1 files changed, 84 insertions, 0 deletions
diff --git a/thread.cc b/thread.cc
new file mode 100644
index 0000000..1450466
--- /dev/null
+++ b/thread.cc
@@ -0,0 +1,84 @@
+// Copyright 2016 Google Inc. All rights reserved
+//
+// 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.
+
+#include "thread.h"
+
+#include <condition_variable>
+#include <mutex>
+#include <stack>
+#include <thread>
+#include <vector>
+
+class ThreadPoolImpl : public ThreadPool {
+ public:
+  explicit ThreadPoolImpl(int num_threads)
+      : is_waiting_(false) {
+    for (int i = 0; i < num_threads; i++) {
+      threads_.push_back(thread([this]() { Loop(); }));
+    }
+  }
+
+  virtual ~ThreadPoolImpl() override {
+  }
+
+  virtual void Submit(function<void(void)> task) override {
+    unique_lock<mutex> lock(mu_);
+    tasks_.push(task);
+    cond_.notify_one();
+  }
+
+  virtual void Wait() override {
+    {
+      unique_lock<mutex> lock(mu_);
+      is_waiting_ = true;
+      cond_.notify_all();
+    }
+
+    for (thread& th : threads_) {
+      th.join();
+    }
+  }
+
+ private:
+  void Loop() {
+    while (true) {
+      function<void(void)> task;
+      {
+        unique_lock<mutex> lock(mu_);
+        if (tasks_.empty()) {
+          if (is_waiting_)
+            return;
+          cond_.wait(lock);
+        }
+
+        if (tasks_.empty())
+          continue;
+
+        task = tasks_.top();
+        tasks_.pop();
+      }
+      task();
+    }
+  }
+
+  vector<thread> threads_;
+  mutex mu_;
+  condition_variable cond_;
+  stack<function<void(void)>> tasks_;
+  bool is_waiting_;
+};
+
+ThreadPool* NewThreadPool(int num_threads) {
+  return new ThreadPoolImpl(num_threads);
+}