PAdaptiveDelay Class Reference

Class for implementing an "adaptive" delay. More...

#include <delaychan.h>

Inheritance diagram for PAdaptiveDelay:

Collaboration diagram for PAdaptiveDelay:

Public Member Functions
Construction
	PAdaptiveDelay (const PTimeInterval &maximumSlip=0, const PTimeInterval &minimumDelay=0)
	Create a new adaptive delay with the specified parameters. More...
Operating Parameters
void	SetMaximumSlip (const PTimeInterval &maximumSlip)
	Set the number of milliseconds that the delay may "catch up" by using zero delays. More...
PTimeInterval	GetMaximumSlip () const
	Get the current slip time. More...
const PTimeInterval &	GetActualDelay () const
	Get the actual sleep time of the last call to the delay function. More...
Public Member Functions inherited from PObject
__inline unsigned	GetTraceContextIdentifier () const
	Get PTRACE context identifier. More...
__inline void	SetTraceContextIdentifier (unsigned id)
__inline void	SetTraceContextIdentifier (const PObject &obj)
__inline void	SetTraceContextIdentifier (const PObject *obj)
__inline void	CopyTraceContextIdentifier (PObject &obj) const
__inline void	CopyTraceContextIdentifier (PObject *obj) const
virtual	~PObject ()
__inline const char *	GetClass () const
__inline bool	IsClass (const char *name) const
__inline const PObject *	PTraceObjectInstance () const
virtual PObject *	Clone () const
	Create a copy of the class on the heap. More...
template<class CLS >
CLS *	CloneAs () const
	As for Clone() but converts to specified type. More...
virtual PINDEX	HashFunction () const
	This function yields a hash value required by the PDictionary class. More...
virtual Comparison	Compare (const PObject &obj) const
	Compare the two objects and return their relative rank. More...
virtual Comparison	CompareObjectMemoryDirect (const PObject &obj) const
	Determine the byte wise comparison of two objects. More...
bool	operator== (const PObject &obj) const
	Compare the two objects. More...
bool	operator!= (const PObject &obj) const
	Compare the two objects. More...
bool	operator< (const PObject &obj) const
	Compare the two objects. More...
bool	operator> (const PObject &obj) const
	Compare the two objects. More...
bool	operator<= (const PObject &obj) const
	Compare the two objects. More...
bool	operator>= (const PObject &obj) const
	Compare the two objects. More...
virtual void	PrintOn (ostream &strm) const
	Output the contents of the object to the stream. More...
virtual void	ReadFrom (istream &strm)
	Input the contents of the object from the stream. More...

Protected Attributes
PTimeInterval	m_maximumSlip
PTimeInterval	m_minimumDelay
PTimeInterval	m_actualDelay
PTime	m_targetTime
bool	m_firstTime
Protected Attributes inherited from PObject
unsigned	m_traceContextIdentifier

Functionality
enum	DelayResult {   eOnTime, eOverSlept, eLate, eSlipped,   eBadDelta }
	< Result of call to Delay() or DelayInterval() function call More...
DelayResult	Delay (int deltaMS)
	Wait until the specified number of milliseconds have elapsed from the previous call (on average). More...
DelayResult	DelayInterval (const PTimeInterval &delta)
	As for Delay() but for more accurate timing. More...
void	Restart ()
	Invalidate the timer. More...

