/** @file
 * IPRT - XML Helper APIs.
 */

/*
 * Copyright (C) 2007-2022 Oracle and/or its affiliates.
 *
 * This file is part of VirtualBox base platform packages, as
 * available from https://www.virtualbox.org.
 *
 * 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, in version 3 of the
 * License.
 *
 * 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 <https://www.gnu.org/licenses>.
 *
 * The contents of this file may alternatively be used under the terms
 * of the Common Development and Distribution License Version 1.0
 * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
 * in the VirtualBox distribution, in which case the provisions of the
 * CDDL are applicable instead of those of the GPL.
 *
 * You may elect to license modified versions of this file under the
 * terms and conditions of either the GPL or the CDDL or both.
 *
 * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
 */

#ifndef IPRT_INCLUDED_cpp_xml_h
#define IPRT_INCLUDED_cpp_xml_h
#ifndef RT_WITHOUT_PRAGMA_ONCE
# pragma once
#endif

#ifndef IN_RING3
# error "There are no XML APIs available in Ring-0 Context!"
#endif
#ifdef IPRT_NO_CRT
# error "Not available in no-CRT mode because it depends on exceptions, std::list, std::map and stdio.h."
#endif

#include <iprt/list.h>
#include <iprt/cpp/exception.h>
#include <iprt/cpp/utils.h>

#include <list>
#include <memory>


/** @defgroup grp_rt_cpp_xml    C++ XML support
 * @ingroup grp_rt_cpp
 * @{
 */

/* Forwards */
typedef struct _xmlParserInput xmlParserInput;
typedef xmlParserInput *xmlParserInputPtr;
typedef struct _xmlParserCtxt xmlParserCtxt;
typedef xmlParserCtxt *xmlParserCtxtPtr;
typedef struct _xmlError xmlError;
typedef xmlError *xmlErrorPtr;

typedef struct _xmlAttr xmlAttr;
typedef struct _xmlNode xmlNode;

#define RT_XML_CONTENT_SMALL _8K
#define RT_XML_CONTENT_LARGE _128K
#define RT_XML_ATTR_TINY 64
#define RT_XML_ATTR_SMALL _1K
#define RT_XML_ATTR_MEDIUM _8K
#define RT_XML_ATTR_LARGE _64K

/** @} */

namespace xml
{

/**
 * @addtogroup grp_rt_cpp_xml
 * @{
 */

// Exceptions
//////////////////////////////////////////////////////////////////////////////

class RT_DECL_CLASS LogicError : public RTCError
{
public:

    LogicError(const char *aMsg = NULL)
        : RTCError(aMsg)
    {}

    LogicError(RT_SRC_POS_DECL);
};

class RT_DECL_CLASS RuntimeError : public RTCError
{
public:

    RuntimeError(const char *aMsg = NULL)
        : RTCError(aMsg)
    {}
};

class RT_DECL_CLASS XmlError : public RuntimeError
{
public:
    XmlError(xmlErrorPtr aErr);

    static char* Format(xmlErrorPtr aErr);
};

// Logical errors
//////////////////////////////////////////////////////////////////////////////

class RT_DECL_CLASS ENotImplemented : public LogicError
{
public:
    ENotImplemented(const char *aMsg = NULL) : LogicError(aMsg) {}
    ENotImplemented(RT_SRC_POS_DECL) : LogicError(RT_SRC_POS_ARGS) {}
};

class RT_DECL_CLASS EInvalidArg : public LogicError
{
public:
    EInvalidArg(const char *aMsg = NULL) : LogicError(aMsg) {}
    EInvalidArg(RT_SRC_POS_DECL) : LogicError(RT_SRC_POS_ARGS) {}
};

class RT_DECL_CLASS EDocumentNotEmpty : public LogicError
{
public:
    EDocumentNotEmpty(const char *aMsg = NULL) : LogicError(aMsg) {}
    EDocumentNotEmpty(RT_SRC_POS_DECL) : LogicError(RT_SRC_POS_ARGS) {}
};

class RT_DECL_CLASS ENodeIsNotElement : public LogicError
{
public:
    ENodeIsNotElement(const char *aMsg = NULL) : LogicError(aMsg) {}
    ENodeIsNotElement(RT_SRC_POS_DECL) : LogicError(RT_SRC_POS_ARGS) {}
};

// Runtime errors
//////////////////////////////////////////////////////////////////////////////

class RT_DECL_CLASS EIPRTFailure : public RuntimeError
{
public:

    EIPRTFailure(int aRC, const char *pszContextFmt, ...);

    int rc() const
    {
        return mRC;
    }

private:
    int mRC;
};

/**
 * The Stream class is a base class for I/O streams.
 */
class RT_DECL_CLASS Stream
{
public:

    virtual ~Stream() {}

    virtual const char *uri() const = 0;

    /**
     * Returns the current read/write position in the stream. The returned
     * position is a zero-based byte offset from the beginning of the file.
     *
     * Throws ENotImplemented if this operation is not implemented for the
     * given stream.
     */
    virtual uint64_t pos() const = 0;

