net.sf.saxon.functions
Class KeyFn

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.FunctionCall
          net.sf.saxon.functions.SystemFunction
              net.sf.saxon.functions.KeyFn

All Implemented Interfaces:

Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, XSLTFunction, InstructionInfoProvider

public class KeyFn
extends SystemFunction
implements XSLTFunction

See Also:

Serialized Form

Field Summary

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

KeyFn()

Method Summary

void	checkArguments(StaticContext env) Method called during static type checking
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
int	getStaticKeyFingerprint() Get the fingerprint of the key name, if known statically.
static KeyFn	internalKeyCall(NamePool pool, int fingerprint, String name, Expression value, Expression doc) Non-standard constructor to create an internal call on key() with a known key fingerprint
SequenceIterator	iterate(XPathContext context) Enumerate the results of the expression
Expression	preEvaluate(StaticContext env) preEvaluate: this method suppresses compile-time evaluation by doing nothing
Expression	simplify(StaticContext env) Simplify: add a third implicit argument, the context document
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression.

Methods inherited from class net.sf.saxon.functions.SystemFunction

computeCardinality, display, getDetails, getErrorCodeForTypeErrors, getItemType, main, makeSystemFunction, optimize, setDetails

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

getArguments, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, promote, replaceSubExpression, setArguments, setFunctionNameCode

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation

Methods inherited from class java.lang.Object

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

Constructor Detail

KeyFn

public KeyFn()

Method Detail

getStaticKeyFingerprint

public int getStaticKeyFingerprint()

Get the fingerprint of the key name, if known statically. If not known statically, return -1.

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.

Overrides:

typeCheck in class FunctionCall

Parameters:

env - the static context of the expression

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 to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

internalKeyCall

public static KeyFn internalKeyCall(NamePool pool,
                                    int fingerprint,
                                    String name,
                                    Expression value,
                                    Expression doc)

Non-standard constructor to create an internal call on key() with a known key fingerprint

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify: add a third implicit argument, the context document

Overrides:

simplify in class FunctionCall

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

checkArguments

public void checkArguments(StaticContext env)
                    throws XPathException

Description copied from class: SystemFunction

Method called during static type checking

Overrides:

checkArguments in class SystemFunction

Throws:

XPathException

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if a property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:

computeSpecialProperties in class SystemFunction

preEvaluate

public Expression preEvaluate(StaticContext env)

preEvaluate: this method suppresses compile-time evaluation by doing nothing

Overrides:

preEvaluate in class FunctionCall

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Enumerate the results of the expression

Specified by:

iterate in interface SequenceIterable

Overrides:

iterate in class Expression

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression