uk.ac.starlink.table

Class Tables

java.lang.Object

uk.ac.starlink.table.Tables

public class Tables
extends java.lang.Object

Utility class for miscellaneous table-related functionality.

Field Summary

Fields

Modifier and Type	Field and Description
static DefaultValueInfo	DEC_INFO ValueInfo representing Declination.
static ValueInfo	NULL_VALUE_INFO ValueInfo which may be used as part of a column's metadata to indicate a special value (preferably a Number that should be interpreted as a null (blank).
static DefaultValueInfo	RA_INFO ValueInfo representing Right Ascension.
static ValueInfo	UBYTE_FLAG_INFO ValueInfo which may be used as part of a column's auxiliary metadata to indicate that the column's data represents, and can be serialised as, unsigned byte values.

Constructor Summary

Constructors

Constructor and Description
Tables()

Method Summary

Modifier and Type	Method and Description
static TableSequence	arrayTableSequence(StarTable[] tables) Convenience method to construct a TableSequence for a supplied array of tables.
static int	assertLongToInt(long lval) Casts a long to an int, with an assertion that no truncation occurs.
static int	checkedLongToInt(long lval) Convenience method to get an int value from a long.
static long	checksumData(RowSequence rseq, java.util.zip.Checksum checksum) Feeds the data from a row sequence to a supplied checksum accumulator.
static int	checksumData(StarTable table) Returns a checksum of all the cell data in a given table.
static void	checkTable(StarTable table) Diagnostic method which tests the invariants of a StarTable.
static java.lang.String	collapseWhitespace(java.lang.String txt) Collapses whitespace in a string.
static StarTable	deleteColumn(StarTable startab, int icol) Returns a table equivalent to the original but with a given column deleted.
static void	fixColumns(ColumnInfo[][] infoLists, JoinFixAction[] fixActs) Performs deduplication of column names for N lists of column metadata objects that will be combined to form a new table.
static <T> T	getAuxDatumValue(ValueInfo info, ValueInfo auxKey, java.lang.Class<T> auxClazz) Utility method to return an auxiliary metadata item from a ValueInfo.
static ColumnInfo[]	getColumnInfos(StarTable startab) Convenience method to return an array of all the column headers in a given table.
static RowSplittable	getDefaultRowSplittable(StarTable table) Returns a RowSplittable object with generic characteristics for a given table.
static DescribedValue	getDescribedValueByName(java.util.Collection<DescribedValue> dvals, java.lang.String name) Utility method to locate an element in a list of DescribedValue given the name of its ValueInfo member.
static java.lang.String[]	getElementLabels(int[] shape) Returns an array of strings suitable as labels or label suffixes for elements of an array as returned by ValueInfo.getShape().
static <T> T	getTypedValue(DescribedValue dval, java.lang.Class<T> clazz) Utility method to get a typed value from a, possibly null, described value.
static java.lang.String	getUtype(ValueInfo info) Deprecated. use ValueInfo.getUtype() instead
static java.lang.Object	getValue(java.util.Collection<DescribedValue> dvals, ValueInfo info) Returns the value from a list of DescribedValue objects which corresponds to a given info key.
static java.lang.String	getXtype(ValueInfo info) Deprecated. use ValueInfo.getXtype() instead
static boolean	isBlank(java.lang.Object value) Indicates whether a given value is conventionally regarded as a blank value.
static StarTable	randomTable(StarTable startab) Returns a table based on a given table and guaranteed to have random access.
static void	setDescribedValue(java.util.Collection<DescribedValue> dvals, DescribedValue dval) Utility method to update a list of DescribedValues with a new entry.
static void	setUtype(ValueInfo info, java.lang.String utype) Deprecated. use DefaultValueInfo.setUtype(java.lang.String) instead
static void	setXtype(ValueInfo info, java.lang.String xtype) Deprecated. use DefaultValueInfo.setXtype(java.lang.String) instead
static TableSequence	singleTableSequence(StarTable table) Convenience method to construct a TableSequence for a single table.
static StarTable	sortTable(StarTable table, int[] colIndices, boolean up, boolean nullsLast) Returns a sorted version of a table.
static void	streamStarTable(StarTable source, TableSink sink) Copies the data and metadata from a StarTable into a table sink.
static StarTable[]	tableArray(TableSequence tseq) Convenience method to construct an array of StarTables from a TableSequence.
static java.lang.String	tableToString(StarTable table, java.lang.String ofmt) Returns the contents of a table as a string.

