uk.ac.starlink.table

Class TimeMapper

java.lang.Object

uk.ac.starlink.table.TimeMapper

All Implemented Interfaces:

DomainMapper

public abstract class TimeMapper
extends Object
implements DomainMapper

DomainMapper for mapping values to epochs in a common time scale.

Since:

12 Aug 2013

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static TimeMapper	DECIMAL_YEAR Mapper for numeric values in decimal year (since 0 AD).
static TimeMapper	ISO_8601 Mapper for ISO-8601 strings.
static TimeMapper	JD Mapper for numeric values in Julian Day.
static TimeMapper	MJD Mapper for numeric values in Modified Julian Date.
static TimeMapper	UNIX_SECONDS Mapper for numeric values (already) in unix seconds.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	TimeMapper(Class<?> sourceClass, String sourceName, String sourceDescription) Constructor.

Method Summary

Modifier and Type	Method and Description
Class<?>	getSourceClass() Returns the type of values from which this mapper instance can convert.
String	getSourceDescription() Returns a description of the type of source values which this mapper can convert from.
String	getSourceName() Returns a short name for the type of source values which this mapper can convert from.
TimeDomain	getTargetDomain() Returns TimeDomain.INSTANCE.
static TimeMapper[]	getTimeMappers() Returns a selection of time mapper instances.
abstract double	toUnixSeconds(Object sourceValue) Maps a source value to time in seconds since the Unix epoch (1970-01-01T00:00:00).

Methods inherited from class java.lang.Object

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

Field Detail

DECIMAL_YEAR

public static final TimeMapper DECIMAL_YEAR

Mapper for numeric values in decimal year (since 0 AD).

MJD

public static final TimeMapper MJD

Mapper for numeric values in Modified Julian Date.

JD

public static final TimeMapper JD

Mapper for numeric values in Julian Day.

UNIX_SECONDS

public static final TimeMapper UNIX_SECONDS

Mapper for numeric values (already) in unix seconds.

ISO_8601

public static final TimeMapper ISO_8601

Mapper for ISO-8601 strings.

Constructor Detail

TimeMapper

protected TimeMapper(Class<?> sourceClass,
                     String sourceName,
                     String sourceDescription)

Constructor.

Parameters:

sourceClass - source class

sourceName - source type name

sourceDescription - source type description

Method Detail

getTargetDomain

public TimeDomain getTargetDomain()

Returns TimeDomain.INSTANCE.

Specified by:

getTargetDomain in interface DomainMapper

Returns:

domain identifier

getSourceClass

public Class<?> getSourceClass()

Description copied from interface: DomainMapper

Returns the type of values from which this mapper instance can convert. This should be as specific as possible to cover all the possible options, but in some cases that may mean it has simply to return Object.class.

Specified by:

getSourceClass in interface DomainMapper

Returns:

class of mappable source objects to which this mapper can be applied

getSourceName

public String getSourceName()

Description copied from interface: DomainMapper

Returns a short name for the type of source values which this mapper can convert from.

Specified by:

getSourceName in interface DomainMapper

Returns:

mapper source type name

getSourceDescription

public String getSourceDescription()

Description copied from interface: DomainMapper

Returns a description of the type of source values which this mapper can convert from.

Specified by:

getSourceDescription in interface DomainMapper

Returns:

mapper source type description

toUnixSeconds

public abstract double toUnixSeconds(Object sourceValue)

Maps a source value to time in seconds since the Unix epoch (1970-01-01T00:00:00). The time scale is generally assumed to be UTC, though conversions may not always be performed, for instance for values in which the intended time scale is not obvious.

A java (IEEE 754) double has 52+1 bits of precision, which I make 52*ln(2)/ln(10)=15.65 decimal places, and a year contains 3.15e7 seconds, which gives you the following precisions:

• epoch +/- 1.7 months: 1 nanosecond precision
• epoch +/- 140 years: 1 microsecond precision
• epoch +/- 140 kyears: 1 millisecond precision
• epoch +/- 140 Myears: 1 second precision

That means around microsecond precision for values near the current epoch (unless this software proves more long lasting than I anticipate). It should be OK for most purposes.

Parameters:

sourceValue - value in source domain

Returns:

number of seconds since midnight 1 Jan 1970

getTimeMappers

public static TimeMapper[] getTimeMappers()

Returns a selection of time mapper instances.