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## net.sf.saxon.instruct
Class CopyOf

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.instruct.Instruction
              net.sf.saxon.instruct.CopyOf

All Implemented Interfaces:
  java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, TailCallReturner, InstructionInfo, org.xml.sax.Locator

    public class CopyOf

extends Instruction

An xsl:copy-of element in the stylesheet.

See Also:
  Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression
`EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties`

Constructor Summary
`CopyOf(Expression select, boolean copyNamespaces, int validation, SchemaType schemaType, boolean rejectDuplicateAttributes)` Create an xsl:copy-of instruction (also used in XQuery for implicit copying)

Method Summary
`Expression` | `copy()` Copy an expression.
`boolean` | `createsNewNodes()` Determine whether this instruction creates new nodes.
`Item` | `evaluateItem(XPathContext context)` Return the first item if there is one, or null if not
`void` | `explain(ExpressionPresenter out)` Diagnostic print of expression structure.
`int` | `getCardinality()` Determine the static cardinality of the expression.
`int` | `getDependencies()` Determine which aspects of the context the expression depends on.
`int` | `getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
`int` | `getInstructionNameCode()` Get the name of this instruction, for diagnostics and tracing
`ItemType` | `getItemType(TypeHierarchy th)` Get the item type of the items returned by evaluating this instruction
`SchemaType` | `getSchemaType()` Get the schema type to be used for validation
`Expression` | `getSelectExpression()` Get the expression that selects the nodes to be copied
`int` | `getValidationMode()` Get the validation mode
`boolean` | `isCopyForUpdate()` Ask whether this instruction is creating a copy for the purpose of updating (XQuery transform expression)
`boolean` | `isCopyNamespaces()` Determine whether namespaces are to be copied or not
`boolean` | `isDocumentOrElementRequired()` Test whether this expression requires a document or element node
`SequenceIterator` | `iterate(XPathContext context)` Return an Iterator to iterate over the values of a sequence.
`java.util.Iterator` | `iterateSubExpressions()` Get the immediate sub-expressions of this expression.
`Expression` | `optimize(ExpressionVisitor visitor, ItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
`TailCall` | `processLeavingTail(XPathContext context)` Process this xsl:copy-of instruction
`protected void` | `promoteInst(PromotionOffer offer)` Handle promotion offers, that is, non-local tree rewrites.
`boolean` | `replaceSubExpression(Expression original, Expression replacement)` Replace one subexpression by a replacement subexpression
`void` | `setCopyForUpdate(boolean forUpdate)` Set whether this instruction is creating a copy for the purpose of updating (XQuery transform expression)
`void` | `setCopyLineNumbers(boolean copy)` Set whether line numbers are to be copied from the source to the result.
`void` | `setReadOnce(boolean b)` Set the "saxon:read-once" optimization mode
`void` | `setRequireDocumentOrElement(boolean requireDocumentOrElement)` For XQuery, the operand (select) must be a single element or document node.
`void` | `setStaticBaseUri(java.lang.String base)` Set the static base URI of the xsl:copy-of instruction
`Expression` | `simplify(ExpressionVisitor visitor)` Simplify an expression.
`Expression` | `typeCheck(ExpressionVisitor visitor, ItemType contextItemType)` Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.instruct.Instruction
`assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, getConstructType, getSourceLocator, isXSLT, process, promote`

Methods inherited from class net.sf.saxon.expr.Expression
`addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, findParentOf, getColumnNumber, getColumnNumber, getContainer, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, toString, typeError`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Methods inherited from interface javax.xml.transform.SourceLocator
`getColumnNumber, getLineNumber, getPublicId, getSystemId`

Constructor Detail

### CopyOf

    public CopyOf(Expression select,
                  boolean copyNamespaces,
                  int validation,
                  SchemaType schemaType,
                  boolean rejectDuplicateAttributes)

  Create an xsl:copy-of instruction (also used in XQuery for implicit copying)

  Parameters:
    `select` - expression that selects the nodes to be copied
    `copyNamespaces` - true if namespaces are to be copied
    `validation` - validation mode for the result tree
    `schemaType` - schema type for validating the result tree
    `rejectDuplicateAttributes` - true if duplicate attributes are to be rejected (XQuery). False if duplicates are handled by discarding all but the first (XSLT).

Method Detail

### getSelectExpression

    public Expression getSelectExpression()

  Get the expression that selects the nodes to be copied

  Returns:
    the select expression

### getValidationMode

    public int getValidationMode()

  Get the validation mode

  Returns:
    the validation mode

### getSchemaType

    public SchemaType getSchemaType()

  Get the schema type to be used for validation

  Returns:
    the schema type, or null if not validating against a type

### setStaticBaseUri

    public void setStaticBaseUri(java.lang.String base)

  Set the static base URI of the xsl:copy-of instruction

  Parameters:
    `base` - the static base URI

### setReadOnce

    public void setReadOnce(boolean b)

  Set the "saxon:read-once" optimization mode

  Parameters:
    `b` - true to enable the optimization

### setCopyLineNumbers

    public void setCopyLineNumbers(boolean copy)

  Set whether line numbers are to be copied from the source to the result. Default is false.

  Parameters:
    `copy` - true if line numbers are to be copied

### createsNewNodes

    public final boolean createsNewNodes()

  Determine whether this instruction creates new nodes. The result depends on the type of the select expression.

  Overrides:
    `createsNewNodes` in class `Instruction`
  Returns:
    true if the instruction creates new nodes (or if it can't be proved that it doesn't)

### getInstructionNameCode

    public int getInstructionNameCode()

  Get the name of this instruction, for diagnostics and tracing

  Overrides:
    `getInstructionNameCode` in class `Instruction`
  Returns:
    a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

### setRequireDocumentOrElement

    public void setRequireDocumentOrElement(boolean requireDocumentOrElement)

  For XQuery, the operand (select) must be a single element or document node.

