// Copyright (C) 2003 Adam Megacz <adam@xwt.org> all rights reserved.
//
// You may modify, copy, and redistribute this code under the terms of
// the GNU Library Public License version 2.1, with the exception of
// the portion of clause 6a after the semicolon (aka the "obnoxious
// relink clause")

package org.xwt.util;

import java.io.Reader;
import java.io.IOException;
import java.io.EOFException;

/**
 * An Event-Driving, Non-Validating XML Parser with Namespace support.
 *
 * A subclass can implement the abstract functions for receiving details
 * about an xml file as it is parsed. To initate a parse, use the parse()
 * function. 
 *
 * <h3>Implementation Notes</h3>
 * <p>As the parser traverses into an element, it adds it to the linked list
 * called <tt>elements</tt>. However, <tt>elements</tt> has been pre-filled
 * with instances of the Element inner class. So in the vast majority of
 * cases, the pointer current is moved along one, and the values for the
 * new element are filled into the current object.</p>
 *
 * <p>This parser supports all the unicode ranges required by the XML
 * Specification. However, it is optimised for well-formed ASCII documents.
 * Documents containing unicode Names and Attributes will take much longer
 * to process, and invalid documents (badly formed Names or invalid attributes)
 * will be run through a test on every single unicode character range before 
 * being declared invalid.</p> 
 *
 * <ul>
 *  <li>Each time the buffer offset <tt>off</tt> is moved, the length
 *   <tt>len</tt> must be decreased.</li>
 *  <li>Each time the buffer length is decreased, it must be checked to make
 *   sure it is >0.</li>
 *  <li><i>error</i> is defined as a Validity Constraint Violation and
 *   is recoverable</li>
 *  <li><i>fatal error</i> is defined as a Well-formedness Constraint
 *   Violation and is not recoverable</li>
 * </ul> 
 *
 * @author David Crawshaw 
 * @see <a href="http://w3.org/TR/REC-xml">XML Specification</a> 
 * @see <a href="http://w3.org/TR/REC-xml-names">XML Namespaces</a>
 */
public abstract class XML
{
    /////////////////////////////////////////////////////////////////////////////////////////////
    // XML Parser
    /////////////////////////////////////////////////////////////////////////////////////////////

    public static final int BUFFER_SIZE = 255;

    /** static pool of XML.Element instances shared by all XML Parsers. */
    private static final Queue elements = new Queue(30);

    private static final char[] single_amp  = new char[] { '&'  };
    private static final char[] single_apos = new char[] { '\'' };
    private static final char[] single_gt   = new char[] { '>'  };
    private static final char[] single_lt   = new char[] { '<'  };
    private static final char[] single_quot = new char[] { '"'  };

    private int line;
    private int col;

    private Reader in;
    private char[] buf;
    private int    off;
    private int    len;

    private Element current;

    // used in readEntity() to process a single character without creating a new array
    private char[] singlechar = new char[1];


    public XML() { this(BUFFER_SIZE); }

    public XML(int bSize) {
        buf = new char[bSize];

        current = (Element)elements.remove(false);
        if (current == null) current = new Element();
    }


    /** Returns the line number at the beginning of the last process call. */
    public int getLine() { return line; }

    /** Returns the column number at the beginning of the last process call. */
    public int getCol()  { return col; }

    /**
     * Parse given input and call the abstract event functions.
     *
     * Careful with threading, as this function is not synchronized.
     */ 
    public final void parse(Reader reader) throws IOException, Exn {
        in  = reader;
        off = len = 0;
        line = col = 1;

        clear(); // clean up possible mid-way linked-list element

        try {
            // process the stream
            while (true) {
                if (!buffer(1)) {
                    if (current.qName == null) break;
                    throw new Exn("reached eof without closing <"+current.qName+"> element", Exn.WFC, getLine(), getCol());
                }

                if (buf[off] == '<') readTag();
                readChars(current.qName != null);
            }
        } finally { clear(); } // clean up elements
    }

    /** remove any leftover elements from the linked list and queue them */
    private final void clear() {
        for (Element last = current; current.parent != null; ) {
            current = current.parent;
            last.clear();
            elements.append(last);
        }
        current.clear();
    }

    /** reads in a tag. expects <tt>buf[off] == '<'</tt> */
    private final void readTag() throws IOException, Exn {
        // Start Tag    '<' Name (S Attribute)* S? '>'
        boolean starttag  = true;

        // End Tag     '</' Name S? '>'
        boolean endtag    = false;

        // if (starttag & endtag) then: EmptyElemTag '<' Name (S Attribute)* S? '/>'

        // Position in the name of the ':' namespace prefix
        int prefix = -1;

        int namelen   = 0;

        col++; off++; len--;
        if (!buffer(1)) throw new EOFException("Unexpected EOF processing element tag");

        // work out what we can from the beginning of the tag
        char s = buf[off]; 
        if (s == '!') {
            // definitions here don't necessarily conform to xml spec (as DTDs not yet implemented)
            col++; off++; len--; 
            if (!buffer(4)) throw new EOFException("Unexpected EOF processing <! element");

            boolean bad = false;
            switch (buf[off]) {
                case '-':
                    if (buf[off+1] != '-') { bad = true; break; }
                    col += 2; off += 2; len -= 2;

                    // Comment        '<!--'      ((Char - '-') | ('-' (Char - '-')))* '-->'
                    readChars(false, "-->", false); 
                    col += 3; off += 3; len -= 3;
                    break;

                // we don't care about the following definitions

                case 'A':
                    if (!buffer(7)
                            || buf[off+1] != 'T' || buf[off+2] != 'T' || buf[off+3] != 'L'
                            || buf[off+4] != 'I' || buf[off+5] != 'S' || buf[off+6] != 'T') {
                        bad = true; break;
                    } 
                    col += 7; off += 7; len -= 7; 

                    // ATTLIST        '<!ATTLIST'   (Char* - '>') '>'
                    readChars(false, ">", true); 
                    col++; off++; len--;
                    break;
                case 'D':
                    if (!buffer(7)
                            || buf[off+1] != 'O' || buf[off+2] != 'C' || buf[off+3] != 'T'
                            || buf[off+4] != 'Y' || buf[off+5] != 'P' || buf[off+6] != 'E') {
                        bad = true; break;
                    }
                    col += 7; off += 7; len -= 7;

