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Starlink Tables Infrastructure Library
package uk.ac.starlink.votable;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import uk.ac.starlink.table.DomainMapper;
import uk.ac.starlink.table.TimeMapper;
import uk.ac.starlink.table.ValueInfo;
/**
* Utility class for identifying domain mappers for VOTable columns.
*
* @author Mark Taylor
* @since 15 Aug 2013
*/
class VOTableDomainMappers {
/** Regex in unit string that might indicate ISO-8601 values. */
static final Pattern ISO8601_UNIT_PATTERN =
Pattern.compile( "iso.?8601", Pattern.CASE_INSENSITIVE );
/** Regex in UCD that might indicate ISO-8601 values. */
static final Pattern ISO8601_UCD_PATTERN =
Pattern.compile( "time(\\.(epoch|start|end))?(;.*)?|TIME_DATE(_.*)?",
Pattern.CASE_INSENSITIVE );
/** Regex in Utype that looks like an ObsCore MJD-mandated value. */
static final Pattern OBSCORE_T_UTYPE_PATTERN =
Pattern.compile( ".*Char\\.TimeAxis\\.Coverage\\.Bounds\\.Limits.*",
Pattern.CASE_INSENSITIVE );
/**
* Identifies suitable DomainMapper objects to associate with a column.
*
* @param info column basic metadata
* @return array of mappers; may be empty
*/
public static DomainMapper[] getMappers( ValueInfo info ) {
TimeMapper tmapper = getTimeMapper( info );
return tmapper == null ? new DomainMapper[ 0 ]
: new DomainMapper[] { tmapper };
}
/**
* Tries to identify a TimeMapper to associated with a column.
*
* @param info column basic metadata
* @return domain mapper for time data, or null if not successful
*/
private static TimeMapper getTimeMapper( ValueInfo info ) {
Class clazz = info.getContentClass();
String units = info.getUnitString();
String ucd = info.getUCD();
String utype = info.getUtype();
String xtype = info.getXtype();
if ( xtype == null ) {
xtype = "";
}
if ( units == null ) {
units = "";
}
if ( ucd == null ) {
ucd = "";
}
if ( utype == null ) {
utype = "";
}
/* Unquote the string. This tackles a convention in use
* at CDS which uses values of the unit attribute in VOTables
* to represent non-standard values, e.g. unit='"hms"'.
* Also trim it for good measure. */
units = unquote( units.trim() ).trim();
/* If it's a string, see if it looks like an ISO-8601 date. */
if ( String.class.isAssignableFrom( clazz ) ) {
if ( "iso8601".equals( xtype ) ||
ISO8601_UNIT_PATTERN.matcher( xtype ).matches() ||
"adql:TIMESTAMP".equalsIgnoreCase( xtype ) ||
"timestamp".equalsIgnoreCase( xtype ) ||
ISO8601_UNIT_PATTERN.matcher( units ).matches() ||
ISO8601_UCD_PATTERN.matcher( ucd ).matches() ) {
return TimeMapper.ISO_8601;
}
}
/* Look for metadata imported from TIMESYS elements, which is how
* it's supposed to be done post VOTable 1.4. Just use the timeorigin,
* don't attempt anything clever with the refposition or timescale.
* Note that this ignores TIMESYS references where timeorigin is
* not set; that corresponds to an absolute date in years from 0AD.
* If timescale and refposition are to be extracted in future,
* handling for those cases will need to be added. */
Timesys tsys = Timesys.getTimesys( info );
if ( tsys != null && Number.class.isAssignableFrom( clazz ) ) {
double jdOrigin = tsys.getTimeorigin();
final double unitSec = getUnitInSeconds( units );
if ( ! Double.isNaN( unitSec ) &&
! Double.isNaN( jdOrigin ) ) {
double unixDayOrigin = jdOrigin - 2440587.5;
final double unixSecOrigin = unixDayOrigin * 60 * 60 * 24;
return new TimeMapper( clazz, "TIMESYS", tsys.toString() ) {
public double toUnixSeconds( Object sourceValue ) {
double val = sourceValue instanceof Number
? ((Number) sourceValue).doubleValue()
: Double.NaN;
return Double.isNaN( val )
? Double.NaN
: ( val * unitSec ) + unixSecOrigin;
}
};
}
}
/* Otherwise try some ad hoc numeric domains. */
if ( Number.class.isAssignableFrom( clazz ) ) {
if ( "mjd".equalsIgnoreCase( xtype ) ||
( OBSCORE_T_UTYPE_PATTERN.matcher( utype ).matches() &&
"d".equals( units ) ) ) {
return TimeMapper.MJD;
}
else if ( "jd".equalsIgnoreCase( xtype ) ) {
return TimeMapper.JD;
}
else if ( "yr".equals( units ) ||
"a".equals( units ) ||
"year".equals( units ) ) {
return TimeMapper.DECIMAL_YEAR;
}
}
/* There may be some other conventions that I could spot here -
* ask CDS for known indicators of epoch-like columns? */
return null;
}
/**
* Removes matched single or double quotes from the ends of a string,
* if they are present. If they aren't, returns the original string.
*
* @param str quoted or unquoted string
* @return unquoted string
*/
private static String unquote( String str ) {
int leng = str.length();
if ( ( leng > 1 ) &&
( ( str.charAt( 0 ) == '\'' && str.charAt( leng - 1 ) == '\'' ) ||
( str.charAt( 0 ) == '"' && str.charAt( leng - 1 ) == '"' ) ) ) {
return str.substring( 1, leng - 1 );
}
else {
return str;
}
}
/**
* Returns the numeric size of a unit in seconds given the VOTable
* units attribute value.
*
* Note: this does not currently implement
* all of VOUnits; for instance SI prefixes (kilodays etc)
* are not understood.
*
* @param units unit string
* @return extent of unit in seconds, or NaN if not understood
*/
private static double getUnitInSeconds( String units ) {
if ( "s".equals( units ) ) {
return 1.0;
}
else if ( "d".equals( units ) ) {
return 60 * 60 * 24;
}
else if ( "a".equals( units ) ||
"yr".equals( units ) ||
"year".equals( units ) ) {
return 60 * 60 * 24 * 365.25;
}
else {
return Double.NaN;
}
}
}