text: /*
   * Copyright 2012-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 <folly/Random.h>
  #include <folly/Synchronized.h>
  #include <folly/container/Foreach.h>
  #include <folly/portability/GTest.h>
  #include <glog/logging.h>
  #include <algorithm>
  #include <condition_variable>
  #include <functional>
  #include <map>
  #include <random>
  #include <thread>
  #include <vector>
  
  namespace folly {
  namespace sync_tests {
  
  inline std::mt19937& getRNG() {
    static const auto seed = folly::randomNumberSeed();
    static std::mt19937 rng(seed);
    return rng;
  }
  
  void randomSleep(std::chrono::milliseconds min, std::chrono::milliseconds max) {
    std::uniform_int_distribution<> range(min.count(), max.count());
    std::chrono::milliseconds duration(range(getRNG()));
    /* sleep override */
    std::this_thread::sleep_for(duration);
  }
  
  /*
   * Run a functon simultaneously in a number of different threads.
   *
   * The function will be passed the index number of the thread it is running in.
   * This function makes an attempt to synchronize the start of the threads as
   * best as possible.  It waits for all threads to be allocated and started
   * before invoking the function.
   */
  template <class Function>
  void runParallel(size_t numThreads, const Function& function) {
    std::vector<std::thread> threads;
    threads.reserve(numThreads);
  
    // Variables used to synchronize all threads to try and start them
    // as close to the same time as possible
    folly::Synchronized<size_t, std::mutex> threadsReady(0);
    std::condition_variable readyCV;
    folly::Synchronized<bool, std::mutex> go(false);
    std::condition_variable goCV;
  
    auto worker = [&](size_t threadIndex) {
      // Signal that we are ready
      ++(*threadsReady.lock());
      readyCV.notify_one();
  
      // Wait until we are given the signal to start
      // The purpose of this is to try and make sure all threads start
      // as close to the same time as possible.
      {
        auto lockedGo = go.lock();
        goCV.wait(lockedGo.getUniqueLock(), [&] { return *lockedGo; });
      }
  
      function(threadIndex);
    };
  
    // Start all of the threads
    for (size_t threadIndex = 0; threadIndex < numThreads; ++threadIndex) {
      threads.emplace_back([threadIndex, &worker]() { worker(threadIndex); });
    }
  
    // Wait for all threads to become ready
    {
      auto readyLocked = threadsReady.lock();
      readyCV.wait(readyLocked.getUniqueLock(), [&] {
        return *readyLocked == numThreads;
      });
    }
    // Now signal the threads that they can go
    go = true;
    goCV.notify_all();
  
    // Wait for all threads to finish
    for (auto& thread : threads) {
      thread.join();
    }
  }
  
  // testBasic() version for shared lock types
  template <class Mutex>
  typename std::enable_if<folly::LockTraits<Mutex>::is_shared>::type
  testBasicImpl() {
    folly::Synchronized<std::vector<int>, Mutex> obj;
    const auto& constObj = obj;
  
    obj.wlock()->resize(1000);
  
    folly::Synchronized<std::vector<int>, Mutex> obj2{*obj.wlock()};
    EXPECT_EQ(1000, obj2.rlock()->size());
  
    {
      auto lockedObj = obj.wlock();
      lockedObj->push_back(10);
      EXPECT_EQ(1001, lockedObj->size());
      EXPECT_EQ(10, lockedObj->back());
      EXPECT_EQ(1000, obj2.wlock()->size());
      EXPECT_EQ(1000, obj2.rlock()->size());
  
      {
        auto unlocker = lockedObj.scopedUnlock();
        EXPECT_EQ(1001, obj.wlock()->size());
      }
    }
  
    {
      auto lockedObj = obj.rlock();
      EXPECT_EQ(1001, lockedObj->size());
      EXPECT_EQ(1001, obj.rlock()->size());
      {
        auto unlocker = lockedObj.scopedUnlock();
        EXPECT_EQ(1001, obj.wlock()->size());
      }
    }
  
    obj.wlock()->front() = 2;
  