                    // DTD            '<!DOCTYPE'   (Char* - '>') '>'
                    readChars(false, ">", true); 
                    col++; off++; len--;
                    break; 
                case 'E':
                    if (!buffer(7)) {
                        bad = true;
                    } else if (buf[off+1] == 'L' && buf[off+2] == 'E' && buf[off+3] == 'M'
                            && buf[off+4] == 'E' && buf[off+5] == 'N' && buf[off+6] == 'T') {
                        // ELEMENT        '<!ELEMENT'   (Char* - '>') '>'
                        readChars(false, ">", true); 
                        col++; off++; len--;

                    } else if (buf[off+1] == 'N' && buf[off+2] == 'T' && buf[off+3] == 'I'
                            && buf[off+4] == 'T' && buf[off+5] == 'Y') {
                        // ENTITY         '<!ENTITY'    (Char* - '>') '>'
                        readChars(false, ">", true); 
                        col++; off++; len--;

                    } else {
                        bad = true;
                    }
                    break;

                case 'N':
                    if (!buffer(8)
                            || buf[off+1] != 'O' || buf[off+2] != 'T' || buf[off+3] != 'A' || buf[off+4] != 'T'
                            || buf[off+5] != 'I' || buf[off+6] != 'O' || buf[off+7] != 'N') {
                        bad = true; break;
                    }
                    col += 8; off += 8; len -= 8;
                    // NOTATION       '<!NOTATION'  (Char* - '>') '>'
                    readChars(false, ">", true); 
                    col++; off++; len--;

                    break;
                default: bad = true;
            }

            if (bad) throw new Exn("element tag start character is invalid", Exn.MARKUP, getLine(), getCol());

        } else if (s == '?') {
            // PI (Ignored)   '<?'  (Char* - (Char* '?>' Char*))  '?>'
            col++; off++; len--;
            readChars(false, "?>", true);
            if (!buffer(2)) throw new EOFException("Unexpected EOF at end of Processing Instruction");
            col += 2; off += 2; len -= 2;

        } else if (s == '[') {
            if (!buffer(7)
                    || buf[off+1] != 'C' || buf[off+2] != 'D' || buf[off+3] != 'A'
                    || buf[off+4] != 'T' || buf[off+5] != 'A' || buf[off+6] != '[') {
                col++; off--; len++; 
                // Conditional    '<![' (Char* - (Char* ']]>' Char*)) ']]>'
                readChars(false, "]]>", false); 
            } else {
                col += 7; off += 7; len -=7;
                // CDATA          '<![CDATA[' (Char* - (Char* ']]>' Char*))        ']]>'
                readChars(true, "]]>", false);
            } 
            col += 3; off += 3; len -= 3;
        } else {
            if (s == '/') {
                // End Tag        '</' Name S? '>'
                starttag = false; 
                endtag = true;

                col++; off++; len--;
                if (!buffer(1)) throw new EOFException("Unexpected EOF processing end tag");
                s = buf[off];
            }

            if (!Name(s)) throw new Exn("invalid starting character in element name", Exn.MARKUP, getLine(), getCol()); 

            // find the element name (defined in XML Spec: section 2.3)
            for (namelen = 0; ; namelen++) {
                if (!buffer(namelen+1)) throw new EOFException("Unexpected EOF in element tag name");

                s = buf[off+namelen];

                if (S(s) || s == '>') {
                    break;
                } else if (s == '/') {
                    endtag = true;
                    break;
                } else if (s == ':' && namelen > 0 && prefix < 1) {
                    // we have a definition of the prefix range available
                    prefix = namelen; 
                } else if (!NameChar(s)) {
                    throw new Exn("element name contains invalid character", Exn.MARKUP, getLine(), getCol());
                }
            }

            // process name (based on calculated region)
            if (namelen < 1) throw new Exn("element name is null", Exn.MARKUP, getLine(), getCol()); 

            // we have marked out the name region, so turn it into a string and move on
            String qName = new String(buf, off, namelen);

            col += namelen; off += namelen; len -= namelen;

            if (starttag) {
                // create the in-memory element representation of this beast
                // if current.qName == null then this is the root element we're dealing with
                if (current.qName != null) {
                    Element next = (Element)elements.remove(false);
                    if (next == null) next = new Element();
                    //next.clear(); // TODO: remove as elements now checked as they're added to the queue
                    next.parent = current;
                    current = next;
                }

                current.qName = qName;

                if (prefix > 0) {
                    current.prefix = current.qName.substring(0, prefix);
                    current.localName = current.qName.substring(prefix+1);
                } else {
                    current.prefix = null;
                    current.localName = current.qName;
                }

                // process attributes
                readWhitespace(); 
                if (!buffer(1)) throw new EOFException("Unexpected EOF - processing attributes part 1");
                while (buf[off] != '/' && buf[off] != '>') {
                    readAttribute();
                    if (!buffer(1)) throw new EOFException("Unexpected EOF - processing attributes part 2");
                    readWhitespace();
                }

                // work out the uri of this element
                current.uri = current.getUri(current.getPrefix()); 
                if (current.getUri().equals("") && current.getPrefix() != null)
                    current.addError(new Exn("undefined prefix '"+current.getPrefix()+"'", Exn.NC, getLine(), getCol()));

            } else {
                // this is an end-of-element tag
                if (!qName.equals(current.getQName())) throw new Exn(
                    "end tag </"+qName+"> does not line up with start tag <"+current.getQName()+">", Exn.WFC, getLine(), getCol()
                );
            }

            // deal with whitespace
            readWhitespace(); 

            // process tag close
            if (!buffer(1)) throw new EOFException("Unexpected EOF before end of tag"); 
            if (buf[off] == '/') {
                endtag = true;
                off++; len--; col++;
            }
            if (!buffer(1)) throw new EOFException("Unexpected EOF before end of endtag"); 
            if (buf[off] == '>') {
                off++; len--; col++;
            } else {
                throw new Exn("missing '>' character from element '"+qName+"'", Exn.MARKUP, getLine(), getCol());
            }

