org.apache.xpath.axes.WalkerFactory

public class WalkerFactory
extends 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

Fields
Modifier and Type	Field	Description
`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

Constructors

Constructor Description

WalkerFactory()

Method Summary

Modifier and Type	Method	Description
`static boolean`	`canCrissCross(int analysis)`
`static boolean`	`canSkipSubtrees(int analysis)`
`static void`	`diagnoseIterator(String name, int analysis, Compiler compiler)`
`static int`	`getAnalysisBitFromAxes(int axis)`	Get a corresponding BIT_XXX from an axis.
`static String`	`getAnalysisString(int analysis)`
`static int`	`getAxisFromStep(Compiler compiler, int stepOpCodePos)`	Special purpose function to see if we can optimize the pattern for a DescendantIterator.
`static int`	`getStepCount(int analysis)`
`static boolean`	`hasPredicate(int analysis)`
`static boolean`	`isAbsolute(int analysis)`
`static boolean`	`isDownwardAxisOfMany(int axis)`	Tell if the given axis goes downword.
`static boolean`	`isNaturalDocOrder(int analysis)`	Tell if the pattern can be 'walked' with the iteration steps in natural document order, without duplicates.
`static boolean`	`isOneStep(int analysis)`
`static boolean`	`isSet(int analysis, int bits)`
`static boolean`	`isWild(int analysis)`
`static boolean`	`mightBeProximate(Compiler compiler, int opPos, int stepType)`	Tell if the predicates need to have proximity knowledge.
`static DTMIterator`	`newDTMIterator(Compiler compiler, int opPos, boolean isTopLevel)`	Create a new LocPathIterator iterator.
`static boolean`	`walksAncestors(int analysis)`
`static boolean`	`walksAttributes(int analysis)`
`static boolean`	`walksChildren(int analysis)`
`static boolean`	`walksChildrenAndExtraAndSelfOnly(int analysis)`
`static boolean`	`walksChildrenOnly(int analysis)`
`static boolean`	`walksDescendants(int analysis)`
`static boolean`	`walksDescendantsAndExtraAndSelfOnly(int analysis)`
`static boolean`	`walksDownExtraOnly(int analysis)`
`static boolean`	`walksDownOnly(int analysis)`
`static boolean`	`walksExtraNodes(int analysis)`
`static boolean`	`walksExtraNodesOnly(int analysis)`
`static boolean`	`walksFilteredList(int analysis)`
`static boolean`	`walksFollowingOnlyMaybeAbsolute(int analysis)`
`static boolean`	`walksInDocOrder(int analysis)`
`static boolean`	`walksNamespaces(int analysis)`
`static boolean`	`walksSelfOnly(int analysis)`
`static boolean`	`walksSideways(int analysis)`
`static boolean`	`walksSubtree(int analysis)`
`static boolean`	`walksSubtreeOnly(int analysis)`
`static boolean`	`walksSubtreeOnlyFromRootOrContext(int analysis)`
`static boolean`	`walksSubtreeOnlyMaybeAbsolute(int analysis)`
`static boolean`	`walksUp(int analysis)`
`static boolean`	`walksUpOnly(int analysis)`

Methods inherited from class java.lang.Object

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

Field Details
- 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!!!
  
  See Also:
  
  Constant Field Values
- BITS_RESERVED
  
  public static final int BITS_RESERVED
  
  4 bits are reserved for future use.
  
  See Also:
  
  Constant Field Values
- BIT_PREDICATE
  
  public static final int BIT_PREDICATE
  
  Bit is on if the expression contains a top-level predicate.
  
  See Also:
  
  Constant Field Values
- BIT_ANCESTOR
  
  public static final int BIT_ANCESTOR
  
  Bit is on if any of the walkers contain an ancestor step.
  
  See Also:
  
  Constant Field Values
- 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.
  
  See Also:
  
  Constant Field Values
- BIT_ATTRIBUTE
  
  public static final int BIT_ATTRIBUTE
  
  Bit is on if any of the walkers contain an attribute step.
  
  See Also:
  
  Constant Field Values
- BIT_CHILD
  
  public static final int BIT_CHILD
  
  Bit is on if any of the walkers contain a child step.
  
  See Also:
  
  Constant Field Values
- BIT_DESCENDANT
  
  public static final int BIT_DESCENDANT
  
  Bit is on if any of the walkers contain a descendant step.
  
  See Also:
  
  Constant Field Values
- 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.
  
  See Also:
  
  Constant Field Values
- BIT_FOLLOWING
  
  public static final int BIT_FOLLOWING
  
  Bit is on if any of the walkers contain a following step.
  
  See Also:
  
  Constant Field Values
- BIT_FOLLOWING_SIBLING
  
  public static final int BIT_FOLLOWING_SIBLING
  
  Bit is on if any of the walkers contain a following-sibiling step.
  
  See Also:
  
  Constant Field Values
- BIT_NAMESPACE
  
  public static final int BIT_NAMESPACE
  
  Bit is on if any of the walkers contain a namespace step.
  
  See Also:
  
  Constant Field Values
- BIT_PARENT
  
  public static final int BIT_PARENT
  
  Bit is on if any of the walkers contain a parent step.
  
  See Also:
  
  Constant Field Values
- BIT_PRECEDING
  
  public static final int BIT_PRECEDING
  
  Bit is on if any of the walkers contain a preceding step.
  
  See Also:
  
  Constant Field Values
- BIT_PRECEDING_SIBLING
  
  public static final int BIT_PRECEDING_SIBLING
  
  Bit is on if any of the walkers contain a preceding-sibling step.
  
  See Also:
  
  Constant Field Values
- BIT_SELF
  
  public static final int BIT_SELF
  
  Bit is on if any of the walkers contain a self step.
  
