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

native_client_sdk/src/libraries/sdk_util/thread_safe_queue.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.
+
+#ifndef LIBRARIES_SDK_UTIL_THREAD_SAFE_QUEUE_H_
+#define LIBRARIES_SDK_UTIL_THREAD_SAFE_QUEUE_H_
+
+#include <pthread.h>
+
+#include <list>
+
+#include "sdk_util/auto_lock.h"
+#include "sdk_util/macros.h"
+
+
+// ThreadSafeQueue
+//
+// A simple template to support multithreaded and optionally blocking access
+// to a Queue of object pointers.
+//
+template<class T> class ThreadSafeQueue {
+ public:
+  ThreadSafeQueue() {
+    pthread_mutex_init(&mutex_, NULL);
+    pthread_cond_init(&cond_, NULL);
+  }
+
+  ~ThreadSafeQueue() {
+    pthread_mutex_destroy(&mutex_);
+    pthread_cond_destroy(&cond_);
+  }
+
+  void Enqueue(T* item) {
+    AutoLock lock(&mutex_);
+    list_.push_back(item);
+
+    pthread_cond_signal(&cond_);
+  }
+
+  T* Dequeue(bool block) {
+    AutoLock lock(&mutex_);
+
+    // If blocking enabled, wait until we queue is non-empty
+    if (block) {
+      while (list_.empty()) pthread_cond_wait(&cond_, &mutex_);
+    }
+
+    if (list_.empty()) return NULL;
+
+    T* item = list_.front();
+    list_.pop_front();
+    return item;
+  }
+
+ private:
+  std::list<T*> list_;
+  pthread_cond_t  cond_;
+  pthread_mutex_t mutex_;
+  DISALLOW_COPY_AND_ASSIGN(ThreadSafeQueue);
+};
+
+#endif  // LIBRARIES_SDK_UTIL_THREAD_SAFE_QUEUE_H_
+