            // send element signals
            if (starttag) startElement(current);
            if (endtag) {
                endElement(current);

                // we just closed an element, so remove it from the element 'stack'
                if (current.getParent() == null) {
                    // we just finished the root element
                    current.clear(); 
                } else {
                    Element last = current;
                    current = current.parent;
                    last.clear();
                    elements.append(last);
                }
            }
        }
    }

    /** reads in an attribute of an element. expects Name(buf[off]) */
    private final void readAttribute() throws IOException, Exn {
        int ref = 0;
        int prefix = 0;
        String n, v, p, u; // attribute name, value, prefix and uri respectively
        n = v = p = u = null;
        char s;

        // find the element name (defined in XML Spec: section 2.3)
        for (ref= 0; ; ref++) {
            if (!buffer(ref+1)) throw new EOFException("Unexpected EOF in read attribute loop part 1");

            s = buf[off+ref];

            if (s == '=' || S(s)) {
                break;
            } else if (s == ':' && ref > 0 && prefix < 1) {
                // we have a definition of the prefix range available
                prefix = ref+1;
            } else if (!NameChar(s)) {
                throw new Exn("attribute name contains invalid characters", Exn.MARKUP, getLine(), getCol());
            }
        }

        // determine prefix and key name
        if (prefix > 0) {
            p = new String(buf, off, prefix-1);
            col += prefix; off += prefix; len -= prefix; ref -= prefix;
        }
        n = new String(buf, off, ref);
        col += ref; off += ref; len -= ref;

        // find name/value divider ('=')
        readWhitespace();
        if (!buffer(1)) throw new EOFException("Unexpected EOF before attribute '=' divider");
        if (buf[off] != '=') throw new Exn("attribute name not followed by '=' sign", Exn.MARKUP, getLine(), getCol());

        col++; off++; len--;
        readWhitespace();

        if (!buffer(1)) throw new EOFException("Unexpected EOF after attribute '=' divider");

        char wrap;
        if (buf[off] == '\'' || buf[off] == '"') {
            wrap = buf[off];
        } else {
            throw new Exn("attribute '"+n+"' must have attribute wrapped in ' or \"", Exn.MARKUP, getLine(), getCol());
        }
        col++; off++; len--;

        // find the attribute value
        attval: for (ref = 0; ; ref++) {
            if (!buffer(ref+1)) throw new EOFException("Unexpected EOF in attribute value");

            if (buf[off+ref] == wrap) {
                break attval;
            } else if (buf[off+ref] == '<') {
                throw new Exn("attribute value for '"+n+"' must not contain '<'", Exn.WFC, getLine(), getCol());
            } 
        }

        v = new String(buf, off, ref);
        col += ref; off += ref; len -= ref;

        // remove end wrapper character
        col++; off++; len--;

        // process attribute
        if (p != null && p.equals("xmlns")) {
            current.addUri(n, v);
        } else if (n.equals("xmlns")) {
            if (current.getUri().equals("")) {
                current.addUri("", v);
            } else {
                current.addError(new Exn("default namespace definition repeated", Exn.NC, getLine(), getCol()));
            }
        } else {
            // find attribute uri
            u = current.getUri(p); 
            if (p != null && u.equals("")) current.addError(new Exn("undefined attribute prefix '"+p+"'", Exn.NC, getLine(), getCol()));

            // check to see if attribute is a repeat
            for (int i=0; current.len > i; i++) if (n.equals(current.getAttrKey(i)) && u.equals(current.getAttrUri(i))) throw new Exn(
                "attribute name '"+n+"' may not appear more than once in the same element tag", Exn.WFC, getLine(), getCol()
            );

            current.addAttr(n, v, u); 
        }
    }

    /** reads an entity and processes out its value. expects buf[off] == '&' */
    private final void readEntity() throws IOException, Exn {
        off++; len--;
        if (!buffer(2)) throw new EOFException("Unexpected EOF reading entity");

        boolean unknown = false;
        switch (buf[off]) {
            case '#':
                off++; len--;

                int radix;
                if (buf[off] == 'x') { off++; len--; radix = 16; } else { radix = 10; }
                int c = 0;

                // read in each char, then shift total value to the left and add the extra
                // style of loop is slightly different from all the others, as this should run a limited number of times 
                findchar: while (true) {
                    if (!buffer(1)) throw new EOFException("Unexpected EOF reading entity");
                    int d = Character.digit(buf[off], radix);
                    if (d == -1) {
                        if (buf[off] != ';') throw new Exn("illegal characters in entity reference", Exn.WFC, getLine(), getCol());
                        off++; len--; col++;
                        break findchar;
                    }
                    c = (c * radix) + d;

                    off++; len--;
                }

                singlechar[0] = Character.forDigit(c, radix);
                characters(singlechar, 0, 1);
                break;

            case 'a':
                if (buffer(4) && buf[off+1] == 'm' && buf[off+2] == 'p' && buf[off+3] == ';') {
                    characters(single_amp, 0, 1); // &
                    off += 4; len -= 4; col++;
                } else if (buffer(5) && buf[off+1] == 'p' && buf[off+2] == 'o' && buf[off+3] == 's' && buf[off+4] == ';') {
                    characters(single_apos, 0, 1); // '
                    off += 5; len -= 5; col++;
                } else {
                    unknown = true;
                }
                break;

            case 'g':
                if (buffer(3) && buf[off+1] == 't' && buf[off+2] == ';') {
                    characters(single_gt, 0, 1); // >
                    off += 3; len -= 3; col++;
                } else {
                    unknown = true;
                }
                break;

            case 'l':
                if (buffer(3) && buf[off+1] == 't' && buf[off+2] == ';') {
                    characters(single_lt, 0, 1); // <
                    off += 3; len -= 3; col++;
                } else {
                    unknown = true;
                }
                break;

            case 'q':
                if (buffer(5) && buf[off+1] == 'u' && buf[off+2] == 'o' && buf[off+3] == 't' && buf[off+4] == ';') {
                    characters(single_quot, 0, 1); // "
                    off += 5; len -= 5; col++;
                } else {
                    unknown = true;
                }
                break;

