/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xerces" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 2002, International
 * Business Machines, Inc., http://www.apache.org.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

package com.sun.org.apache.xerces.internal.impl;

import java.io.IOException;

import com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidatorFilter;
import com.sun.org.apache.xerces.internal.impl.msg.XMLMessageFormatter;
import com.sun.org.apache.xerces.internal.util.XMLAttributesImpl;
import com.sun.org.apache.xerces.internal.util.XMLSymbols;
import com.sun.org.apache.xerces.internal.xni.NamespaceContext;
import com.sun.org.apache.xerces.internal.xni.QName;
import com.sun.org.apache.xerces.internal.xni.XMLDocumentHandler;
import com.sun.org.apache.xerces.internal.xni.XNIException;
import com.sun.org.apache.xerces.internal.xni.parser.XMLComponentManager;
import com.sun.org.apache.xerces.internal.xni.parser.XMLConfigurationException;
import com.sun.org.apache.xerces.internal.xni.parser.XMLDocumentSource;

/**
 * The scanner acts as the source for the document
 * information which is communicated to the document handler.
 *
 * This class scans an XML document, checks if document has a DTD, and if
 * DTD is not found the scanner will remove the DTD Validator from the pipeline and perform
 * namespace binding.
 *
 * Note: This scanner should only be used when the namespace processing is on!
 *
 * <p>
 * This component requires the following features and properties from the
 * component manager that uses it:
 * <ul>
 *  <li>http://xml.org/sax/features/namespaces {true} -- if the value of this
 *      feature is set to false this scanner must not be used.</li>
 *  <li>http://xml.org/sax/features/validation</li>
 *  <li>http://apache.org/xml/features/nonvalidating/load-external-dtd</li>
 *  <li>http://apache.org/xml/features/scanner/notify-char-refs</li>
 *  <li>http://apache.org/xml/features/scanner/notify-builtin-refs</li>
 *  <li>http://apache.org/xml/properties/internal/symbol-table</li>
 *  <li>http://apache.org/xml/properties/internal/error-reporter</li>
 *  <li>http://apache.org/xml/properties/internal/entity-manager</li>
 *  <li>http://apache.org/xml/properties/internal/dtd-scanner</li>
 * </ul>
 *
 * @author Elena Litani, IBM
 * @author Michael Glavassevich, IBM
 * 
 * @version $Id: XML11NSDocumentScannerImpl.java,v 1.11 2004/04/30 15:36:38 mrglavas Exp $
 */
public class XML11NSDocumentScannerImpl extends XML11DocumentScannerImpl {

    /** 
     * If is true, the dtd validator is no longer in the pipeline
     * and the scanner should bind namespaces 
     */
    protected boolean fBindNamespaces;

    /** 
     * If validating parser, make sure we report an error in the
     *  scanner if DTD grammar is missing.
     */
    protected boolean fPerformValidation;

    // private data
    //

    /** DTD validator */
    private XMLDTDValidatorFilter fDTDValidator;
    
    /** 
     * Saw spaces after element name or between attributes.
     * 
     * This is reserved for the case where scanning of a start element spans
     * several methods, as is the case when scanning the start of a root element 
     * where a DTD external subset may be read after scanning the element name.
     */
    private boolean fSawSpace;

    /**
     * The scanner is responsible for removing DTD validator
     * from the pipeline if it is not needed.
     * 
     * @param validator the DTD validator from the pipeline
     */
    public void setDTDValidator(XMLDTDValidatorFilter validator) {
        fDTDValidator = validator;
    }

    /**
     * Scans a start element. This method will handle the binding of
     * namespace information and notifying the handler of the start
     * of the element.
     * <p>
     * <pre>
     * [44] EmptyElemTag ::= '<' Name (S Attribute)* S? '/>'
     * [40] STag ::= '<' Name (S Attribute)* S? '>'
     * </pre>
     * <p>
     * <strong>Note:</strong> This method assumes that the leading
     * '<' character has been consumed.
     * <p>
     * <strong>Note:</strong> This method uses the fElementQName and
     * fAttributes variables. The contents of these variables will be
     * destroyed. The caller should copy important information out of
     * these variables before calling this method.
     *
     * @return True if element is empty. (i.e. It matches
     *          production [44].
     */
    protected boolean scanStartElement() throws IOException, XNIException {
        if (DEBUG_CONTENT_SCANNING)
            System.out.println(">>> scanStartElementNS()");

