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// Copyright 2020 The Marl Authors.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef marl_task_h
#define marl_task_h
#include "export.h"
#include <functional>
namespace marl {
// Task is a unit of work for the scheduler.
class Task {
using Function = std::function<void()>;
enum class Flags {
None = 0,
// SameThread ensures the task will be run on the same thread that scheduled
// the task. This can offer performance improvements if the current thread
// is immediately going to block on the newly scheduled task, by reducing
// overheads of waking another thread.
SameThread = 1,
MARL_NO_EXPORT inline Task();
MARL_NO_EXPORT inline Task(const Task&);
MARL_NO_EXPORT inline Task(Task&&);
MARL_NO_EXPORT inline Task(const Function& function,
Flags flags = Flags::None);
MARL_NO_EXPORT inline Task(Function&& function, Flags flags = Flags::None);
MARL_NO_EXPORT inline Task& operator=(const Task&);
MARL_NO_EXPORT inline Task& operator=(Task&&);
MARL_NO_EXPORT inline Task& operator=(const Function&);
MARL_NO_EXPORT inline Task& operator=(Function&&);
// operator bool() returns true if the Task has a valid function.
MARL_NO_EXPORT inline operator bool() const;
// operator()() runs the task.
MARL_NO_EXPORT inline void operator()() const;
// is() returns true if the Task was created with the given flag.
MARL_NO_EXPORT inline bool is(Flags flag) const;
Function function;
Flags flags = Flags::None;
Task::Task() {}
Task::Task(const Task& o) : function(o.function), flags(o.flags) {}
Task::Task(Task&& o) : function(std::move(o.function)), flags(o.flags) {}
Task::Task(const Function& function_, Flags flags_ /* = Flags::None */)
: function(function_), flags(flags_) {}
Task::Task(Function&& function_, Flags flags_ /* = Flags::None */)
: function(std::move(function_)), flags(flags_) {}
Task& Task::operator=(const Task& o) {
function = o.function;
flags = o.flags;
return *this;
Task& Task::operator=(Task&& o) {
function = std::move(o.function);
flags = o.flags;
return *this;
Task& Task::operator=(const Function& f) {
function = f;
flags = Flags::None;
return *this;
Task& Task::operator=(Function&& f) {
function = std::move(f);
flags = Flags::None;
return *this;
Task::operator bool() const {
return function.operator bool();
void Task::operator()() const {
bool Task::is(Flags flag) const {
return (static_cast<int>(flags) & static_cast<int>(flag)) ==
} // namespace marl
#endif // marl_task_h