUNNING, 
    AWAITING, 
    AWAITING_IMMEDIATE, 
    YIELDED, 
  };

  State state_{INVALID}; 
  friend class Baton;
  friend class FiberManager;

  explicit Fiber(FiberManager& fiberManager);

  void init(bool recordStackUsed);

  template <typename F>
  void setFunction(F&& func);

  template <typename F, typename G>
  void setFunctionFinally(F&& func, G&& finally);

  [[noreturn]] void fiberFunc();

  void preempt(State state);

  void recordStackPosition();

  FiberManager& fiberManager_; 
  size_t fiberStackSize_;
  unsigned char* fiberStackLimit_;
  FiberImpl fiberImpl_; 
  std::shared_ptr<RequestContext> rcontext_; 
  folly::Function<void()> func_; 
  bool recordStackUsed_{false};
  bool stackFilledWithMagic_{false};

  folly::AtomicIntrusiveLinkedListHook<Fiber> nextRemoteReady_;

  static constexpr size_t kUserBufferSize = 256;
  std::aligned_storage<kUserBufferSize>::type userBuffer_;

  void* getUserBuffer();

  folly::Function<void()> resultFunc_;
  folly::Function<void()> finallyFunc_;

  class LocalData {
   public:
    LocalData() {}
    ~LocalData();
    LocalData(const LocalData& other);
    LocalData& operator=(const LocalData& other);

    template <typename T>
    T& get() {
      if (data_) {
        assert(*dataType_ == typeid(T));
        return *reinterpret_cast<T*>(data_);
      }
      return getSlow<T>();
    }

    void reset();

    // private:
    template <typename T>
    FOLLY_NOINLINE T& getSlow();

    static void* allocateHeapBuffer(size_t size);
    static void freeHeapBuffer(void* buffer);

    template <typename T>
    static void dataCopyConstructor(void*, const void*);
    template <typename T>
    static void dataBufferDestructor(void*);
    template <typename T>
    static void dataHeapDestructor(void*);

    static constexpr size_t kBufferSize = 128;
    std::aligned_storage<kBufferSize>::type buffer_;
    size_t dataSize_;

    const std::type_info* dataType_;
    void (*dataDestructor_)(void*);
    void (*dataCopyConstructor_)(void*, const void*);
    void* data_{nullptr};
  };

  LocalData localData_;

  folly::IntrusiveListHook listHook_; 
  folly::IntrusiveListHook globalListHook_; 
  std::thread::id threadId_{};

#ifdef FOLLY_SANITIZE_ADDRESS
  void* asanFakeStack_{nullptr};
  const void* asanMainStackBase_{nullptr};
  size_t asanMainStackSize_{0};
#endif
};
} // namespace fibers
} // namespace folly

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