Package org.htmlunit.xpath.axes
Class WalkerFactory
java.lang.Object
org.htmlunit.xpath.axes.WalkerFactory
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.
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
Bit is on if any of the walkers contain an ancestor step.static final int
Bit is on if any of the walkers contain an ancestor-or-self step.static final int
Found "//foo" patternstatic final int
Bit is on if any of the walkers contain an attribute step.static final int
Bit is on if any of the walkers contain a child step.static final int
Bit is on if any of the walkers contain a descendant step.static final int
Bit is on if any of the walkers contain a descendant-or-self step.static final int
Bit is on if any of the walkers contain a filter (i.e.static final int
Bit is on if any of the walkers contain a following step.static final int
Bit is on if any of the walkers contain a following-sibiling step.static final int
Bit is on if the expression is a match pattern.static final int
Bit is on if any of the walkers contain a namespace step.static final int
Bit is on if any of the walkers contain an node() test.static final int
Bit is on if any of the walkers contain a parent step.static final int
Bit is on if any of the walkers contain a preceding step.static final int
Bit is on if any of the walkers contain a preceding-sibling step.static final int
Bit is on if the expression contains a top-level predicate.static final int
Bit is on if any of the walkers contain a root step.static final int
Bit is on if any of the walkers contain a self step.static final int
First 8 bits are the number of top-level location steps.(package private) static final boolean
Set to true for diagnostics about iterator creation(package private) static final boolean
Set to true for diagnostics about walker creation(package private) static final boolean
Set to true for diagnostics about walker creation -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate static int
Analyze the location path and return 32 bits that give information about the location path as a whole.(package private) static boolean
analyzePredicate
(Compiler compiler, int opPos, int stepType) Analyze a step and give information about it's predicates.static boolean
canCrissCross
(int analysis) static boolean
canSkipSubtrees
(int analysis) private static StepPattern
createDefaultStepPattern
(Compiler compiler, int opPos) Create a StepPattern that is contained within a LocationPath.private static AxesWalker
createDefaultWalker
(Compiler compiler, int opPos, WalkingIterator lpi, int analysis) Create the proper Walker from the axes type.static void
diagnoseIterator
(String name, int analysis, Compiler compiler) (package private) static boolean
functionProximateOrContainsProximate
(Compiler compiler, int opPos) 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.private static boolean
isNaturalDocOrder
(Compiler compiler, int stepOpCodePos, int analysis) Tell if the pattern can be 'walked' with the iteration steps in natural document order, without duplicates.static boolean
isOneStep
(int analysis) private static boolean
isOptimizableForDescendantIterator
(Compiler compiler, int stepOpCodePos) Special purpose function to see if we can optimize the pattern for a DescendantIterator.(package private) static boolean
isProximateInnerExpr
(Compiler compiler, int opPos) static boolean
isSet
(int analysis, int bits) static boolean
isWild
(int analysis) (package private) static StepPattern
Read a LocationPath as a generalized match pattern.(package private) static AxesWalker
loadWalkers
(WalkingIterator lpi, Compiler compiler, int stepOpCodePos) This method is for building an array of possible levels where the target element(s) could be found for a match.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
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
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
walksSubtreeOnlyMaybeAbsolute
(int analysis) static boolean
walksUp
(int analysis) static boolean
walksUpOnly
(int analysis)
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Field Details
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DEBUG_PATTERN_CREATION
static final boolean DEBUG_PATTERN_CREATIONSet to true for diagnostics about walker creation- See Also:
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DEBUG_WALKER_CREATION
static final boolean DEBUG_WALKER_CREATIONSet to true for diagnostics about walker creation- See Also:
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DEBUG_ITERATOR_CREATION
static final boolean DEBUG_ITERATOR_CREATIONSet to true for diagnostics about iterator creation- See Also:
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BITS_COUNT
public static final int BITS_COUNTFirst 8 bits are the number of top-level location steps. Hopefully there will never be more that 255 location steps!!!- See Also:
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BIT_PREDICATE
public static final int BIT_PREDICATEBit is on if the expression contains a top-level predicate.- See Also:
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BIT_ANCESTOR
public static final int BIT_ANCESTORBit 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_SELFBit 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_ATTRIBUTEBit is on if any of the walkers contain an attribute step.- See Also:
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BIT_CHILD
public static final int BIT_CHILDBit is on if any of the walkers contain a child step.- See Also:
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BIT_DESCENDANT
public static final int BIT_DESCENDANTBit is on if any of the walkers contain a descendant step.- See Also:
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BIT_DESCENDANT_OR_SELF
public static final int BIT_DESCENDANT_OR_SELFBit 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_FOLLOWINGBit is on if any of the walkers contain a following step.- See Also:
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BIT_FOLLOWING_SIBLING
public static final int BIT_FOLLOWING_SIBLINGBit 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_NAMESPACEBit is on if any of the walkers contain a namespace step.- See Also:
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BIT_PARENT
public static final int BIT_PARENTBit is on if any of the walkers contain a parent step.- See Also:
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BIT_PRECEDING
public static final int BIT_PRECEDINGBit 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_SIBLINGBit is on if any of the walkers contain a preceding-sibling step.- See Also:
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BIT_SELF
public static final int BIT_SELFBit is on if any of the walkers contain a self step.- See Also:
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BIT_FILTER
public static final int BIT_FILTERBit 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_ROOTBit is on if any of the walkers contain a root step.- See Also:
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BIT_ANY_DESCENDANT_FROM_ROOT
public static final int BIT_ANY_DESCENDANT_FROM_ROOTFound "//foo" pattern- See Also:
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BIT_NODETEST_ANY
public static final int BIT_NODETEST_ANYBit is on if any of the walkers contain an node() test. This is really only useful if the count is 1.- See Also:
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BIT_MATCH_PATTERN
public static final int BIT_MATCH_PATTERNBit is on if the expression is a match pattern.- See Also:
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Constructor Details
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WalkerFactory
public WalkerFactory()
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Method Details
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loadWalkers
static AxesWalker loadWalkers(WalkingIterator lpi, Compiler compiler, int stepOpCodePos) throws TransformerException This method is for building an array of possible levels where the target element(s) could be found for a match.- Parameters:
lpi
- The owning location path iterator object.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:
- non-null AxesWalker derivative.