    {
      // contextualLock() on a const reference should grab a shared lock
      auto lockedObj = constObj.contextualLock();
      EXPECT_EQ(2, lockedObj->front());
      EXPECT_EQ(2, constObj.rlock()->front());
      EXPECT_EQ(2, obj.rlock()->front());
    }
  
    EXPECT_EQ(1001, obj.rlock()->size());
    EXPECT_EQ(2, obj.rlock()->front());
    EXPECT_EQ(10, obj.rlock()->back());
    EXPECT_EQ(1000, obj2.rlock()->size());
  }
  
  // testBasic() version for non-shared lock types
  template <class Mutex>
  typename std::enable_if<!folly::LockTraits<Mutex>::is_shared>::type
  testBasicImpl() {
    folly::Synchronized<std::vector<int>, Mutex> obj;
    const auto& constObj = obj;
  
    obj.lock()->resize(1000);
  
    folly::Synchronized<std::vector<int>, Mutex> obj2{*obj.lock()};
    EXPECT_EQ(1000, obj2.lock()->size());
  
    {
      auto lockedObj = obj.lock();
      lockedObj->push_back(10);
      EXPECT_EQ(1001, lockedObj->size());
      EXPECT_EQ(10, lockedObj->back());
      EXPECT_EQ(1000, obj2.lock()->size());
  
      {
        auto unlocker = lockedObj.scopedUnlock();
        EXPECT_EQ(1001, obj.lock()->size());
      }
    }
    {
      auto lockedObj = constObj.lock();
      EXPECT_EQ(1001, lockedObj->size());
      EXPECT_EQ(10, lockedObj->back());
      EXPECT_EQ(1000, obj2.lock()->size());
    }
  
    obj.lock()->front() = 2;
  
    EXPECT_EQ(1001, obj.lock()->size());
    EXPECT_EQ(2, obj.lock()->front());
    EXPECT_EQ(2, obj.contextualLock()->front());
    EXPECT_EQ(10, obj.lock()->back());
    EXPECT_EQ(1000, obj2.lock()->size());
  }
  
  template <class Mutex>
  void testBasic() {
    testBasicImpl<Mutex>();
  }
  
  // testWithLock() version for shared lock types
  template <class Mutex>
  typename std::enable_if<folly::LockTraits<Mutex>::is_shared>::type
  testWithLock() {
    folly::Synchronized<std::vector<int>, Mutex> obj;
    const auto& constObj = obj;
  
    // Test withWLock() and withRLock()
    obj.withWLock([](std::vector<int>& lockedObj) {
      lockedObj.resize(1000);
      lockedObj.push_back(10);
      lockedObj.push_back(11);
    });
    obj.withWLock([](const std::vector<int>& lockedObj) {
      EXPECT_EQ(1002, lockedObj.size());
    });
    constObj.withWLock([](const std::vector<int>& lockedObj) {
      EXPECT_EQ(1002, lockedObj.size());
      EXPECT_EQ(11, lockedObj.back());
    });
    obj.withRLock([](const std::vector<int>& lockedObj) {
      EXPECT_EQ(1002, lockedObj.size());
      EXPECT_EQ(11, lockedObj.back());
    });
    constObj.withRLock([](const std::vector<int>& lockedObj) {
      EXPECT_EQ(1002, lockedObj.size());
    });
  
  #if __cpp_generic_lambdas >= 201304
    obj.withWLock([](auto& lockedObj) { lockedObj.push_back(12); });
    obj.withWLock(
        [](const auto& lockedObj) { EXPECT_EQ(1003, lockedObj.size()); });
    constObj.withWLock([](const auto& lockedObj) {
      EXPECT_EQ(1003, lockedObj.size());
      EXPECT_EQ(12, lockedObj.back());
    });
    obj.withRLock([](const auto& lockedObj) {
      EXPECT_EQ(1003, lockedObj.size());
      EXPECT_EQ(12, lockedObj.back());
    });
    constObj.withRLock(
        [](const auto& lockedObj) { EXPECT_EQ(1003, lockedObj.size()); });
    obj.withWLock([](auto& lockedObj) { lockedObj.pop_back(); });
  #endif
  
