com.saxonica.xsltextn
Class MergeInstr

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.instruct.Instruction
          extended by com.saxonica.xsltextn.MergeInstr
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, TailCallReturner, InstructionInfo, Locator

public class MergeInstr
extends Instruction

See Also:
Serialized Form

Nested Class Summary
static class MergeInstr.ItemWithMergeKeys
          Inner class representing an item together with its merge keys, suitable for encapsulation as an ObjectValue.
static class MergeInstr.MergeSource
          Inner class representing one merge source
 
Field Summary
protected  Expression action
           
protected  AtomicComparer[] comparators
           
protected  MergeInstr.MergeSource[] mergeSources
           
 
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
MergeInstr(MergeInstr.MergeSource[] mSources, Expression action)
          Create the merge instruction
 
Method Summary
 void 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.
 Expression copy()
          Copy an expression.
 boolean createsNewNodes()
          Determine whether this instruction creates new nodes.
 void explain(ExpressionPresenter out)
          Diagnostic print of expression structure.
 Expression getAction()
           
 ItemOrderComparer getComparer(SortKeyDefinition[] sKeys, AtomicComparer[] comps)
           
 Expression getGroupingKey()
          Get the grouping key expression expression (the group-by or group-adjacent expression, or a PatternSponsor containing the group-starting-with or group-ending-with expression)
 int getInstructionNameCode()
          Get the namecode of the instruction for use in diagnostics
 ItemType getItemType(TypeHierarchy th)
          Get the item type of the items returned by evaluating this instruction
 MergeInstr.MergeSource[] getMergeSourceExpr()
           
 boolean hasLoopingSubexpression(Expression child)
          Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly
 SequenceIterator iterate(XPathContext context)
          Return an Iterator to iterate over the values of a sequence.
 Iterator<Expression> iterateSameFocusSubExpressions()
          Get the immediate sub-expressions of this expression that are evaluated with the same focus (context item, position, and size) as the parent expression.
 Iterator<Expression> iterateSubExpressions()
          Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
 Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
          Perform optimisation of an expression and its subexpressions.
 TailCall processLeavingTail(XPathContext context)
          ProcessLeavingTail: called to do the real work of this instruction.
 boolean replaceSubExpression(Expression original, Expression replacement)
          Replace one subexpression by a replacement subexpression
 Expression simplify(ExpressionVisitor visitor)
          Simplify an expression.
 Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
          Perform type checking of an expression and its subexpressions.
 
Methods inherited from class net.sf.saxon.expr.instruct.Instruction
assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getConstructType, getExpressionName, getImplementationMethod, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, process, promote, promoteInst
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, 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
 

Field Detail

mergeSources

protected MergeInstr.MergeSource[] mergeSources

action

protected Expression action

comparators

protected AtomicComparer[] comparators
Constructor Detail

MergeInstr

public MergeInstr(MergeInstr.MergeSource[] mSources,
                  Expression action)
Create the merge instruction

Parameters:
mSources - the set of merge source definitions
action - the action to be performed on each group of items with identical merge keys
Method Detail

getMergeSourceExpr

public MergeInstr.MergeSource[] getMergeSourceExpr()

getAction

public Expression getAction()

getInstructionNameCode

public int getInstructionNameCode()
Get the namecode of the instruction for use in diagnostics

Overrides:
getInstructionNameCode in class Instruction
Returns:
a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

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.

Overrides:
checkPermittedContents in class Expression
Parameters:
parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type
env - the static context
whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content
Throws:
XPathException - if the value delivered by this expression cannot be part of the content model of the given type

getItemType

public ItemType getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction

Overrides:
getItemType in class Instruction
Parameters:
th - the type hierarchy cache
Returns:
the static item type of the instruction

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ExpressionVisitor.ContextItemType contextItemType)
                     throws XPathException
Description copied from class: 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 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.

Overrides:
typeCheck in class Expression
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 to perform necessary run-time type checks, and to perform other type-related optimizations
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

hasLoopingSubexpression

public boolean hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly

Overrides:
hasLoopingSubexpression in class Expression
Parameters:
child - the immediate subexpression
Returns:
true if the child expression is evaluated repeatedly

createsNewNodes

public final boolean createsNewNodes()
Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).

Overrides:
createsNewNodes in class Instruction
Returns:
true if the instruction creates new nodes (or if it can't be proved that it doesn't)

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace one subexpression by a replacement subexpression

Overrides:
replaceSubExpression in class Expression
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ExpressionVisitor.ContextItemType contextItemType)
                    throws XPathException
Description copied from class: 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.

Overrides:
optimize in class Expression
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)

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Description copied from class: Instruction
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 class Instruction
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

iterateSubExpressions

public Iterator<Expression> iterateSubExpressions()
Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)

Overrides:
iterateSubExpressions in class Expression
Returns:
an iterator containing the sub-expressions of this expression

iterateSameFocusSubExpressions

public Iterator<Expression> iterateSameFocusSubExpressions()
Get the immediate sub-expressions of this expression that are evaluated with the same focus (context item, position, and size) as the parent expression.

Overrides:
iterateSameFocusSubExpressions in class Expression
Returns:
an iterator containing those sub-expressions of this expression that are evaluated with the same focus as the parent expression

getGroupingKey

public Expression getGroupingKey()
Get the grouping key expression expression (the group-by or group-adjacent expression, or a PatternSponsor containing the group-starting-with or group-ending-with expression)

Returns:
the expression used to calculate grouping keys

getComparer

public ItemOrderComparer getComparer(SortKeyDefinition[] sKeys,
                                     AtomicComparer[] comps)

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).

Specified by:
simplify in class Instruction
Parameters:
visitor - expression visitor object
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

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

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:
explain in class Expression
Parameters:
out - the expression presenter used to display the structure

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException
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 interface TailCallReturner
Specified by:
processLeavingTail in class Instruction
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


Copyright (c) 2004-2011 Saxonica Limited. All rights reserved.