Methods inherited from class java.lang.Object

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

Field Detail

NULL_VALUE_INFO

public static final ValueInfo NULL_VALUE_INFO

ValueInfo which may be used as part of a column's metadata to indicate a special value (preferably a Number that should be interpreted as a null (blank). This should only be used on nullable columns, and really only on ones with a contentClass which is an integer (or possibly boolean) type; for other types, there is usually a value which can conventionally be understood to mean blank. Note this is here as a standard key to use when software components wish to communicate this information; the table system does not guarantee to honour instances of this value in a column's auxiliary data. It is the job of a StarTable instance to ensure that a null is returned from the table interrogation methods if that is what is meant.

UBYTE_FLAG_INFO

public static final ValueInfo UBYTE_FLAG_INFO

ValueInfo which may be used as part of a column's auxiliary metadata to indicate that the column's data represents, and can be serialised as, unsigned byte values. If so, the value is set to Boolean.TRUE (other values are treated as if absent). Data representing unsigned byte values will normally be represented within STIL by Short (16-bit integer) signed values, since there is no unsigned byte type in java. However, this flag may be used to indicate that the values can be serialised to unsigned-byte-capable output formats (for instance FITS and VOTable) using an unsigned byte serialisation. This annotation will normally only be honoured if the data type of the column is (scalar or array) short integer (16-bit) values. Some care should be exercised in applying this flag or (especially) modifying values in columns it applies to, that the actual column value range remains in the unsigned byte data range (0..255), since otherwise problems will result if it is serialised.

RA_INFO

public static final DefaultValueInfo RA_INFO

ValueInfo representing Right Ascension. The units are radians and it is non-nullable.

DEC_INFO

public static final DefaultValueInfo DEC_INFO

ValueInfo representing Declination. The units are radians and it is non-nullable.

Constructor Detail

Tables

public Tables()

Method Detail

randomTable

public static StarTable randomTable(StarTable startab)
                             throws java.io.IOException

Returns a table based on a given table and guaranteed to have random access. If the original table stab has random access then it is returned, otherwise a new random access table is built using its data.

This convenience method is equivalent to calling StoragePolicy.getDefaultPolicy().randomTable(startab).

Parameters:

startab - original table

Returns:

a table with the same data as startab and with isRandom()==true

Throws:

java.io.IOException

getColumnInfos

public static ColumnInfo[] getColumnInfos(StarTable startab)

Convenience method to return an array of all the column headers in a given table. Modifying this array will not affect the table.

Parameters:

startab - the table being enquired about

Returns:

an array of all the column headers

deleteColumn

public static StarTable deleteColumn(StarTable startab,
                                     int icol)

Returns a table equivalent to the original but with a given column deleted. The result may or may not be the same object as the input table.

Parameters:

startab - the table from which to delete a column

icol - the index of the column to be deleted

Throws:

java.lang.IndexOutOfBoundsException - if startab has no column at icol

streamStarTable

public static void streamStarTable(StarTable source,
                                   TableSink sink)
                            throws java.io.IOException

Copies the data and metadata from a StarTable into a table sink. This method is supplied for convenience; its implementation is very straightforward.

Parameters:

source - table to be copied

sink - table destination

Throws:

java.io.IOException

getDefaultRowSplittable

public static RowSplittable getDefaultRowSplittable(StarTable table)
                                             throws java.io.IOException

Returns a RowSplittable object with generic characteristics for a given table. For a random-access table the splitting will be based on RowAccess objects, and for a non-random table it will not be capable of splits.

Parameters:

table - table

Returns:

splittable for potentially parallel iteration over rows

Throws:

java.io.IOException

checkTable

public static void checkTable(StarTable table)
                       throws java.io.IOException

Diagnostic method which tests the invariants of a StarTable. This method returns no value, and throws an exception if a table is illegal in some way. If this method throws an exception when called on a given StarTable, that table is deemed to be bad in some way (buggy implementation or I/O trouble during access). This method is provided for convenience and diagnostics because there are a number of ways, some of them subtle, in which a StarTable can fail to fulfil its general contract.