        // Note: namespace processing is on by default
        fEntityScanner.scanQName(fElementQName);
        // REVISIT - [Q] Why do we need this local variable? -- mrglavas
        String rawname = fElementQName.rawname;
        if (fBindNamespaces) {
            fNamespaceContext.pushContext();
            if (fScannerState == SCANNER_STATE_ROOT_ELEMENT) {
                if (fPerformValidation) {
                    fErrorReporter.reportError(
                        XMLMessageFormatter.XML_DOMAIN,
                        "MSG_GRAMMAR_NOT_FOUND",
                        new Object[] { rawname },
                        XMLErrorReporter.SEVERITY_ERROR);

                    if (fDoctypeName == null
                        || !fDoctypeName.equals(rawname)) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XML_DOMAIN,
                            "RootElementTypeMustMatchDoctypedecl",
                            new Object[] { fDoctypeName, rawname },
                            XMLErrorReporter.SEVERITY_ERROR);
                    }
                }
            }
        }

        // push element stack
        fCurrentElement = fElementStack.pushElement(fElementQName);

        // attributes
        boolean empty = false;
        fAttributes.removeAllAttributes();
        do {
            // spaces
            boolean sawSpace = fEntityScanner.skipSpaces();

            // end tag?
            int c = fEntityScanner.peekChar();
            if (c == '>') {
                fEntityScanner.scanChar();
                break;
            } else if (c == '/') {
                fEntityScanner.scanChar();
                if (!fEntityScanner.skipChar('>')) {
                    reportFatalError(
                        "ElementUnterminated",
                        new Object[] { rawname });
                }
                empty = true;
                break;
            } else if (!isValidNameStartChar(c) || !sawSpace) {
                // Second chance. Check if this character is a high
                // surrogate of a valid name start character.
                if (!isValidNameStartHighSurrogate(c) || !sawSpace) {
                    reportFatalError(
                        "ElementUnterminated",
                        new Object[] { rawname });
                }
            }

            // attributes
            scanAttribute(fAttributes);

        } while (true);

        if (fBindNamespaces) {
            // REVISIT: is it required? forbit xmlns prefix for element
            if (fElementQName.prefix == XMLSymbols.PREFIX_XMLNS) {
                fErrorReporter.reportError(
                    XMLMessageFormatter.XMLNS_DOMAIN,
                    "ElementXMLNSPrefix",
                    new Object[] { fElementQName.rawname },
                    XMLErrorReporter.SEVERITY_FATAL_ERROR);
            }

            // bind the element
            String prefix =
                fElementQName.prefix != null
                    ? fElementQName.prefix
                    : XMLSymbols.EMPTY_STRING;
            // assign uri to the element
            fElementQName.uri = fNamespaceContext.getURI(prefix);
            // make sure that object in the element stack is updated as well
            fCurrentElement.uri = fElementQName.uri;

            if (fElementQName.prefix == null && fElementQName.uri != null) {
                fElementQName.prefix = XMLSymbols.EMPTY_STRING;
                // making sure that the object in the element stack is updated too.
                fCurrentElement.prefix = XMLSymbols.EMPTY_STRING;
            }
            if (fElementQName.prefix != null && fElementQName.uri == null) {
                fErrorReporter.reportError(
                    XMLMessageFormatter.XMLNS_DOMAIN,
                    "ElementPrefixUnbound",
                    new Object[] {
                        fElementQName.prefix,
                        fElementQName.rawname },
                    XMLErrorReporter.SEVERITY_FATAL_ERROR);
            }

            // bind attributes (xmlns are already bound bellow)
            int length = fAttributes.getLength();
            for (int i = 0; i < length; i++) {
                fAttributes.getName(i, fAttributeQName);

                String aprefix =
                    fAttributeQName.prefix != null
                        ? fAttributeQName.prefix
                        : XMLSymbols.EMPTY_STRING;
                String uri = fNamespaceContext.getURI(aprefix);
                // REVISIT: try removing the first "if" and see if it is faster.
                //
                if (fAttributeQName.uri != null
                    && fAttributeQName.uri == uri) {
                    continue;
                }
                if (aprefix != XMLSymbols.EMPTY_STRING) {
                    fAttributeQName.uri = uri;
                    if (uri == null) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "AttributePrefixUnbound",
                            new Object[] {
                                fElementQName.rawname,
                                fAttributeQName.rawname,
                                aprefix },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    }
                    fAttributes.setURI(i, uri);
                }
            }

            if (length > 1) {
                QName name = fAttributes.checkDuplicatesNS();
                if (name != null) {
                    if (name.uri != null) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "AttributeNSNotUnique",
                            new Object[] {
                                fElementQName.rawname,
                                name.localpart,
                                name.uri },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    } else {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "AttributeNotUnique",
                            new Object[] {
                                fElementQName.rawname,
                                name.rawname },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    }
                }
            }
        }

