Examples of org.pdf4j.saxon.om.SequenceIterator

org.pdf4j.saxon.om.SequenceIterator
A SequenceIterator is used to iterate over any XPath 2 sequence (of values or nodes). To get the next item in a sequence, call next(); if this returns null, you've reached the end of the sequence.
A SequenceIterator keeps track of the current Item and the current position. The objects returned by the SequenceIterator will always be either nodes (class NodeInfo) or singleton values (class AtomicValue): these are represented collectively by the interface Item.
This interface forms part of the public Saxon API. The JavaDoc "since" flag is used from release 8.4 onwards to indicate methods that are considered to be a stable part of the API. Methods without a "since" flag should not be regarded as a stable part of the API.
Note that the stability of this interface applies to classes that use the interface, not to classes that implement it. The interface may be extended in future to add new methods. @author Michael H. Kay @since 8.4

        // Then create a MappingIterator which applies a mapping function to each
        // item in the base sequence. The mapping function is essentially the "return"
        // expression, wrapped in a MappingAction object that is responsible also for
        // setting the range variable at each step.


        SequenceIterator base = sequence.iterate(context);
        int pslot = (positionVariable == null ? -1 : positionVariable.getLocalSlotNumber());
        MappingFunction map = new MappingAction(context, getLocalSlotNumber(), pslot, action);
        return new MappingIterator(base, map);
    }

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        // Then create an EventMappingIterator which applies a mapping function to each
        // item in the base sequence. The mapping function is essentially the "return"
        // expression, wrapped in an EventMappingAction object that is responsible also for
        // setting the range variable at each step.


        SequenceIterator base = sequence.iterate(context);
        EventMappingFunction map = new EventMappingAction(context, getLocalSlotNumber(), positionVariable, action);
        return new EventMappingIterator(base, map);
    }

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     * Process this expression as an instruction, writing results to the current
     * outputter
     */


    public void process(XPathContext context) throws XPathException {
        SequenceIterator iter = sequence.iterate(context);
        int position = 1;
        int slot = getLocalSlotNumber();
        int pslot = -1;
        if (positionVariable != null) {
            pslot = positionVariable.getLocalSlotNumber();
        }
        while (true) {
            Item item = iter.next();
            if (item == null) break;
            context.setLocalVariable(slot, item);
            if (pslot >= 0) {
                context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
            }

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     * @param context the XPath dynamic evaluation context
     * @param pul     the pending update list to which the results should be written
     */


    public void evaluatePendingUpdates(XPathContext context, PendingUpdateList pul) throws XPathException {
        SequenceIterator iter = sequence.iterate(context);
        int position = 1;
        int slot = getLocalSlotNumber();
        int pslot = -1;
        if (positionVariable != null) {
            pslot = positionVariable.getLocalSlotNumber();
        }
        while (true) {
            Item item = iter.next();
            if (item == null) break;
            context.setLocalVariable(slot, item);
            if (pslot >= 0) {
                context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
            }

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    public boolean effectiveBooleanValue(XPathContext context) throws XPathException {


        // First create an iteration of the base sequence.


        SequenceIterator base = sequence.iterate(context);


        // Now test to see if some or all of the tests are true. The same
        // logic is used for the SOME and EVERY operators


        final boolean some = (operator==Token.SOME);
        int slot = getLocalSlotNumber();
        while (true) {
            final Item it = base.next();
            if (it == null) {
                break;
            }
            context.setLocalVariable(slot, it);
            if (some == action.effectiveBooleanValue(context)) {
                base.close();
                return some;
            }
        }
        return !some;
    }

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        // iteration of the filter expression than are absolutely essential.


