Create WorkerThread, an abstraction to perform some work on an interval.

util/thread/worker_thread.h

Index: util/thread/worker_thread.h
diff --git a/util/thread/worker_thread.h b/util/thread/worker_thread.h
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+// Copyright 2015 The Crashpad Authors. 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.
+
+#ifndef CRASHPAD_UTIL_THREAD_WORKER_THREAD_H_
+#define CRASHPAD_UTIL_THREAD_WORKER_THREAD_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace crashpad {
+
+namespace internal {
+class WorkerThreadImpl;
+}  // namespace internal
+
+//! \brief A WorkerThread executes its Delegate's DoWork method repeatedly on a
+//!     dedicated thread at a set time interval.
+class WorkerThread {
+ public:
+  //! \brief An interface for doing work on a WorkerThread.
+  class Delegate {
+   public:
+    //! \brief The work function executed by the WorkerThread every work
+    //!     interval.
+    virtual void DoWork(const WorkerThread* thread) = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  //! \brief Creates a new WorkerThread that is not yet running.
+  //!
+  //! \param[in] work_interval The time interval in seconds at which the \a
+  //!     delegate runs. The interval counts from the completion of
+  //!     Delegate::DoWork() to the next invocation.
+  //! \param[in] delegate The work delegate to invoke every interval.
+  WorkerThread(double work_interval, Delegate* delegate);
+  ~WorkerThread();
+
+  //! \brief Starts the worker thread.
+  //!
+  //! This may not be called if the thread is_running().
+  //!
+  //! \param[in] initial_work_delay The amount of time in seconds to wait
+  //!     before invoking the \a delegate for the first time. Pass `0` for
+  //!     no delay.
+  void Start(double initial_work_delay);
+
+  //! \brief Stops the worker thread from running.
+  //!
+  //! This may only be called if the thread is_running().
+  //!
+  //! If the work function is currently executing, this will not interrupt it.
+  //! This method stops any future work from occurring. This method is safe
+  //! to call from any thread with the exception of the worker thread itself,
+  //! as this joins the thread.
+  void Stop();
+
+  //! \brief Interrupts a \a work_interval to execute the work function
+  //!     immediately. This invokes Delegate::DoWork() on the thread, without
+  //!     waiting for the current \a work_interval to expire. After the
+  //!     delegate is invoked, the WorkerThread will start waiting for a new
+  //!     \a work_interval.
+  void DoWorkNow();
+
+  //! \return `true` if the thread is running, `false` if it is not.
+  bool is_running() const { return running_; }
+
+ private:
+  friend class internal::WorkerThreadImpl;
+
+  double work_interval_;
+  Delegate* delegate_;  // weak
+  scoped_ptr<internal::WorkerThreadImpl> impl_;
+  bool running_;
+
+  DISALLOW_COPY_AND_ASSIGN(WorkerThread);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_THREAD_WORKER_THREAD_H_