uk.ac.starlink.array

Class BufferIterator

java.lang.Object

uk.ac.starlink.array.BufferIterator

All Implemented Interfaces:

Iterator

public class BufferIterator
extends Object
implements Iterator

Provides buffers for convenient stepping through an array. At each step a primitive buffer of a given type of just the right size to match the current chunk is returned. This class is provided as a convenience for applications code which wishes to iterate through an array in sections, using a buffer of the size matching the section at each step.

This class provides a thin convenience wrapper around ChunkStepper, which is itself a simple class which steps from zero to a given limit in chunks. The only additional functionality provided by a BufferIterator is that it will ensure a suitable primitive buffer is available at each step, and (since the next method actually returns something, namely the buffer), it implements the Iterator interface which ChunkStepper does not.

A typical use of BufferIterator is as follows:

     ArrayAccess acc = ndarray.getAccess();
     for ( BufferIterator bufIt = new BufferIterator( npix, Type.DOUBLE );
           bufIt.hasNext(); ) {
         double[] buf = (double[]) bIt.next();
         acc.read( buf, 0, buf.length );
         doStuff( buf );
     }
 

Author:

Mark Taylor (Starlink)

See Also:

ChunkStepper

Constructor Summary

Constructors

Constructor and Description
BufferIterator(long length) Create a new BufferIterator with a default chunk size.
BufferIterator(long length, Type type, int chunkSize) Create a new BufferIterator with a given chunk size.

Method Summary

Modifier and Type	Method and Description
long	getBase() The offset of the base of the chunk most recently returned by next.
boolean	hasNext() See if iteration has finished.
Object	next() Returns a primitive buffer of this object's type, with a length matching that of this chunk.
void	remove() Remove functionality is not implemented by this class.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

BufferIterator

public BufferIterator(long length,
                      Type type,
                      int chunkSize)

Create a new BufferIterator with a given chunk size.

Parameters:

length - the total number of elements to iterate over

type - the type of the primitive buffer which the next method will return at each iteration

chunkSize - the size of buffer which will be used (except perhaps for the last chunk)

Throws:

IllegalArgumentException - if chunkSize<=0 or length<0

BufferIterator

public BufferIterator(long length)

Create a new BufferIterator with a default chunk size.

Parameters:

length - the total number of elements to iterate over

Method Detail

next

public Object next()

Returns a primitive buffer of this object's type, with a length matching that of this chunk. Note it is not necessarily a new buffer created for each iteration, the one returned by this method may be the same one that it returned last time (in fact it will be, except perhaps for the last iteration when a smaller one may be required).

Specified by:

next in interface Iterator

Returns:

a primitive array of the same size as this chunk

Throws:

NoSuchElementException - if hasNext would return false

hasNext

public boolean hasNext()

See if iteration has finished.

Specified by:

hasNext in interface Iterator

Returns:

true iff there are more chunks

remove

public void remove()

Remove functionality is not implemented by this class.

Specified by:

remove in interface Iterator

Throws:

UnsupportedOperationException - always

getBase

public long getBase()

The offset of the base of the chunk most recently returned by next. This will be zero for the first chunk, and increasing by the size of the buffer returned by next with each iteration after that.

Returns:

the base of the current chunk

Throws:

IllegalStateException - if called before the first call of next