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admin/node_modules/@parcel/watcher/src/Watcher.cc

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+#include "Watcher.hh"
+#include <unordered_set>
+
+using namespace Napi;
+
+struct WatcherHash {
+  std::size_t operator() (WatcherRef const &k) const {
+    return std::hash<std::string>()(k->mDir);
+  }
+};
+
+struct WatcherCompare {
+  size_t operator() (WatcherRef const &a, WatcherRef const &b) const {
+    return *a == *b;
+  }
+};
+
+static std::unordered_set<WatcherRef , WatcherHash, WatcherCompare> sharedWatchers;
+
+WatcherRef Watcher::getShared(std::string dir, std::unordered_set<std::string> ignorePaths, std::unordered_set<Glob> ignoreGlobs) {
+  WatcherRef watcher = std::make_shared<Watcher>(dir, ignorePaths, ignoreGlobs);
+  auto found = sharedWatchers.find(watcher);
+  if (found != sharedWatchers.end()) {
+    return *found;
+  }
+
+  sharedWatchers.insert(watcher);
+  return watcher;
+}
+
+void removeShared(Watcher *watcher) {
+  for (auto it = sharedWatchers.begin(); it != sharedWatchers.end(); it++) {
+    if (it->get() == watcher) {
+      sharedWatchers.erase(it);
+      break;
+    }
+  }
+
+  // Free up memory.
+  if (sharedWatchers.size() == 0) {
+    sharedWatchers.rehash(0);
+  }
+}
+
+Watcher::Watcher(std::string dir, std::unordered_set<std::string> ignorePaths, std::unordered_set<Glob> ignoreGlobs)
+  : mDir(dir),
+    mIgnorePaths(ignorePaths),
+    mIgnoreGlobs(ignoreGlobs) {
+      mDebounce = Debounce::getShared();
+      mDebounce->add(this, [this] () {
+        triggerCallbacks();
+      });
+    }
+
+Watcher::~Watcher() {
+  mDebounce->remove(this);
+}
+
+void Watcher::wait() {
+  std::unique_lock<std::mutex> lk(mMutex);
+  mCond.wait(lk);
+}
+
+void Watcher::notify() {
+  std::unique_lock<std::mutex> lk(mMutex);
+  mCond.notify_all();
+
+  if (mCallbacks.size() > 0 && mEvents.size() > 0) {
+    // We must release our lock before calling into the debouncer
+    // to avoid a deadlock: the debouncer thread itself will require
+    // our lock from its thread when calling into `triggerCallbacks`
+    // while holding its own debouncer lock.
+    lk.unlock();
+    mDebounce->trigger();
+  }
+}
+
+struct CallbackData {
+  std::string error;
+  std::vector<Event> events;
+  CallbackData(std::string error, std::vector<Event> events) : error(error), events(events) {}
+};
+
+Value callbackEventsToJS(const Env &env, std::vector<Event> &events) {
+  EscapableHandleScope scope(env);
+  Array arr = Array::New(env, events.size());
+  size_t currentEventIndex = 0;
+  for (auto eventIterator = events.begin(); eventIterator != events.end(); eventIterator++) {
+    arr.Set(currentEventIndex++, eventIterator->toJS(env));
+  }
+  return scope.Escape(arr);
+}
+
+void callJSFunction(Napi::Env env, Function jsCallback, CallbackData *data) {
+  HandleScope scope(env);
+  auto err = data->error.size() > 0 ? Error::New(env, data->error).Value() : env.Null();
+  auto events = callbackEventsToJS(env, data->events);
+  jsCallback.Call({err, events});
+  delete data;
+
+  // Throw errors from the callback as fatal exceptions
+  // If we don't handle these node segfaults...