Additional Inherited Members
Public Types inherited from PObject
enum	Comparison { LessThan = -1, EqualTo = 0, GreaterThan = 1 }
	Result of the comparison operation performed by the Compare() function. More...
Static Public Member Functions inherited from PObject
static __inline void	CopyTraceContextIdentifier (PObject &to, const PObject &from)
static __inline void	CopyTraceContextIdentifier (PObject &to, const PObject *from)
static __inline void	CopyTraceContextIdentifier (PObject *to, const PObject &from)
static __inline void	CopyTraceContextIdentifier (PObject *to, const PObject *from)
static __inline const char *	Class ()
static __inline const PObject *	PTraceObjectInstance (const char *)
static __inline const PObject *	PTraceObjectInstance (const PObject *obj)
template<typename T >
static Comparison	Compare2 (T v1, T v2)
	Compare two types, returning Comparison type. More...
static Comparison	InternalCompareObjectMemoryDirect (const PObject *obj1, const PObject *obj2, PINDEX size)
	Internal function caled from CompareObjectMemoryDirect() More...
Protected Member Functions inherited from PObject
	PObject ()
	Constructor for PObject, made protected so cannot ever create one on its own. More...

Detailed Description

Class for implementing an "adaptive" delay.

This class will cause the the caller to, on average, delay the specified number of milliseconds between calls. This can be used to simulate hardware timing for a sofwtare only device

Member Enumeration Documentation

enum PAdaptiveDelay::DelayResult

< Result of call to Delay() or DelayInterval() function call

Enumerator
eOnTime	The function was called within the delta time of the expected time and a possible sleep was performed. A sleep may be skipped if below m_minimumDelay, as very short sleeps are not performed very well by many operating systems.
eOverSlept	The function was called in time, and a sleep was performed, but the operating system did not return control within two delta time intervals of the expected delay. The next two calls to the delay function will not pause at all.
eLate	The function was called greater than delta time intervals late, no sleep was made.
eSlipped	The function was called more than the m_maximumSlip time late, the adaptation is reset, no sleep is performed.
eBadDelta	The delta time interval was zero or negative.

Constructor & Destructor Documentation

PAdaptiveDelay::PAdaptiveDelay	(	const PTimeInterval &	maximumSlip = 0,
		const PTimeInterval &	minimumDelay = 0
	)

Create a new adaptive delay with the specified parameters.

The maximum slip time can also be set later using SetMaximumSlip.

Parameters

maximumSlip	Maximum slip time in milliseconds
minimumDelay	Minimum delay (usually OS time slice)

Member Function Documentation

DelayResult PAdaptiveDelay::Delay ( int  deltaMS )

inline

Wait until the specified number of milliseconds have elapsed from the previous call (on average).

The first time the function is called, no delay occurs. If the maximum slip time is set and the caller is "too late", the timer is restarted automatically and no delay occurs.

If the calculated delay is less than the OS timer resolution specified on costruction, no delay occurs now ("better sooner than later" strategy).

Returns

true if we are "too late" of time milliseconds (unrelated to the maximum slip time).

References DelayInterval().

DelayResult PAdaptiveDelay::DelayInterval

(

const PTimeInterval &

delta

)

As for Delay() but for more accurate timing.

Referenced by Delay().

const PTimeInterval& PAdaptiveDelay::GetActualDelay ( ) const

inline

Get the actual sleep time of the last call to the delay function.

References m_actualDelay.

PTimeInterval PAdaptiveDelay::GetMaximumSlip ( ) const

inline

Get the current slip time.

References m_maximumSlip.

void PAdaptiveDelay::Restart

(

)

Invalidate the timer.

The timing of this function call is not important, the timer will restart at the next call to Delay().

void PAdaptiveDelay::SetMaximumSlip ( const PTimeInterval &  maximumSlip )

inline

Set the number of milliseconds that the delay may "catch up" by using zero delays.

This is caused by the Delay() function not being called for a time by external factors.

If maximumSlip is 0, this feature is disabled.

References m_maximumSlip.

Member Data Documentation

PTimeInterval PAdaptiveDelay::m_actualDelay

protected

Referenced by GetActualDelay().

bool PAdaptiveDelay::m_firstTime

protected

PTimeInterval PAdaptiveDelay::m_maximumSlip

protected

Referenced by GetMaximumSlip(), and SetMaximumSlip().

PTimeInterval PAdaptiveDelay::m_minimumDelay

protected

PTime PAdaptiveDelay::m_targetTime

protected

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

• delaychan.h