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 boolean canCrissCross(int analysis)
           
static boolean canSkipSubtrees(int analysis)
           
static void diagnoseIterator(java.lang.String name, int analysis, Compiler compiler)
           
static int getAnalysisBitFromAxes(int axis)
          Get a corresponding BIT_XXX from an axis.
static java.lang.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
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

isSet

public static boolean isSet(int analysis,
                            int bits)

diagnoseIterator

public static void diagnoseIterator(java.lang.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.

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 java.lang.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)


Copyright 2006 Apache XML Project. All Rights Reserved.