Class GeneralVariable

All Implemented Interfaces:
Serializable, SourceLocator, Binding, Container, Expression, TailCallReturner, InstructionInfoProvider
Direct Known Subclasses:
Assign, GlobalVariable, LocalParam, LocalVariable, SQLColumn.ColumnInstruction, WithParam

public abstract class GeneralVariable extends Instruction implements Binding
This class defines common behaviour across xsl:variable, xsl:param, and xsl:with-param; also saxon:assign
See Also:
  • Field Details

    • select

      Expression select
    • nameCode

      protected int nameCode
    • requiredType

      SequenceType requiredType
    • slotNumber

      protected int slotNumber
    • referenceCount

      protected int referenceCount
    • evaluationMode

      protected int evaluationMode
  • Constructor Details

    • GeneralVariable

      public GeneralVariable()
  • Method Details

    • init

      public void init(Expression select, int nameCode)
    • setSelectExpression

      public void setSelectExpression(Expression select)
    • getSelectExpression

      public Expression getSelectExpression()
    • setRequiredType

      public void setRequiredType(SequenceType required)
    • getRequiredType

      public SequenceType getRequiredType()
    • setNameCode

      public void setNameCode(int nameCode)
    • getNameCode

      public int getNameCode()
    • setAssignable

      public void setAssignable(boolean assignable)
    • setRequiredParam

      public void setRequiredParam(boolean requiredParam)
    • setImplicitlyRequiredParam

      public void setImplicitlyRequiredParam(boolean requiredParam)
    • setTunnel

      public void setTunnel(boolean tunnel)
    • setReferenceCount

      public void setReferenceCount(int refCount)
    • isAssignable

      public final boolean isAssignable()
      Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be true if the extra attribute saxon:assignable="yes" is present.
      Specified by:
      isAssignable in interface Binding
    • getVariableFingerprint

      public int getVariableFingerprint()
      Get the name of the variable (as a NamePool fingerprint)
      Returns:
      the NamePool fingerprint of the variable's expanded name.
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Get the type of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.
      Specified by:
      getItemType in interface Expression
      Overrides:
      getItemType in class Instruction
      Parameters:
      th -
      Returns:
      the empty type.
    • getCardinality

      public int getCardinality()
      Get the cardinality of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.
      Specified by:
      getCardinality in interface Expression
      Overrides:
      getCardinality in class ComputedExpression
      Returns:
      the empty cardinality.
    • isGlobal

      public boolean isGlobal()
      Description copied from interface: Binding
      Indicate whether the binding is local or global. A global binding is one that has a fixed value for the life of a query or transformation; any other binding is local.
      Specified by:
      isGlobal in interface Binding
    • getLocalSlotNumber

      public int getLocalSlotNumber()
      If this is a local variable held on the local stack frame, return the corresponding slot number. In other cases, return -1.
      Specified by:
      getLocalSlotNumber in interface Binding
    • isRequiredParam

      public final boolean isRequiredParam()
    • isImplicitlyRequiredParam

      public final boolean isImplicitlyRequiredParam()
    • isTunnelParam

      public final boolean isTunnelParam()
    • getInstructionNameCode

      public int getInstructionNameCode()
      Description copied from class: Instruction
      Get the namecode of the instruction for use in diagnostics
      Overrides:
      getInstructionNameCode in class Instruction
    • simplify

      public Expression simplify(StaticContext env) throws XPathException
      Description copied from class: Instruction
      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 interface Expression
      Specified by:
      simplify in class Instruction
      Parameters:
      env - the static context
      Returns:
      the simplified expression
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      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.

      Specified by:
      typeCheck in interface Expression
      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 Type.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.

      Specified by:
      optimize in interface Expression
      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 Type.ITEM_TYPE
      Returns:
      the original expression, rewritten if appropriate to optimize execution
      Throws:
      XPathException
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
      Specified by:
      evaluateItem in interface Expression
      Overrides:
      evaluateItem in class Instruction
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • 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.
      Specified by:
      iterate in interface Expression
      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
    • getSelectValue

      public ValueRepresentation getSelectValue(XPathContext context) throws XPathException
      Evaluate the variable. That is, get the value of the select expression if present or the content of the element otherwise, either as a tree or as a sequence
      Throws:
      XPathException
    • promoteInst

      protected void promoteInst(PromotionOffer offer) throws XPathException
      Handle promotion offers, that is, non-local tree rewrites.
      Overrides:
      promoteInst in class Instruction
      Parameters:
      offer - The type of rewrite being offered
      Throws:
      XPathException
    • 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)
      Specified by:
      iterateSubExpressions in interface Expression
      Overrides:
      iterateSubExpressions in class ComputedExpression
      Returns:
      an iterator containing the sub-expressions of this expression
    • replaceSubExpression

      public boolean replaceSubExpression(Expression original, Expression replacement)
      Replace one subexpression by a replacement subexpression
      Specified by:
      replaceSubExpression in interface Container
      Overrides:
      replaceSubExpression in class ComputedExpression
      Parameters:
      original - the original subexpression
      replacement - the replacement subexpression
      Returns:
      true if the original subexpression is found
    • display

      public void display(int level, PrintStream out, Configuration config)
      Diagnostic print of expression structure. The expression is written to the System.err output stream
      Specified by:
      display in interface Expression
      Parameters:
      level - indentation level for this expression
      out -
      config -
    • getSlotNumber

      public int getSlotNumber()
    • setSlotNumber

      public void setSlotNumber(int s)
    • setVariableName

      public void setVariableName(String s)
    • getVariableName

      public String getVariableName()