        // The code is almost identical to the code in ExpressionTool#effectiveBooleanValue
        // except for the handling of a numeric result


        SequenceIterator iterator = filter.iterate(filterContext);
        Item first = iterator.next();
        if (first == null) {
            return false;
        }
        if (first instanceof NodeInfo) {
            return true;
        } else {
            if (first instanceof BooleanValue) {
                if (iterator.next() != null) {
                    ExpressionTool.ebvError("sequence of two or more items starting with a boolean");
                }
                return ((BooleanValue)first).getBooleanValue();
            } else if (first instanceof StringValue) {
                if (iterator.next() != null) {
                    ExpressionTool.ebvError("sequence of two or more items starting with a string");
                }
                return (first.getStringValueCS().length()!=0);
            } else if (first instanceof Int64Value) {
                if (iterator.next() != null) {
                    ExpressionTool.ebvError("sequence of two or more items starting with a numeric value");
                }
                return ((Int64Value)first).longValue() == base.position();


            } else if (first instanceof NumericValue) {
                if (iterator.next() != null) {
                    ExpressionTool.ebvError("sequence of two or more items starting with a numeric value");
                }
                return ((NumericValue)first).compareTo(base.position()) == 0;
            } else {
                ExpressionTool.ebvError("sequence starting with an atomic value other than a boolean, number, or string");

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    */


    public SequenceIterator iterate(XPathContext context) throws XPathException {
        final XPathContextMajor cm = (XPathContextMajor)context;
        while (true) {
            SequenceIterator iter = operand.iterate(cm);
            ValueRepresentation extent = SequenceExtent.makeSequenceExtent(iter);
            UserFunction fn = cm.getTailCallFunction();
            if (fn == null) {
                return Value.asIterator(extent);
            }

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    /**
    * Evaluate the expression
    */


    public Item evaluateItem(XPathContext context) throws XPathException {
        SequenceIterator forwards = operand.iterate(context);
        if (forwards instanceof ReversibleIterator) {
            return ((ReversibleIterator)forwards).getReverseIterator().next();
        } else {
            Item current = null;
            while (true) {
                Item item = forwards.next();
                if (item == null) {
                    return current;
                }
                current = item;
            }

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        action.checkPermittedContents(parentType, env, false);
    }


    public TailCall processLeavingTail(XPathContext context) throws XPathException {
        Controller controller = context.getController();
        SequenceIterator iter = select.iterate(context);


        XPathContextMajor c2 = context.newContext();
        c2.setOrigin(this);
        c2.setCurrentIterator(iter);
        c2.setCurrentTemplateRule(null);


        if (containsTailCall) {
            if (controller.isTracing()) {
                TraceListener listener = controller.getTraceListener();
                Item item = iter.next();
                if (item == null) {
                    return null;
                }
                listener.startCurrentItem(item);
                TailCall tc = ((TailCallReturner)action).processLeavingTail(c2);
                listener.endCurrentItem(item);
                return tc;
            } else {
                Item item = iter.next();
                if (item == null) {
                    return null;
                }
                return ((TailCallReturner)action).processLeavingTail(c2);
            }
        } else {
            if (controller.isTracing()) {
                TraceListener listener = controller.getTraceListener();
                while(true) {
                    Item item = iter.next();
                    if (item == null) {
                        break;
                    }
                    listener.startCurrentItem(item);
                    action.process(c2);
                    listener.endCurrentItem(item);
                }
            } else {
                while(true) {
                    Item item = iter.next();
                    if (item == null) {
                        break;
                    }
                    action.process(c2);
                }

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     * @return a SequenceIterator that can be used to iterate over the result
     *     of the expression
     */


    public SequenceIterator iterate(XPathContext context) throws XPathException {
        SequenceIterator master = select.iterate(context);
        XPathContextMajor c2 = context.newContext();
        c2.setOrigin(this);
        c2.setCurrentTemplateRule(null);
        c2.setCurrentIterator(master);
        master = new ContextMappingIterator(this, c2);

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Related Classes of org.pdf4j.saxon.om.SequenceIterator

org.pdf4j.saxon.dom.DOMNodeList

org.pdf4j.saxon.evpull.Decomposer

org.pdf4j.saxon.expr.AtomicMappingExpression

org.pdf4j.saxon.expr.AtomicSequenceConverter

org.pdf4j.saxon.expr.CardinalityChecker

org.pdf4j.saxon.expr.CastableExpression

org.pdf4j.saxon.expr.ContextMappingIterator

org.pdf4j.saxon.expr.FilterIterator

org.pdf4j.saxon.expr.FirstItemExpression

org.pdf4j.saxon.expr.ForExpression

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