src/base/threading/worker_pool.cc

// Copyright (c) 2012 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.

#include "base/threading/worker_pool.h"

#include "base/bind.h"
#include "base/compiler_specific.h"
#include "base/lazy_instance.h"
#include "base/task_runner.h"
#include "base/threading/post_task_and_reply_impl.h"
#include "base/tracked_objects.h"

namespace base {

namespace {

class PostTaskAndReplyWorkerPool : public internal::PostTaskAndReplyImpl {
 public:
  PostTaskAndReplyWorkerPool(bool task_is_slow) : task_is_slow_(task_is_slow) {
  }

 private:
  virtual bool PostTask(const tracked_objects::Location& from_here,
                        const Closure& task) OVERRIDE {
    return WorkerPool::PostTask(from_here, task, task_is_slow_);
  }

  bool task_is_slow_;
};

// WorkerPoolTaskRunner ---------------------------------------------
// A TaskRunner which posts tasks to a WorkerPool with a
// fixed ShutdownBehavior.
//
// Note that this class is RefCountedThreadSafe (inherited from TaskRunner).
class WorkerPoolTaskRunner : public TaskRunner {
 public:
  WorkerPoolTaskRunner(bool tasks_are_slow);

  // TaskRunner implementation
  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
                               const Closure& task,
                               TimeDelta delay) OVERRIDE;
  virtual bool RunsTasksOnCurrentThread() const OVERRIDE;

 private:
  virtual ~WorkerPoolTaskRunner();

  // Helper function for posting a delayed task. Asserts that the delay is
  // zero because non-zero delays are not supported.
  bool PostDelayedTaskAssertZeroDelay(
      const tracked_objects::Location& from_here,
      const Closure& task,
      base::TimeDelta delay);

  const bool tasks_are_slow_;

  DISALLOW_COPY_AND_ASSIGN(WorkerPoolTaskRunner);
};

WorkerPoolTaskRunner::WorkerPoolTaskRunner(bool tasks_are_slow)
    : tasks_are_slow_(tasks_are_slow) {
}

WorkerPoolTaskRunner::~WorkerPoolTaskRunner() {
}

bool WorkerPoolTaskRunner::PostDelayedTask(
    const tracked_objects::Location& from_here,
    const Closure& task,
    TimeDelta delay) {
  return PostDelayedTaskAssertZeroDelay(from_here, task, delay);
}

bool WorkerPoolTaskRunner::RunsTasksOnCurrentThread() const {
  return WorkerPool::RunsTasksOnCurrentThread();
}

bool WorkerPoolTaskRunner::PostDelayedTaskAssertZeroDelay(
    const tracked_objects::Location& from_here,
    const Closure& task,
    base::TimeDelta delay) {
  DCHECK_EQ(delay.InMillisecondsRoundedUp(), 0)
      << "WorkerPoolTaskRunner does not support non-zero delays";
  return WorkerPool::PostTask(from_here, task, tasks_are_slow_);
}

struct TaskRunnerHolder {
  TaskRunnerHolder() {
    taskrunners_[0] = new WorkerPoolTaskRunner(false);
    taskrunners_[1] = new WorkerPoolTaskRunner(true);
  }
  scoped_refptr<TaskRunner> taskrunners_[2];
};

base::LazyInstance<TaskRunnerHolder>::Leaky
    g_taskrunners = LAZY_INSTANCE_INITIALIZER;

}  // namespace

bool WorkerPool::PostTaskAndReply(const tracked_objects::Location& from_here,
                                  const Closure& task,
                                  const Closure& reply,
                                  bool task_is_slow) {
  return PostTaskAndReplyWorkerPool(task_is_slow).PostTaskAndReply(
      from_here, task, reply);
}

// static
const scoped_refptr<TaskRunner>&
WorkerPool::GetTaskRunner(bool tasks_are_slow) {
  return g_taskrunners.Get().taskrunners_[tasks_are_slow];
}

}  // namespace base