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 <memory>
   9 #include <utility>
  10
  11 #include "base/bind.h"
  12 #include "base/bind_helpers.h"
  13 #include "base/callback.h"
  14 #include "base/logging.h"
  15 #include "base/post_task_and_reply_with_result_internal.h"
  16 #include "base/task_runner.h"
  17
  18 namespace base {
  19
  20 // When you have these methods
  21 //
  22 //   R DoWorkAndReturn();
  23 //   void Callback(const R& result);
  24 //
  25 // and want to call them in a PostTaskAndReply kind of fashion where the
  26 // result of DoWorkAndReturn is passed to the Callback, you can use
  27 // PostTaskAndReplyWithResult as in this example:
  28 //
  29 // PostTaskAndReplyWithResult(
  30 //     target_thread_.task_runner(),
  31 //     FROM_HERE,
  32 //     BindOnce(&DoWorkAndReturn),
  33 //     BindOnce(&Callback));
  34 template <typename TaskReturnType, typename ReplyArgType>
  35 bool PostTaskAndReplyWithResult(TaskRunner* task_runner,
  36                                 const Location& from_here,
  37                                 OnceCallback<TaskReturnType()> task,
  38                                 OnceCallback<void(ReplyArgType)> reply) {
  39   DCHECK(task);
  40   DCHECK(reply);
  41   // std::unique_ptr used to avoid the need of a default constructor.
  42   auto* result = new std::unique_ptr<TaskReturnType>();
  43   return task_runner->PostTaskAndReply(
  44       from_here,
  45       BindOnce(&internal::ReturnAsParamAdapter<TaskReturnType>, std::move(task),
  46                result),
  47       BindOnce(&internal::ReplyAdapter<TaskReturnType, ReplyArgType>,
  48                std::move(reply), Owned(result)));
  49 }
  50
  51 // Callback version of PostTaskAndReplyWithResult above.
  52 // Though RepeatingCallback is convertible to OnceCallback, we need this since
  53 // we cannot use template deduction and object conversion at once on the
  54 // overload resolution.
  55 // TODO(crbug.com/714018): Update all callers of the Callback version to use
  56 // OnceCallback.
  57 template <typename TaskReturnType, typename ReplyArgType>
  58 bool PostTaskAndReplyWithResult(TaskRunner* task_runner,
  59                                 const Location& from_here,
  60                                 Callback<TaskReturnType()> task,
  61                                 Callback<void(ReplyArgType)> reply) {
  62   return PostTaskAndReplyWithResult(
  63       task_runner, from_here, OnceCallback<TaskReturnType()>(std::move(task)),
  64       OnceCallback<void(ReplyArgType)>(std::move(reply)));
  65 }
  66
  67 }  // namespace base
  68
  69 #endif  // BASE_TASK_RUNNER_UTIL_H_