uk.ac.starlink.array

Class DefaultArrayAccess

java.lang.Object

uk.ac.starlink.array.DefaultArrayDescription

uk.ac.starlink.array.DefaultArrayAccess

All Implemented Interfaces:

ArrayAccess, ArrayDescription

public class DefaultArrayAccess
extends DefaultArrayDescription
implements ArrayAccess

Default implementation of the ArrayAccess interface, based on an AccessImpl. The underlying AccessImpl must be private to this object, and not used by any other clients during the lifetime of this object.

Exemplifies the Bridge Pattern.

Author:

Mark Taylor (Starlink)

Field Summary

Fields inherited from class uk.ac.starlink.array.DefaultArrayDescription

arrayDims, arrayHandler, arrayIsRandom, arrayIsReadable, arrayIsWritable, arrayNdim, arrayNpix, arrayOrder, arrayOrigin, arrayShape, arrayType

Constructor Summary

Constructors

Constructor and Description
DefaultArrayAccess(ArrayDescription adesc, AccessImpl impl, Object mappedArray) Constructs an ArrayAccess object from a description of the array's characteristics and a basic implementation of pixel access functionality.

Method Summary

Modifier and Type	Method and Description
protected void	checkOpen()
void	close() Shuts down this accessor for further data access.
protected void	doClose()
Object	getMapped() Returns a single primitive array holding all the data of this array.
long	getOffset() Returns the current offset into the array for read/write.
long[]	getPosition() Returns the coordinates at which the next read/write will occur.
boolean	isMapped() Indicates whether mapped access is available.
void	read(Object buffer, int start, int size) Reads a number of pixels from the current offset into a specified part of a supplied primitive array.
void	readTile(Object buffer, NDShape tile) Reads a tile of pixels into a supplied primitive array.
void	setOffset(long off) Sets the offset into the array for the next read/write to occur.
void	setPosition(long[] pos) Sets the coordinates for the next read/write to occur.
String	toString()
void	write(Object buffer, int start, int size) Writes a number of pixels starting at the current offset from a specified part of a supplied primitive array.
void	writeTile(Object buffer, NDShape tile) Writes a tile of pixels from a supplied primitive array.

Methods inherited from class uk.ac.starlink.array.DefaultArrayDescription

getBadHandler, getShape, getType, isRandom, isReadable, isWritable

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.starlink.array.ArrayDescription

getBadHandler, getShape, getType, isRandom, isReadable, isWritable

Constructor Detail

DefaultArrayAccess

public DefaultArrayAccess(ArrayDescription adesc,
                          AccessImpl impl,
                          Object mappedArray)

Constructs an ArrayAccess object from a description of the array's characteristics and a basic implementation of pixel access functionality.

Parameters:

adesc - array characteristics description

impl - array access service provider, available for exclusive use by this object

mappedArray - a java primitve array containing all the pixel data of the accessed array. May be null if mapped access is not provided

Method Detail

getOffset

public long getOffset()

Description copied from interface: ArrayAccess

Returns the current offset into the array for read/write.

Specified by:

getOffset in interface ArrayAccess

Returns:

the index of the next element to be read/written

setOffset

public void setOffset(long off)
               throws IOException

Description copied from interface: ArrayAccess

Sets the offset into the array for the next read/write to occur. Attempting to set the offset to a lower value than its current one will fail if random access is not available (isRandom is false).

Specified by:

setOffset in interface ArrayAccess

Parameters:

off - the position at which the next read/write will start

Throws:

IOException - if some unexpected I/O error occurs

getPosition

public long[] getPosition()

Description copied from interface: ArrayAccess

Returns the coordinates at which the next read/write will occur.

Specified by:

getPosition in interface ArrayAccess

Returns:

an N-element array giving the coordinates of the next read/write

setPosition

public void setPosition(long[] pos)
                 throws IOException

Description copied from interface: ArrayAccess

Sets the coordinates for the next read/write to occur. Attempting to set the coordinates so that the new offset corresponds to a lower value than its current one will fail if random access is not available (isRandom returns false).

Specified by:

setPosition in interface ArrayAccess

Parameters:

pos - an N-element array giving the coordinates for the next read/write

Throws:

IOException - if some unexpected I/O error occurs

read

public void read(Object buffer,
                 int start,
                 int size)
          throws IOException

Description copied from interface: ArrayAccess

Reads a number of pixels from the current offset into a specified part of a supplied primitive array. The current offset will be updated accordingly (to the point after the read pixels).

An IOException during the read will have the effect of closing this accessor for further access.