    // Test withWLockPtr() and withRLockPtr()
    using SynchType = folly::Synchronized<std::vector<int>, Mutex>;
  #if __cpp_generic_lambdas >= 201304
    obj.withWLockPtr([](auto&& lockedObj) { lockedObj->push_back(13); });
    obj.withRLockPtr([](auto&& lockedObj) {
      EXPECT_EQ(1003, lockedObj->size());
      EXPECT_EQ(13, lockedObj->back());
    });
    constObj.withRLockPtr([](auto&& lockedObj) {
      EXPECT_EQ(1003, lockedObj->size());
      EXPECT_EQ(13, lockedObj->back());
    });
    obj.withWLockPtr([&](auto&& lockedObj) {
      lockedObj->push_back(14);
      {
        auto unlocker = lockedObj.scopedUnlock();
        obj.wlock()->push_back(15);
      }
      EXPECT_EQ(15, lockedObj->back());
    });
    constObj.withWLockPtr([](auto&& lockedObj) {
      EXPECT_EQ(1005, lockedObj->size());
      EXPECT_EQ(15, lockedObj->back());
    });
  #else
    obj.withWLockPtr([](typename SynchType::LockedPtr&& lockedObj) {
      lockedObj->push_back(13);
      lockedObj->push_back(14);
      lockedObj->push_back(15);
    });
  #endif
  
    obj.withWLockPtr([](typename SynchType::LockedPtr&& lockedObj) {
      lockedObj->push_back(16);
      EXPECT_EQ(1006, lockedObj->size());
    });
    constObj.withWLockPtr([](typename SynchType::ConstWLockedPtr&& lockedObj) {
      EXPECT_EQ(1006, lockedObj->size());
      EXPECT_EQ(16, lockedObj->back());
    });
    obj.withRLockPtr([](typename SynchType::ConstLockedPtr&& lockedObj) {
      EXPECT_EQ(1006, lockedObj->size());
      EXPECT_EQ(16, lockedObj->back());
    });
    constObj.withRLockPtr([](typename SynchType::ConstLockedPtr&& lockedObj) {
      EXPECT_EQ(1006, lockedObj->size());
      EXPECT_EQ(16, lockedObj->back());
    });
  }
  
  // testWithLock() version for non-shared lock types
  template <class Mutex>
  typename std::enable_if<!folly::LockTraits<Mutex>::is_shared>::type
  testWithLock() {
    folly::Synchronized<std::vector<int>, Mutex> obj;
  
    // Test withLock()
    obj.withLock([](std::vector<int>& lockedObj) {
      lockedObj.resize(1000);
      lockedObj.push_back(10);
      lockedObj.push_back(11);
    });
    obj.withLock([](const std::vector<int>& lockedObj) {
      EXPECT_EQ(1002, lockedObj.size());
    });
  
  #if __cpp_generic_lambdas >= 201304
    obj.withLock([](auto& lockedObj) { lockedObj.push_back(12); });
    obj.withLock(
        [](const auto& lockedObj) { EXPECT_EQ(1003, lockedObj.size()); });
    obj.withLock([](auto& lockedObj) { lockedObj.pop_back(); });
  #endif
  
    // Test withLockPtr()
    using SynchType = folly::Synchronized<std::vector<int>, Mutex>;
  #if __cpp_generic_lambdas >= 201304
    obj.withLockPtr([](auto&& lockedObj) { lockedObj->push_back(13); });
    obj.withLockPtr([](auto&& lockedObj) {
      EXPECT_EQ(1003, lockedObj->size());
      EXPECT_EQ(13, lockedObj->back());
    });
    obj.withLockPtr([&](auto&& lockedObj) {
      lockedObj->push_back(14);
      {
        auto unlocker = lockedObj.scopedUnlock();
        obj.lock()->push_back(15);
      }
      EXPECT_EQ(1005, lockedObj->size());
      EXPECT_EQ(15, lockedObj->back());
    });
  #else
    obj.withLockPtr([](typename SynchType::LockedPtr&& lockedObj) {
      lockedObj->push_back(13);
      lockedObj->push_back(14);
      lockedObj->push_back(15);
    });
  #endif
  