    /**
     * Sets the current read/write position in the stream.
     *
     * @param aPos Zero-based byte offset from the beginning of the stream.
     *
     * Throws ENotImplemented if this operation is not implemented for the
     * given stream.
     */
    virtual void setPos (uint64_t aPos) = 0;
};

/**
 * The Input class represents an input stream.
 *
 * This input stream is used to read the settings tree from.
 * This is an abstract class that must be subclassed in order to fill it with
 * useful functionality.
 */
class RT_DECL_CLASS Input : virtual public Stream
{
public:

    /**
     * Reads from the stream to the supplied buffer.
     *
     * @param aBuf Buffer to store read data to.
     * @param aLen Buffer length.
     *
     * @return Number of bytes read.
     */
    virtual int read (char *aBuf, int aLen) = 0;
};

/**
 *
 */
class RT_DECL_CLASS Output : virtual public Stream
{
public:

    /**
     * Writes to the stream from the supplied buffer.
     *
     * @param aBuf Buffer to write data from.
     * @param aLen Buffer length.
     *
     * @return Number of bytes written.
     */
    virtual int write (const char *aBuf, int aLen) = 0;

    /**
     * Truncates the stream from the current position and upto the end.
     * The new file size will become exactly #pos() bytes.
     *
     * Throws ENotImplemented if this operation is not implemented for the
     * given stream.
     */
    virtual void truncate() = 0;
};


//////////////////////////////////////////////////////////////////////////////

/**
 * The File class is a stream implementation that reads from and writes to
 * regular files.
 *
 * The File class uses IPRT File API for file operations. Note that IPRT File
 * API is not thread-safe. This means that if you pass the same RTFILE handle to
 * different File instances that may be simultaneously used on different
 * threads, you should care about serialization; otherwise you will get garbage
 * when reading from or writing to such File instances.
 */
class RT_DECL_CLASS File : public Input, public Output
{
public:

    /**
     * Possible file access modes.
     */
    enum Mode { Mode_Read, Mode_WriteCreate, Mode_Overwrite, Mode_ReadWrite };

    /**
     * Opens a file with the given name in the given mode. If @a aMode is Read
     * or ReadWrite, the file must exist. If @a aMode is Write, the file must
     * not exist. Otherwise, an EIPRTFailure exception will be thrown.
     *
     * @param aMode     File mode.
     * @param aFileName File name.
     * @param aFlushIt  Whether to flush a writable file before closing it.
     */
    File(Mode aMode, const char *aFileName, bool aFlushIt = false);

    /**
     * Uses the given file handle to perform file operations. This file
     * handle must be already open in necessary mode (read, or write, or mixed).
     *
     * The read/write position of the given handle will be reset to the
     * beginning of the file on success.
     *
     * Note that the given file handle will not be automatically closed upon
     * this object destruction.
     *
     * @note It you pass the same RTFILE handle to more than one File instance,
     *       please make sure you have provided serialization in case if these
     *       instasnces are to be simultaneously used by different threads.
     *       Otherwise you may get garbage when reading or writing.
     *
     * @param aHandle   Open file handle.
     * @param aFileName File name (for reference).
     * @param aFlushIt  Whether to flush a writable file before closing it.
     */
    File(RTFILE aHandle, const char *aFileName = NULL, bool aFlushIt = false);

    /**
     * Destroys the File object. If the object was created from a file name
     * the corresponding file will be automatically closed. If the object was
     * created from a file handle, it will remain open.
     */
    virtual ~File();

    const char *uri() const;

    uint64_t pos() const;
    void setPos(uint64_t aPos);

    /**
     * See Input::read(). If this method is called in wrong file mode,
     * LogicError will be thrown.
     */
    int read(char *aBuf, int aLen);

    /**
     * See Output::write(). If this method is called in wrong file mode,
     * LogicError will be thrown.
     */
    int write(const char *aBuf, int aLen);

    /**
     * See Output::truncate(). If this method is called in wrong file mode,
     * LogicError will be thrown.
     */
    void truncate();

private:

    /* Obscure class data */
    struct Data;
    Data *m;

    /* auto_ptr data doesn't have proper copy semantics */
    DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(File);
};

/**
 * The MemoryBuf class represents a stream implementation that reads from the
 * memory buffer.
 */
class RT_DECL_CLASS MemoryBuf : public Input
{
public:

    MemoryBuf (const char *aBuf, size_t aLen, const char *aURI = NULL);

    virtual ~MemoryBuf();

    const char *uri() const;

    int read(char *aBuf, int aLen);
    uint64_t pos() const;
    void setPos(uint64_t aPos);

private:
    /* Obscure class data */
    struct Data;
    Data *m;

    /* auto_ptr data doesn't have proper copy semantics */
    DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(MemoryBuf);
};


