net.sf.saxon.pull

Class VirtualTreeWalker

public class VirtualTreeWalker extends Object implements PullProvider, NamespaceDeclarations

A virtual tree walker provides a sequence of pull events describing the structure and content of a tree that is conceptually being constructed by expressions in a query or stylesheet; in fact the tree is not necessarily constructed in memory, and exists only as this stream of pull events.

The tree is physically constructed if operations are requested that depend on the identity of the nodes in the tree, or that navigate within the tree. Operations such as copying or atomizing the tree can be done directly, without building it in memory. (Note however that if such operations are done more than once, the underlying instructions may be evaluated repeatedly.)

Constructor Summary
VirtualTreeWalker(ParentNodeConstructor instruction, XPathContext context)
Create a VirtualTreeWalker to navigate the tree constructed by evaluating a given instruction in a given dyamic context
Method Summary
voidclose()
Close the event reader.
intcurrent()
Get the event most recently returned by next(), or by other calls that change the position, for example getStringValue() and skipToMatchingEnd().
AtomicValuegetAtomicValue()
Get an atomic value.
AttributeCollectiongetAttributes()
Get the attributes associated with the current element.
intgetFingerprint()
Get the fingerprint of the name of the element.
intgetNameCode()
Get the nameCode identifying the name of the current node.
NamePoolgetNamePool()
Get the namepool
intgetNamespaceCode(int index)
Get the n'th declaration in the list in the form of a namespace code.
int[]getNamespaceCodes(int[] buffer)
Get all the namespace codes, as an array.
NamespaceDeclarationsgetNamespaceDeclarations()
Get the namespace declarations associated with the current element.
intgetNumberOfNamespaces()
Get the number of declarations (and undeclarations) in this list.
PipelineConfigurationgetPipelineConfiguration()
Get configuration information.
StringgetPrefix(int index)
Get the prefix of the n'th declaration (or undeclaration) in the list, counting from zero.
SourceLocatorgetSourceLocator()
Get the location of the current event.
CharSequencegetStringValue()
Get the string value of the current element, text node, processing-instruction, or top-level attribute or namespace node, or atomic value.
intgetTypeAnnotation()
Get the type annotation of the current attribute or element node, or atomic value.
StringgetURI(int index)
Get the namespace URI of the n'th declaration (or undeclaration) in the list, counting from zero.
intnext()
Get the next event
voidsetNameCode(int nameCode)
Set the initial nameCode (the nameCode of the node at the root of the tree being walked)
voidsetPipelineConfiguration(PipelineConfiguration pipe)
Set configuration information.
intskipToMatchingEnd()
Skip the current subtree.

Constructor Detail

VirtualTreeWalker

public VirtualTreeWalker(ParentNodeConstructor instruction, XPathContext context)
Create a VirtualTreeWalker to navigate the tree constructed by evaluating a given instruction in a given dyamic context

Parameters: instruction the instruction (this will always be an instruction that creates element or document nodes) context the dynamic evaluation context

Method Detail

close

public void close()
Close the event reader. This indicates that no further events are required. It is not necessary to close an event reader after VirtualTreeWalker has been reported, but it is recommended to close it if reading terminates prematurely. Once an event reader has been closed, the effect of further calls on next() is undefined.

current

public int current()
Get the event most recently returned by next(), or by other calls that change the position, for example getStringValue() and skipToMatchingEnd(). This method does not change the position of the PullProvider.

Returns: the current event

getAtomicValue

public AtomicValue getAtomicValue()
Get an atomic value. This call may be used only when the last event reported was ATOMIC_VALUE. This indicates that the PullProvider is reading a sequence that contains a free-standing atomic value; it is never used when reading the content of a node.

getAttributes

public AttributeCollection getAttributes()
Get the attributes associated with the current element. This method must be called only after a START_ELEMENT event has been notified. The contents of the returned AttributeCollection are guaranteed to remain unchanged until the next START_ELEMENT event, but may be modified thereafter. The object should not be modified by the client.

Attributes may be read before or after reading the namespaces of an element, but must not be read after the first child node has been read, or after calling one of the methods skipToEnd(), getStringValue(), or getTypedValue().

Returns: an AttributeCollection representing the attributes of the element that has just been notified.

getFingerprint

public int getFingerprint()
Get the fingerprint of the name of the element. This is similar to the nameCode, except that it does not contain any information about the prefix: so two elements with the same fingerprint have the same name, excluding prefix. This method can be used after the VirtualTreeWalker, VirtualTreeWalker, VirtualTreeWalker, VirtualTreeWalker, or VirtualTreeWalker events. If called at other times, the result is undefined and may result in an IllegalStateException. If called when the current node is an unnamed namespace node (a node representing the default namespace) the returned value is -1.

Returns: the fingerprint. The fingerprint can be used to obtain the local name and namespace URI from the name pool.

getNameCode

public int getNameCode()
Get the nameCode identifying the name of the current node. This method can be used after the VirtualTreeWalker, VirtualTreeWalker, VirtualTreeWalker, VirtualTreeWalker, or VirtualTreeWalker events. With some PullProvider implementations, but not this one, it can also be used after VirtualTreeWalker. If called at other times, the result is undefined and may result in an IllegalStateException. If called when the current node is an unnamed namespace node (a node representing the default namespace) the returned value is -1.