    obj.withLockPtr([](typename SynchType::LockedPtr&& lockedObj) {
      lockedObj->push_back(16);
      EXPECT_EQ(1006, lockedObj->size());
    });
    const auto& constObj = obj;
    constObj.withLockPtr([](typename SynchType::ConstLockedPtr&& lockedObj) {
      EXPECT_EQ(1006, lockedObj->size());
      EXPECT_EQ(16, lockedObj->back());
    });
  }
  
  template <class Mutex>
  void testUnlockCommon() {
    folly::Synchronized<int, Mutex> value{7};
    const auto& cv = value;
  
    {
      auto lv = value.contextualLock();
      EXPECT_EQ(7, *lv);
      *lv = 5;
      lv.unlock();
      EXPECT_TRUE(lv.isNull());
      EXPECT_FALSE(lv);
  
      auto rlv = cv.contextualLock();
      EXPECT_EQ(5, *rlv);
      rlv.unlock();
      EXPECT_TRUE(rlv.isNull());
      EXPECT_FALSE(rlv);
  
      auto rlv2 = cv.contextualRLock();
      EXPECT_EQ(5, *rlv2);
      rlv2.unlock();
  
      lv = value.contextualLock();
      EXPECT_EQ(5, *lv);
      *lv = 9;
    }
  
    EXPECT_EQ(9, *value.contextualRLock());
  }
  
  // testUnlock() version for shared lock types
  template <class Mutex>
  typename std::enable_if<folly::LockTraits<Mutex>::is_shared>::type
  testUnlock() {
    folly::Synchronized<int, Mutex> value{10};
    {
      auto lv = value.wlock();
      EXPECT_EQ(10, *lv);
      *lv = 5;
      lv.unlock();
      EXPECT_FALSE(lv);
      EXPECT_TRUE(lv.isNull());
  
      auto rlv = value.rlock();
      EXPECT_EQ(5, *rlv);
      rlv.unlock();
      EXPECT_FALSE(rlv);
      EXPECT_TRUE(rlv.isNull());
  
      auto lv2 = value.wlock();
      EXPECT_EQ(5, *lv2);
      *lv2 = 7;
  
      lv = std::move(lv2);
      EXPECT_FALSE(lv2);
      EXPECT_TRUE(lv2.isNull());
      EXPECT_FALSE(lv.isNull());
      EXPECT_EQ(7, *lv);
    }
  
    testUnlockCommon<Mutex>();
  }
  
  // testUnlock() version for non-shared lock types
  template <class Mutex>
  typename std::enable_if<!folly::LockTraits<Mutex>::is_shared>::type
  testUnlock() {
    folly::Synchronized<int, Mutex> value{10};
    {
      auto lv = value.lock();
      EXPECT_EQ(10, *lv);
      *lv = 5;
      lv.unlock();
      EXPECT_TRUE(lv.isNull());
      EXPECT_FALSE(lv);
  
      auto lv2 = value.lock();
      EXPECT_EQ(5, *lv2);
      *lv2 = 6;
      lv2.unlock();
      EXPECT_TRUE(lv2.isNull());
      EXPECT_FALSE(lv2);
  
      lv = value.lock();
      EXPECT_EQ(6, *lv);
      *lv = 7;
  
      lv2 = std::move(lv);
      EXPECT_TRUE(lv.isNull());
      EXPECT_FALSE(lv);
      EXPECT_FALSE(lv2.isNull());
      EXPECT_EQ(7, *lv2);
    }
  
    testUnlockCommon<Mutex>();
  }
  
  // Testing the deprecated SYNCHRONIZED and SYNCHRONIZED_CONST APIs
  template <class Mutex>
  void testDeprecated() {
    folly::Synchronized<std::vector<int>, Mutex> obj;
  
    obj->resize(1000);
  
    auto obj2 = obj;
    EXPECT_EQ(1000, obj2->size());
  
