uk.ac.starlink.pds4

Class FieldReader<S,A>

java.lang.Object

uk.ac.starlink.pds4.FieldReader<S,A>

public abstract class FieldReader<S,A>
extends Object

Adapts a FieldAdapter to return a typed value. The NASA-provided FieldAdapter class does the work of reading bytes or text to turn them into some numeric or string value, but this class augments that to provide an object that knows what type of object should be read. An instance of this class may be used to read either scalar values or (within a Field_Group_*) array values.

Since:

24 Nov 2021

Author:

Mark Taylor

Method Summary

Modifier and Type	Method and Description
abstract A	createArray(int nel) Creates a new instance of an array value corresponding to this reader's array type.
Class<A>	getArrayClass() Returns the type of array value into which this reader can store values.
FieldType	getFieldType() Returns the field type for this reader.
static FieldReader<?,?>	getInstance(FieldType ftype, String[] blankTxts) Returns a FieldReader instance for a given FieldType.
Class<S>	getScalarClass() Returns the type of scalar object that this reader will read.
abstract void	readElement(byte[] buf, int offset, int length, int startBit, int endBit, A array, int iel) Reads an value from a buffer in accordance with this field type and stores it in one element of a supplied typed array.
abstract S	readScalar(byte[] buf, int offset, int length, int startBit, int endBit) Reads a typed scalar value from a buffer in accordance with this field type.

Methods inherited from class java.lang.Object

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

Method Detail

readScalar

public abstract S readScalar(byte[] buf,
                             int offset,
                             int length,
                             int startBit,
                             int endBit)

Reads a typed scalar value from a buffer in accordance with this field type.

The startBit and endBit arguments reflect their appearence in the corresponding NASA classes, but I don't know what they do.

Parameters:

buf - byte buffer containing data

offset - index into buf of byte at which data value begins

length - number of bytes over which value is represented

startBit - ??

endBit - ??

Returns:

typed data value

readElement

public abstract void readElement(byte[] buf,
                                 int offset,
                                 int length,
                                 int startBit,
                                 int endBit,
                                 A array,
                                 int iel)

Reads an value from a buffer in accordance with this field type and stores it in one element of a supplied typed array. There is a limit to what null handling can be done in this case.

The startBit and endBit arguments reflect their appearence in the corresponding NASA classes, but I don't know what they do.

Parameters:

buf - byte buffer containing data

offset - index into buf of byte at which data value begins

length - number of bytes over which value is represented

startBit - ??

endBit - ??

array - array into which read value is stored

iel - index into array a wich value is written

createArray

public abstract A createArray(int nel)

Creates a new instance of an array value corresponding to this reader's array type.

Parameters:

nel - array size

Returns:

new array

getScalarClass

public Class<S> getScalarClass()

Returns the type of scalar object that this reader will read.

Returns:

scalar content class

getArrayClass

public Class<A> getArrayClass()

Returns the type of array value into which this reader can store values.

Returns:

array content class

getFieldType

public FieldType getFieldType()

Returns the field type for this reader.

Returns:

field type

getInstance

public static FieldReader<?,?> getInstance(FieldType ftype,
                                           String[] blankTxts)

Returns a FieldReader instance for a given FieldType.

Parameters:

ftype - field type

blankTxts - array of string values representing field values that are to be mapped to null when read

Returns:

field reader