src/xml/GXml.cpp

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/***************************************************************************
 *                          GXml.cpp - XML class                           *
 * ----------------------------------------------------------------------- *
 *  copyright (C) 2010-2016 by Juergen Knoedlseder                         *
 * ----------------------------------------------------------------------- *
 *                                                                         *
 *  This program is free software: you can redistribute it and/or modify   *
 *  it under the terms of the GNU General Public License as published by   *
 *  the Free Software Foundation, either version 3 of the License, or      *
 *  (at your option) any later version.                                    *
 *                                                                         *
 *  This program is distributed in the hope that it will be useful,        *
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of         *
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the          *
 *  GNU General Public License for more details.                           *
 *                                                                         *
 *  You should have received a copy of the GNU General Public License      *
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.  *
 *                                                                         *
 ***************************************************************************/
/**
 * @file GXml.cpp
 * @brief XML class implementation
 * @author Juergen Knoedlseder
 */

/* __ Includes ___________________________________________________________ */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "GTools.hpp"
#include "GException.hpp"
#include "GFilename.hpp"
#include "GUrlFile.hpp"
#include "GUrlString.hpp"
#include "GXml.hpp"
#include "GXmlNode.hpp"
#include "GXmlDocument.hpp"
#include "GXmlText.hpp"
#include "GXmlElement.hpp"
#include "GXmlComment.hpp"
#include "GXmlPI.hpp"

/* __ Method name definitions ____________________________________________ */
#define G_LOAD                                     "GXml::load(std::string&)"
#define G_PARSE                                          "GXml::parse(GUrl&)"
#define G_PROCESS              "GXml::process(GXmlNode*, const std::string&)"

/* __ Macros _____________________________________________________________ */

/* __ Coding definitions _________________________________________________ */

/* __ Debug definitions __________________________________________________ */


/*==========================================================================
 =                                                                         =
 =                        Constructors/destructors                         =
 =                                                                         =
 ==========================================================================*/

/***********************************************************************//**
 * @brief Void constructor
 ***************************************************************************/
GXml::GXml(void)
{
    // Initialise members
    init_members();

    // Return
    return;
}


/***********************************************************************//**
 * @brief Copy constructor
 *
 * @param[in] xml XML object.
 ***************************************************************************/
GXml::GXml(const GXml& xml)
{
    // Initialise members
    init_members();

    // Copy members
    copy_members(xml);

    // Return
    return;
}


/***********************************************************************//**
 * @brief XML document constructor
 *
 * @param[in] xml XML text string or file name.
 *
 * Constructs GXml object by either parsing a text string or a file. If the
 * @p xml argument starts with @p <?xml it is interpreted as a XML file and
 * parsed directly. Otherwise the constructor will interpret @p xml as a
 * filename, and opens the file for parsing.
 ***************************************************************************/
GXml::GXml(const std::string& xml)
{
    // Initialise members
    init_members();

    // If the string is an XML text then parse it directly
    if (xml.compare(0, 5, "<?xml") == 0) {
        GUrlString url(xml);
        read(url);
        url.close();
    }

    // ... otherwise interpret the string as a filename
    else {
        load(xml);
    }

    // Return
    return;
}


/***********************************************************************//**
 * @brief Destructor
 ***************************************************************************/
GXml::~GXml(void)
{
    // Free members
    free_members();

    // Return
    return;
}


/*==========================================================================
 =                                                                         =
 =                                Operators                                =
 =                                                                         =
 ==========================================================================*/

/***********************************************************************//**
 * @brief Assignment operator
 *
 * @param[in] xml XML object.
 * @return XML object.
 ***************************************************************************/
GXml& GXml::operator=(const GXml& xml)
{
    // Execute only if object is not identical
    if (this != &xml) {

        // Free members
        free_members();

        // Initialise members
        init_members();

        // Copy members
        copy_members(xml);

    } // endif: object was not identical

    // Return
    return *this;
}


/***********************************************************************//**
 * @brief Return pointer to child of XML document root element
 *
 * @param[in] index Node index [0,...,size()-1].
 * @return Pointer to child of XML document root element.
 *
 * Returns a pointer to the child number @p index of the XML document root
 * element. An exception will be thrown if the @p index is not valid.
 ***************************************************************************/
GXmlNode* GXml::operator[](const int& index)
{
    // Return pointer
    return m_root[index];
}