That a table passes this test does not guarantee that the table has no bugs. This method should not generally be used in production code, since it may be expensive in time and/or memory.

Parameters:

table - table to test

Throws:

java.lang.AssertionError - if an invariant is violated

java.io.IOException - if there is an I/O error

checksumData

public static int checksumData(StarTable table)
                        throws java.io.IOException

Returns a checksum of all the cell data in a given table. Currently, the Adler32 checksum is used.

Parameters:

table - table to checksum

Returns:

checksum value

Throws:

java.io.IOException

checksumData

public static long checksumData(RowSequence rseq,
                                java.util.zip.Checksum checksum)
                         throws java.io.IOException

Feeds the data from a row sequence to a supplied checksum accumulator.

Parameters:

rseq - row sequence containing data

checksum - checksum accumulator

Returns:

number of rows checksummed (note this is not the checksum value)

Throws:

java.io.IOException

isBlank

public static boolean isBlank(java.lang.Object value)

Indicates whether a given value is conventionally regarded as a blank value. For most objects this is equivalent to testing whether it is equall to null, but some classes have additional non-null values which count as blanks, for instance zero-length Strings and floating Not-A-Number values.

Parameters:

value - value to test

Returns:

true iff value counts as a blank value

collapseWhitespace

public static java.lang.String collapseWhitespace(java.lang.String txt)

Collapses whitespace in a string. This normalises the text in the sense of the XML Schema facet whitespace='collapse': leading and trailing whitespace is removed, and any other run of whitespace is replaced by a single space character.

Parameters:

txt - input string (may be null)

Returns:

string with whitespaces collapsed

singleTableSequence

public static TableSequence singleTableSequence(StarTable table)

Convenience method to construct a TableSequence for a single table.

Parameters:

table - table

Returns:

table sequence with just one element

arrayTableSequence

public static TableSequence arrayTableSequence(StarTable[] tables)

Convenience method to construct a TableSequence for a supplied array of tables.

Parameters:

tables - table array

Returns:

table sequence containing input tables

tableArray

public static StarTable[] tableArray(TableSequence tseq)
                              throws java.io.IOException

Convenience method to construct an array of StarTables from a TableSequence.

Parameters:

tseq - table sequence

Returns:

array containing tables from sequence

Throws:

java.io.IOException

sortTable

public static StarTable sortTable(StarTable table,
                                  int[] colIndices,
                                  boolean up,
                                  boolean nullsLast)
                           throws java.io.IOException

Returns a sorted version of a table. The sorting is done on the values of one or more columns, as specified by the colIndices argument; the first element is the primary sort key, but in case of a tie the second element is used, and so on. The original table is not affected. The natural comparison order of the values in the table is used, and blank values may be ranked at the start or end of the collation order.

Parameters:

table - table to sort - must be random access

colIndices - indices of the columns which are to act as sort keys; first element is primary key etc

up - true for sorting into ascending order, false for descending order

nullsLast - true if blank values should be considered last in the collation order, false if they should be considered first

Returns:

a table with the same rows as table but in an order determined by the other arguments

Throws:

java.io.IOException - if table.isRandom is not true

tableToString

public static java.lang.String tableToString(StarTable table,
                                             java.lang.String ofmt)

Returns the contents of a table as a string. Only intended for small tables, for instance during debugging.

Parameters:

table - input table

ofmt - output format specifier, or null for plain text output

Returns:

stringified table

checkedLongToInt

public static int checkedLongToInt(long lval)

Convenience method to get an int value from a long. If the supplied long integer lval is out of the range which can be represented in an int, then unlike a typecast, this method will throw an IllegalArgumentException.

Parameters:

lval - the long value to convert

Returns:

an int value which has the same value as lval

Throws:

java.lang.IllegalArgumentException - if the conversion cannot be done

assertLongToInt

public static int assertLongToInt(long lval)

Casts a long to an int, with an assertion that no truncation occurs.