/*
 * GlobalLock
 *
 *
 */


typedef DECLCALLBACKTYPE_EX(xmlParserInput *, RT_NOTHING, FNEXTERNALENTITYLOADER,(const char *aURI, const char *aID,
                                                                                  xmlParserCtxt *aCtxt));
typedef FNEXTERNALENTITYLOADER *PFNEXTERNALENTITYLOADER; /**< xmlExternalEntityLoader w/ noexcept. */

class RT_DECL_CLASS GlobalLock
{
public:
    GlobalLock();
    ~GlobalLock();

    void setExternalEntityLoader(PFNEXTERNALENTITYLOADER pFunc);

    static xmlParserInput* callDefaultLoader(const char *aURI,
                                             const char *aID,
                                             xmlParserCtxt *aCtxt);

private:
    /* Obscure class data. */
    struct Data;
    struct Data *m;
};

class ElementNode;
typedef std::list<const ElementNode*> ElementNodesList;

class AttributeNode;

class ContentNode;

/**
 * Node base class.
 *
 * Cannot be used directly, but ElementNode, ContentNode and AttributeNode
 * derive from this.  This does implement useful public methods though.
 *
 *
 */
class RT_DECL_CLASS Node
{
public:
    virtual ~Node();

    const char *getName() const;
    const char *getPrefix() const;
    const char *getNamespaceURI() const;
    bool nameEqualsNS(const char *pcszNamespace, const char *pcsz) const;
    bool nameEquals(const char *pcsz) const
    {
        return nameEqualsNS(NULL, pcsz);
    }
    bool nameEqualsN(const char *pcsz, size_t cchMax, const char *pcszNamespace = NULL) const;

    const char *getValue() const;
    const char *getValueN(size_t cchValueLimit) const;
    bool copyValue(int32_t &i) const;
    bool copyValue(uint32_t &i) const;
    bool copyValue(int64_t &i) const;
    bool copyValue(uint64_t &i) const;

    /** @name Introspection.
     * @{ */
    /** Is this an ElementNode instance.
     * @returns true / false  */
    bool isElement() const
    {
        return m_Type == IsElement;
    }

    /** Is this an ContentNode instance.
     * @returns true / false  */
    bool isContent() const
    {
        return m_Type == IsContent;
    }

    /** Is this an AttributeNode instance.
     * @returns true / false  */
    bool isAttribute() const
    {
        return m_Type == IsAttribute;
    }

    int getLineNumber() const;
    /** @} */

    /** @name General tree enumeration.
     *
     * Use the introspection methods isElement() and isContent() before doing static
     * casting.  Parents are always or ElementNode type, but siblings and children
     * can be of both ContentNode and ElementNode types.
     *
     * @remarks Attribute node are in the attributes list, while both content and
     *          element nodes are in the list of children. See ElementNode.
     *
     * @remarks Careful mixing tree walking with node removal!
     * @{
     */
    /** Get the parent node
     * @returns Pointer to the parent node, or NULL if root. */
    const Node *getParent() const
    {
        return m_pParent;
    }

    /** Get the previous sibling.
     * @returns Pointer to the previous sibling node, NULL if first child.
     */
    const Node *getPrevSibiling() const
    {
        if (!m_pParentListAnchor)
            return NULL;
        return RTListGetPrevCpp(m_pParentListAnchor, this, const Node, m_listEntry);
    }

    /** Get the next sibling.
     * @returns Pointer to the next sibling node, NULL if last child. */
    const Node *getNextSibiling() const
    {
        if (!m_pParentListAnchor)
            return NULL;
        return RTListGetNextCpp(m_pParentListAnchor, this, const Node, m_listEntry);
    }
    /** @} */

protected:
    /** Node types. */
    typedef enum { IsElement, IsAttribute, IsContent } EnumType;

    /** The type of node this is an instance of. */
    EnumType    m_Type;
    /** The parent node (always an element), NULL if root. */
    Node       *m_pParent;

    xmlNode    *m_pLibNode;            ///< != NULL if this is an element or content node
    xmlAttr    *m_pLibAttr;            ///< != NULL if this is an attribute node
    const char *m_pcszNamespacePrefix; ///< not always set
    const char *m_pcszNamespaceHref;   ///< full http:// spec
    const char *m_pcszName;            ///< element or attribute name, points either into pLibNode or pLibAttr;
                                       ///< NULL if this is a content node

    /** Child list entry of this node. (List head m_pParent->m_children or
     *  m_pParent->m_attribute depending on the type.) */
    RTLISTNODE      m_listEntry;
    /** Pointer to the parent list anchor.
     * This allows us to use m_listEntry both for children and attributes. */
    PRTLISTANCHOR   m_pParentListAnchor;

    // hide the default constructor so people use only our factory methods
    Node(EnumType type,
         Node *pParent,
         PRTLISTANCHOR pListAnchor,
         xmlNode *pLibNode,
         xmlAttr *pLibAttr);
    Node(const Node &x);      // no copying

    friend class AttributeNode;
    friend class ElementNode; /* C list hack. */
};

