Looper Class Reference

#include "steam/control/looper.hpp"

Description

Encapsulated control logic for the session thread loop.

This helper component was factored out from the loop body for sake of clarity and to allow unit testing of the logic in isolation. It is based on logical relations together with the following assumptions

• Looper::shallLoop controls the loop's while condition
• at the begin of the loop the thread possibly enters a blocking wait state; the wake-up condition is provided by Looper::requireAction.
• then, in the actual loop body, depending on the predicates calculated here, either the builder run is triggered, or a single command is dispatched from the queue to work on the session.
• after returning from these active operations, at the end of the loop, the state evaluation is updated by Looper::markStateProcessed

Warning

the Looper is not threadsafe, since it is intended to be run exclusively from the Session working thread.

See also

DispatcherLoop::run()

Definition at line 105 of file looper.hpp.

Public Member Functions
template<class FUN >
	Looper (FUN determine_commands_are_waiting)
bool	isDying () const
bool	isDisabled () const
bool	useTimeout () const
bool	isWorking () const
bool	idleBuild () const
bool	runBuild () const
bool	isIdle () const
void	triggerShutdown ()
void	enableProcessing (bool yes=true)
void	markStateProcessed ()
	invoking this function signals that all consequences of past state changes have been processed and are duly resolved.
bool	hasPendingChanges () const
	< "check point"
bool	requireAction ()
	state fusion to control (timed) wait
bool	shallLoop () const
	state fusion to control looping
milliseconds	getTimeout () const

Private Types
using	Predicate = std::function< bool(void)>

Private Member Functions
void	startBuilderTimeout ()
bool	forceBuild () const

Static Private Member Functions
static uint	wakeTimeout_ms ()
static uint	slowdownFactor ()

Private Attributes
bool	shutdown_ = false
bool	disabled_ = false
bool	inChange_ = false
bool	hasWork_ = false
bool	isDirty_ = false
TimeVar	gotDirty_ = Time::NEVER
Predicate	hasCommandsPending_

Constructor & Destructor Documentation

Looper()

template<class FUN >

Looper ( FUN  determine_commands_are_waiting )

inline

Definition at line 122 of file looper.hpp.

Member Typedef Documentation

Predicate

using Predicate = std::function<bool(void)>

private

Definition at line 107 of file looper.hpp.

Member Function Documentation

isDying()

bool isDying ( ) const

inline

Definition at line 131 of file looper.hpp.

References Looper::shutdown_.

Referenced by Looper::isDisabled(), Looper::requireAction(), DispatcherLoop::runSessionThread(), and Looper::shallLoop().

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isDisabled()

bool isDisabled ( ) const

inline

Definition at line 132 of file looper.hpp.

References Looper::disabled_, and Looper::isDying().

Referenced by Looper::isIdle(), Looper::isWorking(), Looper::runBuild(), DispatcherLoop::updateState(), and Looper::useTimeout().

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useTimeout()

bool useTimeout ( ) const

inline

Definition at line 133 of file looper.hpp.

References Looper::isDirty_, and Looper::isDisabled().

Referenced by Looper::getTimeout(), and Looper::requireAction().

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isWorking()

bool isWorking ( ) const

inline

Definition at line 134 of file looper.hpp.

References Looper::hasWork_, and Looper::isDisabled().

Referenced by Looper::getTimeout(), Looper::isIdle(), Looper::requireAction(), and DispatcherLoop::runSessionThread().

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idleBuild()

bool idleBuild ( ) const

inline

Definition at line 135 of file looper.hpp.

References Looper::hasWork_, and Looper::isDirty_.

Referenced by Looper::runBuild().

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runBuild()

bool runBuild ( ) const

inline

Definition at line 136 of file looper.hpp.

References Looper::forceBuild(), Looper::idleBuild(), and Looper::isDisabled().

Referenced by Looper::isIdle(), Looper::markStateProcessed(), and DispatcherLoop::runSessionThread().

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isIdle()

bool isIdle ( ) const

inline

Definition at line 137 of file looper.hpp.

References Looper::isDisabled(), Looper::isWorking(), and Looper::runBuild().

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triggerShutdown()

void triggerShutdown ( )

inline

Definition at line 143 of file looper.hpp.

References Looper::shutdown_.

Referenced by DispatcherLoop::requestStop().

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enableProcessing()

void enableProcessing ( bool  yes = true )

inline

Definition at line 149 of file looper.hpp.

References Looper::disabled_.

Referenced by DispatcherLoop::activateCommandProecssing(), and DispatcherLoop::deactivateCommandProecssing().

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markStateProcessed()

void markStateProcessed ( )

inline

invoking this function signals that all consequences of past state changes have been processed and are duly resolved.

