Handler for xsl:for-each-group elements in stylesheet. This is a new instruction
defined in XSLT 2.0
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.
- addToPathMap in interface Expression
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
-
- 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)
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.
- checkPermittedContents in interface Expression
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.
- computeDependencies in interface Expression
- the depencies, as a bit-mask
copy
public Expression copy()
Copy an expression. This makes a deep copy.
- copy in interface Expression
- 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).
- createsNewNodes in interface Instruction
explain
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree
is written to the supplied output destination.
- explain in interface Expression
getActionExpression
public Expression getActionExpression()
Get the action expression (the content of the for-each-group)
- 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)
- the expression used to calculate grouping keys
getInstructionNameCode
public int getInstructionNameCode()
Get the name of this instruction for diagnostic and tracing purposes
- getInstructionNameCode in interface Instruction
- the name of the instruction
getItemType
public ItemType getItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction
- getItemType in interface Instruction
th
- the type hierarchy cache
- 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
- hasLoopingSubexpression in interface Expression
child
- the immediate subexpression
- true if the child expression is evaluated repeatedly
iterate
public SequenceIterator iterate(XPathContext context)
throws XPathException
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.
- iterate in interface SequenceIterable
- iterate in interface Instruction
context
- supplies the context for evaluation
- a SequenceIterator that can be used to iterate over the result
of the expression
XPathException
- if any dynamic error occurs evaluating the
expression
iterateSubExpressions
public Iterator 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)
- iterateSubExpressions in interface Expression
map
public SequenceIterator map(XPathContext context)
throws XPathException
Map one item to a sequence.
- map in interface ContextMappingFunction
context
- The processing context. This is supplied only for mapping constructs that
set the context node, position, and size. Otherwise it is null.
- 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)
throws XPathException
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.
- optimize in interface Expression
visitor
- an expression visitorcontextItemType
- 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
- the original expression, rewritten if appropriate to optimize execution
XPathException
- if an error is discovered during this phase
(typically a type error)
processLeavingTail
public TailCall processLeavingTail(XPathContext context)
throws XPathException
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.
- processLeavingTail in interface TailCallReturner
- processLeavingTail in interface Instruction
context
- The dynamic context of the transformation, giving access to the current node,
the current variables, etc.
- 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.
replaceSubExpression
public boolean replaceSubExpression(Expression original,
Expression replacement)
Replace one subexpression by a replacement subexpression
- replaceSubExpression in interface Expression
original
- the original subexpressionreplacement
- the replacement subexpression
- true if the original subexpression is found
typeCheck
public Expression typeCheck(ExpressionVisitor visitor,
ItemType contextItemType)
throws XPathException
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.
- typeCheck in interface Expression
visitor
- an expression visitorcontextItemType
- 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
- the original expression, rewritten to perform necessary run-time type checks,
and to perform other type-related optimizations
XPathException
- if an error is discovered during this phase
(typically a type error)