/**
 * Node subclass that represents an attribute of an element.
 *
 * For attributes, Node::getName() returns the attribute name, and Node::getValue()
 * returns the attribute value, if any.
 *
 * Since the Node constructor is private, one can create new attribute nodes
 * only through the following factory methods:
 *
 *  --  ElementNode::setAttribute()
 */
class RT_DECL_CLASS AttributeNode : public Node
{
public:

protected:
    // hide the default constructor so people use only our factory methods
    AttributeNode(const ElementNode *pElmRoot,
                  Node *pParent,
                  PRTLISTANCHOR pListAnchor,
                  xmlAttr *pLibAttr);
    AttributeNode(const AttributeNode &x);      // no copying

    friend class Node;
    friend class ElementNode;
};

/**
 *  Node subclass that represents an element.
 *
 *  For elements, Node::getName() returns the element name, and Node::getValue()
 *  returns the text contents, if any.
 *
 *  Since the Node constructor is private, one can create element nodes
 *  only through the following factory methods:
 *
 *  --  Document::createRootElement()
 *  --  ElementNode::createChild()
 */
class RT_DECL_CLASS ElementNode : public Node
{
public:
    int getChildElements(ElementNodesList &children, const char *pcszMatch = NULL) const;

    const ElementNode *findChildElementNS(const char *pcszNamespace, const char *pcszMatch) const;
    const ElementNode *findChildElement(const char *pcszMatch) const
    {
        return findChildElementNS(NULL, pcszMatch);
    }
    const ElementNode *findChildElementFromId(const char *pcszId) const;

    /** Finds the first decendant matching the name at the end of @a pcszPath and
     *  optionally namespace.
     *
     * @returns Pointer to the child string value, NULL if not found or no value.
     * @param   pcszPath        Path to the child element.  Slashes can be used to
     *                          make a simple path to any decendant.
     * @param   pcszNamespace   The namespace to match, NULL (default) match any
     *                          namespace.  When using a path, this matches all
     *                          elements along the way.
     * @see     findChildElement, findChildElementP
     */
    const ElementNode *findChildElementP(const char *pcszPath, const char *pcszNamespace = NULL) const;

    /** Finds the first child with matching the give name and optionally namspace,
     *  returning its value.
     *
     * @returns Pointer to the child string value, NULL if not found or no value.
     * @param   pcszPath        Path to the child element.  Slashes can be used to
     *                          make a simple path to any decendant.
     * @param   pcszNamespace   The namespace to match, NULL (default) match any
     *                          namespace.  When using a path, this matches all
     *                          elements along the way.
     * @see     findChildElement, findChildElementP
     */
    const char *findChildElementValueP(const char *pcszPath, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getValue();
        return NULL;
    }

    /** Finds the first child with matching the give name and optionally namspace,
     *  returning its value. Checks the length against the limit.
     *
     * @returns Pointer to the child string value, NULL if not found or no value.
     * @param   pcszPath        Path to the child element.  Slashes can be used to
     *                          make a simple path to any decendant.
     * @param   cchValueLimit   If the length of the returned value exceeds this
     *                          limit a EIPRTFailure exception will be thrown.
     * @param   pcszNamespace   The namespace to match, NULL (default) match any
     *                          namespace.  When using a path, this matches all
     *                          elements along the way.
     * @see     findChildElement, findChildElementP
     */
    const char *findChildElementValuePN(const char *pcszPath, size_t cchValueLimit, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getValueN(cchValueLimit);
        return NULL;
    }

    /** Combines findChildElementNS and findAttributeValue.
     *
     * @returns Pointer to attribute string value, NULL if either the element or
     *          the attribute was not found.
     * @param   pcszChild           The child element name.
     * @param   pcszAttribute       The attribute name.
     * @param   pcszChildNamespace  The namespace to match @a pcszChild with, NULL
     *                              (default) match any namespace.
     * @param   pcszAttributeNamespace  The namespace prefix to apply to the
     *                              attribute, NULL (default) match any namespace.
     * @see     findChildElementNS and findAttributeValue
     * @note    The findChildElementAttributeValueP() method would do the same thing
     *          given the same inputs, but it would be slightly slower, thus the
     *          separate method.
                                                                                    */
    const char *findChildElementAttributeValue(const char *pcszChild, const char *pcszAttribute,
                                               const char *pcszChildNamespace = NULL,
                                               const char *pcszAttributeNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementNS(pcszChildNamespace, pcszChild);
        if (pElem)
            return pElem->findAttributeValue(pcszAttribute, pcszAttributeNamespace);
        return NULL;
    }

    /** Combines findChildElementP and findAttributeValue.
     *
     * @returns Pointer to attribute string value, NULL if either the element or
     *          the attribute was not found.
     * @param   pcszPath            Path to the child element.  Slashes can be used
     *                              to make a simple path to any decendant.
     * @param   pcszAttribute       The attribute name.
     * @param   pcszPathNamespace   The namespace to match @a pcszPath with, NULL
     *                              (default) match any namespace.  When using a
     *                              path, this matches all elements along the way.
     * @param   pcszAttributeNamespace  The namespace prefix to apply to the
     *                              attribute, NULL (default) match any namespace.
     * @see     findChildElementP and findAttributeValue
     */
    const char *findChildElementAttributeValueP(const char *pcszPath, const char *pcszAttribute,
                                                const char *pcszPathNamespace = NULL,
                                                const char *pcszAttributeNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszPathNamespace);
        if (pElem)
            return pElem->findAttributeValue(pcszAttribute, pcszAttributeNamespace);
        return NULL;
    }