/***********************************************************************//**
 * @brief Return pointer to child of XML document root element (const variant)
 *
 * @param[in] index Node index [0,...,size()-1].
 * @return Pointer to child of XML document root element.
 *
 * Returns a pointer to the child number @p index of the XML document root
 * element. An exception will be thrown if the @p index is not valid.
 ***************************************************************************/
const GXmlNode* GXml::operator[](const int& index) const
{
    // Return pointer
    return m_root[index];
}


/*==========================================================================
 =                                                                         =
 =                             Public methods                              =
 =                                                                         =
 ==========================================================================*/

/***********************************************************************//**
 * @brief Clear XML object
 *
 * Resets XML object to a clean initial state.
 ***************************************************************************/
void GXml::clear(void)
{
    // Free memory and initialise members
    free_members();
    init_members();

    // Return
    return;
}


/***********************************************************************//**
 * @brief Clone XML object
 *
 * @return Pointer to deep copy of XML object.
 ***************************************************************************/
GXml* GXml::clone(void) const
{
    // Clone object
    return new GXml(*this);
}


/***********************************************************************//**
 * @brief Set child node in XML document root
 *
 * @param[in] index Child node index [0,...,size()-1].
 * @param[in] node XML child node.
 * @return Pointer to deep copy of child node.
 *
 * Set @p node with @p index of XML document root.
 ***************************************************************************/
GXmlNode* GXml::set(const int& index, const GXmlNode& node)
{
    // Set node and return pointer
    return (m_root.set(index, node));
}


/***********************************************************************//**
 * @brief Append child node to XML document root
 *
 * @param[in] node Child node.
 * @return Pointer to appended child node.
 *
 * Appends node to XML document root by making a deep copy of the @p node.
 ***************************************************************************/
GXmlNode* GXml::append(const GXmlNode& node)
{
    // Append node and return pointer
    return (m_root.append(node));
}


/***********************************************************************//**
 * @brief Append child node to XML document root
 *
 * @param[in] segment XML child node.
 * @return Pointer to appended child node.
 *
 * Appends XML element that is constructed from a text @p segment. The text
 * segment is parsed and the element name and attributes are extracted using
 * the GXmlElement::parse_start() method. The method returns a pointer to the
 * XML element child node that has been appended.
 ***************************************************************************/
GXmlElement* GXml::append(const std::string& segment)
{
    // Append node and return pointer
    return (m_root.append(segment));
}


/***********************************************************************//**
 * @brief Insert child node into XML document root
 *
 * @param[in] index Child node index [0,...,size()-1].
 * @param[in] node XML child node.
 * @return Pointer to inserted child node.
 *
 * Inserts the XML child @p node before the node with the specified @p index.
 * A deep copy of the node will be made and the pointer to this node will be
 * stored.
 ***************************************************************************/
GXmlNode* GXml::insert(const int& index, const GXmlNode& node)
{
    // Insert node and return pointer
    return (m_root.insert(index, node));
}


/***********************************************************************//**
 * @brief Remove child node from XML document root
 *
 * @param[in] index Child node index [0,...,size()-1].
 *
 * Remove XML child node at @p index from the XML document root.
 ***************************************************************************/
void GXml::remove(const int& index)
{
    // Remove node
    m_root.remove(index);

    // Return
    return;
}


/***********************************************************************//**
 * @brief Reserve space for child nodes in XML document root
 *
 * @param[in] num Number of nodes.
 *
 * Reserves space for @p num nodes in the XML document root.
 ***************************************************************************/
void GXml::reserve(const int& num)
{
    // Reservers space node
    m_root.reserve(num);

    // Return
    return;
}


/***********************************************************************//**
 * @brief Append all XML child nodes from another XML node in the XML
 *        document root
 *
 * @param[in] node XML child node.
 *
 * Append all XML child nodes found in @p node to the XML document root.
 * Nodes are copied deeply so that they live now on their on in the actual
 * object.
 ***************************************************************************/
void GXml::extend(const GXmlNode& node)
{
    // Extend node
    m_root.extend(node);

    // Return
    return;
}


/***********************************************************************//**
 * @brief Return number of child elements in XML document root
 *
 * @return Number of child elements in XML document root.
 *
 * Returns the number of GXmlElement child elements of the XML document root.
 * GXMLElement child elements are nodes of type NT_ELEMENT.
 ***************************************************************************/
int GXml::elements(void) const
{
    // Return number
    return m_root.elements();
}