  See Also:
  
  Constant Field Values
- 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.
  
  See Also:
  
  Constant Field Values
- BIT_ROOT
  
  public static final int BIT_ROOT
  
  Bit is on if any of the walkers contain a root step.
  
  See Also:
  
  Constant Field Values
- 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.
  
  See Also:
  
  Constant Field Values
- 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.
  
  See Also:
  
  Constant Field Values
- BIT_ANY_DESCENDANT_FROM_ROOT
  
  public static final int BIT_ANY_DESCENDANT_FROM_ROOT
  
  Found "//foo" pattern
  
  See Also:
  
  Constant Field Values
- 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.
  
  See Also:
  
  Constant Field Values
- BIT_MATCH_PATTERN
  
  public static final int BIT_MATCH_PATTERN
  
  Bit is on if the expression is a match pattern.
  
  See Also:
  
  Constant Field Values
Constructor Details
- WalkerFactory
  
  public WalkerFactory()
Method Details
- isSet
  
  public static boolean isSet(int analysis, int bits)
- diagnoseIterator
  
  public static void diagnoseIterator(String name, int analysis, Compiler compiler)
- newDTMIterator
  
  public static DTMIterator newDTMIterator(Compiler compiler, int opPos, boolean isTopLevel) 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
- getAxisFromStep
  
  public static int getAxisFromStep(Compiler compiler, int stepOpCodePos) throws TransformerException
  
  Special purpose function to see if we can optimize the pattern for a DescendantIterator.
  
  Parameters:
  
  compiler - non-null reference to compiler object that has processed the XPath operations into an opcode map.
  
  stepOpCodePos - The opcode position for the step.
  
  Returns:
  
  32 bits as an integer that give information about the location path as a whole.
  
  Throws:
  
  TransformerException
- getAnalysisBitFromAxes
  
  public static int getAnalysisBitFromAxes(int axis)
  
  Get a corresponding BIT_XXX from an axis.
  
  Parameters:
  
  axis - One of Axis.ANCESTOR, etc.
  
  Returns:
  
  One of BIT_ANCESTOR, etc.
- mightBeProximate
  
  public static boolean mightBeProximate(Compiler compiler, int opPos, int stepType) throws TransformerException
  
  Tell if the predicates need to have proximity knowledge.
  
  Throws:
  
  TransformerException
- isDownwardAxisOfMany
  
  public static boolean isDownwardAxisOfMany(int axis)
  
  Tell if the given axis goes downword. Bogus name, if you can think of a better one, please do tell. This really has to do with inverting attribute axis.
  
  Parameters:
  
  axis - One of Axis.XXX.
  
  Returns:
  
  true if the axis is not a child axis and does not go up from the axis root.
- getAnalysisString
  
  public static String getAnalysisString(int analysis)
- hasPredicate
  
  public static boolean hasPredicate(int analysis)
- isWild
  
  public static boolean isWild(int analysis)
- walksAncestors
  
  public static boolean walksAncestors(int analysis)
- walksAttributes
  
  public static boolean walksAttributes(int analysis)
- walksNamespaces
  
  public static boolean walksNamespaces(int analysis)
- walksChildren
  
  public static boolean walksChildren(int analysis)
- walksDescendants
  
  public static boolean walksDescendants(int analysis)
- walksSubtree
  
  public static boolean walksSubtree(int analysis)
- walksSubtreeOnlyMaybeAbsolute
  
  public static boolean walksSubtreeOnlyMaybeAbsolute(int analysis)
- walksSubtreeOnly
  
  public static boolean walksSubtreeOnly(int analysis)
- walksFilteredList
  
  public static boolean walksFilteredList(int analysis)
- walksSubtreeOnlyFromRootOrContext
  
  public static boolean walksSubtreeOnlyFromRootOrContext(int analysis)
- walksInDocOrder
  
  public static boolean walksInDocOrder(int analysis)
- walksFollowingOnlyMaybeAbsolute
  
  public static boolean walksFollowingOnlyMaybeAbsolute(int analysis)
- walksUp
  
  public static boolean walksUp(int analysis)
- walksSideways
  
  public static boolean walksSideways(int analysis)
- walksExtraNodes
  
  public static boolean walksExtraNodes(int analysis)
- walksExtraNodesOnly
  
  public static boolean walksExtraNodesOnly(int analysis)
- isAbsolute
  
  public static boolean isAbsolute(int analysis)
- walksChildrenOnly
  
  public static boolean walksChildrenOnly(int analysis)
- walksChildrenAndExtraAndSelfOnly
  
  public static boolean walksChildrenAndExtraAndSelfOnly(int analysis)
- walksDescendantsAndExtraAndSelfOnly
  
  public static boolean walksDescendantsAndExtraAndSelfOnly(int analysis)
- walksSelfOnly
  
  public static boolean walksSelfOnly(int analysis)
- walksUpOnly
  
  public static boolean walksUpOnly(int analysis)
- walksDownOnly
  
  public static boolean walksDownOnly(int analysis)
- walksDownExtraOnly
  
  public static boolean walksDownExtraOnly(int analysis)
- canSkipSubtrees
  
  public static boolean canSkipSubtrees(int analysis)
- canCrissCross
  
  public static boolean canCrissCross(int analysis)
- isNaturalDocOrder
  
  public static boolean isNaturalDocOrder(int analysis)
  
  Tell if the pattern can be 'walked' with the iteration steps in natural document order, without duplicates.
  
  Parameters:
  
  analysis - The general analysis of the pattern.
  
  Returns:
  
  true if the walk can be done in natural order.
  
  Throws:
  
  TransformerException
- isOneStep
  
  public static boolean isOneStep(int analysis)
- getStepCount
  
  public static int getStepCount(int analysis)

Class WalkerFactory

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Details

Constructor Details

Method Details