  Parameters:
    `requireDocumentOrElement` - true if the argument must be a single element or document node

### isDocumentOrElementRequired

    public boolean isDocumentOrElementRequired()

  Test whether this expression requires a document or element node

  Returns:
    true if this expression requires the value of the argument to be a document or element node, false if there is no such requirement

### setCopyForUpdate

    public void setCopyForUpdate(boolean forUpdate)

  Set whether this instruction is creating a copy for the purpose of updating (XQuery transform expression)

  Parameters:
    `forUpdate` - true if this copy is being created to support an update

### isCopyForUpdate

    public boolean isCopyForUpdate()

  Ask whether this instruction is creating a copy for the purpose of updating (XQuery transform expression)

  Returns:
    true if this copy is being created to support an update

### getImplementationMethod

    public int getImplementationMethod()

  An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided. This implementation provides both iterate() and process() methods natively.

  Overrides:
    `getImplementationMethod` in class `Instruction`
  Returns:
    the implementation method, for example `Expression.ITERATE_METHOD` or `Expression.EVALUATE_METHOD` or `Expression.PROCESS_METHOD`

### isCopyNamespaces

    public boolean isCopyNamespaces()

  Determine whether namespaces are to be copied or not

  Returns:
    true if namespaces are to be copied (the default)

### copy

    public Expression copy()

  Copy an expression. This makes a deep copy.

  Specified by:
    `copy` in class `Expression`
  Returns:
    the copy of the original expression

### simplify

    public Expression simplify(ExpressionVisitor visitor)
                        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 class `Instruction`
  Parameters:
    `visitor` - an expression visitor
  Returns:
    the simplified expression
  Throws:
    `XPathException` - if an error is discovered during expression rewriting

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Description copied from class: `Instruction`
  Get the item type of the items returned by evaluating this instruction

  Overrides:
    `getItemType` in class `Instruction`
  Parameters:
    `th` - the type hierarchy cache
  Returns:
    the static item type of the instruction

### getCardinality

    public int getCardinality()

  Description copied from class: `Expression`
  Determine the static cardinality of the expression. This establishes how many items there will be in the result of the expression, at compile time (i.e., without actually evaluating the result.

  Overrides:
    `getCardinality` in class `Expression`
  Returns:
    one of the values Cardinality.ONE_OR_MORE, Cardinality.ZERO_OR_MORE, Cardinality.EXACTLY_ONE, Cardinality.ZERO_OR_ONE, Cardinality.EMPTY. This default implementation returns ZERO_OR_MORE (which effectively gives no information).

### getDependencies

    public int getDependencies()

  Description copied from class: `Expression`
  Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE. The default implementation combines the intrinsic dependencies of this expression with the dependencies of the subexpressions, computed recursively. This is overridden for expressions such as FilterExpression where a subexpression's dependencies are not necessarily inherited by the parent expression.

  Overrides:
    `getDependencies` in class `Expression`
  Returns:
    a set of bit-significant flags identifying the dependencies of the expression

### promoteInst

    protected void promoteInst(PromotionOffer offer)
                        throws XPathException

  Description copied from class: `Instruction`
  Handle promotion offers, that is, non-local tree rewrites.

  Overrides:
    `promoteInst` in class `Instruction`
  Parameters:
    `offer` - The type of rewrite being offered
  Throws:
    `XPathException`

### typeCheck

    public Expression typeCheck(ExpressionVisitor visitor,
                                ItemType contextItemType)
                         throws XPathException

  Description copied from class: `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.

  Overrides:
    `typeCheck` in class `Expression`
  Parameters:
    `visitor` - an expression visitor
    `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` - if an error is discovered during this phase (typically a type error)

### optimize

    public Expression optimize(ExpressionVisitor visitor,
                               ItemType contextItemType)
                        throws XPathException

  Description copied from class: `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.

  Overrides:
    `optimize` in class `Expression`
  Parameters:
    `visitor` - an expression visitor
    `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` - if an error is discovered during this phase (typically a type error)

### explain

    public void explain(ExpressionPresenter out)

  Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

  Specified by:
    `explain` in class `Expression`
  Parameters:
    `out` - the expression presenter used to display the structure

### iterateSubExpressions

    public java.util.Iterator iterateSubExpressions()

  Description copied from class: `Expression`
  Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

  Overrides:
    `iterateSubExpressions` in class `Expression`
  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

  Overrides:
    `replaceSubExpression` in class `Expression`
  Parameters:
    `original` - the original subexpression
    `replacement` - the replacement subexpression
  Returns:
    true if the original subexpression is found

### processLeavingTail

    public TailCall processLeavingTail(XPathContext context)
                                throws XPathException

  Process this xsl:copy-of instruction

  Specified by:
    `processLeavingTail` in interface `TailCallReturner`
  Specified by:
    `processLeavingTail` in class `Instruction`
  Parameters:
    `context` - the dynamic context for the transformation
  Returns:
    null - this implementation of the method never returns a TailCall
  Throws:
    `XPathException`

### evaluateItem

    public Item evaluateItem(XPathContext context)
                      throws XPathException

  Return the first item if there is one, or null if not

  Specified by:
    `evaluateItem` in interface `EvaluableItem`
  Overrides:
    `evaluateItem` in class `Instruction`
  Parameters:
    `context` - the XPath dynamic context
  Returns:
    the result of evaluating the instruction
  Throws:
    `XPathException`

### iterate

    public SequenceIterator iterate(XPathContext context)
                             throws XPathException

  Description copied from class: `Instruction`
  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 handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

  Specified by:
    `iterate` in interface `SequenceIterable`
  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

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Copyright (c) Saxonica Limited. All rights reserved.