net.sf.saxon.functions
Class SystemFunction

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

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

Direct Known Subclasses:

Adjust, Aggregate, Available, AvailableEnvironmentVariables, BaseURI, BooleanFn, CodepointEqual, CodepointsToString, CollatingFunction, Collection, CompileTimeFunction, Component, Concat, Current, CurrentDateTime, CurrentGroup, CurrentGroupingKey, DateTimeConstructor, Doc, DocAvailable, DocumentFn, Error, EscapeURI, FilterFn, FoldLeftFn, FoldRightFn, ForceCase, FormatDate, FormatInteger, FormatNumber, FunctionArity, FunctionName, GetEnvironmentVariable, Id, Idref, InScopePrefixes, Insert, KeyFn, Lang, Last, MapFn, MapPairsFn, Matches, NamePart, NamespaceForPrefix, Nilled, NormalizeSpace, NormalizeUnicode, NumberFn, ParseXml, PartialApply, Position, Put, QNameFn, RegexGroup, Remove, Replace, ResolveQName, ResolveURI, Reverse, Root, Rounding, Serialize, SnapshotFn, StringFn, StringJoin, StringLength, StringToCodepoints, Subsequence, Substring, SystemProperty, Tokenize, Trace, Translate, TreatFn, UnparsedEntity, UnparsedText, UriCollection

public abstract class SystemFunction
extends FunctionCall

Abstract superclass for system-defined and user-defined functions

See Also:

Serialized Form

Field Summary

protected int

operation

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

argument

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

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD

Constructor Summary

SystemFunction()

Method Summary

protected void	addContextDocumentArgument(int pos, String augmentedName) Add an implicit argument referring to the context document.
PathMap.PathMapNodeSet	addDocToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodes) Add a representation of a doc() call or similar function to a PathMap.
void	checkArguments(ExpressionVisitor visitor) Method called during static type checking
int	computeCardinality() Determine the cardinality of the function.
int	computeSpecialProperties() Determine the special properties of this expression.
Expression	copy() Copy an expression.
StandardFunction.Entry	getDetails() Get the details of the function signature
String	getErrorCodeForTypeErrors() Return the error code to be used for type errors.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType(TypeHierarchy th) Determine the item type of the value returned by the function
protected SequenceType	getRequiredType(int arg) Get the required type of the nth argument
static FunctionCall	makeSystemFunction(String name, Expression[] arguments) Make a system function call (one in the standard function namespace).
Expression	optimize(ExpressionVisitor visitor, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
void	setDetails(StandardFunction.Entry entry) Set the details of this type of function
protected void	useContextItemAsDefault() Set "." as the default value for the first and only argument.

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

addExternalFunctionCallToPathMap, checkArgumentCount, equals, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

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

Field Detail

operation

protected int operation

Constructor Detail

SystemFunction

public SystemFunction()

Method Detail

makeSystemFunction

public static FunctionCall makeSystemFunction(String name,
                                              Expression[] arguments)

Make a system function call (one in the standard function namespace).

Parameters:

name - The local name of the function.

arguments - the arguments to the function call

Returns:

a FunctionCall that implements this function, if it exists, or null if the function is unknown.

setDetails

public void setDetails(StandardFunction.Entry entry)

Set the details of this type of function

Parameters:

entry - information giving details of the function signature

getDetails

public StandardFunction.Entry getDetails()

Get the details of the function signature

Returns:

information about the function signature

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

Overrides:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

checkArguments

public void checkArguments(ExpressionVisitor visitor)
                    throws XPathException

Method called during static type checking

Specified by:

checkArguments in class FunctionCall

Parameters:

visitor - the expression visitor

Throws:

XPathException

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 class FunctionCall

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)

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

getErrorCodeForTypeErrors

public String getErrorCodeForTypeErrors()

Return the error code to be used for type errors. This is overridden for functions such as exactly-one(), one-or-more(), ...

Returns:

the error code to be used for type errors in the function call. Normally XPTY0004, but different codes are used for functions such as exactly-one()

getRequiredType

protected SequenceType getRequiredType(int arg)

Get the required type of the nth argument

Parameters:

arg - the number of the argument whose type is requested, zero-based

Returns:

the required type of the argument as defined in the function signature

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the item type of the value returned by the function

Specified by:

getItemType in class Expression

Parameters:

th - the type hierarchy cache

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

computeCardinality

public int computeCardinality()

Determine the cardinality of the function.

Specified by:

computeCardinality in class Expression

Returns:

the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression. The general rule is that a system function call is non-creative if its return type is atomic, or if all its arguments are non-creative. This is overridden for the generate-id() function, which is considered creative if its operand is creative (because the result depends on the identity of the operand)

Overrides:

computeSpecialProperties in class Expression

Returns:

the special properties, as a bit-significant integer

useContextItemAsDefault

protected final void useContextItemAsDefault()

Set "." as the default value for the first and only argument. Called from subclasses.

addContextDocumentArgument

protected final void addContextDocumentArgument(int pos,
                                                String augmentedName)
                                         throws XPathException

Add an implicit argument referring to the context document. Called by functions such as id() and key() that take the context document as an implicit argument

Parameters:

pos - the position of the argument whose default value is ".", zero-based

augmentedName - the name to be used for the function call with its extra argument. There are some cases where user function calls cannot supply the argument directly (notably unparsed-entity-uri() and unparsed-entity-public-id()) and in these cases a synthesized function name is used for the new function call.

Throws:

XPathException

addDocToPathMap

public PathMap.PathMapNodeSet addDocToPathMap(PathMap pathMap,
                                              PathMap.PathMapNodeSet pathMapNodes)

Add a representation of a doc() call or similar function to a PathMap. This is a convenience method called by the addToPathMap() methods for doc(), document(), collection() and similar functions. These all create a new root expression in the path map.

Parameters:

pathMap - the PathMap to which the expression should be added

pathMapNodes - the node in the PathMap representing the focus at the point where this expression is called. Set to null if this expression appears at the top level.

Returns:

the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression