Move thread_pool.h into utils so it can be shared by more than one example.

native_client_sdk/src/libraries/sdk_util/thread_pool.h

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Simple thread pool class
+
+#ifndef LIBRARIES_SDK_UTIL_THREAD_POOL_H_
+#define LIBRARIES_SDK_UTIL_THREAD_POOL_H_
+
+#include <pthread.h>
+#include <semaphore.h>
+
+// typdef helper for work function
+typedef void (*WorkFunction)(int task_index, void* data);
+
+// ThreadPool is a class to manage num_threads and assign
+// them num_tasks of work at a time. Each call
+// to Dispatch(..) will block until all tasks complete.
+// If 0 is passed in for num_threads, all tasks will be
+// issued on the dispatch thread.
+
+class ThreadPool {
+ public:
+  void Dispatch(int num_tasks, WorkFunction work, void* data);
+  explicit ThreadPool(int num_threads);
+  ~ThreadPool();
+ private:
+  int DecCounter();
+  void Setup(int counter, WorkFunction work, void* data);
+  void DispatchMany(int num_tasks, WorkFunction work, void* data);
+  void DispatchHere(int num_tasks, WorkFunction work, void* data);
+  void WorkLoop();
+  static void* WorkerThreadEntry(void* data);
+  void PostExitAndJoinAll();
+  pthread_t* threads_;
+  int counter_;
+  const int num_threads_;
+  bool exiting_;
+  void* user_data_;
+  WorkFunction user_work_function_;
+  sem_t work_sem_;
+  sem_t done_sem_;
+};
+#endif  // LIBRARIES_SDK_UTIL_THREAD_POOL_H_
+