net.sf.saxon.functions

Class Count

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.FunctionCall

net.sf.saxon.functions.SystemFunctionCall

net.sf.saxon.functions.FoldingFunction

net.sf.saxon.functions.Count

All Implemented Interfaces:

SourceLocator, Callable, IdentityComparable, InstructionInfo

public class Count
extends FoldingFunction

Implementation of the fn:count function

Field Summary

Fields inherited from class net.sf.saxon.functions.SystemFunctionCall

operation

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

argument

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
Count()

Method Summary

Methods

Modifier and Type	Method and Description
IntegerValue	call(XPathContext context, Sequence[] arguments) Evaluate the expression
static int	count(SequenceIterator iter) Get the number of items in a sequence identified by a SequenceIterator
Int64Value	evaluateItem(XPathContext context) Evaluate the function
ExpressionCompiler	getExpressionCompiler() Return the compiler of the Sum expression
Fold	getFold(XPathContext context, Sequence... additionalArguments) Create the Fold object which actually performs the evaluation.
int	getImplementationMethod() Get implementation method
IntegerValue[]	getIntegerBounds() For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis.
CountAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.

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

iterate

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

addContextDocumentArgument, addDocToPathMap, bindStaticContext, checkArguments, computeCardinality, computeSpecialProperties, copy, equalOrNull, equals, getContextNode, getConvertingCallable, getDefaultArgumentNode, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getItemType, getOperation, getRequiredType, makeSystemFunction, operands, setDetails, toShortString, useContextItemAsDefault

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

addExternalFunctionCallToPathMap, checkArgumentCount, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, preEvaluate, promote, replaceOperand, setArguments, setFunctionName, simplifyArguments, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getConfiguration, getConstructType, getContainer, getDependencies, getEvaluationMethod, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getObjectName, getPosture, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, setPostureAndSweep, simplify, staticTypeCheck, suppressValidation, toPattern, toStreamingPattern, typeError, unordered

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Count

public Count()

Method Detail

optimize

public Expression optimize(ExpressionVisitor visitor,
                  ContextItemStaticInfo contextItemType)
                    throws XPathException

Description copied from class: SystemFunctionCall

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 class SystemFunctionCall

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)

getImplementationMethod

public int getImplementationMethod()

Description copied from class: FoldingFunction

Get implementation method

Overrides:

getImplementationMethod in class FoldingFunction

Returns:

a value that indicates this function is capable of being streamed

getIntegerBounds

public IntegerValue[] getIntegerBounds()

For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.

Overrides:

getIntegerBounds in class Expression

Returns:

the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.

getFold

public Fold getFold(XPathContext context,
           Sequence... additionalArguments)
             throws XPathException

Create the Fold object which actually performs the evaluation. Must be implemented in every subclass.

Specified by:

getFold in class FoldingFunction

Parameters:

context - the dynamic evaluation context

additionalArguments - the values of all arguments other than the first.

Returns:

the Fold object used to compute the function

Throws:

XPathException - if a dynamic error occurs

evaluateItem

public Int64Value evaluateItem(XPathContext context)
                        throws XPathException

Evaluate the function

Overrides:

evaluateItem in class FoldingFunction

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

count

public static int count(SequenceIterator iter)
                 throws XPathException

Get the number of items in a sequence identified by a SequenceIterator

Parameters:

iter - The SequenceIterator. This method moves the current position of the supplied iterator; if this isn't safe, make a copy of the iterator first by calling getAnother(). The supplied iterator must be positioned before the first item (there must have been no call on next()).

Returns:

the number of items in the underlying sequence

Throws:

XPathException - if a failure occurs reading the input sequence

call

public IntegerValue call(XPathContext context,
                Sequence[] arguments)
                  throws XPathException

Evaluate the expression

Specified by:

call in interface Callable

Overrides:

call in class FoldingFunction

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as Sequences

Returns:

the result of the evaluation, in the form of a Sequence

Throws:

XPathException - if a dynamic error occurs during the evaluation of the expression

getStreamingAdjunct

public CountAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class FoldingFunction

Returns:

the relevant StreamingAdjunct, or null if none is available

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the Sum expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler