net.sf.saxon.instruct
Class GeneralVariable

java.lang.Object
  extended bynet.sf.saxon.expr.ComputedExpression
      extended bynet.sf.saxon.instruct.Instruction
          extended bynet.sf.saxon.instruct.GeneralVariable
All Implemented Interfaces:
Binding, Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator
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:
Serialized Form

Field Summary
protected  int nameCode
           
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
GeneralVariable()
           
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Perform static analysis of an expression and its subexpressions.
 void display(int level, NamePool pool, java.io.PrintStream out)
          Diagnostic print of expression structure.
 Item evaluateItem(XPathContext context)
          Evaluate an expression as a single item.
 int getCardinality()
          Get the cardinality of the result of this instruction.
 int getInstructionNameCode()
          Get the namecode of the instruction for use in diagnostics
 ItemType getItemType()
          Get the type of the result of this instruction.
 int getNameCode()
           
 SequenceType getRequiredType()
           
 Expression getSelectExpression()
           
 ValueRepresentation getSelectValue(XPathContext context)
          Evaluate the variable.
 int getSlotNumber()
           
 int getVariableFingerprint()
          Get the name of the variable (as a NamePool fingerprint)
 java.lang.String getVariableName()
           
 void init(Expression select, int nameCode)
           
 boolean isAssignable()
          Test whether it is permitted to assign to the variable using the saxon:assign extension element.
 boolean isGlobal()
          Indicate whether the binding is local or global.
 boolean isRequiredParam()
           
 boolean isTunnelParam()
           
 SequenceIterator iterate(XPathContext context)
          Return an Iterator to iterate over the values of a sequence.
 java.util.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)
protected  void promoteInst(PromotionOffer offer)
          Handle promotion offers, that is, non-local tree rewrites.
 void setAssignable(boolean assignable)
           
 void setNameCode(int nameCode)
           
 void setRequiredParam(boolean requiredParam)
           
 void setRequiredType(SequenceType required)
           
 void setSelectExpression(Expression select)
           
 void setSlotNumber(int s)
           
 void setTunnel(boolean tunnel)
           
 void setVariableName(java.lang.String s)
           
 Expression simplify(StaticContext env)
          Simplify an expression.
 
Methods inherited from class net.sf.saxon.instruct.Instruction
appendItem, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, createsNewNodes, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getImplementationMethod, getInstructionInfo, getSourceLocator, isXSLT, process, processLeavingTail, promote
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, dynamicError, getColumnNumber, getConstructType, getDependencies, getExecutable, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, typeError, typeError
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface net.sf.saxon.expr.Binding
evaluateVariable
 
Methods inherited from interface javax.xml.transform.SourceLocator
getColumnNumber, getLineNumber, getPublicId, getSystemId
 

Field Detail

nameCode

protected int nameCode
Constructor Detail

GeneralVariable

public GeneralVariable()
Method Detail

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)

setTunnel

public void setTunnel(boolean tunnel)

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.


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()
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
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

isRequiredParam

public final boolean isRequiredParam()

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
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

analyze

public Expression analyze(StaticContext env,
                          ItemType contextItemType)
                   throws XPathException
Description copied from class: Instruction
Perform static analysis 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 will only be accurately known if they have been explicitly declared.

Specified by:
analyze in interface Expression
Specified by:
analyze in class Instruction
Parameters:
env - the static context of the expression
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)

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 java.util.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

display

public void display(int level,
                    NamePool pool,
                    java.io.PrintStream out)
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 -
pool - NamePool used to expand any names appearing in the expression

getSlotNumber

public int getSlotNumber()

setSlotNumber

public void setSlotNumber(int s)

setVariableName

public void setVariableName(java.lang.String s)

getVariableName

public java.lang.String getVariableName()