org.apache.xpath.axes
Class WalkerFactory

java.lang.Object
  |
  +--org.apache.xpath.axes.WalkerFactory

public class WalkerFactory

extends java.lang.Object

This class is both a factory for XPath location path expressions, which are built from the opcode map output, and an analysis engine for the location path expressions in order to provide optimization hints.

Field Summary

static int	BIT_ANCESTOR Bit is on if any of the walkers contain an ancestor step.
static int	BIT_ANCESTOR_OR_SELF Bit is on if any of the walkers contain an ancestor-or-self step.
static int	BIT_ANY_DESCENDANT_FROM_ROOT Found "//foo" pattern
static int	BIT_ATTRIBUTE Bit is on if any of the walkers contain an attribute step.
static int	BIT_BACKWARDS_SELF Bit is on if any of the walkers can go backwards in document order from the context node.
static int	BIT_CHILD Bit is on if any of the walkers contain a child step.
static int	BIT_DESCENDANT Bit is on if any of the walkers contain a descendant step.
static int	BIT_DESCENDANT_OR_SELF Bit is on if any of the walkers contain a descendant-or-self step.
static int	BIT_FILTER Bit is on if any of the walkers contain a filter (i.e.
static int	BIT_FOLLOWING Bit is on if any of the walkers contain a following step.
static int	BIT_FOLLOWING_SIBLING Bit is on if any of the walkers contain a following-sibiling step.
static int	BIT_MATCH_PATTERN Bit is on if the expression is a match pattern.
static int	BIT_NAMESPACE Bit is on if any of the walkers contain a namespace step.
static int	BIT_NODETEST_ANY Bit is on if any of the walkers contain an node() test.
static int	BIT_PARENT Bit is on if any of the walkers contain a parent step.
static int	BIT_PRECEDING Bit is on if any of the walkers contain a preceding step.
static int	BIT_PRECEDING_SIBLING Bit is on if any of the walkers contain a preceding-sibling step.
static int	BIT_PREDICATE Bit is on if the expression contains a top-level predicate.
static int	BIT_ROOT Bit is on if any of the walkers contain a root step.
static int	BIT_SELF Bit is on if any of the walkers contain a self step.
static int	BITMASK_TRAVERSES_OUTSIDE_SUBTREE If any of these bits are on, the expression may likely traverse outside the given subtree.
static int	BITS_COUNT First 8 bits are the number of top-level location steps.
static int	BITS_RESERVED 4 bits are reserved for future use.

Constructor Summary

WalkerFactory()

Method Summary

static LocPathIterator

newLocPathIterator(Compiler compiler, int opPos) Create a new LocPathIterator iterator.

Methods inherited from class java.lang.Object

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

Field Detail

BITS_COUNT

public static final int BITS_COUNT

First 8 bits are the number of top-level location steps. Hopefully there will never be more that 255 location steps!!!

BITS_RESERVED

public static final int BITS_RESERVED

4 bits are reserved for future use.

BIT_PREDICATE

public static final int BIT_PREDICATE

Bit is on if the expression contains a top-level predicate.

BIT_ANCESTOR

public static final int BIT_ANCESTOR

Bit is on if any of the walkers contain an ancestor step.

BIT_ANCESTOR_OR_SELF

public static final int BIT_ANCESTOR_OR_SELF

Bit is on if any of the walkers contain an ancestor-or-self step.

BIT_ATTRIBUTE

public static final int BIT_ATTRIBUTE

Bit is on if any of the walkers contain an attribute step.

BIT_CHILD

public static final int BIT_CHILD

Bit is on if any of the walkers contain a child step.

BIT_DESCENDANT

public static final int BIT_DESCENDANT

Bit is on if any of the walkers contain a descendant step.

BIT_DESCENDANT_OR_SELF

public static final int BIT_DESCENDANT_OR_SELF

Bit is on if any of the walkers contain a descendant-or-self step.

BIT_FOLLOWING

public static final int BIT_FOLLOWING

Bit is on if any of the walkers contain a following step.

BIT_FOLLOWING_SIBLING

public static final int BIT_FOLLOWING_SIBLING

Bit is on if any of the walkers contain a following-sibiling step.

BIT_NAMESPACE

public static final int BIT_NAMESPACE

Bit is on if any of the walkers contain a namespace step.

BIT_PARENT

public static final int BIT_PARENT

Bit is on if any of the walkers contain a parent step.

BIT_PRECEDING

public static final int BIT_PRECEDING

Bit is on if any of the walkers contain a preceding step.

BIT_PRECEDING_SIBLING

public static final int BIT_PRECEDING_SIBLING

Bit is on if any of the walkers contain a preceding-sibling step.

BIT_SELF

public static final int BIT_SELF

Bit is on if any of the walkers contain a self step.

BIT_FILTER

public static final int BIT_FILTER

Bit is on if any of the walkers contain a filter (i.e. id(), extension function, etc.) step.

BIT_ROOT

public static final int BIT_ROOT

Bit is on if any of the walkers contain a root step.

BITMASK_TRAVERSES_OUTSIDE_SUBTREE

public static final int BITMASK_TRAVERSES_OUTSIDE_SUBTREE

If any of these bits are on, the expression may likely traverse outside the given subtree.

BIT_BACKWARDS_SELF

public static final int BIT_BACKWARDS_SELF

Bit is on if any of the walkers can go backwards in document order from the context node.

BIT_ANY_DESCENDANT_FROM_ROOT

public static final int BIT_ANY_DESCENDANT_FROM_ROOT

Found "//foo" pattern

BIT_NODETEST_ANY

public static final int BIT_NODETEST_ANY

Bit is on if any of the walkers contain an node() test. This is really only useful if the count is 1.

BIT_MATCH_PATTERN

public static final int BIT_MATCH_PATTERN

Bit is on if the expression is a match pattern.

Constructor Detail

WalkerFactory

public WalkerFactory()

Method Detail

newLocPathIterator

public static LocPathIterator newLocPathIterator(Compiler compiler,
                                                 int opPos)
                                          throws TransformerException

Create a new LocPathIterator iterator. The exact type of iterator returned is based on an analysis of the XPath operations.

Parameters:

compiler - non-null reference to compiler object that has processed the XPath operations into an opcode map.

opPos - The position of the operation code for this itterator.

Returns:

non-null reference to a LocPathIterator or derivative.

Throws:

TransformerException -