net.sf.saxon.instruct

Class ForEachGroup

public class ForEachGroup extends Instruction implements ContextMappingFunction, SortKeyEvaluator

Handler for xsl:for-each-group elements in stylesheet. This is a new instruction defined in XSLT 2.0
Field Summary
static intGROUP_ADJACENT
static intGROUP_BY
static intGROUP_BY_SINGLETON
static intGROUP_ENDING
static intGROUP_STARTING
Constructor Summary
ForEachGroup(Expression select, Expression action, byte algorithm, Expression key, StringCollator collator, Expression collationNameExpression, String baseURI, SortKeyDefinition[] sortKeys)
Create a for-each-group instruction
Method Summary
PathMap.PathMapNodeSetaddToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap.
voidcheckPermittedContents(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.
intcomputeDependencies()
Compute the dependencies of an expression, as the union of the dependencies of its subexpressions.
Expressioncopy()
Copy an expression.
booleancreatesNewNodes()
Determine whether this instruction creates new nodes.
ItemevaluateSortKey(int n, XPathContext c)
Callback for evaluating the sort keys
voidexplain(ExpressionPresenter out)
Diagnostic print of expression structure.
ExpressiongetActionExpression()
Get the action expression (the content of the for-each-group)
ExpressiongetGroupingKey()
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)
intgetInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes
ItemTypegetItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction
booleanhasLoopingSubexpression(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
SequenceIteratoriterate(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)
SequenceIteratormap(XPathContext context)
Map one item to a sequence.
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
TailCallprocessLeavingTail(XPathContext context)
protected voidpromoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites.
booleanreplaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression
Expressionsimplify(ExpressionVisitor visitor)
Simplify an expression.
ExpressiontypeCheck(ExpressionVisitor visitor, ItemType contextItemType)

Field Detail

GROUP_ADJACENT

public static final int GROUP_ADJACENT

GROUP_BY

public static final int GROUP_BY

GROUP_BY_SINGLETON

public static final int GROUP_BY_SINGLETON

GROUP_ENDING

public static final int GROUP_ENDING

GROUP_STARTING

public static final int GROUP_STARTING

Constructor Detail

ForEachGroup

public ForEachGroup(Expression select, Expression action, byte algorithm, Expression key, StringCollator collator, Expression collationNameExpression, String baseURI, SortKeyDefinition[] sortKeys)
Create a for-each-group instruction

Parameters: select the select expression (selects the population to be grouped) action the body of the for-each-group (applied to each group in turn) algorithm one of group-by, group-adjacent, group-starting-with, group-ending-with key expression to evaluate the grouping key collator user for comparing strings collationNameExpression expression that yields the name of the collation to be used baseURI static base URI of the expression sortKeys list of xsl:sort keys for sorting the groups

Method Detail

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Parameters: pathMap the PathMap to which the expression should be added pathMapNodeSet

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. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

checkPermittedContents

public 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. 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.

computeDependencies

public int computeDependencies()
Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. (This is overridden for path expressions and filter expressions, where the dependencies of a subexpression are not all propogated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.

Returns: the depencies, as a bit-mask

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

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).

evaluateSortKey

public Item evaluateSortKey(int n, XPathContext c)
Callback for evaluating the sort keys

explain

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

getActionExpression

public Expression getActionExpression()
Get the action expression (the content of the for-each-group)

Returns: the body of the xsl:for-each-group instruction

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

getInstructionNameCode

public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes

Returns: the name of the instruction

getItemType

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

Parameters: th the type hierarchy cache

Returns: the static item type of the instruction

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

Parameters: child the immediate subexpression

Returns: true if the child expression is evaluated repeatedly

iterate

public SequenceIterator iterate(XPathContext context)
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 relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence.

In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.

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

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.

Returns: an iterator containing those sub-expressions of this expression that are evaluated with the same focus as the parent 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)

map

public SequenceIterator map(XPathContext context)
Map one item to a sequence.

Parameters: context The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.

Returns: either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.

optimize

public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)

processLeavingTail

public TailCall processLeavingTail(XPathContext context)

promoteInst

protected void promoteInst(PromotionOffer offer)
Handle promotion offers, that is, non-local tree rewrites.

Parameters: offer The type of rewrite being offered

Throws: XPathException

replaceSubExpression

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

Parameters: original the original subexpression replacement the replacement subexpression

Returns: true if the original subexpression is found

simplify

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

Parameters: visitor an expression visitor

Returns: the simplified expression

Throws: XPathException if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)