- Throws:
TransformerException
- if any
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isSet
public static boolean isSet(int analysis, int bits) -
diagnoseIterator
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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
- if any
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getAxisFromStep
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.
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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.
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functionProximateOrContainsProximate
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isProximateInnerExpr
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mightBeProximate
public static boolean mightBeProximate(Compiler compiler, int opPos, int stepType) throws TransformerException Tell if the predicates need to have proximity knowledge.- Throws:
TransformerException
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isOptimizableForDescendantIterator
private static boolean isOptimizableForDescendantIterator(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
- if any
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analyze
Analyze the location path and return 32 bits that give information about the location path as a whole. See the BIT_XXX constants for meaning about each of the bits.- 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
- if any
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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.
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loadSteps
Read a LocationPath as a generalized match pattern. What this means is that the LocationPath is read backwards, as a test on a given node, to see if it matches the criteria of the selection, and ends up at the context node. Essentially, this is a backwards query from a given node, to find the context node.So, the selection "foo/daz[2]" is, in non-abreviated expanded syntax, "self::node()/following-sibling::foo/child::daz[position()=2]". Taking this as a match pattern for a probable node, it works out to "self::daz/parent::foo[child::daz[position()=2 and isPrevStepNode()] precedingSibling::node()[isContextNodeOfLocationPath()]", adding magic isPrevStepNode and isContextNodeOfLocationPath operations. Predicates in the location path have to be executed by the following step, because they have to know the context of their execution.
- Parameters:
compiler
- The compiler that holds the syntax tree/op map to construct from.stepOpCodePos
- The current op code position within the opmap.- Returns:
- A StepPattern object, which may contain relative StepPatterns.
- Throws:
TransformerException
- if any
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createDefaultStepPattern
private static StepPattern createDefaultStepPattern(Compiler compiler, int opPos) throws TransformerException Create a StepPattern that is contained within a LocationPath.- Parameters:
compiler
- The compiler that holds the syntax tree/op map to construct from.- Returns:
- the head of the list.
- Throws:
TransformerException
- if any
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analyzePredicate
static boolean analyzePredicate(Compiler compiler, int opPos, int stepType) throws TransformerException Analyze a step and give information about it's predicates. Right now this just returns true or false if the step has a predicate.- Parameters:
compiler
- non-null reference to compiler object that has processed the XPath operations into an opcode map.opPos
- The opcode position for the step.stepType
- The type of step, one of OP_GROUP, etc.- Returns:
- true if step has a predicate.
- Throws:
TransformerException
- if any
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createDefaultWalker
private static AxesWalker createDefaultWalker(Compiler compiler, int opPos, WalkingIterator lpi, int analysis) Create the proper Walker from the axes type.- Parameters:
compiler
- non-null reference to compiler object that has processed the XPath operations into an opcode map.opPos
- The opcode position for the step.lpi
- The owning location path iterator.analysis
- 32 bits of analysis, from which the type of AxesWalker may be influenced.- Returns:
- non-null reference to AxesWalker derivative.
- Throws:
RuntimeException
- if the input is bad.
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getAnalysisString
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hasPredicate
public static boolean hasPredicate(int analysis) -
isWild
public static boolean isWild(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) -
walksFilteredList
public static boolean walksFilteredList(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) -
canSkipSubtrees
public static boolean canSkipSubtrees(int analysis) -
canCrissCross
public static boolean canCrissCross(int analysis) -
isNaturalDocOrder
Tell if the pattern can be 'walked' with the iteration steps in natural document order, without duplicates.- 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.analysis
- The general analysis of the pattern.- Returns:
- true if the walk can be done in natural order.
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isOneStep
public static boolean isOneStep(int analysis) -
getStepCount
public static int getStepCount(int analysis)
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