Basically wrote the whole thing.

node_modules/@parcel/watcher/src/shared/BruteForceBackend.cc

@@ -0,0 +1,41 @@
+#include <string>
+#include "../DirTree.hh"
+#include "../Event.hh"
+#include "./BruteForceBackend.hh"
+
+std::shared_ptr<DirTree> BruteForceBackend::getTree(WatcherRef watcher, bool shouldRead) {
+  auto tree = DirTree::getCached(watcher->mDir);
+
+  // If the tree is not complete, read it if needed.
+  if (!tree->isComplete && shouldRead) {
+    readTree(watcher, tree);
+    tree->isComplete = true;
+  }
+
+  return tree;
+}
+
+void BruteForceBackend::writeSnapshot(WatcherRef watcher, std::string *snapshotPath) {
+  std::unique_lock<std::mutex> lock(mMutex);
+  auto tree = getTree(watcher);
+  FILE *f = fopen(snapshotPath->c_str(), "w");
+  if (!f) {
+    throw std::runtime_error(std::string("Unable to open snapshot file: ") + strerror(errno));
+  }
+
+  tree->write(f);
+  fclose(f);
+}
+
+void BruteForceBackend::getEventsSince(WatcherRef watcher, std::string *snapshotPath) {
+  std::unique_lock<std::mutex> lock(mMutex);
+  FILE *f = fopen(snapshotPath->c_str(), "r");
+  if (!f) {
+    throw std::runtime_error(std::string("Unable to open snapshot file: ") + strerror(errno));
+  }
+
+  DirTree snapshot{watcher->mDir, f};
+  auto now = getTree(watcher);
+  now->getChanges(&snapshot, watcher->mEvents);
+  fclose(f);
+}