    SYNCHRONIZED(obj) {
      obj.push_back(10);
      EXPECT_EQ(1001, obj.size());
      EXPECT_EQ(10, obj.back());
      EXPECT_EQ(1000, obj2->size());
    }
  
    SYNCHRONIZED_CONST(obj) {
      EXPECT_EQ(1001, obj.size());
    }
  
    SYNCHRONIZED(lockedObj, *&obj) {
      lockedObj.front() = 2;
    }
  
    EXPECT_EQ(1001, obj->size());
    EXPECT_EQ(10, obj->back());
    EXPECT_EQ(1000, obj2->size());
  
    EXPECT_EQ(FB_ARG_2_OR_1(1, 2), 2);
    EXPECT_EQ(FB_ARG_2_OR_1(1), 1);
  }
  
  template <class Mutex>
  void testConcurrency() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    static const size_t numThreads = 100;
    // Note: I initially tried using itersPerThread = 1000,
    // which works fine for most lock types, but std::shared_timed_mutex
    // appears to be extraordinarily slow.  It could take around 30 seconds
    // to run this test with 1000 iterations per thread using shared_timed_mutex.
    static const size_t itersPerThread = 100;
  
    auto pushNumbers = [&](size_t threadIdx) {
      // Test lock()
      for (size_t n = 0; n < itersPerThread; ++n) {
        v.contextualLock()->push_back((itersPerThread * threadIdx) + n);
        std::this_thread::yield();
      }
    };
    runParallel(numThreads, pushNumbers);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads * itersPerThread, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < itersPerThread * numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
  }
  
  template <class Mutex>
  void testAcquireLocked() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<std::map<int, int>, Mutex> m;
  
    auto dualLockWorker = [&](size_t threadIdx) {
      // Note: this will be less awkward with C++ 17's structured
      // binding functionality, which will make it easier to use the returned
      // std::tuple.
      if (threadIdx & 1) {
        auto ret = acquireLocked(v, m);
        std::get<0>(ret)->push_back(threadIdx);
        (*std::get<1>(ret))[threadIdx] = threadIdx + 1;
      } else {
        auto ret = acquireLocked(m, v);
        std::get<1>(ret)->push_back(threadIdx);
        (*std::get<0>(ret))[threadIdx] = threadIdx + 1;
      }
    };
    static const size_t numThreads = 100;
    runParallel(numThreads, dualLockWorker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
  }
  
  template <class Mutex>
  void testAcquireLockedWithConst() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<std::map<int, int>, Mutex> m;
  
    auto dualLockWorker = [&](size_t threadIdx) {
      const auto& cm = m;
      if (threadIdx & 1) {
        auto ret = acquireLocked(v, cm);
        (void)std::get<1>(ret)->size();
        std::get<0>(ret)->push_back(threadIdx);
      } else {
        auto ret = acquireLocked(cm, v);
        (void)std::get<0>(ret)->size();
        std::get<1>(ret)->push_back(threadIdx);
      }
    };
    static const size_t numThreads = 100;
    runParallel(numThreads, dualLockWorker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
  }
  
  // Testing the deprecated SYNCHRONIZED_DUAL API
  template <class Mutex>
  void testDualLocking() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<std::map<int, int>, Mutex> m;
  
    auto dualLockWorker = [&](size_t threadIdx) {
      if (threadIdx & 1) {
        SYNCHRONIZED_DUAL(lv, v, lm, m) {
          lv.push_back(threadIdx);
          lm[threadIdx] = threadIdx + 1;
        }
      } else {
        SYNCHRONIZED_DUAL(lm, m, lv, v) {
          lv.push_back(threadIdx);
          lm[threadIdx] = threadIdx + 1;
        }
      }
    };
    static const size_t numThreads = 100;
    runParallel(numThreads, dualLockWorker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
  }
  