        // call handler
        if (fDocumentHandler != null) {
            if (empty) {

                //decrease the markup depth..
                fMarkupDepth--;

                // check that this element was opened in the same entity
                if (fMarkupDepth < fEntityStack[fEntityDepth - 1]) {
                    reportFatalError(
                        "ElementEntityMismatch",
                        new Object[] { fCurrentElement.rawname });
                }

                fDocumentHandler.emptyElement(fElementQName, fAttributes, null);

                if (fBindNamespaces) {
                    fNamespaceContext.popContext();
                }
                //pop the element off the stack..
                fElementStack.popElement(fElementQName);
            } else {
                fDocumentHandler.startElement(fElementQName, fAttributes, null);
            }
        }

        if (DEBUG_CONTENT_SCANNING)
            System.out.println("<<< scanStartElement(): " + empty);
        return empty;

    } // scanStartElement():boolean
    
    /**
     * Scans the name of an element in a start or empty tag. 
     * 
     * @see #scanStartElement()
     */
    protected void scanStartElementName ()
        throws IOException, XNIException {
        // Note: namespace processing is on by default
        fEntityScanner.scanQName(fElementQName);
        // Must skip spaces here because the DTD scanner
        // would consume them at the end of the external subset.
        fSawSpace = fEntityScanner.skipSpaces();
    } // scanStartElementName()
    
    /**
     * Scans the remainder of a start or empty tag after the element name.
     * 
     * @see #scanStartElement
     * @return True if element is empty.
     */    
    protected boolean scanStartElementAfterName()
        throws IOException, XNIException {

        // REVISIT - [Q] Why do we need this local variable? -- mrglavas
        String rawname = fElementQName.rawname;
        if (fBindNamespaces) {
            fNamespaceContext.pushContext();
            if (fScannerState == SCANNER_STATE_ROOT_ELEMENT) {
                if (fPerformValidation) {
                    fErrorReporter.reportError(
                        XMLMessageFormatter.XML_DOMAIN,
                        "MSG_GRAMMAR_NOT_FOUND",
                        new Object[] { rawname },
                        XMLErrorReporter.SEVERITY_ERROR);

                    if (fDoctypeName == null
                        || !fDoctypeName.equals(rawname)) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XML_DOMAIN,
                            "RootElementTypeMustMatchDoctypedecl",
                            new Object[] { fDoctypeName, rawname },
                            XMLErrorReporter.SEVERITY_ERROR);
                    }
                }
            }
        }

        // push element stack
        fCurrentElement = fElementStack.pushElement(fElementQName);

        // attributes
        boolean empty = false;
        fAttributes.removeAllAttributes();
        do {
        	
            // end tag?
            int c = fEntityScanner.peekChar();
            if (c == '>') {
                fEntityScanner.scanChar();
                break;
            } else if (c == '/') {
                fEntityScanner.scanChar();
                if (!fEntityScanner.skipChar('>')) {
                    reportFatalError(
                        "ElementUnterminated",
                        new Object[] { rawname });
                }
                empty = true;
                break;
            } else if (!isValidNameStartChar(c) || !fSawSpace) {
                // Second chance. Check if this character is a high
                // surrogate of a valid name start character.
                if (!isValidNameStartHighSurrogate(c) || !fSawSpace) {
                    reportFatalError(
                        "ElementUnterminated",
                        new Object[] { rawname });
                }
            }

            // attributes
            scanAttribute(fAttributes);
            
            // spaces
            fSawSpace = fEntityScanner.skipSpaces();

        } while (true);

        if (fBindNamespaces) {
            // REVISIT: is it required? forbit xmlns prefix for element
            if (fElementQName.prefix == XMLSymbols.PREFIX_XMLNS) {
                fErrorReporter.reportError(
                    XMLMessageFormatter.XMLNS_DOMAIN,
                    "ElementXMLNSPrefix",
                    new Object[] { fElementQName.rawname },
                    XMLErrorReporter.SEVERITY_FATAL_ERROR);
            }