Specified by:

read in interface ArrayAccess

Parameters:

buffer - an array of the appropriate primitive type for this accessor into whose elements start..start+size the next size pixels will be read

start - the starting offset into buffer into which the pixels should be read

size - the number of pixels to read (also the amount by which the current offset will be incremented)

Throws:

IOException - if there is an I/O error

readTile

public void readTile(Object buffer,
                     NDShape tile)
              throws IOException

Description copied from interface: ArrayAccess

Reads a tile of pixels into a supplied primitive array. A tile is an N-dimensional hypercuboid specified by an NDShape object. The pixels are read into a given array in the order implied by the ordering scheme of this object. The specified tile must have the same dimensionality as this accessor, but need not lie wholly or partially within its bounds -- pixels outside the intersection will be given the bad value.

The current offset will be updated to the point after the last pixel in the intersection between the tile and this accessor.

It is possible to read a tile when random access is not available, but only if the first pixel in the requested tile is ahead of the current offset.

An IOException during the read will have the effect of closing this accessor for further access.

Specified by:

readTile in interface ArrayAccess

Parameters:

buffer - an array of the appropriate primitive type for this accessor and at least as long as the number of pixels in tileShape

tile - an NDShape object specifying the shape of the tile to be read

Throws:

IOException - if there is an I/O error

write

public void write(Object buffer,
                  int start,
                  int size)
           throws IOException

Description copied from interface: ArrayAccess

Writes a number of pixels starting at the current offset from a specified part of a supplied primitive array. The current offset will be updated accordingly (to the point after the last write).

If an IOException occurs during the read, this will have the additional effect of closing this accessor for further access.

Specified by:

write in interface ArrayAccess

Parameters:

buffer - an array of the appropriate primitive type for this NDArray whose elements start..start+size will be written out

start - the starting point in buffer from which pixels will be written

size - the number of pixels to write (also the amount by which the current offset will be incremented)

Throws:

IOException - if there is an I/O error

writeTile

public void writeTile(Object buffer,
                      NDShape tile)
               throws IOException

Description copied from interface: ArrayAccess

Writes a tile of pixels from a supplied primitive array. A tile is an N-dimensional hypercuboid specified by an NDShape object. The ordering of pixels in the array is implied by the ordering scheme of this object. The specified tile must have the same dimensionality as this accessor, but need not lie wholly or partially within its bounds -- pixels outside the intersection will simply be ignored.

The current offset will be updated to the point after the last pixel in the intersection between the tile and this accessor.

It is possible to read a tile when random access is not available, but only if the first pixel in the requested tile is ahead of the current offset.

If an IOException occurs during the write, this will have the additional effect of closing this accessor for further access.

Specified by:

writeTile in interface ArrayAccess

Parameters:

buffer - an array of the appropriate primitive type for this NDArray and at least as long as the number of pixels in tileShape (elements after this limit will be ignored)

tile - an NDShape object specifying the shape of the tile to be written

Throws:

IOException - if there is an I/O error

isMapped

public boolean isMapped()

Description copied from interface: ArrayAccess

Indicates whether mapped access is available. If true, the getMapped method will return a reference to the java primitive array containing all the pixels of this NDArray. The return value must not change over the lifetime of this object.

Specified by:

isMapped in interface ArrayAccess

Returns:

true if mapped access is possible

getMapped

public Object getMapped()

Description copied from interface: ArrayAccess

Returns a single primitive array holding all the data of this array. Calling this method does not do significant work, but returns a reference to an existing mapped array. Access to the array data using this method, if available, will be more efficient than by using the read/write methods. 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 accessor which is not writable, the effect of making changes to the returned array is undefined; in particular it may result in an exception.

The method will fail unless isMapped returns true.

Specified by:

getMapped in interface ArrayAccess

Returns:

a primitive array, of type implied by the Type of this object, containing all the pixels of this array, in its natural ordering

close

public void close()
           throws IOException

Description copied from interface: ArrayAccess

Shuts down this accessor for further data access. Following a call to close the offset will have an illegal value and calls to any read, write or position setting methods will fail with an IllegalStateException. A close should always be called on an ArrayAccess when it is finished with. In the case of a readable object it enables release of associated resources beyond those taken care of by the garbage collector, and in the case of writable object it may also be required to ensure that data is actually flushed to the underlying data storage. This method may harmlessly be called on an accessor which has already been closed.

Specified by:

close in interface ArrayAccess

Throws:

IOException - if there is an I/O error

doClose

protected void doClose()

checkOpen

protected void checkOpen()

toString

public String toString()

Overrides:

toString in class Object