/***********************************************************************//**
 * @brief Return number of child elements with a given name in XML
 *        document root
 *
 * @param[in] name Name of child elements.
 * @return Number of child elements with a given @p name in XML
 *         document root.
 *
 * Returns the number of GXMLElement child elements of the XML document root
 * that have a given @p name. GXmlElement child elements are nodes of type
 * NT_ELEMENT.
 ***************************************************************************/
int GXml::elements(const std::string& name) const
{
    // Return number
    return m_root.elements(name);
}


/***********************************************************************//**
 * @brief Return pointer to child element
 *
 * @param[in] index Node index [0,...,elements()-1].
 * @return Pointer to child element.
 *
 * Returns a pointer to the child number @p index of the XML document root.
 * An exception will be thrown if the @p index is not valid.
 ***************************************************************************/
GXmlElement* GXml::element(const int& index)
{
    // Return pointer
    return m_root.element(index);
}


/***********************************************************************//**
 * @brief Return pointer to child element (const variant)
 *
 * @param[in] index Node index [0,...,elements()-1].
 * @return Pointer to child element.
 *
 * Returns a pointer to the child number @p index of the XML document root.
 * An exception will be thrown if the @p index is not valid.
 ***************************************************************************/
const GXmlElement* GXml::element(const int& index) const
{
    // Return pointer
    return m_root.element(index);
}


/***********************************************************************//**
 * @brief Return pointer to child element by hierarchy
 *
 * @param[in] name Child element hierarchy.
 * @return Pointer to child element.
 *
 * Returns a pointer to the child element described by a hierarchy of the
 * following syntax
 *
 *     params > param[1] > value > struct
 *
 * The > symbols indicate subsequent hierarchy levels, the square brackets
 * provides the index in case that multiple tags with the same name exist
 * at a given hierarchy level. Omitting the index means that the first
 * tag with the specified name is accessed.
 ***************************************************************************/
GXmlElement* GXml::element(const std::string& name)
{
    // Return pointer
    return m_root.element(name);
}


/***********************************************************************//**
 * @brief Return pointer to child element by hierarchy (const version)
 *
 * @param[in] name Child element hierarchy.
 * @return Pointer to child element.
 *
 * Returns a pointer to the child element described by a hierarchy of the
 * following syntax
 *
 *     params > param[1] > value > struct
 *
 * The > symbols indicate subsequent hierarchy levels, the square brackets
 * provides the index in case that multiple tags with the same name exist
 * at a given hierarchy level. Omitting the index means that the first
 * tag with the specified name is accessed.
 ***************************************************************************/
const GXmlElement* GXml::element(const std::string& name) const
{
    // Return pointer
    return m_root.element(name);
}


/***********************************************************************//**
 * @brief Return pointer to child element of a given name
 *
 * @param[in] name Name of child element.
 * @param[in] index Node index [0,...,elements()-1].
 * @return Pointer to child element.
 *
 * Returns a pointer to the child number @p index with @p name of the XML
 * document root. An exception will be thrown if the @p index is not valid.
 ***************************************************************************/
GXmlElement* GXml::element(const std::string& name, const int& index)
{
    // Return pointer
    return m_root.element(name, index);
}


/***********************************************************************//**
 * @brief Return pointer to child element of a given name (const variant)
 *
 * @param[in] name Name of child element.
 * @param[in] index Node index [0,...,elements()-1].
 * @return Pointer to child element.
 *
 * Returns a pointer to the child number @p index with @p name of the XML
 * document root. An exception will be thrown if the @p index is not valid.
 ***************************************************************************/
const GXmlElement* GXml::element(const std::string& name, const int& index) const
{
    // Return pointer
    return m_root.element(name, index);
}


/***********************************************************************//**
 * @brief Load XML document from file
 *
 * @param[in] filename File name.
 *
 * Loads a XML document from a file by reading from the file's Unified
 * Resource Locator (URL). The read() method is invoked for this purpose.
 *
 * The method uses the GUrlFile file opening constructor to open the URL.
 * This constructor will automatically expand any environment variables that
 * are present in the filename.
 *
 * @todo Ideally, we would like to extract the URL type from the filename
 * so that any kind of URL can be used for loading.
 ***************************************************************************/
void GXml::load(const GFilename& filename)
{
    // Throw an exception if file does not exist
    if (!filename.exists()) {
        throw GException::file_open_error(G_LOAD, filename);
    }