            // bind the element
            String prefix =
                fElementQName.prefix != null
                    ? fElementQName.prefix
                    : XMLSymbols.EMPTY_STRING;
            // assign uri to the element
            fElementQName.uri = fNamespaceContext.getURI(prefix);
            // make sure that object in the element stack is updated as well
            fCurrentElement.uri = fElementQName.uri;

            if (fElementQName.prefix == null && fElementQName.uri != null) {
                fElementQName.prefix = XMLSymbols.EMPTY_STRING;
                // making sure that the object in the element stack is updated too.
                fCurrentElement.prefix = XMLSymbols.EMPTY_STRING;
            }
            if (fElementQName.prefix != null && fElementQName.uri == null) {
                fErrorReporter.reportError(
                    XMLMessageFormatter.XMLNS_DOMAIN,
                    "ElementPrefixUnbound",
                    new Object[] {
                        fElementQName.prefix,
                        fElementQName.rawname },
                    XMLErrorReporter.SEVERITY_FATAL_ERROR);
            }

            // bind attributes (xmlns are already bound bellow)
            int length = fAttributes.getLength();
            for (int i = 0; i < length; i++) {
                fAttributes.getName(i, fAttributeQName);

                String aprefix =
                    fAttributeQName.prefix != null
                        ? fAttributeQName.prefix
                        : XMLSymbols.EMPTY_STRING;
                String uri = fNamespaceContext.getURI(aprefix);
                // REVISIT: try removing the first "if" and see if it is faster.
                //
                if (fAttributeQName.uri != null
                    && fAttributeQName.uri == uri) {
                    continue;
                }
                if (aprefix != XMLSymbols.EMPTY_STRING) {
                    fAttributeQName.uri = uri;
                    if (uri == null) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "AttributePrefixUnbound",
                            new Object[] {
                                fElementQName.rawname,
                                fAttributeQName.rawname,
                                aprefix },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    }
                    fAttributes.setURI(i, uri);
                }
            }

            if (length > 1) {
                QName name = fAttributes.checkDuplicatesNS();
                if (name != null) {
                    if (name.uri != null) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "AttributeNSNotUnique",
                            new Object[] {
                                fElementQName.rawname,
                                name.localpart,
                                name.uri },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    } else {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "AttributeNotUnique",
                            new Object[] {
                                fElementQName.rawname,
                                name.rawname },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    }
                }
            }
        }

        // call handler
        if (fDocumentHandler != null) {
            if (empty) {

                //decrease the markup depth..
                fMarkupDepth--;

                // check that this element was opened in the same entity
                if (fMarkupDepth < fEntityStack[fEntityDepth - 1]) {
                    reportFatalError(
                        "ElementEntityMismatch",
                        new Object[] { fCurrentElement.rawname });
                }

                fDocumentHandler.emptyElement(fElementQName, fAttributes, null);

                if (fBindNamespaces) {
                    fNamespaceContext.popContext();
                }
                //pop the element off the stack..
                fElementStack.popElement(fElementQName);
            } else {
                fDocumentHandler.startElement(fElementQName, fAttributes, null);
            }
        }

        if (DEBUG_CONTENT_SCANNING)
            System.out.println("<<< scanStartElementAfterName(): " + empty);
        return empty;
        
    } // scanStartElementAfterName()

    /**
     * Scans an attribute.
     * <p>
     * <pre>
     * [41] Attribute ::= Name Eq AttValue
     * </pre>
     * <p>
     * <strong>Note:</strong> This method assumes that the next
     * character on the stream is the first character of the attribute
     * name.
     * <p>
     * <strong>Note:</strong> This method uses the fAttributeQName and
     * fQName variables. The contents of these variables will be
     * destroyed.
     *
     * @param attributes The attributes list for the scanned attribute.
     */
    protected void scanAttribute(XMLAttributesImpl attributes)
        throws IOException, XNIException {
        if (DEBUG_CONTENT_SCANNING)
            System.out.println(">>> scanAttribute()");

        // name
        fEntityScanner.scanQName(fAttributeQName);

        // equals
        fEntityScanner.skipSpaces();
        if (!fEntityScanner.skipChar('=')) {
            reportFatalError(
                "EqRequiredInAttribute",
                new Object[] {
                    fCurrentElement.rawname,
                    fAttributeQName.rawname });
        }
        fEntityScanner.skipSpaces();

        // content
        int attrIndex;

        if (fBindNamespaces) {
            attrIndex = attributes.getLength();
            attributes.addAttributeNS(
                fAttributeQName,
                XMLSymbols.fCDATASymbol,
                null);
        } else {
            int oldLen = attributes.getLength();
            attrIndex =
                attributes.addAttribute(
                    fAttributeQName,
                    XMLSymbols.fCDATASymbol,
                    null);