            // TODO: check a parser-level Hash of defined entities
        }

        if (unknown) throw new Exn("unknown entity (<!ENTITY> not supported)", Exn.WFC, getLine(), getCol());
    }

    /** reads until the passed string is encountered. */
    private final void readChars(boolean p, String match, boolean entities) throws IOException, Exn {
        int ref;
        char[] end = match.toCharArray();

        for (boolean more = true; more;) {
            if (!buffer(1)) return;

            buf: for (ref = 0; ref < len; ref++) {
                switch (buf[off+ref]) {
                    case '\r': // windows or macos9 newline
                        // normalise and process
                        buf[off+ref] = '\n'; ref++;
                        if (p) characters(buf, off, ref);
                        off += ref; len -= ref; ref = -1;
                        line++; col = 1;

                        // windows double-char newline; skip the next char
                        if (!buffer(1)) return;
                        if (buf[off] == '\n') { off++; len--; }
                        break;

                    case '\n': // unix newline
                        ref++;
                        if (p) characters(buf, off, ref);
                        off += ref; len -= ref; ref = -1;
                        line++; col = 1;
                        break;

                    case '&':  // entity
                        if (entities) {
                            if (p) {
                                if (ref > 0) characters(buf, off, ref);
                                off += ref; len -= ref; ref = -1;
                                readEntity();
                            }
                            break;
                        }

                    default:
                        if (!buffer(ref+end.length)) continue buf;
                        for (int i=0; end.length > i; i++) if (end[i] != buf[off+ref+i]) continue buf;
                        more = false;
                        break buf;
                }
            }

            if (p && ref > 0) characters(buf, off, ref);
            off += ref; len -= ref; col += ref;
        }
    }

    /**
     * reads until a <tt><</tt> symbol is encountered
     * @param p If true call the characters(char[],int,int) funciton for the processed characters 
     */
    private final void readChars(boolean p) throws IOException, Exn {
        int ref;

        for (boolean more = true; more;) {
            if (!buffer(1)) return;

            buf: for (ref = 0; ref < len; ref++) {
                switch (buf[off+ref]) {
                    case '\r': // windows or macos9 newline
                        // normalise and process
                        buf[off+ref] = '\n'; ref++;
                        if (p) characters(buf, off, ref);
                        off += ref; len -= ref; ref = -1;
                        line++; col = 1;

                        // windows double-char newline; skip the next char
                        if (!buffer(1)) return;
                        if (buf[off] == '\n') { off++; len--; }
                        break;

                    case '\n': // unix newline
                        ref++;
                        if (p) characters(buf, off, ref);
                        off += ref; len -= ref; ref = -1;
                        line++; col = 1;
                        break;

                    case '&':  // entity
                        if (p) {
                            if (ref > 0) characters(buf, off, ref);
                            off += ref; len -= ref; ref = -1;
                            readEntity();
                        }
                        break;

                    case '<':  // end of chars section
                        more = false;
                        break buf;
                }
            }

            if (p && ref > 0) characters(buf, off, ref);
            off += ref; len -= ref; col += ref;
        }
    }

    /** reads until a non-whitespace symbol is encountered */
    private final void readWhitespace() throws IOException, Exn {
        int ref;

        for (boolean more = true; more;) {
            if (!buffer(1)) return;

            buf: for (ref = 0; ref < len; ref++) {
                switch (buf[off+ref]) {
                    case '\r': // windows or macos9 newline
                        // normalise and process
                        buf[off+ref] = '\n';
                        whitespace(buf, off, ++ref);
                        off += ref; len -= ref; ref = -1;
                        line++; col = 1;

                        // windows double-char newline; skip the next char
                        if (!buffer(1)) return;
                        if (buf[off] == '\n') { off++; len--; }
                        break;

                    case '\n': // unix newline
                        whitespace(buf, off, ++ref);
                        off += ref; len -= ref; ref = -1;
                        line++; col = 1;
                        break;

                    case ' ':  // space
                    case '\t': // tab
                        break;

                    default:   // end of whitespace
                        more = false;
                        break buf;
                }
            }

            off += ref; len -= ref; col += ref;
        }
    }

    /**
     * attempt to fill the buffer.
     *
     * @param min Minimum number of characters to read (even if we have to block to do it).
     * @return return false if min can't be reached.
     */
    private final boolean buffer(int min) throws IOException {
        if (len > min) return true;

        if (buf.length - (off+len) >= min) {
            // plenty of space left on the end of the buffer
        } else if (off >= min) {
            // moving offset data to start will leave enough free space on the end
            System.arraycopy(buf, off, buf, 0, len); 
            off = 0;
        } else {
            // buffer size will have to be increased
            char[] newbuf = new char[buf.length * 2];
            System.arraycopy(buf, off, newbuf, 0, len);
            buf = newbuf;
            off = 0;
        }

        while (min > len) {
            int newlen = in.read(buf, off+len, buf.length-(off+len));
            if (newlen < 0) return false; 
            len += newlen;
        }

        return true;
    }


    /////////////////////////////////////////////////////////////////////////////////////////////
    // Abstract SAX-Like Interface
    /////////////////////////////////////////////////////////////////////////////////////////////

    /**
     * Called when the start of an element is processed.
     *
     * <p><b>DO NOT</b> store a reference to the Element object, as
     * they are reused by XML Parser.</p>
     */ 
    public abstract void startElement(Element e) throws Exn;

    /**
     * Represents up to a line of character data. 
     *
     * <p>Newlines are all normalised to the Unix \n as per the XML Spec,
     * and a newline will only appear as the last character in the passed
     * array segment.</p>
     *
     * <p>XML.getLine() and XML.getCol() report the position at the
     * beginning of this character segment, which can be processed in a
     * line-by-line fashion due to the above newline restriction.</p>
     */
    public abstract void characters(char[] ch, int start, int length) throws Exn, IOException;

    /** Represents up to a line of ignorable whitespace. */
    public abstract void whitespace(char[] ch, int start, int length) throws Exn, IOException;

    /** Represents the end of an Element. */
    public abstract void endElement(Element e) throws Exn, IOException;