    // Open XML URL as file for reading
    GUrlFile url(filename.url().c_str(), "r");

    // Read XML document from URL
    read(url);

    // Close URL
    url.close();

    // Store filename in XML document
    m_root.filename(filename);

    // Return
    return;
}


/***********************************************************************//**
 * @brief Save XML document into file
 *
 * @param[in] filename File name.
 *
 * Saves the XML document into a file by writing into the file's Unified
 * Resource Locator (URL). The write() method is invoked for this purpose.
 *
 * The method uses the GUrlFile file opening constructor to open the URL.
 * This constructor will automatically expand any environment variables that
 * are present in the filename.
 *
 * @todo Ideally, we would like to extract the URL type from the filename
 * so that any kind of URL can be used for loading.
 ***************************************************************************/
void GXml::save(const GFilename& filename) const
{
    // Open XML file for writing
    GUrlFile url(filename.url().c_str(), "w");

    // Store filename in XML document (circumvent const correctness)
    const_cast<GXmlDocument*>(&m_root)->filename(filename);

    // Write XML document
    write(url, 0);

    // Close file
    url.close();

    // Return
    return;
}


/***********************************************************************//**
 * @brief Read XML document from URL
 *
 * @param[in] url Unified Resource Locator.
 *
 * Reads in the XML document by parsing a Unified Resource Locator of any
 * type.
 ***************************************************************************/
void GXml::read(const GUrl& url)
{
    // Clear object
    clear();

    // Parse URL
    parse(url);

    // Return
    return;
}


/***********************************************************************//**
 * @brief Write XML document into URL
 *
 * @param[in] url Unified Resource Locator.
 * @param[in] indent Indentation (default = 0).
 *
 * Writes the XML document in a Unified Resource Locator. Formatting of the
 * document can be adapted using the @p indent parameter.
 ***************************************************************************/
void GXml::write(GUrl& url, const int& indent) const
{
    // Write XML document
    m_root.write(url);

    // Return
    return;
}


/***********************************************************************//**
 * @brief Print XML object
 *
 * @param[in] chatter Chattiness.
 * @param[in] indent Text indentation.
 * @return String containing XML object.
 ***************************************************************************/
std::string GXml::print(const GChatter& chatter, const int& indent) const
{
    // Initialise result string
    std::string result;

    // Continue only if chatter is not silent
    if (chatter != SILENT) {

        // Append header
        result.append("=== GXml ===");

        // Append model
        result.append("\n"+m_root.print(chatter, 0));

    } // endif: chatter was not silent

    // Return result
    return result;
}


/***********************************************************************//**
 * @brief Print XML object
 *
 * @param[in] chatter Chattiness.
 * @return String containing XML object.
 ***************************************************************************/
std::string GXml::print(const GChatter& chatter) const
{
    // Set result string
    std::string result = print(chatter, 0);

    // Return result
    return result;
}


/*==========================================================================
 =                                                                         =
 =                             Private methods                             =
 =                                                                         =
 ==========================================================================*/

/***********************************************************************//**
 * @brief Initialise class members
 ***************************************************************************/
void GXml::init_members(void)
{
    // Initialise members
    m_root.clear();

    // Return
    return;
}


/***********************************************************************//**
 * @brief Copy class members
 *
 * @param[in] xml Object from which members which should be copied.
 ***************************************************************************/
void GXml::copy_members(const GXml& xml)
{
    // Copy attributes
    m_root = xml.m_root;

    // Return
    return;
}


/***********************************************************************//**
 * @brief Delete class members
 ***************************************************************************/
void GXml::free_members(void)
{
    // Return
    return;
}


/***********************************************************************//**
 * @brief Parse XML URL
 *
 * @param[in] url Unified Resource Locator.
 *
 * @exception GException::xml_syntax_error
 *            XML syntax error.
 *
 * Parses either a XML file or a XML text string and creates all associated
 * nodes. The XML file is split into segments, made either of text or of
 * tags.
 ***************************************************************************/
void GXml::parse(const GUrl& url)
{
    // Initialise parser
    int         c;
    bool        in_markup  = false;
    bool        in_comment = false;
    std::string segment;
    GXmlNode*   current = &m_root;