Parameters:

lval - long value, asserted to be in the range Integer.MIN_VALUE..Integer.MAX_VALUE

Returns:

truncated version of lval

getElementLabels

public static java.lang.String[] getElementLabels(int[] shape)

Returns an array of strings suitable as labels or label suffixes for elements of an array as returned by ValueInfo.getShape(). If the given shape cannot be decomposed into a fixed size array, returns null.

Parameters:

shape - vector giving dimensions of an array value

Returns:

array with one element for each element of the array values (in their natural order), or null for non-array shapes

getUtype

@Deprecated
public static java.lang.String getUtype(ValueInfo info)

Deprecated. use ValueInfo.getUtype() instead

Returns the Utype associated with a given metadata item.

Parameters:

info - metadata item

Returns:

utype string, or null if none is available

See Also:

setUtype(uk.ac.starlink.table.ValueInfo, java.lang.String)

setUtype

@Deprecated
public static void setUtype(ValueInfo info,
                                        java.lang.String utype)

Deprecated. use DefaultValueInfo.setUtype(java.lang.String) instead

Tries to set the Utype for a given metadata item.

Parameters:

info - metadata item

utype - new utype value

See Also:

getUtype(uk.ac.starlink.table.ValueInfo)

getXtype

@Deprecated
public static java.lang.String getXtype(ValueInfo info)

Deprecated. use ValueInfo.getXtype() instead

Returns the extended type value associated with a given metadata item. The XType corresponds to the xtype attribute of the VOTable format. Other table formats may or may not be able to represent it.

Parameters:

info - metadata item

Returns:

xtype string, or null if none is available

setXtype

@Deprecated
public static void setXtype(ValueInfo info,
                                        java.lang.String xtype)

Deprecated. use DefaultValueInfo.setXtype(java.lang.String) instead

Tries to set the Xtype for a given metadata item.

Parameters:

info - metadata item

xtype - new xtype value

See Also:

getXtype(uk.ac.starlink.table.ValueInfo)

setDescribedValue

public static void setDescribedValue(java.util.Collection<DescribedValue> dvals,
                                     DescribedValue dval)

Utility method to update a list of DescribedValues with a new entry. If an item with the same name as the new entry already exists, it is removed.

Parameters:

dvals - list to modify

dval - new entry to add

getDescribedValueByName

public static DescribedValue getDescribedValueByName(java.util.Collection<DescribedValue> dvals,
                                                     java.lang.String name)

Utility method to locate an element in a list of DescribedValue given the name of its ValueInfo member.

Parameters:

dvals - list to query

name - required value of name

Returns:

element of dvals for which getInfo().getName() matches name

getAuxDatumValue

public static <T> T getAuxDatumValue(ValueInfo info,
                                     ValueInfo auxKey,
                                     java.lang.Class<T> auxClazz)

Utility method to return an auxiliary metadata item from a ValueInfo.

Parameters:

info - metadata item

auxKey - info identifying aux metadata entry in info

auxClazz - required result type

Returns:

typed aux metadata item requested, or null if it doesn't exist or has the wrong type

getTypedValue

public static <T> T getTypedValue(DescribedValue dval,
                                  java.lang.Class<T> clazz)

Utility method to get a typed value from a, possibly null, described value.

Parameters:

dval - described value, or null

clazz - required return type

Returns:

typed value of dval, or null if dval is null, or if dval's value has the wrong type

getValue

public static java.lang.Object getValue(java.util.Collection<DescribedValue> dvals,
                                        ValueInfo info)

Returns the value from a list of DescribedValue objects which corresponds to a given info key. If the key is not represented in the list, or if its value is null, then null is returned.

Parameters:

dvals - list of DescribedValue objects

info - key giving the value you want

Returns:

matching value

fixColumns

public static void fixColumns(ColumnInfo[][] infoLists,
                              JoinFixAction[] fixActs)

Performs deduplication of column names for N lists of column metadata objects that will be combined to form a new table. The arguments are matched arrays; each list of column infos has a corresponding renaming policy. The ColumnInfo objects are renamed in place as required.

Parameters:

infoLists - array of N arrays of column metadata objects

fixActs - array of N policies for renaming columns