    /** Combines findChildElementP and findAttributeValueN.
     *
     * @returns Pointer to attribute string value, NULL if either the element or
     *          the attribute was not found.
     * @param   pcszPath            The attribute name.  Slashes can be used to make a
     *                              simple path to any decendant.
     * @param   pcszAttribute       The attribute name.
     * @param   cchValueLimit       If the length of the returned value exceeds this
     *                              limit a EIPRTFailure exception will be thrown.
     * @param   pcszPathNamespace   The namespace to match @a pcszPath with, NULL
     *                              (default) match any namespace.  When using a
     *                              path, this matches all elements along the way.
     * @param   pcszAttributeNamespace  The namespace prefix to apply to the
     *                              attribute, NULL (default) match any namespace.
     * @see     findChildElementP and findAttributeValue
     */
    const char *findChildElementAttributeValuePN(const char *pcszPath, const char *pcszAttribute,
                                                 size_t cchValueLimit,
                                                 const char *pcszPathNamespace = NULL,
                                                 const char *pcszAttributeNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszPathNamespace);
        if (pElem)
            return pElem->findAttributeValueN(pcszAttribute, cchValueLimit, pcszAttributeNamespace);
        return NULL;
    }


    /** @name Tree enumeration.
     * @{ */

    /** Get the next tree element in a full tree enumeration.
     *
     * By starting with the root node, this can be used to enumerate the entire tree
     * (or sub-tree if @a pElmRoot is used).
     *
     * @returns Pointer to the next element in the tree, NULL if we're done.
     * @param   pElmRoot            The root of the tree we're enumerating.  NULL if
     *                              it's the entire tree.
     */
    ElementNode const *getNextTreeElement(ElementNode const *pElmRoot = NULL) const;
    RT_CPP_GETTER_UNCONST_RET(ElementNode *, ElementNode, getNextTreeElement, (const ElementNode *pElmRoot = NULL), (pElmRoot))

    /** Get the first child node.
     * @returns Pointer to the first child node, NULL if no children. */
    const Node *getFirstChild() const
    {
        return RTListGetFirstCpp(&m_children, const Node, m_listEntry);
    }
    RT_CPP_GETTER_UNCONST_RET(Node *, ElementNode, getFirstChild,(),())

    /** Get the last child node.
     * @returns Pointer to the last child node, NULL if no children. */
    const Node *getLastChild() const
    {
        return RTListGetLastCpp(&m_children, const Node, m_listEntry);
    }

    /** Get the first child node.
     * @returns Pointer to the first child node, NULL if no children. */
    const ElementNode *getFirstChildElement() const;

    /** Get the last child node.
     * @returns Pointer to the last child node, NULL if no children. */
    const ElementNode *getLastChildElement() const;

    /** Get the previous sibling element.
     * @returns Pointer to the previous sibling element, NULL if first child
     *          element.
     * @see getNextSibilingElement, getPrevSibling
     */
    const ElementNode *getPrevSibilingElement() const;

    /** Get the next sibling element.
     * @returns Pointer to the next sibling element, NULL if last child element.
     * @see getPrevSibilingElement, getNextSibling
     */
    const ElementNode *getNextSibilingElement() const;

    /** Find the previous element matching the given name and namespace (optionally).
     * @returns Pointer to the previous sibling element, NULL if first child
     *          element.
     * @param   pcszName        The element name to match.
     * @param   pcszNamespace   The namespace name, default is NULL which means
     *                          anything goes.
     * @note    Changed the order of the arguments.
     */
    const ElementNode *findPrevSibilingElement(const char *pcszName, const char *pcszNamespace = NULL) const;

    /** Find the next element matching the given name and namespace (optionally).
     * @returns Pointer to the previous sibling element, NULL if first child
     *          element.
     * @param   pcszName        The element name to match.
     * @param   pcszNamespace   The namespace name, default is NULL which means
     *                          anything goes.
     * @note    Changed the order of the arguments.
     */
    const ElementNode *findNextSibilingElement(const char *pcszName, const char *pcszNamespace = NULL) const;
    /** @} */

    /** @name Attribute enumeration
     * @{ */

    /** Get the first attribute node.
     * @returns Pointer to the first child node, NULL if no attributes. */
    const AttributeNode *getFirstAttribute() const
    {
        return RTListGetFirstCpp(&m_attributes, const AttributeNode, m_listEntry);
    }

    /** Get the last attribute node.
     * @returns Pointer to the last child node, NULL if no attributes. */
    const AttributeNode *getLastAttribute() const
    {
        return RTListGetLastCpp(&m_attributes, const AttributeNode, m_listEntry);
    }

