Package net.sf.saxon.expr.instruct
Class Instruction
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.instruct.Instruction
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,TailCallReturner
,InstructionInfo
,Locator
- Direct Known Subclasses:
AnalyzeString
,ApplyImports
,ApplyTemplates
,Block
,CallTemplate
,Choose
,CopyOf
,Doctype
,ForEach
,ForEachGroup
,LocalParamBlock
,LocalParamSetter
,Message
,ParentNodeConstructor
,ProcessRegexMatchInstruction
,ResultDocument
,SimpleNodeConstructor
,TraceExpression
,UseAttributeSets
Abstract superclass for all instructions in the compiled stylesheet.
This represents a compiled instruction, and as such, the minimum information is
retained from the original stylesheet.
Note: this class implements SourceLocator: that is, it can identify where in the stylesheet the source instruction was located.
Note: this class implements SourceLocator: that is, it can identify where in the stylesheet the source instruction was located.
- See Also:
-
Field Summary
Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionstatic ParameterSet
assembleParams
(XPathContext context, WithParam[] actualParams) Assemble a ParameterSet.static ParameterSet
assembleTunnelParams
(XPathContext context, WithParam[] actualParams) Assemble a ParameterSet.int
Get the cardinality of the sequence returned by evaluating this instructionint
Get the static properties of this expression (other than its type).boolean
Determine whether this instruction creates new nodes.protected static XPathException
dynamicError
(SourceLocator loc, XPathException error, XPathContext context) Construct an exception with diagnostic information.final CharSequence
evaluateAsString
(XPathContext context) Evaluate an expression as a String.evaluateItem
(XPathContext context) Evaluate an expression as a single item.int
Get the type of this expression for use in tracing and diagnosticsGet a name identifying the kind of expression, in terms meaningful to a user.int
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().Get a name identifying the kind of instruction, in terms meaningful to a user.int
Get the namecode of the instruction for use in diagnosticsGet the item type of the items returned by evaluating this instructionprotected final SequenceIterator
<? extends Item> getIteratorFromProcessMethod
(XPathContext context) Helper method to construct an iterator over the results of the expression when all that the expression itself offers is a process() method.Get a SourceLocator identifying the location of this instructionboolean
isXSLT()
Establish whether this is an XSLT instruction or an XQuery instruction (used to produce appropriate diagnostics)SequenceIterator
<? extends Item> iterate
(XPathContext context) Return an Iterator to iterate over the values of a sequence.void
process
(XPathContext context) Process the instruction, without returning any tail callsabstract TailCall
processLeavingTail
(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.promote
(PromotionOffer offer, Expression parent) Offer promotion for this subexpression.protected void
promoteInst
(PromotionOffer offer) Handle promotion offers, that is, non-local tree rewrites.abstract Expression
simplify
(ExpressionVisitor visitor) Simplify an expression.Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, copy, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, explain, getCardinality, getColumnNumber, getColumnNumber, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, iterateSubExpressions, markTailFunctionCalls, optimize, replaceSubExpression, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeCheck, typeError
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface javax.xml.transform.SourceLocator
getColumnNumber, getLineNumber, getPublicId, getSystemId
-
Constructor Details
-
Instruction
public Instruction()Constructor
-
-
Method Details
-
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 prefered. For instructions this is the process() method.- Overrides:
getImplementationMethod
in classExpression
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
-
getInstructionNameCode
public int getInstructionNameCode()Get the namecode of the instruction for use in diagnostics- Returns:
- a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace
-
getInstructionName
Get a name identifying the kind of instruction, in terms meaningful to a user. This method is not used in the case where the instruction name code is a standard name (invalid input: '<'1024).- Returns:
- a name identifying the kind of instruction, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the instruction.
-
getExpressionName
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionName
in classExpression
- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
-
getItemType
Get the item type of the items returned by evaluating this instruction- Specified by:
getItemType
in classExpression
- Parameters:
th
- the type hierarchy cache- Returns:
- the static item type of the instruction
-
computeCardinality
public int computeCardinality()Get the cardinality of the sequence returned by evaluating this instruction- Specified by:
computeCardinality
in classExpression
- Returns:
- the static cardinality
-
processLeavingTail
ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.- Specified by:
processLeavingTail
in interfaceTailCallReturner
- Parameters:
context
- The dynamic context of the transformation, giving access to the current node, the current variables, etc.- Returns:
- null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.