Returns: the nameCode. The nameCode can be used to obtain the prefix, local name, and namespace URI from the name pool.

getNamePool

public NamePool getNamePool()
Get the namepool

getNamespaceCode

public int getNamespaceCode(int index)
Get the n'th declaration in the list in the form of a namespace code. Namespace codes can be translated into a prefix and URI by means of methods in the NamePool

Parameters: index the index identifying which declaration is required.

Returns: the namespace code. This is an integer whose upper half indicates the prefix (0 represents the default namespace), and whose lower half indicates the URI (0 represents an undeclaration).

Throws: IndexOutOfBoundsException if the index is out of range.

See Also: NamePool NamePool

getNamespaceCodes

public int[] getNamespaceCodes(int[] buffer)
Get all the namespace codes, as an array.

Parameters: buffer a sacrificial array that the method is free to use to contain the result. May be null.

Returns: an integer array containing namespace codes. The array may be filled completely with namespace codes, or it may be incompletely filled, in which case a -1 integer acts as a terminator.

getNamespaceDeclarations

public NamespaceDeclarations getNamespaceDeclarations()
Get the namespace declarations associated with the current element. This method must be called only after a START_ELEMENT event has been notified. In the case of a top-level START_ELEMENT event (that is, an element that either has no parent node, or whose parent is not included in the sequence being read), the NamespaceDeclarations object returned will contain a namespace declaration for each namespace that is in-scope for this element node. In the case of a non-top-level element, the NamespaceDeclarations will contain a set of namespace declarations and undeclarations, representing the differences between this element and its parent.

It is permissible for this method to return namespace declarations that are redundant.

The NamespaceDeclarations object is guaranteed to remain unchanged until the next START_ELEMENT event, but may then be overwritten. The object should not be modified by the client.

Namespaces may be read before or after reading the attributes of an element, but must not be read after the first child node has been read, or after calling one of the methods skipToEnd(), getStringValue(), or getTypedValue().

*

getNumberOfNamespaces

public int getNumberOfNamespaces()
Get the number of declarations (and undeclarations) in this list.

getPipelineConfiguration

public PipelineConfiguration getPipelineConfiguration()
Get configuration information.

getPrefix

public String getPrefix(int index)
Get the prefix of the n'th declaration (or undeclaration) in the list, counting from zero.

Parameters: index the index identifying which declaration is required.

Returns: the namespace prefix. For a declaration or undeclaration of the default namespace, this is the zero-length string.

Throws: IndexOutOfBoundsException if the index is out of range.

getSourceLocator

public SourceLocator getSourceLocator()
Get the location of the current event. For an event stream representing a real document, the location information should identify the location in the lexical XML source. For a constructed document, it should identify the location in the query or stylesheet that caused the node to be created. A value of null can be returned if no location information is available.

getStringValue

public CharSequence getStringValue()
Get the string value of the current element, text node, processing-instruction, or top-level attribute or namespace node, or atomic value.

In other situations the result is undefined and may result in an IllegalStateException.

If the most recent event was a VirtualTreeWalker, this method causes the content of the element to be read. The current event on completion of this method will be the corresponding VirtualTreeWalker. The next call of next() will return the event following the END_ELEMENT event.

Returns: the String Value of the node in question, defined according to the rules in the XPath data model.

getTypeAnnotation

public int getTypeAnnotation()
Get the type annotation of the current attribute or element node, or atomic value. The result of this method is undefined unless the most recent event was START_ELEMENT, ATTRIBUTE, or ATOMIC_VALUE.

Returns: the type annotation. This code is the fingerprint of a type name, which may be resolved to a SchemaType by access to the Configuration.

getURI

public String getURI(int index)
Get the namespace URI of the n'th declaration (or undeclaration) in the list, counting from zero.

Parameters: index the index identifying which declaration is required.

Returns: the namespace URI. For a namespace undeclaration, this is the zero-length string.

Throws: IndexOutOfBoundsException if the index is out of range.

next

public int next()
Get the next event

Returns: an integer code indicating the type of event. The code VirtualTreeWalker is returned at the end of the sequence.

setNameCode

public void setNameCode(int nameCode)
Set the initial nameCode (the nameCode of the node at the root of the tree being walked)

setPipelineConfiguration

public void setPipelineConfiguration(PipelineConfiguration pipe)
Set configuration information. This must only be called before any events have been read.

skipToMatchingEnd

public int skipToMatchingEnd()
Skip the current subtree. This method may be called only immediately after a START_DOCUMENT or START_ELEMENT event. This call returns the matching END_DOCUMENT or END_ELEMENT event; the next call on next() will return the event following the END_DOCUMENT or END_ELEMENT.

Throws: IllegalStateException if the method is called at any time other than immediately after a START_DOCUMENT or START_ELEMENT event.