    /////////////////////////////////////////////////////////////////////////////////////////////
    // Inner Classes for Parser Support
    /////////////////////////////////////////////////////////////////////////////////////////////

    /**
     * Represents an element in an XML document. Stores a reference to its
     * parent, forming a one-way linked list.
     *
     * Element objects are reused, so client code making use of them must
     * drop their references after the specific element process function
     * has returned.
     */
    public static final class Element {

        private static final int DEFAULT_ATTR_SIZE = 10;

        protected Element parent = null;

        protected String uri = null;
        protected String localName = null;
        protected String qName = null;
        protected String prefix = null;

        protected Hash urimap = new Hash(3,3);

        protected String[] keys = new String[DEFAULT_ATTR_SIZE];
        protected String[] vals = new String[DEFAULT_ATTR_SIZE];
        protected String[] uris = new String[DEFAULT_ATTR_SIZE];
        protected int len = 0;

        protected Exn[] errors = new Exn[] {};


        /** Parent of current element. */
        public Element getParent() { return parent; }

        /** Qualified Name of current element.  XML Namespace Spec 14-Jan-1999 [6] */
        public String getQName() { return qName; }

        /** LocalPart of current element. XML Namespace Spec 14-Jan-1999 [8] */
        public String getLocalName() { return localName; }

        /** Prefix of current element. Substring of qName. XML Namespace Spec 14-Jan-1999 [7] */
        public String getPrefix() { return prefix; }

        /** URI of current tag. XML Namespace Spec 14-Jan-1999 section 1 */
        public String getUri() { return getUri(prefix); }

        /** URI of a given prefix. Never returns null, instead gives "". */
        public String getUri(String p) {
            String ret = null;
            for (Element e = this; e != null && ret == null; e = e.getParent()) {
                ret = (String)e.urimap.get(p == null ? "" : p);
            }
            return ret == null ? "" : ret;
        }

        /** An array of attribute names. */
        public String getAttrKey(int pos) { return len > pos ? keys[pos] : null; }

        /** An array of attribute values. */
        public String getAttrVal(int pos) { return len > pos ? vals[pos] : null; }

        /** An array of attribute uris. */
        public String getAttrUri(int pos) { return len > pos ? uris[pos] : null; }

        /** Current number of attributes in the element. */
        public int getAttrLen() { return len; }

        /** An array of non-fatal errors related to this element. */
        public Exn[] getErrors() { return errors; }


        protected Element() { }

        /** Add (replace if exists in current element) a Namespace prefix/uri map. */
        protected void addUri(String name, String value) {
            urimap.put(name, value);
        }

        /** Add an attribute. */
        protected void addAttr(String key, String val, String uri) {
            if (len == keys.length) {
                // increase the size of the attributes arrays
                String[] newkeys = new String[keys.length*2];
                String[] newvals = new String[vals.length*2];
                String[] newuris = new String[uris.length*2];
                System.arraycopy(keys, 0, newkeys, 0, keys.length);
                System.arraycopy(vals, 0, newvals, 0, vals.length);
                System.arraycopy(uris, 0, newuris, 0, uris.length);
                keys = newkeys; vals = newvals; uris = newuris;
            }

            keys[len] = key;
            vals[len] = val;
            uris[len] = uri;
            len++;
        }

        /** Add an error. */
        protected void addError(Exn e) {
            // it doesn't really matter about continually expanding the array, as this case is quite rare
            Exn[] newe = new Exn[errors.length+1];
            System.arraycopy(errors, 0, newe, 0, errors.length);
            newe[errors.length] = e;
            errors = newe;
        }

        /** Empty out all the data from the Element. */
        protected void clear() {
            parent = null;
            uri = localName = qName = prefix = null;
            urimap.clear();

            if (keys.length != vals.length || vals.length != uris.length) {
                keys = new String[DEFAULT_ATTR_SIZE];
                vals = new String[DEFAULT_ATTR_SIZE];
                uris = new String[DEFAULT_ATTR_SIZE];
            } else {
                for (int i=0; keys.length > i; i++) { keys[i] = null; vals[i] = null; uris[i] = null; };
            }
            len = 0;

            errors = new Exn[] {};
        }
    }

    /** Parse or Structural Error */
    public static class Exn extends Exception {
        /** Violation of Markup restrictions in XML Specification - Fatal Error */
        public static final int MARKUP = 1;

        /** Well-Formedness Constraint Violation - Fatal Error */
        public static final int WFC = 2;

        /** Namespace Constraint Violation - Recoverable Error */
        public static final int NC = 3;

        /** Schema Violation - Fatal Error */
        public static final int SCHEMA = 4;

        private String error;
        private int type;
        private int line;
        private int col;

        public Exn(String e) { this(e, MARKUP, -1, -1); }

        public Exn(String e, int type, int line, int col) {
            this.error = e;
            this.type  = type;
            this.line  = line;
            this.col   = col;
        }

        public int getType() { return this.type; }
        public int getLine() { return this.line; }
        public int getCol()  { return this.col;  }
        public String getMessage() { return this.error + (line >= 0 && col >= 0 ? " at " + line + ":" + col: ""); }
    }


    /////////////////////////////////////////////////////////////////////////////////////////////
    // Static Support Functions for the XML Specification 
    /////////////////////////////////////////////////////////////////////////////////////////////
 
    // attempt to avoid these functions unless you *expect* the input to fall in the given range.

