Package org.apache.xpath.axes

Class WalkerFactory

java.lang.Object
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 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.
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    • BIT_PREDICATE

      public static final int BIT_PREDICATE
      Bit is on if the expression contains a top-level predicate.
      See Also:
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    • BIT_ANCESTOR

      public static final int BIT_ANCESTOR
      Bit is on if any of the walkers contain an ancestor step.
      See Also:
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    • 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:
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    • BIT_ATTRIBUTE

      public static final int BIT_ATTRIBUTE
      Bit is on if any of the walkers contain an attribute step.
      See Also:
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    • BIT_CHILD

      public static final int BIT_CHILD
      Bit is on if any of the walkers contain a child step.
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    • BIT_DESCENDANT

      public static final int BIT_DESCENDANT
      Bit is on if any of the walkers contain a descendant step.
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    • 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:
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    • BIT_FOLLOWING

      public static final int BIT_FOLLOWING
      Bit is on if any of the walkers contain a following step.
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    • 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:
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    • BIT_NAMESPACE

      public static final int BIT_NAMESPACE
      Bit is on if any of the walkers contain a namespace step.
      See Also:
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    • BIT_PARENT

      public static final int BIT_PARENT
      Bit is on if any of the walkers contain a parent step.
      See Also:
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    • BIT_PRECEDING

      public static final int BIT_PRECEDING
      Bit is on if any of the walkers contain a preceding step.
      See Also:
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    • BIT_PRECEDING_SIBLING

      public static final int BIT_PRECEDING_SIBLING
      Bit is on if any of the walkers contain a preceding-sibling step.
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    • BIT_SELF

      public static final int BIT_SELF
      Bit is on if any of the walkers contain a self step.
      See Also:
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    • 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:
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    • BIT_ROOT

      public static final int BIT_ROOT
      Bit is on if any of the walkers contain a root step.
      See Also:
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    • 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.
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    • 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:
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    • 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)