net.sf.saxon.expr

Class Atomizer

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator

public final class Atomizer
extends UnaryExpression

An Atomizer is an expression corresponding essentially to the fn:data() function: it maps a sequence by replacing nodes with their typed values

Nested Class Summary

static class
Atomizer.AtomizingFunction
Implement the mapping function.

Field Summary

Fields inherited from class net.sf.saxon.expr.UnaryExpression

operand

Fields inherited from class net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

Atomizer(Expression sequence, Configuration config)
Constructor

Method Summary

PathMap.PathMapNodeSet
addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap.
int
computeCardinality()
Determine the static cardinality of the expression
int
computeSpecialProperties()
Determine the special properties of this expression
Expression
copy()
Copy an expression.
String
displayExpressionName()
Diagnostic print of expression structure.
Item
evaluateItem(XPathContext context)
Evaluate as an Item.
static ItemType
getAtomizedItemType(Expression operand, boolean alwaysUntyped, TypeHierarchy th)
Compute the type that will result from atomizing the result of a given expression
static SequenceIterator
getAtomizingIterator(SequenceIterator base)
Get an iterator that returns the result of atomizing the sequence delivered by the supplied iterator
ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible
SequenceIterator
iterate(XPathContext context)
Iterate over the sequence of values
Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expression
simplify(ExpressionVisitor visitor)
Simplify an expression
Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

Methods inherited from class net.sf.saxon.expr.UnaryExpression

computeCardinality, computeSpecialProperties, displayExpressionName, displayOperator, equals, explain, getBaseExpression, getItemType, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString, typeCheck

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

Atomizer

public Atomizer(Expression sequence,
                Configuration config)
Constructor
Parameters:
sequence - the sequence to be atomized
config - the Configuration. Used only for optimization, may be null. Atomization is faster if it is known in advance that all nodes will be untyped.

Method Details

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Overrides:
addToPathMap in interface Expression
Parameters:
pathMap - the PathMap to which the expression should be added
pathMapNodeSet - the PathMapNodeSet to which the paths embodied in this expression should be added
Returns:
the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

computeCardinality

public int computeCardinality()
Determine the static cardinality of the expression
Overrides:
computeCardinality in interface UnaryExpression

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression
Overrides:
computeSpecialProperties in interface UnaryExpression

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

displayExpressionName

public String displayExpressionName()
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
Overrides:
displayExpressionName in interface UnaryExpression

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate as an Item. This should only be called if the Atomizer has cardinality zero-or-one, which will only be the case if the underlying expression has cardinality zero-or-one.
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface Expression

getAtomizedItemType

public static ItemType getAtomizedItemType(Expression operand,
                                           boolean alwaysUntyped,
                                           TypeHierarchy th)
Compute the type that will result from atomizing the result of a given expression
Parameters:
operand - the given expression
alwaysUntyped - true if it is known that nodes will always be untyped
th - the type hierarchy cache
Returns:
the item type of the result of evaluating the operand expression, after atomization

getAtomizingIterator

public static SequenceIterator getAtomizingIterator(SequenceIterator base)
Get an iterator that returns the result of atomizing the sequence delivered by the supplied iterator
Parameters:
base - the supplied iterator, the input to atomization
Returns:
an iterator that returns atomic values, the result of the atomization

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible
Overrides:
getItemType in interface UnaryExpression
Parameters:
th - the type hierarchy cache
Returns:
a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the result is always an atomic type, but it might be more specific.

iterate

public SequenceIterator iterate(XPathContext context)
            throws XPathException
Iterate over the sequence of values
Specified by:
iterate in interface SequenceIterable
Overrides:
iterate in interface Expression

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
            throws XPathException
Perform optimisation of an expression and its subexpressions.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:
optimize in interface UnaryExpression
Parameters:
visitor - an expression visitor
contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
Returns:
the original expression, rewritten if appropriate to optimize execution
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

simplify

public Expression simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify an expression
Overrides:
simplify in interface UnaryExpression
Parameters:
visitor - an expression visitor

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression
Overrides:
typeCheck in interface UnaryExpression