// 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.
#ifndef BASE_TASK_RUNNER_UTIL_H_
#define BASE_TASK_RUNNER_UTIL_H_
#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/callback_internal.h"
#include "base/logging.h"
#include "base/task_runner.h"
namespace base {
namespace internal {
// Adapts a function that produces a result via a return value to
// one that returns via an output parameter.
template <typename ReturnType>
void ReturnAsParamAdapter(const Callback<ReturnType(void)>& func,
ReturnType* result) {
*result = func.Run();
}
// Adapts a T* result to a callblack that expects a T.
template <typename TaskReturnType, typename ReplyArgType>
void ReplyAdapter(const Callback<void(ReplyArgType)>& callback,
TaskReturnType* result) {
// TODO(ajwong): Remove this conditional and add a DCHECK to enforce that
// |reply| must be non-null in PostTaskAndReplyWithResult() below after
// current code that relies on this API softness has been removed.
// http://crbug.com/162712
if (!callback.is_null())
callback.Run(CallbackForward(*result));
}
} // namespace internal
// When you have these methods
//
// R DoWorkAndReturn();
// void Callback(const R& result);
//
// and want to call them in a PostTaskAndReply kind of fashion where the
// result of DoWorkAndReturn is passed to the Callback, you can use
// PostTaskAndReplyWithResult as in this example:
//
// PostTaskAndReplyWithResult(
// target_thread_.message_loop_proxy(),
// FROM_HERE,
// Bind(&DoWorkAndReturn),
// Bind(&Callback));
template <typename TaskReturnType, typename ReplyArgType>
bool PostTaskAndReplyWithResult(
TaskRunner* task_runner,
const tracked_objects::Location& from_here,
const Callback<TaskReturnType(void)>& task,
const Callback<void(ReplyArgType)>& reply) {
TaskReturnType* result = new TaskReturnType();
return task_runner->PostTaskAndReply(
from_here,
base::Bind(&internal::ReturnAsParamAdapter<TaskReturnType>, task,
result),
base::Bind(&internal::ReplyAdapter<TaskReturnType, ReplyArgType>, reply,
base::Owned(result)));
}
} // namespace base
#endif // BASE_TASK_RUNNER_UTIL_H_