org.eclipse.scada.hds

Class Quantizer

java.lang.Object

org.eclipse.scada.hds.Quantizer

public class Quantizer
extends Object

A helper class to calculate quantized time frames

The basic idea is to align timestamp. This is done by splitting up time in quantized time frames. The size of these time frames is defined by time and unit.

This class provides some helper methods to calculate timestamp based on parameters provided in the constructor.

The Quantizer can also be initialized with a maximum number of time frames (count).

Constructor Summary

Constructors

Constructor and Description
Quantizer(long time, TimeUnit unit)
Quantizer(long time, TimeUnit unit, int count)

Method Summary

Modifier and Type	Method and Description
Date	getEnd(Date timestamp) Get the end timestamp of a time frame
Date	getEndOfPeriod(Date now)
Date	getNext(Date start) Get the timestamp following a quantized timestamp
Date	getPrevious(Date start) Get the timestamp preceeding a quantized timestamp
Date	getStart(Date timestamp) Quantize to starting point before or at given timestamp
Date	getValidStart(Date timestamp) Get a quantized start timestamp if the timestamp is in the valid period of the quantizer This method calculates a quantized timestamp pointing at the start of the time frame the timestamp is in.
protected Date	getValidStart(Date timestamp, Date now)
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Quantizer

public Quantizer(long time,
                 TimeUnit unit)

Quantizer

public Quantizer(long time,
                 TimeUnit unit,
                 int count)

Method Detail

getEndOfPeriod

public Date getEndOfPeriod(Date now)

getValidStart

protected Date getValidStart(Date timestamp,
                             Date now)

getValidStart

public Date getValidStart(Date timestamp)

Get a quantized start timestamp if the timestamp is in the valid period of the quantizer
This method calculates a quantized timestamp pointing at the start of the time frame the timestamp is in. If the timestamp is outside the valid range of the quantizer ( before "count * time" ) then it returns null.

Parameters:

timestamp - an un-quantized timestamp

Returns:

the quantized start timestamp or null if the timestamp is out of range

getStart

public Date getStart(Date timestamp)

Quantize to starting point before or at given timestamp

Parameters:

timestamp - the given timestamp (not quantized)

Returns:

the quantized timestamp or null if given timestamp was null

getNext

public Date getNext(Date start)

Get the timestamp following a quantized timestamp

Parameters:

start - an already quantized timestamp

Returns:

the timestamp which is exactly one step behind the given timstamp

getPrevious

public Date getPrevious(Date start)

Get the timestamp preceeding a quantized timestamp

Parameters:

start - an already quantized timestamp

Returns:

the timestamp which is exactly one step before the given timstamp

getEnd

public Date getEnd(Date timestamp)

Get the end timestamp of a time frame

Parameters:

timestamp - an already quantized timestamp

Returns:

the timestamp of the end of the time frame the timestamp is in.

toString

public String toString()

Overrides:

toString in class Object