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node_modules/react-native/ReactCommon/react/runtime/BufferedRuntimeExecutor.cpp

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+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "BufferedRuntimeExecutor.h"
+
+namespace facebook::react {
+
+BufferedRuntimeExecutor::BufferedRuntimeExecutor(
+    RuntimeExecutor runtimeExecutor)
+    : runtimeExecutor_(std::move(runtimeExecutor)),
+      isBufferingEnabled_(true),
+      lastIndex_(0) {}
+
+void BufferedRuntimeExecutor::execute(Work&& callback) {
+  if (!isBufferingEnabled_) {
+    // Fast path: Schedule directly to RuntimeExecutor, without locking
+    runtimeExecutor_(std::move(callback));
+    return;
+  }
+
+  /**
+   * Note: std::mutex doesn't have a FIFO ordering.
+   * To preserve the order of the buffered work, use a priority queue and
+   * track the last known work index.
+   */
+  uint64_t newIndex = lastIndex_++;
+  std::scoped_lock guard(lock_);
+  if (isBufferingEnabled_) {
+    queue_.push({.index_ = newIndex, .work_ = std::move(callback)});
+    return;
+  }
+
+  // Force flush the queue to maintain the execution order.
+  unsafeFlush();
+
+  runtimeExecutor_(std::move(callback));
+}
+
+void BufferedRuntimeExecutor::flush() {
+  std::scoped_lock guard(lock_);
+  unsafeFlush();
+  isBufferingEnabled_ = false;
+}
+
+void BufferedRuntimeExecutor::unsafeFlush() {
+  while (!queue_.empty()) {
+    const BufferedWork& bufferedWork = queue_.top();
+    Work work = bufferedWork.work_;
+    runtimeExecutor_(std::move(work));
+    queue_.pop();
+  }
+}
+
+} // namespace facebook::react