+  if (env.IsExceptionPending()) {
+    Napi::Error err = env.GetAndClearPendingException();
+    napi_fatal_exception(env, err.Value());
+  }
+}
+
+void Watcher::notifyError(std::exception &err) {
+  std::unique_lock<std::mutex> lk(mMutex);
+  for (auto it = mCallbacks.begin(); it != mCallbacks.end(); it++) {
+    CallbackData *data = new CallbackData(err.what(), {});
+    it->tsfn.BlockingCall(data, callJSFunction);
+  }
+
+  clearCallbacks();
+}
+
+// This function is called from the debounce thread.
+void Watcher::triggerCallbacks() {
+  std::unique_lock<std::mutex> lk(mMutex);
+  if (mCallbacks.size() > 0 && (mEvents.size() > 0 || mEvents.hasError())) {
+    auto error = mEvents.getError();
+    auto events = mEvents.getEvents();
+    mEvents.clear();
+
+    for (auto it = mCallbacks.begin(); it != mCallbacks.end(); it++) {
+      it->tsfn.BlockingCall(new CallbackData(error, events), callJSFunction);
+    }
+  }
+}
+
+// This should be called from the JavaScript thread.
+bool Watcher::watch(Function callback) {
+  std::unique_lock<std::mutex> lk(mMutex);
+
+  auto it = findCallback(callback);
+  if (it != mCallbacks.end()) {
+    return false;
+  }
+
+  auto tsfn = ThreadSafeFunction::New(
+    callback.Env(),
+    callback,
+    "Watcher callback",
+    0, // Unlimited queue
+    1 // Initial thread count
+  );
+
+  mCallbacks.push_back(Callback {
+    tsfn,
+    Napi::Persistent(callback),
+    std::this_thread::get_id()
+  });
+
+  return true;
+}
+
+// This should be called from the JavaScript thread.
+std::vector<Callback>::iterator Watcher::findCallback(Function callback) {
+  for (auto it = mCallbacks.begin(); it != mCallbacks.end(); it++) {
+    // Only consider callbacks created by the same thread, or V8 will panic.
+    if (it->threadId == std::this_thread::get_id() && it->ref.Value() == callback) {
+      return it;
+    }
+  }
+
+  return mCallbacks.end();
+}
+
+// This should be called from the JavaScript thread.
+bool Watcher::unwatch(Function callback) {
+  std::unique_lock<std::mutex> lk(mMutex);
+
+  bool removed = false;
+  auto it = findCallback(callback);
+  if (it != mCallbacks.end()) {
+    it->tsfn.Release();
+    it->ref.Unref();
+    mCallbacks.erase(it);
+    removed = true;
+  }
+
+  if (removed && mCallbacks.size() == 0) {
+    unref();
+    return true;
+  }
+
+  return false;
+}
+
+void Watcher::unref() {
+  if (mCallbacks.size() == 0) {
+    removeShared(this);
+  }
+}
+
+void Watcher::destroy() {
+  std::unique_lock<std::mutex> lk(mMutex);
+  clearCallbacks();
+}
+
+// Private because it doesn't lock.
+void Watcher::clearCallbacks() {
+  for (auto it = mCallbacks.begin(); it != mCallbacks.end(); it++) {
+    it->tsfn.Release();
+    it->ref.Unref();
+  }
+
+  mCallbacks.clear();
+  unref();
+}
+
+bool Watcher::isIgnored(std::string path) {
+  for (auto it = mIgnorePaths.begin(); it != mIgnorePaths.end(); it++) {
+    auto dir = *it + DIR_SEP;
+    if (*it == path || path.compare(0, dir.size(), dir) == 0) {
+      return true;
+    }
+  }
+
+  auto basePath = mDir + DIR_SEP;
+
+  if (path.rfind(basePath, 0) != 0) {
+    return false;
+  }
+
+  auto relativePath = path.substr(basePath.size());
+
+  for (auto it = mIgnoreGlobs.begin(); it != mIgnoreGlobs.end(); it++) {
+    if (it->isIgnored(relativePath)) {
+      return true;
+    }
+  }
+
+  return false;
+}