net.sf.saxon.expr.instruct

Class AbstractBlockIterator

java.lang.Object

net.sf.saxon.expr.instruct.AbstractBlockIterator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, SequenceIterator

Direct Known Subclasses:

BlockIterator

public abstract class AbstractBlockIterator
extends java.lang.Object
implements SequenceIterator

Iterate over the instructions in a sequence of instructions (or an XPath comma expression), concatenating the result of each instruction into a single combined sequence. This abstract class has concrete subclasses handling the interpreted and compiled cases

Field Summary

Fields

Modifier and Type	Field and Description
protected XPathContext	context
protected SequenceIterator	currentIter
protected int	currentOperand
protected int	size

Constructor Summary

Constructors

Constructor and Description
AbstractBlockIterator()
AbstractBlockIterator(int size, XPathContext context)

Method Summary

Modifier and Type	Method and Description
void	close() Close the iterator.
void	discharge() Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence.
abstract SequenceIterator	getNthChildIterator(int n)
void	init(int size, XPathContext context) Initializer for use from bytecode
Item	next() Get the next item in the sequence.

Methods inherited from class java.lang.Object

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

Field Detail

size

protected int size

currentOperand

protected int currentOperand

currentIter

protected SequenceIterator currentIter

context

protected XPathContext context

Constructor Detail

AbstractBlockIterator

public AbstractBlockIterator()

AbstractBlockIterator

public AbstractBlockIterator(int size,
                             XPathContext context)

Method Detail

init

public void init(int size,
                 XPathContext context)

Initializer for use from bytecode

Parameters:

size - the size

context - the XPath context

discharge

public void discharge()

Description copied from interface: SequenceIterator

Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence. This may require the iterator to calculate the rest of the sequence eagerly. The method is called by a client if it anticipates that it might not read the iterator to completion, but it cannot guarantee that SequenceIterator.close() will be called when no more items are needed.

Specified by:

discharge in interface SequenceIterator

next

public Item next()

Get the next item in the sequence.

Specified by:

next in interface SequenceIterator

Returns:

the next item, or null if there are no more items.

getNthChildIterator

public abstract SequenceIterator getNthChildIterator(int n)
                                              throws XPathException

Throws:

XPathException

close

public void close()

Description copied from interface: SequenceIterator

Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

Closing an iterator is important when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.

Closing an iterator is not necessary if the iterator is read to completion: if a call on SequenceIterator.next() returns null, the iterator will be closed automatically. An explicit call on SequenceIterator.close() is needed only when iteration is abandoned prematurely.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface SequenceIterator