- Throws:
XPathException
- if a dynamic error occurs during the evaluation of the instruction
-
process
Process the instruction, without returning any tail calls- Overrides:
process
in classExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
- if a dynamic error occurs
-
getSourceLocator
Get a SourceLocator identifying the location of this instruction- Returns:
- the location of this instruction in the source stylesheet or query
-
dynamicError
protected static XPathException dynamicError(SourceLocator loc, XPathException error, XPathContext context) Construct an exception with diagnostic information. Note that this method returns the exception, it does not throw it: that is up to the caller.- Parameters:
loc
- the location of the errorerror
- The exception containing information about the errorcontext
- The controller of the transformation- Returns:
- an exception based on the supplied exception, but with location information added relating to this instruction
-
assembleParams
public static ParameterSet assembleParams(XPathContext context, WithParam[] actualParams) throws XPathException Assemble a ParameterSet. Method used by instructions that have xsl:with-param children. This method is used for the non-tunnel parameters.- Parameters:
context
- the XPath dynamic contextactualParams
- the set of with-param parameters that specify tunnel="no"- Returns:
- a ParameterSet
- Throws:
XPathException
- if an error occurs evaluating one of the parameters
-
assembleTunnelParams
public static ParameterSet assembleTunnelParams(XPathContext context, WithParam[] actualParams) throws XPathException Assemble a ParameterSet. Method used by instructions that have xsl:with-param children. This method is used for the tunnel parameters.- Parameters:
context
- the XPath dynamic contextactualParams
- the set of with-param parameters that specify tunnel="yes"- Returns:
- a ParameterSet
- Throws:
XPathException
- if an error occurs evaluating one of the tunnel parameters
-
simplify
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.- Overrides:
simplify
in classExpression
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
-
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 property bit is set, it is true, but if it is unset, the value is unknown.- Overrides:
computeSpecialProperties
in classExpression
- Returns:
- a set of flags indicating static properties of this expression
-
createsNewNodes
public boolean createsNewNodes()Determine whether this instruction creates new nodes. This implementation returns a default value of false- Returns:
- true if the instruction creates new nodes (or if it can't be proved that it doesn't)
-
promoteInst
Handle promotion offers, that is, non-local tree rewrites.- Parameters:
offer
- The type of rewrite being offered- Throws:
XPathException
- if an error occurs
-
promote
Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. This method is always called at compile time.- Overrides:
promote
in classExpression
- Parameters:
offer
- details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expressionparent
- the parent of the subexpression- Returns:
- if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
- Throws:
XPathException
- if any error is detected
-
evaluateItem
Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.- Overrides:
evaluateItem
in classExpression
- 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
-
iterate
Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.- Overrides:
iterate
in classExpression
- 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
-
getIteratorFromProcessMethod
protected final SequenceIterator<? extends Item> getIteratorFromProcessMethod(XPathContext context) throws XPathException Helper method to construct an iterator over the results of the expression when all that the expression itself offers is a process() method. This builds the entire results of the expression as a sequence in memory and then iterates over it.- Parameters:
context
- the dynamic evaluation context- Returns:
- an iterator over the results of the expression
- Throws:
XPathException
- if a dynamic error occurs
-
evaluateAsString
Evaluate an expression as a String. This function must only be called in contexts where it is known that the expression will return a single string (or where an empty sequence is to be treated as a zero-length string). Implementations should not attempt to convert the result to a string, other than converting () to "". This method is used mainly to evaluate expressions produced by compiling an attribute value template.- Overrides:
evaluateAsString
in classExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".
- Throws:
XPathException
- if any dynamic error occurs evaluating the expressionClassCastException
- if the result type of the expression is not xs:string?
-
getConstructType
public int getConstructType()Get the type of this expression for use in tracing and diagnostics- Specified by:
getConstructType
in interfaceInstructionInfo
- Overrides:
getConstructType
in classExpression
- Returns:
- the type of expression, as enumerated in class
Location
-
isXSLT
public boolean isXSLT()Establish whether this is an XSLT instruction or an XQuery instruction (used to produce appropriate diagnostics)- Returns:
- true for XSLT, false for XQuery
-