net.sf.saxon.instruct

Class UseAttributeSets

public class UseAttributeSets extends Instruction

This instruction corresponds to a use-attribute-sets attribute on a literal result element, xsl:element, or xsl:copy.
Constructor Summary
UseAttributeSets(AttributeSet[] sets)
Method Summary
voiddisplay(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure.
ItemTypegetItemType(TypeHierarchy th)
Get the item type of the items returned by evaluating this instruction
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
TailCallprocessLeavingTail(XPathContext context)
ProcessLeavingTail: called to do the real work of this instruction.
Expressionsimplify(StaticContext env)
Simplify an expression.
ExpressiontypeCheck(StaticContext env, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.

Constructor Detail

UseAttributeSets

public UseAttributeSets(AttributeSet[] sets)

Method Detail

display

public void display(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure. The expression is written to the System.err output stream

Parameters: level indentation level for this expression pool NamePool used to expand any names appearing in the expression out Output destination

getItemType

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

Parameters: th

Returns: the static item type of the instruction

optimize

public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.

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 expression 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 ITEM_TYPE

Returns: the original expression, rewritten if appropriate to optimize execution

Throws: net.sf.saxon.trans.StaticError if an error is discovered during this phase (typically a type error)

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
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.

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.

simplify

public Expression simplify(StaticContext env)
Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.

Returns: the simplified expression

Throws: net.sf.saxon.trans.XPathException if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.

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.

Parameters: env the static context of the expression 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 ITEM_TYPE

Returns: the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws: net.sf.saxon.trans.StaticError if an error is discovered during this phase (typically a type error)