    /** First Character of Name - XML Specification 1.0 [5] */
    private static final boolean Name(char c) {
        return BaseCharAscii(c) || c == '_' || c == ':' || Letter(c);
    } 

    /** NameChar - XML Specification 1.0 [4] */
    private static final boolean NameChar(char c) {
        return BaseCharAscii(c) || c == '.' || c == '-' || c == '_' || c == ':'
            || Digit(c) || Letter(c) || Extender(c); // TODO: || CombiningChar(c);
    } 

    /** BaseChar - XMl Specification 1.0 [84] */
    private static final boolean Letter(char c) {
        return BaseChar(c) || Ideographic(c);
    }

    /** Elements of BaseChar that exist in ASCII. */
    private static final boolean BaseCharAscii(char c) {
        return (c >= '\u0041' && c <= '\u005A') || (c >= '\u0061' && c <= '\u007A');
    }

    /** Char - XML Specification 1.0 [2] */
    private static final boolean Char(char c) {
        // u000A == r and u000D == n, but the javac compiler can't handle the \ u form
        return c == '\u0009' || c == '\r' || c == '\n'
            || (c >= '\u0020' && c <= '\uD7FF')
            || (c >= '\uE000' && c <= '\uFFFD');
    }

    /** BaseChar - XML Specification 1.0 [85] */
    private static final boolean BaseChar(char c) {
        return  BaseCharAscii(c) || (c >= '\u00C0' && c <= '\u00D6')
            || (c >= '\u00D8' && c <= '\u00F6') || (c >= '\u00F8' && c <= '\u00FF') || (c >= '\u0100' && c <= '\u0131')
            || (c >= '\u0134' && c <= '\u013E') || (c >= '\u0141' && c <= '\u0148') || (c >= '\u014A' && c <= '\u017E')
            || (c >= '\u0180' && c <= '\u01C3') || (c >= '\u01CD' && c <= '\u01F0') || (c >= '\u01F4' && c <= '\u01F5')
            || (c >= '\u01FA' && c <= '\u0217') || (c >= '\u0250' && c <= '\u02A8') || (c >= '\u02BB' && c <= '\u02C1')
            || (c == '\u0386')                  || (c >= '\u0388' && c <= '\u038A') || (c == '\u038C')
            || (c >= '\u038E' && c <= '\u03A1') || (c >= '\u03A3' && c <= '\u03CE') || (c >= '\u03D0' && c <= '\u03D6')
            || (c == '\u03DA')                  || (c == '\u03DC')                  || (c == '\u03DE')
            || (c == '\u03E0')
            || (c >= '\u03E2' && c <= '\u03F3') || (c >= '\u0401' && c <= '\u040C') || (c >= '\u040E' && c <= '\u044F')
            || (c >= '\u0451' && c <= '\u045C') || (c >= '\u045E' && c <= '\u0481') || (c >= '\u0490' && c <= '\u04C4')
            || (c >= '\u04C7' && c <= '\u04C8') || (c >= '\u04CB' && c <= '\u04CC') || (c >= '\u04D0' && c <= '\u04EB')
            || (c >= '\u04EE' && c <= '\u04F5') || (c >= '\u04F8' && c <= '\u04F9') || (c >= '\u0531' && c <= '\u0556')
            || (c == '\u0559')
            || (c >= '\u0561' && c <= '\u0586') || (c >= '\u05D0' && c <= '\u05EA') || (c >= '\u05F0' && c <= '\u05F2')
            || (c >= '\u0621' && c <= '\u063A') || (c >= '\u0641' && c <= '\u064A') || (c >= '\u0671' && c <= '\u06B7')
            || (c >= '\u06BA' && c <= '\u06BE') || (c >= '\u06C0' && c <= '\u06CE') || (c >= '\u06D0' && c <= '\u06D3')
            || (c == '\u06D5')
            || (c >= '\u06E5' && c <= '\u06E6') || (c >= '\u0905' && c <= '\u0939')
            || (c == '\u093D')
            || (c >= '\u0958' && c <= '\u0961') || (c >= '\u0985' && c <= '\u098C') || (c >= '\u098F' && c <= '\u0990')
            || (c >= '\u0993' && c <= '\u09A8') || (c >= '\u09AA' && c <= '\u09B0')
            || (c == '\u09B2')
            || (c >= '\u09B6' && c <= '\u09B9') || (c >= '\u09DF' && c <= '\u09E1') || (c >= '\u09F0' && c <= '\u09F1')
            || (c >= '\u0A05' && c <= '\u0A0A') || (c >= '\u0A0F' && c <= '\u0A10') || (c >= '\u0A13' && c <= '\u0A28')
            || (c >= '\u0A2A' && c <= '\u0A30') || (c >= '\u0A32' && c <= '\u0A33') || (c >= '\u0A35' && c <= '\u0A36')
            || (c >= '\u0A38' && c <= '\u0A39') || (c >= '\u0A59' && c <= '\u0A5C')
            || (c == '\u0A5E')
            || (c >= '\u0A72' && c <= '\u0A74') || (c >= '\u0A85' && c <= '\u0A8B')
            || (c == '\u0A8D')
            || (c >= '\u0A8F' && c <= '\u0A91') || (c >= '\u0A93' && c <= '\u0AA8') || (c >= '\u0AAA' && c <= '\u0AB0') 
            || (c >= '\u0AB2' && c <= '\u0AB3') || (c >= '\u0AB5' && c <= '\u0AB9') 
            || (c == '\u0ABD') 
            || (c == '\u0AE0') 
            || (c >= '\u0B05' && c <= '\u0B0C') || (c >= '\u0B0F' && c <= '\u0B10') || (c >= '\u0B13' && c <= '\u0B28') 
            || (c >= '\u0B2A' && c <= '\u0B30') || (c >= '\u0B32' && c <= '\u0B33') || (c >= '\u0B36' && c <= '\u0B39') 