    /** @} */

    const AttributeNode *findAttribute(const char *pcszMatch, const char *pcszNamespace = NULL) const;
    /** Find the first attribute with the given name, returning its value string.
     * @returns Pointer to the attribute string value.
     * @param   pcszName        The attribute name.
     * @param   pcszNamespace   The namespace name, default is NULL which means
     *                          anything goes.
     * @see getAttributeValue
     */
    const char *findAttributeValue(const char *pcszName, const char *pcszNamespace = NULL) const
    {
        const AttributeNode *pAttr = findAttribute(pcszName, pcszNamespace);
        if (pAttr)
            return pAttr->getValue();
        return NULL;
    }
    /** Find the first attribute with the given name, returning its value string.
     * @returns Pointer to the attribute string value.
     * @param   pcszName        The attribute name.
     * @param   cchValueLimit   If the length of the returned value exceeds this
     *                          limit a EIPRTFailure exception will be thrown.
     * @param   pcszNamespace   The namespace name, default is NULL which means
     *                          anything goes.
     * @see getAttributeValue
     */
    const char *findAttributeValueN(const char *pcszName, size_t cchValueLimit, const char *pcszNamespace = NULL) const
    {
        const AttributeNode *pAttr = findAttribute(pcszName, pcszNamespace);
        if (pAttr)
            return pAttr->getValueN(cchValueLimit);
        return NULL;
    }

    bool getAttributeValue(const char *pcszMatch, const char *&pcsz, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &pcsz, pcszNamespace); }
    bool getAttributeValue(const char *pcszMatch, RTCString &str, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &str, pcszNamespace); }
    bool getAttributeValuePath(const char *pcszMatch, RTCString &str, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &str, pcszNamespace); }
    bool getAttributeValue(const char *pcszMatch, int32_t &i, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &i, pcszNamespace); }
    bool getAttributeValue(const char *pcszMatch, uint32_t &i, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &i, pcszNamespace); }
    bool getAttributeValue(const char *pcszMatch, int64_t &i, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &i, pcszNamespace); }
    bool getAttributeValue(const char *pcszMatch, uint64_t &u, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &u, pcszNamespace); }
    bool getAttributeValue(const char *pcszMatch, bool &f, const char *pcszNamespace = NULL) const
    { return getAttributeValue(pcszMatch, &f, pcszNamespace); }
    bool getAttributeValueN(const char *pcszMatch, const char *&pcsz, size_t cchValueLimit, const char *pcszNamespace = NULL) const
    { return getAttributeValueN(pcszMatch, &pcsz, cchValueLimit, pcszNamespace); }
    bool getAttributeValueN(const char *pcszMatch, RTCString &str, size_t cchValueLimit, const char *pcszNamespace = NULL) const
    { return getAttributeValueN(pcszMatch, &str, cchValueLimit, pcszNamespace); }
    bool getAttributeValuePathN(const char *pcszMatch, RTCString &str, size_t cchValueLimit, const char *pcszNamespace = NULL) const
    { return getAttributeValueN(pcszMatch, &str, cchValueLimit, pcszNamespace); }

    /** @name Variants that for clarity does not use references for output params.
     * @{ */
    bool getAttributeValue(const char *pcszMatch, const char **ppcsz, const char *pcszNamespace = NULL) const;
    bool getAttributeValue(const char *pcszMatch, RTCString *pStr, const char *pcszNamespace = NULL) const;
    bool getAttributeValuePath(const char *pcszMatch, RTCString *pStr, const char *pcszNamespace = NULL) const;
    bool getAttributeValue(const char *pcszMatch, int32_t *pi, const char *pcszNamespace = NULL) const;
    bool getAttributeValue(const char *pcszMatch, uint32_t *pu, const char *pcszNamespace = NULL) const;
    bool getAttributeValue(const char *pcszMatch, int64_t *piValue, const char *pcszNamespace = NULL) const;
    bool getAttributeValue(const char *pcszMatch, uint64_t *pu, const char *pcszNamespace = NULL) const;
    bool getAttributeValue(const char *pcszMatch, bool *pf, const char *pcszNamespace = NULL) const;
    bool getAttributeValueN(const char *pcszMatch, const char **ppcsz, size_t cchValueLimit, const char *pcszNamespace = NULL) const;
    bool getAttributeValueN(const char *pcszMatch, RTCString *pStr, size_t cchValueLimit, const char *pcszNamespace = NULL) const;
    bool getAttributeValuePathN(const char *pcszMatch, RTCString *pStr, size_t cchValueLimit, const char *pcszNamespace = NULL) const;
    /** @} */

    /** @name Convenience methods for convering the element value.
     * @{ */
    bool getElementValue(int32_t  *piValue) const;
    bool getElementValue(uint32_t *puValue) const;
    bool getElementValue(int64_t  *piValue) const;
    bool getElementValue(uint64_t *puValue) const;
    bool getElementValue(bool     *pfValue) const;
    /** @} */

