uk.ac.starlink.array

Class DeterministicArrayImpl

java.lang.Object

uk.ac.starlink.array.DeterministicArrayImpl

All Implemented Interfaces:

ArrayImpl

public class DeterministicArrayImpl
extends Object
implements ArrayImpl

Toy ArrayImpl implementation not backed by real data. It is read-only, and its pixels depend only on the offset at which they are read. Mainly for testing purposes. The offsetToValue(long) method may be overridden to provide different determistic array data.

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
DeterministicArrayImpl(NDShape shape, Type type) Constructs a DeterministicArrayImpl of the given type and shape.

Method Summary

Modifier and Type	Method and Description
boolean	canMap() Indicates whether mapped access is available.
void	close() Shuts down this ArrayImpl for pixel access.
AccessImpl	getAccess() Returns an object which can access the pixels of this ArrayImpl.
Number	getBadValue() The magic bad value for data.
Object	getMapped() Returns a single primitive array holding all the pixel data of this array.
OrderedNDShape	getShape() Returns an object representing the shape (origin and dimensions) and pixel sequence of this object.
Type	getType() Returns the primitive type of the data held by this object.
boolean	isRandom() Indicates whether random access is possible.
boolean	isReadable() Indicates whether read access is possible.
boolean	isWritable() Indicates whether write access is possible.
boolean	multipleAccess() Indicates whether the getAccess method may be called more than once.
protected double	offsetToValue(long off) Maps the array offset to the value at that offset.
void	open() Prepares this ArrayImpl for pixel access.

Methods inherited from class java.lang.Object

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

Constructor Detail

DeterministicArrayImpl

public DeterministicArrayImpl(NDShape shape,
                              Type type)

Constructs a DeterministicArrayImpl of the given type and shape.

Parameters:

shape - the shape of the array. If it is an OrderedNDShape its pixel ordering will be used, otherwise a default ordering of Order.COLUMN_MAJOR will be used

Method Detail

offsetToValue

protected double offsetToValue(long off)

Maps the array offset to the value at that offset. The DeterministicArrayImpl class implements it as a simple linear function of the offset, with a smattering of bad values. Override it to get different contents.

Parameters:

off - the offset into the array

Returns:

the pixel value at offset. Double.NaN is permitted and will be converted to a bad value.

getShape

public OrderedNDShape getShape()

Description copied from interface: ArrayImpl

Returns an object representing the shape (origin and dimensions) and pixel sequence of this object. The return value must not change over the lifetime of the object.

Specified by:

getShape in interface ArrayImpl

Returns:

the ordered shape

getType

public Type getType()

Description copied from interface: ArrayImpl

Returns the primitive type of the data held by this object. The return value must not change over the lifetime of the object.

Specified by:

getType in interface ArrayImpl

Returns:

an object representing the type of data held.

getBadValue

public Number getBadValue()

Description copied from interface: ArrayImpl

The magic bad value for data. The returned type should be one of the primitive wrapper types, Byte, Short, Integer, Float, Double as appropriate for the type of this array. It may be null if there is no bad value. The return value must not change over the lifetime of the object.

Specified by:

getBadValue in interface ArrayImpl

Returns:

the bad value

isReadable

public boolean isReadable()

Description copied from interface: ArrayImpl

Indicates whether read access is possible. Reads will only be attempted if this method returns true. The return value must not change over the lifetime of the object.

Specified by:

isReadable in interface ArrayImpl

Returns:

whether read access is available

isWritable

public boolean isWritable()

Description copied from interface: ArrayImpl

Indicates whether write access is possible. Writes will only be attempted if this method returns true. The return value must not change over the lifetime of the object.

Specified by:

isWritable in interface ArrayImpl

Returns:

whether write access is available

isRandom

public boolean isRandom()

Description copied from interface: ArrayImpl

Indicates whether random access is possible. If this method returns true, then it is permissible to set the offset to a value lower than its current value. If it is false, then no such invocations will be attempted. The return value must not change over the lifetime of the object.

Specified by:

isRandom in interface ArrayImpl

Returns:

whether random access is available

canMap

public boolean canMap()

Description copied from interface: ArrayImpl

Indicates whether mapped access is available. If true, then following an open call, the getMapped method will return a reference to the java primitive array containing all the pixels of this array.

Will only be called after an open call, and before any close call.

Specified by:

canMap in interface ArrayImpl

getMapped

public Object getMapped()

Description copied from interface: ArrayImpl

Returns a single primitive array holding all the pixel data of this array. This should be a cheap operation, returning a reference to an existing array rather than doing work to generate one. In the case of a writable accessor, making changes to the returned primitive array will result in changes to the accessor pixel data. In the case of an NDArray which is not writable, the effect of making changes to the returned array is undefined; in particular it may result in an exception.

Will only be called if canMap returns true, and only after an open call and before any close call.

Specified by:

getMapped in interface ArrayImpl

multipleAccess

public boolean multipleAccess()

Description copied from interface: ArrayImpl

Indicates whether the getAccess method may be called more than once.

Specified by:

multipleAccess in interface ArrayImpl

Returns:

true if getAccess may be called more than once

open

public void open()

Description copied from interface: ArrayImpl

Prepares this ArrayImpl for pixel access. This method will be called no more than once, and it will be called prior to any calls of the getAccess method.

Specified by:

open in interface ArrayImpl

close

public void close()

Description copied from interface: ArrayImpl

Shuts down this ArrayImpl for pixel access. This method will be called no more than once. No calls to getAccess, getMapped or open will be made after it is called. If the user makes proper use of the NDArray classes, it will be called after any AccessImpl objects and references to the mapped array are no longer required. If the user misbehaves however it may not get called at all, so an effort should be made to realease non-memory resources and flush buffers where appropriate in the finalizer.

Specified by:

close in interface ArrayImpl

getAccess

public AccessImpl getAccess()

Description copied from interface: ArrayImpl

Returns an object which can access the pixels of this ArrayImpl. Each call to this method returns a new and independent AccessImpl, with an offset initialised to 0 (the start of the array data).

This method will only be called after the sole call to open and before the sole call to close.

This method will only be called more than once if the multipleAccess method returns true.

It is the responsibility of the caller to close the returned AccessImpl when it is no longer required; this enables resources it may hold to be released.

Specified by:

getAccess in interface ArrayImpl

Returns:

an accessor for the pixel data