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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 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.expr;

import net.sf.saxon.om.Item;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.XPathException;

/**
 * A SequenceIterator that throws an exception as soon as its next() method is called. Used when
 * the method that returns the iterator isn't allowed to throw a checked exception itself.
 */
public class ErrorIterator implements SequenceIterator {

    private XPathException exception;

    public ErrorIterator(XPathException exception) {
        this.exception = exception;
    }

    /**
     * Get the next item in the sequence. This method changes the state of the
     * iterator, in particular it affects the result of subsequent calls of
     * position() and current().
     *
     * @return the next item, or null if there are no more items. Once a call
     *         on next() has returned null, no further calls should be made. The preferred
     *         action for an iterator if subsequent calls on next() are made is to return
     *         null again, and all implementations within Saxon follow this rule.
     * @throws net.sf.saxon.trans.XPathException
     *          if an error occurs retrieving the next item
     * @since 8.4
     */

    public Item next() throws XPathException {
        throw exception;
    }

    public void close() {

    }

    /**
     * Get another SequenceIterator that iterates over the same items as the original,
     * but which is repositioned at the start of the sequence.
     * 
     * This method allows access to all the items in the sequence without disturbing the
     * current position of the iterator. Internally, its main use is in evaluating the last()
     * function.
     * 
     * This method does not change the state of the iterator.
     *
     * @return a SequenceIterator that iterates over the same items,
     *         positioned before the first item
     * @throws net.sf.saxon.trans.XPathException
     *          if any error occurs
     * @since 8.4
     */

    /*@NotNull*/
    public ErrorIterator getAnother() throws XPathException {
        return this;
    }

    /**
     * Get properties of this iterator, as a bit-significant integer.
     *
     * @return the properties of this iterator. This will be some combination of
     *         properties such as {@link #GROUNDED}, {@link #LAST_POSITION_FINDER},
     *         and {@link #LOOKAHEAD}. It is always
     *         acceptable to return the value zero, indicating that there are no known special properties.
     *         It is acceptable for the properties of the iterator to change depending on its state.
     * @since 8.6
     */

    public int getProperties() {
        return 0;
    }

}