base/threading/post_task_and_reply_impl.h

// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file contains the implementation for TaskRunner::PostTaskAndReply.

#ifndef BASE_THREADING_POST_TASK_AND_REPLY_IMPL_H_
#define BASE_THREADING_POST_TASK_AND_REPLY_IMPL_H_

#include "base/base_export.h"
#include "base/callback.h"
#include "base/location.h"

namespace base {
namespace internal {

// Inherit from this in a class that implements PostTask to send a task to a
// custom execution context.
//
// If you're looking for a concrete implementation of PostTaskAndReply, you
// probably want a base::TaskRunner (typically obtained from
// base/task/thread_pool.h).
class BASE_EXPORT PostTaskAndReplyImpl {
 public:
  virtual ~PostTaskAndReplyImpl() = default;

  // Posts |task| by calling PostTask(). On completion, posts |reply| to the
  // origin sequence. Can only be called when
  // SequencedTaskRunner::HasCurrentDefault(). Each callback is deleted
  // synchronously after running, or scheduled for asynchronous deletion on the
  // origin sequence if it can't run (e.g. if a TaskRunner skips it on
  // shutdown). See SequencedTaskRunner::DeleteSoon() for when objects scheduled
  // for asynchronous deletion can be leaked. Note: All //base task posting APIs
  // require callbacks to support deletion on the posting sequence if they can't
  // be scheduled.
  bool PostTaskAndReply(const Location& from_here,
                        OnceClosure task,
                        OnceClosure reply);

 private:
  virtual bool PostTask(const Location& from_here, OnceClosure task) = 0;
};

}  // namespace internal
}  // namespace base

#endif  // BASE_THREADING_POST_TASK_AND_REPLY_IMPL_H_