            || (c == '\u0B3D') 
            || (c >= '\u0B5C' && c <= '\u0B5D') || (c >= '\u0B5F' && c <= '\u0B61') || (c >= '\u0B85' && c <= '\u0B8A') 
            || (c >= '\u0B8E' && c <= '\u0B90') || (c >= '\u0B92' && c <= '\u0B95') || (c >= '\u0B99' && c <= '\u0B9A') 
            || (c == '\u0B9C') 
            || (c >= '\u0B9E' && c <= '\u0B9F') || (c >= '\u0BA3' && c <= '\u0BA4') || (c >= '\u0BA8' && c <= '\u0BAA') 
            || (c >= '\u0BAE' && c <= '\u0BB5') || (c >= '\u0BB7' && c <= '\u0BB9') || (c >= '\u0C05' && c <= '\u0C0C') 
            || (c >= '\u0C0E' && c <= '\u0C10') || (c >= '\u0C12' && c <= '\u0C28') || (c >= '\u0C2A' && c <= '\u0C33') 
            || (c >= '\u0C35' && c <= '\u0C39') || (c >= '\u0C60' && c <= '\u0C61') || (c >= '\u0C85' && c <= '\u0C8C') 
            || (c >= '\u0C8E' && c <= '\u0C90') || (c >= '\u0C92' && c <= '\u0CA8') || (c >= '\u0CAA' && c <= '\u0CB3') 
            || (c >= '\u0CB5' && c <= '\u0CB9') 
            || (c == '\u0CDE') 
            || (c >= '\u0CE0' && c <= '\u0CE1') || (c >= '\u0D05' && c <= '\u0D0C') || (c >= '\u0D0E' && c <= '\u0D10') 
            || (c >= '\u0D12' && c <= '\u0D28') || (c >= '\u0D2A' && c <= '\u0D39') || (c >= '\u0D60' && c <= '\u0D61') 
            || (c >= '\u0E01' && c <= '\u0E2E') 
            || (c == '\u0E30') 
            || (c >= '\u0E32' && c <= '\u0E33') || (c >= '\u0E40' && c <= '\u0E45') || (c >= '\u0E81' && c <= '\u0E82') 
            || (c == '\u0E84') 
            || (c >= '\u0E87' && c <= '\u0E88') 
            || (c == '\u0E8A') 
            || (c == '\u0E8D') 
            || (c >= '\u0E94' && c <= '\u0E97') || (c >= '\u0E99' && c <= '\u0E9F') || (c >= '\u0EA1' && c <= '\u0EA3') 
            || (c == '\u0EA5') 
            || (c == '\u0EA7') 
            || (c >= '\u0EAA' && c <= '\u0EAB') || (c >= '\u0EAD' && c <= '\u0EAE') 
            || (c == '\u0EB0') 
            || (c >= '\u0EB2' && c <= '\u0EB3') 
            || (c == '\u0EBD') 
            || (c >= '\u0EC0' && c <= '\u0EC4') || (c >= '\u0F40' && c <= '\u0F47') || (c >= '\u0F49' && c <= '\u0F69') 
            || (c >= '\u10A0' && c <= '\u10C5') || (c >= '\u10D0' && c <= '\u10F6') 
            || (c == '\u1100') 
            || (c >= '\u1102' && c <= '\u1103') || (c >= '\u1105' && c <= '\u1107') 
            || (c == '\u1109') 
            || (c >= '\u110B' && c <= '\u110C') || (c >= '\u110E' && c <= '\u1112') 
            || (c == '\u113C') 
            || (c == '\u113E') 
            || (c == '\u1140') 
            || (c == '\u114C') 
            || (c == '\u114E') 
            || (c == '\u1150') 
            || (c >= '\u1154' && c <= '\u1155') 
            || (c == '\u1159') 
            || (c >= '\u115F' && c <= '\u1161') 
            || (c == '\u1163') 
            || (c == '\u1165') 
            || (c == '\u1167') 
            || (c == '\u1169') 
            || (c >= '\u116D' && c <= '\u116E') || (c >= '\u1172' && c <= '\u1173') 
            || (c == '\u1175') 
            || (c == '\u119E') 
            || (c == '\u11A8') 
            || (c == '\u11AB') 
            || (c >= '\u11AE' && c <= '\u11AF') || (c >= '\u11B7' && c <= '\u11B8') 
            || (c == '\u11BA') 
            || (c >= '\u11BC' && c <= '\u11C2') 
            || (c == '\u11EB') 
            || (c == '\u11F0') 
            || (c == '\u11F9') 
            || (c >= '\u1E00' && c <= '\u1E9B') || (c >= '\u1EA0' && c <= '\u1EF9') || (c >= '\u1F00' && c <= '\u1F15') 
            || (c >= '\u1F18' && c <= '\u1F1D') || (c >= '\u1F20' && c <= '\u1F45') || (c >= '\u1F48' && c <= '\u1F4D') 
            || (c >= '\u1F50' && c <= '\u1F57') 
            || (c == '\u1F59') 
            || (c == '\u1F5B') 
            || (c == '\u1F5D') 
            || (c >= '\u1F5F' && c <= '\u1F7D') || (c >= '\u1F80' && c <= '\u1FB4') || (c >= '\u1FB6' && c <= '\u1FBC') 
            || (c == '\u1FBE') 
            || (c >= '\u1FC2' && c <= '\u1FC4') || (c >= '\u1FC6' && c <= '\u1FCC') || (c >= '\u1FD0' && c <= '\u1FD3') 
            || (c >= '\u1FD6' && c <= '\u1FDB') || (c >= '\u1FE0' && c <= '\u1FEC') || (c >= '\u1FF2' && c <= '\u1FF4') 
            || (c >= '\u1FF6' && c <= '\u1FFC') 
            || (c == '\u2126') 
            || (c >= '\u212A' && c <= '\u212B') 
            || (c == '\u212E') 
            || (c >= '\u2180' && c <= '\u2182') || (c >= '\u3041' && c <= '\u3094') || (c >= '\u30A1' && c <= '\u30FA') 
            || (c >= '\u3105' && c <= '\u312C') || (c >= '\uAC00' && c <= '\uD7A3');
    }