  // Testing the deprecated SYNCHRONIZED_DUAL API
  template <class Mutex>
  void testDualLockingWithConst() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<std::map<int, int>, Mutex> m;
  
    auto dualLockWorker = [&](size_t threadIdx) {
      const auto& cm = m;
      if (threadIdx & 1) {
        SYNCHRONIZED_DUAL(lv, v, lm, cm) {
          (void)lm.size();
          lv.push_back(threadIdx);
        }
      } else {
        SYNCHRONIZED_DUAL(lm, cm, lv, v) {
          (void)lm.size();
          lv.push_back(threadIdx);
        }
      }
    };
    static const size_t numThreads = 100;
    runParallel(numThreads, dualLockWorker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
  }
  
  template <class Mutex>
  void testTimed() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<uint64_t, Mutex> numTimeouts;
  
    auto worker = [&](size_t threadIdx) {
      // Test directly using operator-> on the lock result
      v.contextualLock()->push_back(2 * threadIdx);
  
      // Test using lock with a timeout
      for (;;) {
        auto lv = v.contextualLock(std::chrono::milliseconds(5));
        if (!lv) {
          ++(*numTimeouts.contextualLock());
          continue;
        }
  
        // Sleep for a random time to ensure we trigger timeouts
        // in other threads
        randomSleep(std::chrono::milliseconds(5), std::chrono::milliseconds(15));
        lv->push_back(2 * threadIdx + 1);
        break;
      }
    };
  
    static const size_t numThreads = 100;
    runParallel(numThreads, worker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(2 * numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < 2 * numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
    // We generally expect a large number of number timeouts here.
    // I'm not adding a check for it since it's theoretically possible that
    // we might get 0 timeouts depending on the CPU scheduling if our threads
    // don't get to run very often.
    LOG(INFO) << "testTimed: " << *numTimeouts.contextualRLock() << " timeouts";
  
    // Make sure we can lock with various timeout duration units
    {
      auto lv = v.contextualLock(std::chrono::milliseconds(5));
      EXPECT_TRUE(bool(lv));
      EXPECT_FALSE(lv.isNull());
      auto lv2 = v.contextualLock(std::chrono::microseconds(5));
      // We may or may not acquire lv2 successfully, depending on whether
      // or not this is a recursive mutex type.
    }
    {
      auto lv = v.contextualLock(std::chrono::seconds(1));
      EXPECT_TRUE(bool(lv));
    }
  }
  
  template <class Mutex>
  void testTimedShared() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<uint64_t, Mutex> numTimeouts;
  
    auto worker = [&](size_t threadIdx) {
      // Test directly using operator-> on the lock result
      v.wlock()->push_back(threadIdx);
  
      // Test lock() with a timeout
      for (;;) {
        auto lv = v.rlock(std::chrono::milliseconds(10));
        if (!lv) {
          ++(*numTimeouts.contextualLock());
          continue;
        }
  
        // Sleep while holding the lock.
        //
        // This will block other threads from acquiring the write lock to add
        // their thread index to v, but it won't block threads that have entered
        // the for loop and are trying to acquire a read lock.
        //
        // For lock types that give preference to readers rather than writers,
        // this will tend to serialize all threads on the wlock() above.
        randomSleep(std::chrono::milliseconds(5), std::chrono::milliseconds(15));
        auto found = std::find(lv->begin(), lv->end(), threadIdx);
        CHECK(found != lv->end());
        break;
      }
    };
  
    static const size_t numThreads = 100;
    runParallel(numThreads, worker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
    // We generally expect a small number of timeouts here.
    // For locks that give readers preference over writers this should usually
    // be 0.  With locks that give writers preference we do see a small-ish
    // number of read timeouts.
    LOG(INFO) << "testTimedShared: " << *numTimeouts.contextualRLock()
              << " timeouts";
  }
  
  // Testing the deprecated TIMED_SYNCHRONIZED API
  template <class Mutex>
  void testTimedSynchronized() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<uint64_t, Mutex> numTimeouts;
  
    auto worker = [&](size_t threadIdx) {
      // Test operator->
      v->push_back(2 * threadIdx);
  
      // Aaand test the TIMED_SYNCHRONIZED macro
      for (;;) {
        TIMED_SYNCHRONIZED(5, lv, v) {
          if (lv) {
            // Sleep for a random time to ensure we trigger timeouts
            // in other threads
            randomSleep(
                std::chrono::milliseconds(5), std::chrono::milliseconds(15));
            lv->push_back(2 * threadIdx + 1);
            return;
          }
  