Remarks

the implementation actually does not need to watch out for command processing state directly, only the managing of builder runs requires active state transitions here. When the conditions for triggering the Builder are met, control flow typically just has emptied the command queue. Thus we need to let one invocation pass by; the next loop iteration will begin after waking up from a short sleep and trigger the build, so the following (second) invocation can clear the builder dirty state.

Definition at line 165 of file looper.hpp.

References Looper::inChange_, Looper::isDirty_, and Looper::runBuild().

Referenced by DispatcherLoop::updateState().

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hasPendingChanges()

bool hasPendingChanges ( ) const

inline

< "check point"

Definition at line 173 of file looper.hpp.

References Looper::inChange_.

Referenced by DispatcherLoop::isStateSynched().

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requireAction()

bool requireAction ( )

inline

state fusion to control (timed) wait

Definition at line 180 of file looper.hpp.

References Looper::forceBuild(), Looper::hasCommandsPending_, Looper::hasWork_, Looper::inChange_, Looper::isDirty_, Looper::isDying(), Looper::isWorking(), Looper::startBuilderTimeout(), and Looper::useTimeout().

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shallLoop()

bool shallLoop ( ) const

inline

state fusion to control looping

Definition at line 197 of file looper.hpp.

References Looper::isDying().

Referenced by DispatcherLoop::runSessionThread().

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getTimeout()

milliseconds getTimeout ( ) const

inline

Definition at line 203 of file looper.hpp.

References Looper::isDirty_, Looper::isWorking(), Looper::slowdownFactor(), Looper::useTimeout(), and Looper::wakeTimeout_ms().

Referenced by DispatcherLoop::awaitAction().

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wakeTimeout_ms()

uint wakeTimeout_ms ( )

inlinestaticprivate

establish the typical timeout for idle sleep. When the SteamDispatcher has no work to do, it needs to wake up regularly for a checkpoint, to determine if the Builder needs to be triggered or the shutdown-flag be checked. So the period established here defines some kind of minimal reaction especially for the builder, so to ensure that further commands trickling in get a chance to be enqueued before the builder run effectively blocks command processing. Add to this the typical average running time of the builder, to get the reaction period visible to the user as update response delay within the UI.

Todo:

find a way how to retrieve this value from application config! ////////////////////TICKET #1052 : access application configuration

Definition at line 236 of file looper.hpp.

Referenced by Looper::forceBuild(), and Looper::getTimeout().

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slowdownFactor()

uint slowdownFactor ( )

inlinestaticprivate

Definition at line 242 of file looper.hpp.

Referenced by Looper::forceBuild(), and Looper::getTimeout().

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startBuilderTimeout()

void startBuilderTimeout ( )

inlineprivate

Definition at line 248 of file looper.hpp.

References Looper::gotDirty_, and RealClock::now().

Referenced by Looper::requireAction().

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forceBuild()

bool forceBuild ( ) const

inlineprivate

logic to enforce a builder run, once some extended time period has been passed.

Definition at line 257 of file looper.hpp.

References Looper::gotDirty_, Looper::isDirty_, RealClock::now(), Looper::slowdownFactor(), and Looper::wakeTimeout_ms().

Referenced by Looper::requireAction(), and Looper::runBuild().

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Member Data Documentation

shutdown_

bool shutdown_ = false

private

Definition at line 109 of file looper.hpp.

Referenced by Looper::isDying(), and Looper::triggerShutdown().

disabled_

bool disabled_ = false

private

Definition at line 110 of file looper.hpp.

Referenced by Looper::enableProcessing(), and Looper::isDisabled().

inChange_

bool inChange_ = false

private

Definition at line 111 of file looper.hpp.

Referenced by Looper::hasPendingChanges(), Looper::markStateProcessed(), and Looper::requireAction().

hasWork_

bool hasWork_ = false

private

Definition at line 112 of file looper.hpp.

Referenced by Looper::idleBuild(), Looper::isWorking(), and Looper::requireAction().

isDirty_

bool isDirty_ = false

private

Definition at line 113 of file looper.hpp.

Referenced by Looper::forceBuild(), Looper::getTimeout(), Looper::idleBuild(), Looper::markStateProcessed(), Looper::requireAction(), and Looper::useTimeout().

gotDirty_

TimeVar gotDirty_ = Time::NEVER

private

Definition at line 115 of file looper.hpp.

Referenced by Looper::forceBuild(), and Looper::startBuilderTimeout().

hasCommandsPending_

Predicate hasCommandsPending_

private

Definition at line 117 of file looper.hpp.

Referenced by Looper::requireAction().

Collaboration diagram for Looper:

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The documentation for this class was generated from the following file:

• looper.hpp