net.sf.saxon.functions
Class KeyFn

java.lang.Object
  extended by net.sf.saxon.expr.ComputedExpression
      extended by net.sf.saxon.expr.FunctionCall
          extended by net.sf.saxon.functions.SystemFunction
              extended by net.sf.saxon.functions.KeyFn
All Implemented Interfaces:
java.io.Serializable, javax.xml.transform.SourceLocator, Container, Expression, XSLTFunction, InstructionInfoProvider

public class KeyFn
extends SystemFunction
implements XSLTFunction

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.functions.SystemFunction
operation
 
Fields inherited from class net.sf.saxon.expr.FunctionCall
argument
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface 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).
static KeyFn internalKeyCall(NamePool pool, int fingerprint, java.lang.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
addContextDocumentArgument, computeCardinality, display, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, main, makeSystemFunction, setDetails, useContextItemAsDefault
 
Methods inherited from class net.sf.saxon.expr.FunctionCall
checkArgumentCount, getArguments, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, optimize, promote, replaceSubExpression, setArguments, setFunctionNameCode, simplifyArguments
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

KeyFn

public KeyFn()
Method Detail

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.

Specified by:
typeCheck in interface Expression
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,
                                    java.lang.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

Specified by:
simplify in interface Expression
Overrides:
simplify in class FunctionCall
Parameters:
env - the static context
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 Expression
Overrides:
iterate in class ComputedExpression
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