          ++(*numTimeouts.contextualLock());
        }
      }
    };
  
    static const size_t numThreads = 100;
    runParallel(numThreads, worker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(2 * numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < 2 * numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
    // We generally expect a large number of number timeouts here.
    // I'm not adding a check for it since it's theoretically possible that
    // we might get 0 timeouts depending on the CPU scheduling if our threads
    // don't get to run very often.
    LOG(INFO) << "testTimedSynchronized: " << *numTimeouts.contextualRLock()
              << " timeouts";
  }
  
  // Testing the deprecated TIMED_SYNCHRONIZED_CONST API
  template <class Mutex>
  void testTimedSynchronizedWithConst() {
    folly::Synchronized<std::vector<int>, Mutex> v;
    folly::Synchronized<uint64_t, Mutex> numTimeouts;
  
    auto worker = [&](size_t threadIdx) {
      // Test operator->
      v->push_back(threadIdx);
  
      // Test TIMED_SYNCHRONIZED_CONST
      for (;;) {
        TIMED_SYNCHRONIZED_CONST(10, lv, v) {
          if (lv) {
            // Sleep while holding the lock.
            //
            // This will block other threads from acquiring the write lock to add
            // their thread index to v, but it won't block threads that have
            // entered the for loop and are trying to acquire a read lock.
            //
            // For lock types that give preference to readers rather than writers,
            // this will tend to serialize all threads on the wlock() above.
            randomSleep(
                std::chrono::milliseconds(5), std::chrono::milliseconds(15));
            auto found = std::find(lv->begin(), lv->end(), threadIdx);
            CHECK(found != lv->end());
            return;
          } else {
            ++(*numTimeouts.contextualLock());
          }
        }
      }
    };
  
    static const size_t numThreads = 100;
    runParallel(numThreads, worker);
  
    std::vector<int> result;
    v.swap(result);
  
    EXPECT_EQ(numThreads, result.size());
    sort(result.begin(), result.end());
  
    for (size_t i = 0; i < numThreads; ++i) {
      EXPECT_EQ(i, result[i]);
    }
    // We generally expect a small number of timeouts here.
    // For locks that give readers preference over writers this should usually
    // be 0.  With locks that give writers preference we do see a small-ish
    // number of read timeouts.
    LOG(INFO) << "testTimedSynchronizedWithConst: "
              << *numTimeouts.contextualRLock() << " timeouts";
  }
  
  template <class Mutex>
  void testConstCopy() {
    std::vector<int> input = {1, 2, 3};
    const folly::Synchronized<std::vector<int>, Mutex> v(input);
  
    std::vector<int> result;
  
    v.copy(&result);
    EXPECT_EQ(input, result);
  
    result = v.copy();
    EXPECT_EQ(input, result);
  }
  
  struct NotCopiableNotMovable {
    NotCopiableNotMovable(int, const char*) {}
    NotCopiableNotMovable(const NotCopiableNotMovable&) = delete;
    NotCopiableNotMovable& operator=(const NotCopiableNotMovable&) = delete;
    NotCopiableNotMovable(NotCopiableNotMovable&&) = delete;
    NotCopiableNotMovable& operator=(NotCopiableNotMovable&&) = delete;
  };
  
  template <class Mutex>
  void testInPlaceConstruction() {
    // This won't compile without in_place
    folly::Synchronized<NotCopiableNotMovable> a(folly::in_place, 5, "a");
  }
  
  template <class Mutex>
  void testExchange() {
    std::vector<int> input = {1, 2, 3};
    folly::Synchronized<std::vector<int>, Mutex> v(input);
    std::vector<int> next = {4, 5, 6};
    auto prev = v.exchange(std::move(next));
    EXPECT_EQ((std::vector<int>{{1, 2, 3}}), prev);
    EXPECT_EQ((std::vector<int>{{4, 5, 6}}), v.copy());
  }
  } // namespace sync_tests
  } // namespace folly
  