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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.sxpath;
import net.sf.saxon.expr.Binding;
import net.sf.saxon.expr.BindingReference;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.value.IntegerValue;
import net.sf.saxon.value.SequenceType;
/**
* An object representing an XPath variable for use in the standalone XPath API. The object
* can only be created by calling the declareVariable method of class {@link IndependentContext}.
* Note that once declared, this object is thread-safe: it does not hold the actual variable
* value, which means it can be used with any number of evaluations of a given XPath expression,
* in series or in parallel.
*
* A variable can be given a value by calling
* {@link XPathDynamicContext#setVariable(XPathVariable, net.sf.saxon.om.Sequence)}.
* Note that the value of the variable is not held in the XPathVariable object, but in the
* XPathDynamicContext, which means that the XPathVariable itself can be used in multiple threads.
*/
public final class XPathVariable implements Binding {
private StructuredQName name;
private SequenceType requiredType = SequenceType.ANY_SEQUENCE;
private Sequence defaultValue;
private int slotNumber;
/**
* Private constructor: for use only by the protected factory method make()
*/
private XPathVariable() {}
/**
* Factory method, for use by the declareVariable method of class IndependentContext
* @param name the name of the variable to create
* @return the constructed XPathVariable
*/
protected static XPathVariable make(StructuredQName name) {
XPathVariable v = new XPathVariable();
v.name = name;
return v;
}
/**
* Ask 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. An XPath
* variable is treated as a local variable (largely because it is held on the stack frame)
* @return false (always)
*/
public boolean isGlobal() {
return false;
}
/**
* Test whether it is permitted to assign to the variable using the saxon:assign
* extension element. This will only be for an XSLT global variable where the extra
* attribute saxon:assignable="yes" is present.
* @return false (always)
*/
public final boolean isAssignable() {
return false;
}
/**
* Set the required type of this variable. If no required type is specified,
* the type item()* is assumed.
* @param requiredType the required type
*/
public void setRequiredType(SequenceType requiredType) {
this.requiredType = requiredType;
}
/**
* Get the required type of this variable. If no required type has been specified,
* the type item()* is returned.
* @return the required type of the variable
*/
public SequenceType getRequiredType() {
return requiredType;
}
/**
* If the variable is bound to an integer, get the minimum and maximum possible values.
* Return null if unknown or not applicable
*/
/*@Nullable*/ public IntegerValue[] getIntegerBoundsForVariable() {
return null;
}
/**
* Set the slot number allocated to this variable. This method is for internal use.
* @param slotNumber the slot number to be allocated
*/
public void setSlotNumber(int slotNumber) {
this.slotNumber = slotNumber;
}
/**
* If this is a local variable held on the local stack frame, return the corresponding slot number.
* In other cases, return -1.
*/
public int getLocalSlotNumber() {
return slotNumber;
}
/**
* Get the name of the variable as a QNameValue.
* @return the name of the variable, as a QNameValue
*/
public StructuredQName getVariableQName() {
return name;
}
public void addReference(boolean isLoopingReference) {
}
/**
* Method called by the XPath expression parser to register a reference to this variable.
* This method should not be called by users of the API.
*/
public void registerReference(BindingReference ref) {
ref.setStaticType(requiredType, null, 0);
ref.fixup(this);
}
/**
* Set a default value for the variable, to be used if no specific value is
* supplied when the expression is evaluated
* @param defaultValue the default value for the variable
*/
public void setDefaultValue(Sequence defaultValue) {
this.defaultValue = defaultValue;
}
/**
* Get the default value of the variable
* @return the default value if one has been registered, or null otherwise
*/
public Sequence getDefaultValue() {
return defaultValue;
}
/**
* Get the value of the variable. This method is used by the XPath execution engine
* to retrieve the value. Note that the value is not held within the variable itself,
* but within the dynamic context.
* @param context The dynamic evaluation context
* @return The value of the variable
*/
public Sequence evaluateVariable(XPathContext context) {
return context.evaluateLocalVariable(slotNumber);
}
}