72 lines
2.3 KiB
C
72 lines
2.3 KiB
C
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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_TASK_RUNNER_UTIL_H_
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#define BASE_TASK_RUNNER_UTIL_H_
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#include "base/bind.h"
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#include "base/bind_helpers.h"
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#include "base/callback_internal.h"
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#include "base/logging.h"
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#include "base/task_runner.h"
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namespace base {
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namespace internal {
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// Adapts a function that produces a result via a return value to
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// one that returns via an output parameter.
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template <typename ReturnType>
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void ReturnAsParamAdapter(const Callback<ReturnType(void)>& func,
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ReturnType* result) {
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*result = func.Run();
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}
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// Adapts a T* result to a callblack that expects a T.
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template <typename TaskReturnType, typename ReplyArgType>
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void ReplyAdapter(const Callback<void(ReplyArgType)>& callback,
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TaskReturnType* result) {
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// TODO(ajwong): Remove this conditional and add a DCHECK to enforce that
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// |reply| must be non-null in PostTaskAndReplyWithResult() below after
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// current code that relies on this API softness has been removed.
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// http://crbug.com/162712
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if (!callback.is_null())
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callback.Run(CallbackForward(*result));
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}
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} // namespace internal
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// When you have these methods
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//
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// R DoWorkAndReturn();
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// void Callback(const R& result);
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//
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// and want to call them in a PostTaskAndReply kind of fashion where the
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// result of DoWorkAndReturn is passed to the Callback, you can use
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// PostTaskAndReplyWithResult as in this example:
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//
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// PostTaskAndReplyWithResult(
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// target_thread_.message_loop_proxy(),
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// FROM_HERE,
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// Bind(&DoWorkAndReturn),
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// Bind(&Callback));
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template <typename TaskReturnType, typename ReplyArgType>
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bool PostTaskAndReplyWithResult(
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TaskRunner* task_runner,
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const tracked_objects::Location& from_here,
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const Callback<TaskReturnType(void)>& task,
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const Callback<void(ReplyArgType)>& reply) {
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TaskReturnType* result = new TaskReturnType();
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return task_runner->PostTaskAndReply(
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from_here,
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base::Bind(&internal::ReturnAsParamAdapter<TaskReturnType>, task,
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result),
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base::Bind(&internal::ReplyAdapter<TaskReturnType, ReplyArgType>, reply,
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base::Owned(result)));
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}
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} // namespace base
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#endif // BASE_TASK_RUNNER_UTIL_H_
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