    // Main parsing loop
    while ((c = url.get_char()) != EOF) {

        // Convert special characters into line feeds
        if (c == '\x85' || c == L'\x2028') {
            if (in_markup) {
                 throw GException::xml_syntax_error(G_PARSE, segment,
                                   "invalid character encountered");
            }
            else {
                c = '\x0a';
            }
        }

        // Skip all linefeeds (to avoid extra linefeeds in text segments)
        if (c == '\x0a') {
            continue;
        }

        // If we are not within a markup and if a markup is reached then
        // add the text segment to the nodes and switch to in_markup mode
        if (in_markup == false) {

            // Markup start reached?
            if (c == '<') {

                // Add text segment to nodes (ignores empty segments)
                process_text(&current, segment);

                // Prepare new segment and signal that we are within tag
                segment.clear();
                segment.append(1, (char)c);
                in_markup = true;

            }

            // Markup stop encountered?
            else if (c == '>') {
                 segment.append(1, (char)c);
                 throw GException::xml_syntax_error(G_PARSE, segment,
                       "unexpected closing bracket \">\" encountered");
            }

            // ... otherwise add character to segment
            else {
                segment.append(1, (char)c);
            }
        }

        // If we are within a markup and if a markup end is reached then
        // process the markup and switch to not in_tag mode
        else {

            // Markup stop reached?
            if (c == '>') {

                // Append character to segment
                segment.append(1, (char)c);

                // If we are in comment then check if this is the end of
                // the comment
                if (in_comment) {
                    int n = segment.length();
                    if (n > 2) {
                        if (segment.compare(n-3,3,"-->") == 0) {
                            in_comment = false;
                        }
                    }
                }

                // If we are not in the comment, then process markup
                if (!in_comment) {

                    // Process markup
                    process_markup(&current, segment);

                    // Prepare new segment and signal that we are not
                    // within markup
                    segment.clear();
                    in_markup = false;
                }
            }

            // Markup start encountered?
            else if (!in_comment && c == '<') {

                // Append character to segment
                segment.append(1, (char)c);

                // If we encounter an opening bracket then throw an exception
                throw GException::xml_syntax_error(G_PARSE, segment,
                      "unexpected opening bracket \"<\" encountered");
            }

            // ... otherwise add character to segment
            else {
                segment.append(1, (char)c);
                if (!in_comment && segment == "<!--") {
                    in_comment = true;
                }
            }
        }

    } // endwhile: main parsing loop

    // Process any pending segment
    if (segment.size() > 0) {
        if (in_markup) {
            process_markup(&current, segment);
        }
        else {
            process_text(&current, segment);
        }
    }

    // Verify that we are back to the root node
    if (current != &m_root) {
        std::string message = "closing tag ";
        GXmlElement* element = dynamic_cast<GXmlElement*>(current);
        if (element != NULL) {
            message += "for GXmlElement \""+element->name()+"\"";
        }
        message += " is missing";
        throw GException::xml_syntax_error(G_PARSE, "", message);
    }

    // Return
    return;
}


/***********************************************************************//**
 * @brief Process markup segment
 *
 * @param[in] current Handle to current node.
 * @param[in] segment Segment string.
 *
 * Process markup segment.
 ***************************************************************************/
void GXml::process_markup(GXmlNode** current, const std::string& segment)
{
    // Determine segment tag type
    MarkupType type = get_markuptype(segment);

    // Do tag specific processing
    switch (type) {

    // Handle element start tag
    case MT_ELEMENT_START:
        {
            // Create new element node, set its parent, append it to the
            // current node and make it the current node
            GXmlElement element(segment);
            element.parent(*current);
            (*current)->append(element);
            int last = (*current)->size() - 1;
            (*current) = (*(*current))[last];
        }
        break;

    // Handle element end tag
    case MT_ELEMENT_END:
        {
            // Check if we expect an element end tag
            if ((*current)->type() != GXmlNode::NT_ELEMENT) {
                throw GException::xml_syntax_error(G_PROCESS, segment,
                      "unexpected element end tag encountered");
            }

            // Check if we have the correct end tag
            GXmlElement* element = (GXmlElement*)(*current);
            element->parse_stop(segment);

            // Set current node pointer back to parent of the current node
            (*current) = element->parent();
        }
        break;

