aos/events/shm-event-loop.cc

#include "aos/events/shm-event-loop.h"
#include "aos/common/queue.h"

#include <atomic>
#include <chrono>
#include <stdexcept>

namespace aos {

ShmEventLoop::ShmEventLoop() : thread_state_(std::make_shared<ThreadState>()) {}

namespace {
class ShmFetcher : public RawFetcher {
 public:
  explicit ShmFetcher(RawQueue *queue) : queue_(queue) {}
  ~ShmFetcher() {
    if (msg_) {
      queue_->FreeMessage(msg_);
    }
  }

  bool Fetch() {
    static constexpr Options<RawQueue> kOptions =
        RawQueue::kFromEnd | RawQueue::kNonBlock;
    const FetchValue *msg = static_cast<const FetchValue *>(
        queue_->ReadMessageIndex(kOptions, &index_));
    // Only update the internal pointer if we got a new message.
    if (msg != NULL && msg != msg_) {
      queue_->FreeMessage(msg_);
      msg_ = msg;
      set_most_recent(msg_);
      return true;
    }
    // The message has to get freed if we didn't use it (and
    // RawQueue::FreeMessage is ok to call on NULL).
    queue_->FreeMessage(msg);
    return false;
  }

 private:
  int index_ = 0;
  RawQueue *queue_;
  const FetchValue *msg_ = nullptr;
};

class ShmSender : public RawSender {
 public:
  explicit ShmSender(RawQueue *queue) : queue_(queue) {}

  SendContext *GetContext() override {
    return reinterpret_cast<SendContext *>(queue_->GetMessage());
  }

  void Free(SendContext *context) override { queue_->FreeMessage(context); }

  bool Send(SendContext *msg) override {
    assert(queue_ != NULL);
    return queue_->WriteMessage(msg, RawQueue::kOverride);
  }

 private:
  RawQueue *queue_;
};
}  // namespace

namespace internal {
class WatcherThreadState {
 public:
  WatcherThreadState(std::shared_ptr<ShmEventLoop::ThreadState> thread_state,
                     RawQueue *queue,
                     std::function<void(const aos::Message *message)> watcher)
      : thread_state_(std::move(thread_state)),
        queue_(queue),
        watcher_(std::move(watcher)) {}

  void Run() {
    thread_state_->WaitForStart();

    if (!thread_state_->is_running()) return;

    int32_t index = 0;

    static constexpr Options<RawQueue> kOptions =
        RawQueue::kFromEnd | RawQueue::kNonBlock;
    const void *msg = queue_->ReadMessageIndex(kOptions, &index);

    while (true) {
      if (msg == nullptr) {
        msg = queue_->ReadMessageIndex(RawQueue::kBlock, &index);
        assert(msg != nullptr);
      }

      {
        MutexLocker locker2(&thread_state_->mutex_);
        if (!thread_state_->is_running()) break;

        watcher_(reinterpret_cast<const Message *>(msg));
        // watcher_ may have exited the event loop.
        if (!thread_state_->is_running()) break;
      }
      queue_->FreeMessage(msg);
      msg = nullptr;
    }

    queue_->FreeMessage(msg);
  }

 private:
  std::shared_ptr<ShmEventLoop::ThreadState> thread_state_;
  RawQueue *queue_;
  std::function<void(const Message *message)> watcher_;
};
}  // namespace internal

std::unique_ptr<RawFetcher> ShmEventLoop::MakeRawFetcher(
    const std::string &path, const QueueTypeInfo &type) {
  Take(path);
  return std::unique_ptr<RawFetcher>(new ShmFetcher(
      RawQueue::Fetch(path.c_str(), type.size, type.hash, type.queue_length)));
}

std::unique_ptr<RawSender> ShmEventLoop::MakeRawSender(
    const std::string &path, const QueueTypeInfo &type) {
  return std::unique_ptr<RawSender>(new ShmSender(
      RawQueue::Fetch(path.c_str(), type.size, type.hash, type.queue_length)));
}

void ShmEventLoop::MakeRawWatcher(
    const std::string &path, const QueueTypeInfo &type,
    std::function<void(const Message *message)> watcher) {
  Take(path);
  auto *state = new internal::WatcherThreadState(
      thread_state_,
      RawQueue::Fetch(path.c_str(), type.size, type.hash, type.queue_length),
      std::move(watcher));

  std::thread thread([state] {
    state->Run();
    delete state;
  });
  thread.detach();
}

void ShmEventLoop::OnRun(std::function<void()> on_run) {
  on_run_.push_back(std::move(on_run));
}

void ShmEventLoop::Run() {
  set_is_running(true);
  for (const auto &run : on_run_) run();
  thread_state_->Run();
}

void ShmEventLoop::ThreadState::Run() {
  MutexLocker locker(&mutex_);
  loop_running_ = true;
  if (loop_finished_) ::aos::Die("Cannot restart an ShmEventLoop()");
  loop_running_cond_.Broadcast();
  while (loop_running_) {
    if (loop_running_cond_.Wait()) {
      ::aos::Die("ShmEventLoop mutex lock problem.\n");
    }
  }
}

void ShmEventLoop::ThreadState::WaitForStart() {
  MutexLocker locker(&mutex_);
  while (!(loop_running_ || loop_finished_)) {
    if (loop_running_cond_.Wait()) {
      ::aos::Die("ShmEventLoop mutex lock problem.\n");
    }
  }
}

void ShmEventLoop::Exit() {
  set_is_running(false);
  thread_state_->Exit();
}

void ShmEventLoop::ThreadState::Exit() {
  IPCRecursiveMutexLocker locker(&mutex_);
  if (locker.owner_died()) ::aos::Die("Owner died");
  loop_running_ = false;
  loop_finished_ = true;
  loop_running_cond_.Broadcast();
}

ShmEventLoop::~ShmEventLoop() {
  if (is_running()) {
    ::aos::Die("ShmEventLoop destroyed while running\n");
  }
}

void ShmEventLoop::Take(const std::string &path) {
  if (is_running()) {
    ::aos::Die("Cannot add new objects while running.\n");
  }
  if (!taken_.emplace(path).second) {
    ::aos::Die("%s already has a listener / watcher.", path.c_str());
  }
}

}  // namespace aos