            // WFC: Unique Att Spec
            if (oldLen == attributes.getLength()) {
                reportFatalError(
                    "AttributeNotUnique",
                    new Object[] {
                        fCurrentElement.rawname,
                        fAttributeQName.rawname });
            }
        }

        //REVISIT: one more case needs to be included: external PE and standalone is no
        boolean isVC = fHasExternalDTD && !fStandalone;

        // REVISIT: it seems that this function should not take attributes, and length
        scanAttributeValue(
            this.fTempString,
            fTempString2,
            fAttributeQName.rawname,
            isVC,
            fCurrentElement.rawname);
        String value = fTempString.toString();
        attributes.setValue(attrIndex, value);
        attributes.setNonNormalizedValue(attrIndex, fTempString2.toString());
        attributes.setSpecified(attrIndex, true);

        // record namespace declarations if any.
        if (fBindNamespaces) {

            String localpart = fAttributeQName.localpart;
            String prefix =
                fAttributeQName.prefix != null
                    ? fAttributeQName.prefix
                    : XMLSymbols.EMPTY_STRING;
            // when it's of form xmlns="..." or xmlns:prefix="...",
            // it's a namespace declaration. but prefix:xmlns="..." isn't.
            if (prefix == XMLSymbols.PREFIX_XMLNS
                || prefix == XMLSymbols.EMPTY_STRING
                && localpart == XMLSymbols.PREFIX_XMLNS) {

                // get the internalized value of this attribute
                String uri = fSymbolTable.addSymbol(value);

                // 1. "xmlns" can't be bound to any namespace
                if (prefix == XMLSymbols.PREFIX_XMLNS
                    && localpart == XMLSymbols.PREFIX_XMLNS) {
                    fErrorReporter.reportError(
                        XMLMessageFormatter.XMLNS_DOMAIN,
                        "CantBindXMLNS",
                        new Object[] { fAttributeQName },
                        XMLErrorReporter.SEVERITY_FATAL_ERROR);
                }

                // 2. the namespace for "xmlns" can't be bound to any prefix
                if (uri == NamespaceContext.XMLNS_URI) {
                    fErrorReporter.reportError(
                        XMLMessageFormatter.XMLNS_DOMAIN,
                        "CantBindXMLNS",
                        new Object[] { fAttributeQName },
                        XMLErrorReporter.SEVERITY_FATAL_ERROR);
                }

                // 3. "xml" can't be bound to any other namespace than it's own
                if (localpart == XMLSymbols.PREFIX_XML) {
                    if (uri != NamespaceContext.XML_URI) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "CantBindXML",
                            new Object[] { fAttributeQName },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    }
                }
                // 4. the namespace for "xml" can't be bound to any other prefix
                else {
                    if (uri == NamespaceContext.XML_URI) {
                        fErrorReporter.reportError(
                            XMLMessageFormatter.XMLNS_DOMAIN,
                            "CantBindXML",
                            new Object[] { fAttributeQName },
                            XMLErrorReporter.SEVERITY_FATAL_ERROR);
                    }
                }

                prefix =
                    localpart != XMLSymbols.PREFIX_XMLNS
                        ? localpart
                        : XMLSymbols.EMPTY_STRING;

                // Declare prefix in context. Removing the association between a prefix and a 
                // namespace name is permitted in XML 1.1, so if the uri value is the empty string, 
                // the prefix is being unbound. -- mrglavas
                fNamespaceContext.declarePrefix(
                    prefix,
                    uri.length() != 0 ? uri : null);
                // bind namespace attribute to a namespace
                attributes.setURI(
                    attrIndex,
                    fNamespaceContext.getURI(XMLSymbols.PREFIX_XMLNS));

            } else {
                // attempt to bind attribute
                if (fAttributeQName.prefix != null) {
                    attributes.setURI(
                        attrIndex,
                        fNamespaceContext.getURI(fAttributeQName.prefix));
                }
            }
        }

        if (DEBUG_CONTENT_SCANNING)
            System.out.println("<<< scanAttribute()");
    } // scanAttribute(XMLAttributes)

    /**
     * Scans an end element.
     * <p>
     * <pre>
     * [42] ETag ::= '</' Name S? '>'
     * </pre>
     * <p>
     * <strong>Note:</strong> This method uses the fElementQName variable.
     * The contents of this variable will be destroyed. The caller should
     * copy the needed information out of this variable before calling
     * this method.
     *
     * @return The element depth.
     */
    protected int scanEndElement() throws IOException, XNIException {
        if (DEBUG_CONTENT_SCANNING)
            System.out.println(">>> scanEndElement()");

        // pop context
        fElementStack.popElement(fElementQName);

        // Take advantage of the fact that next string _should_ be "fElementQName.rawName",
        //In scanners most of the time is consumed on checks done for XML characters, we can
        // optimize on it and avoid the checks done for endElement,
        //we will also avoid symbol table lookup - neeraj.bajaj@sun.com

        // this should work both for namespace processing true or false...

