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65 lines
2.4 KiB
65 lines
2.4 KiB
// Copyright 2019 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 PLATFORM_API_TASK_RUNNER_H_
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#define PLATFORM_API_TASK_RUNNER_H_
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#include <future>
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#include <utility>
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#include "platform/api/time.h"
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namespace openscreen {
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// A thread-safe API surface that allows for posting tasks. The underlying
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// implementation may be single or multi-threaded, and all complication should
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// be handled by the implementation class. The implementation must guarantee:
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// (1) Tasks shall not overlap in time/CPU.
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// (2) Tasks shall run sequentially, e.g. posting task A then B implies
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// that A shall run before B.
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// (3) If task A is posted before task B, then any mutation in A happens-before
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// B runs (even if A and B run on different threads).
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class TaskRunner {
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public:
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// Seem to get an error using clang when compiling with -fno-exceptions:
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// error: implicit instantiation of undefined template 'std::__1::packaged_task<void () noexcept>'
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#if __has_feature(cxx_exceptions)
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using Task = std::packaged_task<void() noexcept>;
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#else
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using Task = std::packaged_task<void()>;
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#endif
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virtual ~TaskRunner() = default;
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// Takes any callable target (function, lambda-expression, std::bind result,
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// etc.) that should be run at the first convenient time.
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template <typename Functor>
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inline void PostTask(Functor f) {
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PostPackagedTask(Task(std::move(f)));
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}
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// Takes any callable target (function, lambda-expression, std::bind result,
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// etc.) that should be run no sooner than |delay| time from now. Note that
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// the Task might run after an additional delay, especially under heavier
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// system load. There is no deadline concept.
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template <typename Functor>
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inline void PostTaskWithDelay(Functor f, Clock::duration delay) {
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PostPackagedTaskWithDelay(Task(std::move(f)), delay);
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}
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// Implementations should provide the behavior explained in the comments above
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// for PostTask[WithDelay](). Client code may also call these directly when
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// passing an existing Task object.
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virtual void PostPackagedTask(Task task) = 0;
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virtual void PostPackagedTaskWithDelay(Task task, Clock::duration delay) = 0;
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// Return true if the calling thread is the thread that task runner is using
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// to run tasks, false otherwise.
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virtual bool IsRunningOnTaskRunner() = 0;
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};
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} // namespace openscreen
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#endif // PLATFORM_API_TASK_RUNNER_H_
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