    // Append empty-element tag
    case MT_ELEMENT_EMPTY:
        {
            GXmlElement element(segment.substr(1,segment.length()-3));
            element.parent(*current);
            (*current)->append(element);
        }
        break;

    // Append comment markup
    case MT_COMMENT:
        {
            // Create a new comment node, set its parent and append it to the
            // current node
            GXmlComment comment(segment);
            comment.parent(*current);
            (*current)->append(comment);
        }
        break;

    // Declaration markup
    case MT_DECLARATION:
        {
            // Verify if declaration tag is allowed
            if (*current != &m_root) {
                throw GException::xml_syntax_error(G_PROCESS, segment,
                      "unexpected declaration markup encountered");
            }
            if (!m_root.is_empty()) {
                throw GException::xml_syntax_error(G_PROCESS, segment,
                      "declaration markup only allowed in first line");
            }

            // Create temporary element to read in declaration attributes
            GXmlElement* element = new GXmlElement(segment);
            size_t       pos     = 5;
            while (pos != std::string::npos) {
                element->parse_attribute(&pos, segment);
            }

            // Set attribute values
            std::string version    = element->attribute("version");
            std::string encoding   = element->attribute("encoding");
            std::string standalone = element->attribute("standalone");
            if (version.length() > 0) {
                m_root.version(version);
            }
            if (encoding.length() > 0) {
                m_root.encoding(encoding);
            }
            if (standalone.length() > 0) {
                m_root.standalone(standalone);
            }

            // Delete temporary element
            delete element;
        }
        break;

    // Processing tag
    case MT_PROCESSING:
        {
            // Create a new PI node, set its parent and append it to the
            // current node
            GXmlPI pi(segment);
            pi.parent(*current);
            (*current)->append(pi);
        }
        break;

    // Invalid tag, throw an error
    case MT_INVALID:
        throw GException::xml_syntax_error(G_PROCESS, segment, "invalid tag");
        break;
    }

    // Return
    return;
}


/***********************************************************************//**
 * @brief Process text segment
 *
 * @param[in] current Handle to current node.
 * @param[in] segment Segment string.
 *
 * Process text segment.
 ***************************************************************************/
void GXml::process_text(GXmlNode** current, const std::string& segment)
{
    // Continue only if text segment is not empty
    if (segment.size() > 0) {

        // Continue only if non whitespace characters are found
        size_t pos = segment.find_first_not_of("\x20\x09\x0d\x0a\x85");
        if (pos != std::string::npos) {

            // Append node
            (*current)->append(GXmlText(segment));

        } // endif: there was not only whitespace

    } // endif: segment was not empty

    // Return
    return;
}


/***********************************************************************//**
 * @brief Get Markup type of segment
 *
 * @param[in] segment Segment for which Markup Type should be determined.
 *
 * Returns Markup Type of segment.
 ***************************************************************************/
GXml::MarkupType GXml::get_markuptype(const std::string& segment) const
{
    // Initialise with invalid Markup Type
    MarkupType type = MT_INVALID;

    // Get length of segment
    int n = segment.length();

    // Check for comment
    if (n >= 7 && (segment.compare(0,4,"<!--") == 0) &&
                  (segment.compare(n-3,3,"-->") == 0)) {
        type = MT_COMMENT;
    }

    // Check for declaration
    else if (n >= 7 && (segment.compare(0,6,"<?xml ") == 0) &&
                       (segment.compare(n-2,2,"?>") == 0)) {
        type = MT_DECLARATION;
    }

    // Check for processing instruction
    else if (n >= 4 && (segment.compare(0,2,"<?") == 0) &&
                       (segment.compare(n-2,2,"?>") == 0)) {
        type = MT_PROCESSING;
    }

    // Check for empty element tag
    else if (n >= 3 && (segment.compare(0,1,"<") == 0) &&
                       (segment.compare(n-2,2,"/>") == 0)) {
        type = MT_ELEMENT_EMPTY;
    }

    // Check for element end tag
    else if (n >= 3 && (segment.compare(0,2,"</") == 0) &&
                       (segment.compare(n-1,1,">") == 0)) {
        type = MT_ELEMENT_END;
    }

    // Check for element start tag
    else if (n >= 2 && (segment.compare(0,1,"<") == 0) &&
                       (segment.compare(n-1,1,">") == 0)) {
        type = MT_ELEMENT_START;
    }

    // Return type
    return type;
}

---