        //REVISIT: if the string is not the same as expected.. we need to do better error handling..
        //We can skip this for now... In any case if the string doesn't match -- document is not well formed.
        if (!fEntityScanner.skipString(fElementQName.rawname)) {
            reportFatalError(
                "ETagRequired",
                new Object[] { fElementQName.rawname });
        }

        // end
        fEntityScanner.skipSpaces();
        if (!fEntityScanner.skipChar('>')) {
            reportFatalError(
                "ETagUnterminated",
                new Object[] { fElementQName.rawname });
        }
        fMarkupDepth--;

        //we have increased the depth for two markup "<" characters
        fMarkupDepth--;

        // check that this element was opened in the same entity
        if (fMarkupDepth < fEntityStack[fEntityDepth - 1]) {
            reportFatalError(
                "ElementEntityMismatch",
                new Object[] { fCurrentElement.rawname });
        }

        // call handler
        if (fDocumentHandler != null) {

            fDocumentHandler.endElement(fElementQName, null);
            if (fBindNamespaces) {
                fNamespaceContext.popContext();
            }

        }

        return fMarkupDepth;

    } // scanEndElement():int

    public void reset(XMLComponentManager componentManager)
        throws XMLConfigurationException {

        super.reset(componentManager);
        fPerformValidation = false;
        fBindNamespaces = false;
    }

    /** Creates a content dispatcher. */
    protected Dispatcher createContentDispatcher() {
        return new NS11ContentDispatcher();
    } // createContentDispatcher():Dispatcher

    /**
     * Dispatcher to handle content scanning.
     */
    protected final class NS11ContentDispatcher extends ContentDispatcher {
        /**
         * Scan for root element hook. This method is a hook for
         * subclasses to add code that handles scanning for the root
         * element. This method will also attempt to remove DTD validator
         * from the pipeline, if there is no DTD grammar. If DTD validator
         * is no longer in the pipeline bind namespaces in the scanner.
         *
         *
         * @return True if the caller should stop and return true which
         *          allows the scanner to switch to a new scanning
         *          dispatcher. A return value of false indicates that
         *          the content dispatcher should continue as normal.
         */
        protected boolean scanRootElementHook()
            throws IOException, XNIException {
            
            if (fExternalSubsetResolver != null && !fSeenDoctypeDecl 
                && !fDisallowDoctype && (fValidation || fLoadExternalDTD)) {
                scanStartElementName();
                resolveExternalSubsetAndRead();
                reconfigurePipeline();
                if (scanStartElementAfterName()) {
                    setScannerState(SCANNER_STATE_TRAILING_MISC);
                    setDispatcher(fTrailingMiscDispatcher);
                    return true;
                }
            }
            else {
                reconfigurePipeline();
                if (scanStartElement()) {
                    setScannerState(SCANNER_STATE_TRAILING_MISC);
                    setDispatcher(fTrailingMiscDispatcher);
                    return true;
                }
            }
            return false;

        } // scanRootElementHook():boolean
        
        /**
         * Re-configures pipeline by removing the DTD validator 
         * if no DTD grammar exists. If no validator exists in the
         * pipeline or there is no DTD grammar, namespace binding
         * is performed by the scanner in the enclosing class.
         */
        private void reconfigurePipeline() {
            if (fDTDValidator == null) {
                fBindNamespaces = true;
            }
            else if (!fDTDValidator.hasGrammar()) {
                fBindNamespaces = true;
                fPerformValidation = fDTDValidator.validate();
                // re-configure pipeline
                XMLDocumentSource source = fDTDValidator.getDocumentSource();
                XMLDocumentHandler handler = fDTDValidator.getDocumentHandler();
                source.setDocumentHandler(handler);
                if (handler != null)
                    handler.setDocumentSource(source);
                fDTDValidator.setDocumentSource(null);
                fDTDValidator.setDocumentHandler(null);
            }
        } // reconfigurePipeline()
    }
}