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diff --git a/src/support/threads.h b/src/support/threads.h
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+/*
+ * Copyright 2016 WebAssembly Community Group participants
+ *
+ * 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.
+ */
+
+//
+// Threads helpers.
+//
+
+#ifndef wasm_support_threads_h
+#define wasm_support_threads_h
+
+#include <atomic>
+#include <condition_variable>
+#include <memory>
+#include <mutex>
+#include <thread>
+#include <vector>
+
+namespace wasm {
+
+// The work state of a helper thread - is there more to do,
+// or are we finished for now.
+enum class ThreadWorkState {
+  More,
+  Finished
+};
+
+//
+// A helper thread.
+//
+// You can only create and destroy these on the main thread.
+//
+
+class Thread {
+  std::unique_ptr<std::thread> thread;
+  std::mutex mutex;
+  std::condition_variable condition;
+  bool done = false;
+  std::function<ThreadWorkState ()> doWork = nullptr;
+
+public:
+  Thread();
+  ~Thread();
+
+  // Start to do work, calling doWork() until
+  // it returns false.
+  void work(std::function<ThreadWorkState ()> doWork);
+
+private:
+  static void mainLoop(void *self);
+};
+
+//
+// A pool of helper threads.
+//
+// There is only one, to avoid recursive pools using too many cores.
+//
+
+class ThreadPool {
+  std::vector<std::unique_ptr<Thread>> threads;
+  bool running = false;
+  std::mutex mutex;
+  std::condition_variable condition;
+  std::atomic<size_t> ready;
+
+private:
+  void initialize(size_t num);
+
+public:
+  // Get the singleton threadpool. This can return null
+  // if there is just one thread available.
+  static ThreadPool* get();
+
+  // Execute a bunch of tasks by the pool. This calls
+  // getTask() (in a thread-safe manner) to get tasks, and
+  // sends them to workers to be executed. This method
+  // blocks until all tasks are complete.
+  void work(std::vector<std::function<ThreadWorkState ()>>& doWorkers);
+
+  size_t size();
+
+  static bool isRunning();
+
+  // Called by helper threads when they are free and ready.
+  void notifyThreadIsReady();
+
+private:
+  void resetThreadsAreReady();
+
+  bool areThreadsReady();
+};
+
+} // namespace wasm
+
+#endif  // wasm_support_threads_h