    /** BaseChar - XMl Specification 1.0 [86] */
    private static final boolean Ideographic(char c) {
        return (c >= '\u4E00' && c <= '\u9FA5') || c == '\u3007' || (c >= '\u3021' && c <= '\u3029');
    }
 
    /** CombiningChar - XMl Specification 1.0 [87] */
    /*private static final boolean CombiningChar(char c) {
        return (c >= '\u0300' && c <= '\u0345')
            || (c >= '\u0360' && c <= '\u0361') || (c >= '\u0483' && c <= '\u0486') || (c >= '\u0591' && c <= '\u05A1') 
            || (c >= '\u05A3' && c <= '\u05B9') || (c >= '\u05BB' && c <= '\u05BD') 
            || (c == '\u05BF') 
            || (c >= '\u05C1' && c <= '\u05C2') 
            || (c == '\u05C4') 
            || (c >= '\u064B' && c <= '\u0652') 
            || (c == '\u0670') 
            || (c >= '\u06D6' && c <= '\u06DC') || (c >= '\u06DD' && c <= '\u06DF') || (c >= '\u06E0' && c <= '\u06E4') 
            || (c >= '\u06E7' && c <= '\u06E8') || (c >= '\u06EA' && c <= '\u06ED') || (c >= '\u0901' && c <= '\u0903') 
            || (c == '\u093C') 
            || (c >= '\u093E' && c <= '\u094C') 
            || (c == '\u094D') 
            || (c >= '\u0951' && c <= '\u0954') || (c >= '\u0962' && c <= '\u0963') || (c >= '\u0981' && c <= '\u0983') 
            || (c == '\u09BC') 
            || (c == '\u09BE') 
            || (c == '\u09BF') 
            || (c >= '\u09C0' && c <= '\u09C4') || (c >= '\u09C7' && c <= '\u09C8') || (c >= '\u09CB' && c <= '\u09CD') 
            || (c == '\u09D7') 
            || (c >= '\u09E2' && c <= '\u09E3') 
            || (c == '\u0A02') 
            || (c == '\u0A3C') 
            || (c == '\u0A3E') 
            || (c == '\u0A3F') 
            || (c >= '\u0A40' && c <= '\u0A42') || (c >= '\u0A47' && c <= '\u0A48') || (c >= '\u0A4B' && c <= '\u0A4D') 
            || (c >= '\u0A70' && c <= '\u0A71') || (c >= '\u0A81' && c <= '\u0A83') 
            || (c == '\u0ABC') 
            || (c >= '\u0ABE' && c <= '\u0AC5') || (c >= '\u0AC7' && c <= '\u0AC9') || (c >= '\u0ACB' && c <= '\u0ACD') 
            || (c >= '\u0B01' && c <= '\u0B03') 
            || (c == '\u0B3C') 
            || (c >= '\u0B3E' && c <= '\u0B43') || (c >= '\u0B47' && c <= '\u0B48') || (c >= '\u0B4B' && c <= '\u0B4D') 
            || (c >= '\u0B56' && c <= '\u0B57') || (c >= '\u0B82' && c <= '\u0B83') || (c >= '\u0BBE' && c <= '\u0BC2') 
            || (c >= '\u0BC6' && c <= '\u0BC8') || (c >= '\u0BCA' && c <= '\u0BCD') 
            || (c == '\u0BD7') 
            || (c >= '\u0C01' && c <= '\u0C03') || (c >= '\u0C3E' && c <= '\u0C44') || (c >= '\u0C46' && c <= '\u0C48') 
            || (c >= '\u0C4A' && c <= '\u0C4D') || (c >= '\u0C55' && c <= '\u0C56') || (c >= '\u0C82' && c <= '\u0C83') 
            || (c >= '\u0CBE' && c <= '\u0CC4') || (c >= '\u0CC6' && c <= '\u0CC8') || (c >= '\u0CCA' && c <= '\u0CCD') 
            || (c >= '\u0CD5' && c <= '\u0CD6') || (c >= '\u0D02' && c <= '\u0D03') || (c >= '\u0D3E' && c <= '\u0D43') 
            || (c >= '\u0D46' && c <= '\u0D48') || (c >= '\u0D4A' && c <= '\u0D4D') 
            || (c == '\u0D57') 
            || (c == '\u0E31') 
            || (c >= '\u0E34' && c <= '\u0E3A') || (c >= '\u0E47' && c <= '\u0E4E') 
            || (c == '\u0EB1') 
            || (c >= '\u0EB4' && c <= '\u0EB9') || (c >= '\u0EBB' && c <= '\u0EBC') || (c >= '\u0EC8' && c <= '\u0ECD') 
            || (c >= '\u0F18' && c <= '\u0F19') 
            || (c == '\u0F35') 
            || (c == '\u0F37') 
            || (c == '\u0F39') 
            || (c == '\u0F3E') 
            || (c == '\u0F3F') 
            || (c >= '\u0F71' && c <= '\u0F84') || (c >= '\u0F86' && c <= '\u0F8B') || (c >= '\u0F90' && c <= '\u0F95') 
            || (c == '\u0F97') 
            || (c >= '\u0F99' && c <= '\u0FAD') || (c >= '\u0FB1' && c <= '\u0FB7') 
            || (c == '\u0FB9') 
            || (c >= '\u20D0' && c <= '\u20DC') 
            || (c == '\u20E1') 
            || (c >= '\u302A' && c <= '\u302F') 
            || (c == '\u3099') 
            || (c == '\u309A');
    }*/

    /** Digit - XMl Specification 1.0 [88] */
    private static final boolean Digit(char c) {
        return (c >= '\u0030' && c <= '\u0039') || (c >= '\u0660' && c <= '\u0669') || (c >= '\u06F0' && c <= '\u06F9')
            || (c >= '\u0966' && c <= '\u096F') || (c >= '\u09E6' && c <= '\u09EF') || (c >= '\u0A66' && c <= '\u0A6F')
            || (c >= '\u0AE6' && c <= '\u0AEF') || (c >= '\u0B66' && c <= '\u0B6F') || (c >= '\u0BE7' && c <= '\u0BEF')
            || (c >= '\u0C66' && c <= '\u0C6F') || (c >= '\u0CE6' && c <= '\u0CEF') || (c >= '\u0D66' && c <= '\u0D6F')
            || (c >= '\u0E50' && c <= '\u0E59') || (c >= '\u0ED0' && c <= '\u0ED9') || (c >= '\u0F20' && c <= '\u0F29');
    }

    /** Extender - XMl Specification 1.0 [89] */
    private static final boolean Extender(char c) {
        return c == '\u00B7' || c == '\u02D0' || c == '\u02D1' || c == '\u0387'
            || c == '\u0640' || c == '\u0E46' || c == '\u0EC6' || c == '\u3005'
            || (c >= '\u3031' && c <= '\u3035') || (c >= '\u309D' && c <= '\u309E') || (c >= '\u30FC' && c <= '\u30FE');
    }

    /** Whitespace - XML Specification 1.0 [3] */
    private static final boolean S(char c) {
        return c == '\u0020' || c == '\u0009' || c == '\r' || c == '\n';
    }
}