base/task_runner_util.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_TASK_RUNNER_UTIL_H_
   6 #define BASE_TASK_RUNNER_UTIL_H_
   7
   8 #include <utility>
   9
  10 #include "base/bind.h"
  11 #include "base/bind_helpers.h"
  12 #include "base/callback.h"
  13 #include "base/logging.h"
  14 #include "base/post_task_and_reply_with_result_internal.h"
  15 #include "base/task_runner.h"
  16
  17 namespace base {
  18
  19 // When you have these methods
  20 //
  21 //   R DoWorkAndReturn();
  22 //   void Callback(const R& result);
  23 //
  24 // and want to call them in a PostTaskAndReply kind of fashion where the
  25 // result of DoWorkAndReturn is passed to the Callback, you can use
  26 // PostTaskAndReplyWithResult as in this example:
  27 //
  28 // PostTaskAndReplyWithResult(
  29 //     target_thread_.task_runner(),
  30 //     FROM_HERE,
  31 //     BindOnce(&DoWorkAndReturn),
  32 //     BindOnce(&Callback));
  33 template <typename TaskReturnType, typename ReplyArgType>
  34 bool PostTaskAndReplyWithResult(TaskRunner* task_runner,
  35                                 const Location& from_here,
  36                                 OnceCallback<TaskReturnType()> task,
  37                                 OnceCallback<void(ReplyArgType)> reply) {
  38   DCHECK(task);
  39   DCHECK(reply);
  40   TaskReturnType* result = new TaskReturnType();
  41   return task_runner->PostTaskAndReply(
  42       from_here,
  43       BindOnce(&internal::ReturnAsParamAdapter<TaskReturnType>, std::move(task),
  44                result),
  45       BindOnce(&internal::ReplyAdapter<TaskReturnType, ReplyArgType>,
  46                std::move(reply), Owned(result)));
  47 }
  48
  49 // Callback version of PostTaskAndReplyWithResult above.
  50 // Though RepeatingCallback is convertible to OnceCallback, we need this since
  51 // we cannot use template deduction and object conversion at once on the
  52 // overload resolution.
  53 // TODO(crbug.com/714018): Update all callers of the Callback version to use
  54 // OnceCallback.
  55 template <typename TaskReturnType, typename ReplyArgType>
  56 bool PostTaskAndReplyWithResult(TaskRunner* task_runner,
  57                                 const Location& from_here,
  58                                 Callback<TaskReturnType()> task,
  59                                 Callback<void(ReplyArgType)> reply) {
  60   return PostTaskAndReplyWithResult(
  61       task_runner, from_here, OnceCallback<TaskReturnType()>(std::move(task)),
  62       OnceCallback<void(ReplyArgType)>(std::move(reply)));
  63 }
  64
  65 }  // namespace base
  66
  67 #endif  // BASE_TASK_RUNNER_UTIL_H_