    /** @name Convenience findChildElementValueP and getElementValue.
     * @{ */
    bool getChildElementValueP(const char *pcszPath, int32_t  *piValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        return pElem && pElem->getElementValue(piValue);
    }
    bool getChildElementValueP(const char *pcszPath, uint32_t *puValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        return pElem && pElem->getElementValue(puValue);
    }
    bool getChildElementValueP(const char *pcszPath, int64_t  *piValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        return pElem && pElem->getElementValue(piValue);
    }
    bool getChildElementValueP(const char *pcszPath, uint64_t *puValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        return pElem && pElem->getElementValue(puValue);
    }
    bool getChildElementValueP(const char *pcszPath, bool     *pfValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        return pElem && pElem->getElementValue(pfValue);
    }

    /** @} */

    /** @name Convenience findChildElementValueP and getElementValue with a
     *        default value being return if the child element isn't present.
     *
     * @remarks These will return false on conversion errors.
     * @{ */
    bool getChildElementValueDefP(const char *pcszPath, int32_t  iDefault, int32_t  *piValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getElementValue(piValue);
        *piValue = iDefault;
        return true;
    }
    bool getChildElementValueDefP(const char *pcszPath, uint32_t uDefault, uint32_t *puValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getElementValue(puValue);
        *puValue = uDefault;
        return true;
    }
    bool getChildElementValueDefP(const char *pcszPath, int64_t  iDefault, int64_t  *piValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getElementValue(piValue);
        *piValue = iDefault;
        return true;
    }
    bool getChildElementValueDefP(const char *pcszPath, uint64_t uDefault, uint64_t *puValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getElementValue(puValue);
        *puValue = uDefault;
        return true;
    }
    bool getChildElementValueDefP(const char *pcszPath, bool     fDefault, bool     *pfValue, const char *pcszNamespace = NULL) const
    {
        const ElementNode *pElem = findChildElementP(pcszPath, pcszNamespace);
        if (pElem)
            return pElem->getElementValue(pfValue);
        *pfValue = fDefault;
        return true;
    }
    /** @} */

    ElementNode *createChild(const char *pcszElementName);

    ContentNode *addContent(const char *pcszContent);
    ContentNode *addContent(const RTCString &strContent)
    {
        return addContent(strContent.c_str());
    }

    ContentNode *setContent(const char *pcszContent);
    ContentNode *setContent(const RTCString &strContent)
    {
        return setContent(strContent.c_str());
    }

    AttributeNode *setAttribute(const char *pcszName, const char *pcszValue);
    AttributeNode *setAttribute(const char *pcszName, const RTCString &strValue)
    {
        return setAttribute(pcszName, strValue.c_str());
    }
    AttributeNode *setAttributePath(const char *pcszName, const RTCString &strValue);
    AttributeNode *setAttribute(const char *pcszName, int32_t i);
    AttributeNode *setAttribute(const char *pcszName, uint32_t i);
    AttributeNode *setAttribute(const char *pcszName, int64_t i);
    AttributeNode *setAttribute(const char *pcszName, uint64_t i);
    AttributeNode *setAttributeHex(const char *pcszName, uint32_t i);
    AttributeNode *setAttribute(const char *pcszName, bool f);

    virtual ~ElementNode();

protected:
    // hide the default constructor so people use only our factory methods
    ElementNode(const ElementNode *pElmRoot, Node *pParent, PRTLISTANCHOR pListAnchor, xmlNode *pLibNode);
    ElementNode(const ElementNode &x);      // no copying

    /** We keep a pointer to the root element for attribute namespace handling. */
    const ElementNode  *m_pElmRoot;

    /** List of child elements and content nodes. */
    RTLISTANCHOR        m_children;
    /** List of attributes nodes. */
    RTLISTANCHOR        m_attributes;

    static void buildChildren(ElementNode *pElmRoot);

    friend class Node;
    friend class Document;
    friend class XmlFileParser;
};

/**
 * Node subclass that represents content (non-element text).
 *
 * Since the Node constructor is private, one can create new content nodes
 * only through the following factory methods:
 *
 *  --  ElementNode::addContent()
 */
class RT_DECL_CLASS ContentNode : public Node
{
public:

protected:
    // hide the default constructor so people use only our factory methods
    ContentNode(Node *pParent, PRTLISTANCHOR pListAnchor, xmlNode *pLibNode);
    ContentNode(const ContentNode &x);      // no copying

    friend class Node;
    friend class ElementNode;
};


/**
 * Handy helper class with which one can loop through all or some children
 * of a particular element. See NodesLoop::forAllNodes() for details.
 */
class RT_DECL_CLASS NodesLoop
{
public:
    NodesLoop(const ElementNode &node, const char *pcszMatch = NULL);
    ~NodesLoop();
    const ElementNode* forAllNodes() const;

private:
    /* Obscure class data */
    struct Data;
    Data *m;
};

