Class Block
- All Implemented Interfaces:
Serializable
,SourceLocator
,Container
,Expression
,TailCallReturner
,InstructionInfoProvider
- See Also:
-
Field Summary
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
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
checkPermittedContents
(SchemaType parentType, StaticContext env, boolean whole) Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.final boolean
Determine whether this instruction creates new nodes.void
display
(int level, PrintStream out, Configuration config) Diagnostic print of expression structure.static void
displayChildren
(Expression[] children, int level, Configuration config, PrintStream out) Display the children of an instruction for diagosticsfinal int
Determine the cardinality of the expressionGet the children of this instructionint
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().final ItemType
Determine the data type of the items returned by this expressioniterate
(XPathContext context) Iterate over the results of all the child expressionsGet the immediate sub-expressions of this expression.static Expression
makeBlock
(Expression e1, Expression e2) optimize
(Optimizer opt, StaticContext env, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.processLeavingTail
(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.protected void
promoteInst
(PromotionOffer offer) Handle promotion offers, that is, non-local tree rewrites.boolean
replaceSubExpression
(Expression original, Expression replacement) Replace one subexpression by a replacement subexpressionvoid
setChildren
(Expression[] children) Set the children of this instructionsimplify
(StaticContext env) Simplify an expression.typeCheck
(StaticContext env, ItemType contextItemType) Perform type checking of an expression and its subexpressions.Methods inherited from class net.sf.saxon.instruct.Instruction
appendItem, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getInstructionInfo, getInstructionNameCode, getSourceLocator, isXSLT, process, promote
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface javax.xml.transform.SourceLocator
getColumnNumber, getLineNumber, getPublicId, getSystemId
-
Constructor Details
-
Block
public Block()
-
-
Method Details
-
makeBlock
-
setChildren
Set the children of this instruction- Parameters:
children
- The instructions that are children of this instruction
-
getChildren
Get the children of this instruction- Returns:
- the children of this instruction, as an array of Instruction objects. May return either a zero-length array or null if there are no children
-
iterateSubExpressions
Description copied from class:ComputedExpression
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.- Specified by:
iterateSubExpressions
in interfaceExpression
- Overrides:
iterateSubExpressions
in classComputedExpression
- Returns:
- an iterator containing the sub-expressions of this expression
-
replaceSubExpression
Replace one subexpression by a replacement subexpression- Specified by:
replaceSubExpression
in interfaceContainer
- Overrides:
replaceSubExpression
in classComputedExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
-
getItemType
Determine the data type of the items returned by this expression- Specified by:
getItemType
in interfaceExpression
- Overrides:
getItemType
in classInstruction
- Parameters:
th
-- Returns:
- the data type
-
getCardinality
public final int getCardinality()Determine the cardinality of the expression- Specified by:
getCardinality
in interfaceExpression
- Overrides:
getCardinality
in classComputedExpression
- Returns:
- one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).
-
createsNewNodes
public final boolean createsNewNodes()Determine whether this instruction creates new nodes. This implementation returns true if any child instruction returns true.- Overrides:
createsNewNodes
in classInstruction
-
simplify
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.- Specified by:
simplify
in interfaceExpression
- Specified by:
simplify
in classInstruction
- Parameters:
env
- the static context- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
-
typeCheck
Description copied from interface:Expression
Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.
- Parameters:
env
- the static context of the expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
XPathException
-
optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException Description copied from interface:Expression
Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.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.
- Parameters:
opt
- the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.env
- the static context of the expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
XPathException
-
promoteInst
Handle promotion offers, that is, non-local tree rewrites.- Overrides:
promoteInst
in classInstruction
- Parameters:
offer
- The type of rewrite being offered- Throws:
XPathException
-
checkPermittedContents
public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.- Specified by:
checkPermittedContents
in interfaceExpression
- Overrides:
checkPermittedContents
in classComputedExpression
- Parameters:
parentType
- The schema typeenv
- the static contextwhole
- true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part- Throws:
XPathException
- if the expression doesn't match the required content type
-
display
Diagnostic print of expression structure. The expression is written to the System.err output stream- Parameters:
level
- indentation level for this expressionout
-config
-
-
displayChildren
public static void displayChildren(Expression[] children, int level, Configuration config, PrintStream out) Display the children of an instruction for diagostics -
processLeavingTail
Description copied from class:Instruction
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
- Specified by:
processLeavingTail
in classInstruction
- 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
-
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. This implementation provides both iterate() and process() methods natively.- Specified by:
getImplementationMethod
in interfaceExpression
- Overrides:
getImplementationMethod
in classInstruction
-
iterate
Iterate over the results of all the child expressions- Specified by:
iterate
in interfaceExpression
- Overrides:
iterate
in classInstruction
- 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
-