org.das2.qstream

Class QdsToD2sStream

java.lang.Object

org.das2.qstream.QdsToD2sStream

public class QdsToD2sStream
extends java.lang.Object

Write QDataSets that vary over at most 2 independent variables as a Das2 stream. Since Das2 streams can have at most 2 independent variables, higher dimensional (not necessarily higher rank) QDataSets can't be written using this code. Streams that can be written have the following plane structure X Y [Y Y Y Y ... ] X YScan [YScan YScan YScan ... ] X Y Z [Z Z Z Z ... ] All binary output is streamed in machine-native order. Since datasets written on one architecture are most likely to be read on the same architecture this choice causes the least amount of byte swapping. This is a direct seralization of QDataSet and does not require any legacy das2 dataset classes such as VectorDataset or TableDataset.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAUT_FRAC_SEC
static int	DEFAUT_SIG_DIGIT
static java.lang.String	FORMAT_2_2
static java.lang.String	FORMAT_2_3_BASIC
static java.lang.String	FORMAT_2_3_GENERAL
static java.lang.String[]	formats

Constructor Summary

Constructors

Constructor and Description
QdsToD2sStream(java.lang.String version) Initialize a binary QDataSet to das2 stream exporter
QdsToD2sStream(java.lang.String version, int genSigDigits, int fracSecDigits) Initialize a text QDataSet to das2 stream exporter

Method Summary

Modifier and Type	Method and Description
boolean	canWrite(QDataSet qds) Determine if a given dataset be serialized as a das2 stream
protected boolean	canWriteNonJoin(QDataSet qds)
static java.lang.String	qd2DataAxis(QDataSet qds) Determine the name of the das2 axis on which values from a dataset would typically be plotted.
boolean	write(QDataSet qds, java.io.OutputStream os) Write a QDataSet as a das2 stream To test whether it looks like this code could stream a dataset use the canWrite() function.

Methods inherited from class java.lang.Object

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

Field Detail

FORMAT_2_2

public static final java.lang.String FORMAT_2_2

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Constant Field Values

FORMAT_2_3_BASIC

public static final java.lang.String FORMAT_2_3_BASIC

See Also:

Constant Field Values

FORMAT_2_3_GENERAL

public static final java.lang.String FORMAT_2_3_GENERAL

See Also:

Constant Field Values

formats

public static final java.lang.String[] formats

DEFAUT_FRAC_SEC

public static final int DEFAUT_FRAC_SEC

See Also:

Constant Field Values

DEFAUT_SIG_DIGIT

public static final int DEFAUT_SIG_DIGIT

See Also:

Constant Field Values

Constructor Detail

QdsToD2sStream

public QdsToD2sStream(java.lang.String version)

Initialize a binary QDataSet to das2 stream exporter

Parameters:

version - The output version to write, valid choices are defined in the static formats array

QdsToD2sStream

public QdsToD2sStream(java.lang.String version,
                      int genSigDigits,
                      int fracSecDigits)

Initialize a text QDataSet to das2 stream exporter

Parameters:

version - The output version to write, valid choices are defined in the static formats array

genSigDigits - The number of significant digits used for general text value data output. If you don't know what else to use, 5 is typically a fine precision without being ridiculous.

fracSecDigits - The number of fractional seconds digits to use for ISO-8601 date-time values. The number of fraction seconds can be set as low as 0 and as high as 12 (picoseconds). If successive time values vary by less than the specified precision (but not 0, repeats are accepted) then stream writing fails. Use 3 (i.e. microseconds) if you don't know what else to choose.

Method Detail

canWrite

public boolean canWrite(QDataSet qds)

Determine if a given dataset be serialized as a das2 stream

Parameters:

qds - The dataset to write

Returns:

true if this dataset can be serialized as a das2 stream, false otherwise

write

public boolean write(QDataSet qds,
                     java.io.OutputStream os)
              throws java.io.IOException

Write a QDataSet as a das2 stream To test whether it looks like this code could stream a dataset use the canWrite() function. This function may be called multiple times to add additional data to the stream. If a compatible header has already been emitted for a particular dataset it is not re-sent.

Parameters:

qds - The dataset to write, may have join's bundles etc. but no rank 3 or higher component datasets.

os - an open output stream, which is not closed by this code.

Returns:

true if the entire dataset could be written, false otherwise. IO failures do not return false, they throw. False simply means that this code does not know how (or can't) stream the given dataset. Since deeper inspection occurs when actually writing the data then when testing, false may be returned even if canWrite() returned true.

Throws:

java.io.IOException

canWriteNonJoin

protected boolean canWriteNonJoin(QDataSet qds)

qd2DataAxis

public static java.lang.String qd2DataAxis(QDataSet qds)

Determine the name of the das2 axis on which values from a dataset would typically be plotted. This is a duck-typing check. Which looks at the number of dependencies and planes in a dataset. If the dataset has a PLANE_0 property, the axis of the PLANE_0 values is returned instead of the axis of the primary dataset. The output of this function is an educated guess since coordinates are not denoted as separate from data values in QDataSets or CDFs.

Parameters:

qds -

Returns:

one of "x", "y", "z" or null if we can't figure it out.