/**
 * The XML document class. An instance of this needs to be created by a user
 * of the XML classes and then passed to
 *
 * --   XmlMemParser or XmlFileParser to read an XML document; those classes then
 *      fill the caller's Document with ElementNode, ContentNode and AttributeNode
 *      instances. The typical sequence then is:
 * @code
    Document doc;
    XmlFileParser parser;
    parser.read("file.xml", doc);
    Element *pElmRoot = doc.getRootElement();
   @endcode
 *
 * --   XmlMemWriter or XmlFileWriter to write out an XML document after it has
 *      been created and filled. Example:
 *
 * @code
    Document doc;
    Element *pElmRoot = doc.createRootElement();
    // add children
    xml::XmlFileWriter writer(doc);
    writer.write("file.xml", true);
   @endcode
 */
class RT_DECL_CLASS Document
{
public:
    Document();
    ~Document();

    Document(const Document &x);
    Document& operator=(const Document &x);

    const ElementNode* getRootElement() const;
    ElementNode* getRootElement();

    ElementNode* createRootElement(const char *pcszRootElementName,
                                   const char *pcszComment = NULL);

private:
    friend class XmlMemParser;
    friend class XmlFileParser;
    friend class XmlMemWriter;
    friend class XmlStringWriter;
    friend class XmlFileWriter;

    void refreshInternals();

    /* Obscure class data */
    struct Data;
    Data *m;
};

/*
 * XmlParserBase
 *
 */

class RT_DECL_CLASS XmlParserBase
{
protected:
    XmlParserBase();
    ~XmlParserBase();

    xmlParserCtxtPtr m_ctxt;
};

/*
 * XmlMemParser
 *
 */

class RT_DECL_CLASS XmlMemParser : public XmlParserBase
{
public:
    XmlMemParser();
    ~XmlMemParser();

    void read(const void* pvBuf, size_t cbSize, const RTCString &strFilename, Document &doc);
};

/*
 * XmlFileParser
 *
 */

class RT_DECL_CLASS XmlFileParser : public XmlParserBase
{
public:
    XmlFileParser();
    ~XmlFileParser();

    void read(const RTCString &strFilename, Document &doc);

private:
    /* Obscure class data */
    struct Data;
    struct Data *m;

    static int ReadCallback(void *aCtxt, char *aBuf, int aLen) RT_NOTHROW_PROTO;
    static int CloseCallback(void *aCtxt) RT_NOTHROW_PROTO;
};

/**
 * XmlMemWriter
 */
class RT_DECL_CLASS XmlMemWriter
{
public:
    XmlMemWriter();
    ~XmlMemWriter();

    void write(const Document &doc, void** ppvBuf, size_t *pcbSize);

private:
    void* m_pBuf;
};


/**
 * XmlStringWriter - writes the XML to an RTCString instance.
 */
class RT_DECL_CLASS XmlStringWriter
{
public:
    XmlStringWriter();

    int write(const Document &rDoc, RTCString *pStrDst);

private:
    static int WriteCallbackForSize(void *pvUser, const char *pachBuf, int cbToWrite) RT_NOTHROW_PROTO;
    static int WriteCallbackForReal(void *pvUser, const char *pachBuf, int cbToWrite) RT_NOTHROW_PROTO;
    static int CloseCallback(void *pvUser) RT_NOTHROW_PROTO;

    /** Pointer to the destination string while we're in the write() call.   */
    RTCString  *m_pStrDst;
    /** Set by WriteCallback if we cannot grow the destination string. */
    bool        m_fOutOfMemory;
};


/**
 * XmlFileWriter
 */
class RT_DECL_CLASS XmlFileWriter
{
public:
    XmlFileWriter(Document &doc);
    ~XmlFileWriter();

    /**
     * Writes the XML document to the specified file.
     *
     * @param   pcszFilename    The name of the output file.
     * @param   fSafe           If @c true, some extra safety precautions will be
     *                          taken when writing the file:
     *                              -# The file is written with a '-tmp' suffix.
     *                              -# It is flushed to disk after writing.
     *                              -# Any original file is renamed to '-prev'.
     *                              -# The '-tmp' file is then renamed to the
     *                                 specified name.
     *                              -# The directory changes are flushed to disk.
     *                          The suffixes are available via s_pszTmpSuff and
     *                          s_pszPrevSuff.
     */
    void write(const char *pcszFilename, bool fSafe);

    static int WriteCallback(void *aCtxt, const char *aBuf, int aLen) RT_NOTHROW_PROTO;
    static int CloseCallback(void *aCtxt) RT_NOTHROW_PROTO;

    /** The suffix used by XmlFileWriter::write() for the temporary file. */
    static const char * const s_pszTmpSuff;
    /** The suffix used by XmlFileWriter::write() for the previous (backup) file. */
    static const char * const s_pszPrevSuff;

private:
    void writeInternal(const char *pcszFilename, bool fSafe);

    /* Obscure class data */
    struct Data;
    Data *m;
};

#if defined(_MSC_VER)
#pragma warning (default:4251)
#endif

/** @} */

} // end namespace xml

#endif /* !IPRT_INCLUDED_cpp_xml_h */