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 #ifndef __XRDXMLREADER_HH__
 #define __XRDXMLREADER_HH__
 /******************************************************************************/
 /*                                                                            */
 /*                       X r d X m l R e a d e r . h h                        */
 /*                                                                            */
 /* (c) 2015 by the Board of Trustees of the Leland Stanford, Jr., University  */
 /*   Produced by Andrew Hanushevsky for Stanford University under contract    */
 /*              DE-AC02-76-SFO0515 with the Department of Energy              */
 /*                                                                            */
 /* This file is part of the XRootD software suite.                            */
 /*                                                                            */
 /* XRootD is free software: you can redistribute it and/or modify it under    */
 /* the terms of the GNU Lesser General Public License as published by the     */
 /* Free Software Foundation, either version 3 of the License, or (at your     */
 /* option) any later version.                                                 */
 /*                                                                            */
 /* XRootD 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 Lesser General Public       */
 /* License for more details.                                                  */
 /*                                                                            */
 /* You should have received a copy of the GNU Lesser General Public License   */
 /* along with XRootD in a file called COPYING.LESSER (LGPL license) and file  */
 /* COPYING (GPL license).  If not, see <http://www.gnu.org/licenses/>.        */
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 /* The copyright holder's institutional names and contributor's names may not */
 /* be used to endorse or promote products derived from this software without  */
 /* specific prior written permission of the institution or contributor.       */
 /******************************************************************************/
   
 //-----------------------------------------------------------------------------
 //! The XrdXmlReader object provides a virtual interface to read xml files,
 //! irrespective of the underlying mplementation. Obtain an XML reader using
 //! GetRead(). You may also wish to call Init() prior to obtaining a reader
 //! in multi-threader applications. As some implementations may not be MT-safe.
 //! See GetReader() for more information.
 //-----------------------------------------------------------------------------
 
 class XrdXmlReader
 {
 public:
 
 //-----------------------------------------------------------------------------
 //! Get attributes from an XML tag. GetAttributes() should only be called after
 //! a successful GetElement() call.
 //!
 //! @param  aname    Pointer to an array of attribute names whose values are
 //!                  to be returned. The last entry in the array must be nil.
 //!
 //! @param  aval     Pointer to an array where the corresponding attribute
 //!                  values are to be placed in 1-to-1 correspondence. The
 //!                  values must be freed using free().
 //!
 //! @return true     One or more attributes have been returned.
 //!         false    No specified attributes were found.
 //-----------------------------------------------------------------------------
 
 virtual bool    GetAttributes(const char **aname, char **aval)=0;
 
 //-----------------------------------------------------------------------------
 //! Find an XML tag element.
 //!
 //! @param  ename    Pointer to an array of tag names any of which should be
 //!                  searched for. The last entry in the array must be nil.
 //!                  The first element of the array should contain the name of
 //!                  the context tag. Elements are searched only within the
 //!                  scope of that tag. When searching for the first desired
 //!                  tag, use a null string to indicate document scope.
 //!
 //! @param  reqd     When true one of the tag elements listed in ename must be
 //!                  found otherwise an error is generated.
 //!
 //! @return =0       No specified tag was found. Note that this corresponds to
 //!                  encountering the tag present in ename[0], i.e. scope end.
 //!         >0       A tag was found, the return value is the index into ename
 //!                  that corresponds to the tag's name.
 //-----------------------------------------------------------------------------
 
 virtual int     GetElement(const char **ename, bool reqd=false)=0;
 
 //-----------------------------------------------------------------------------
 //! Get the description of the last error encountered.
 //!
 //! @param  ecode    The error code associated with the error.
 //!
 //! @return Pointer to text describing the error. The text may be destroyed on a
 //!         subsequent call to any other method. Otherwise it is stable. A nil
 //!         pointer indicates that no error is present.
 //-----------------------------------------------------------------------------
 virtual
 const char     *GetError(int &ecode)=0;
 
 //-----------------------------------------------------------------------------
 //! Get a reader object to parse an XML file.
 //!
 //! @param  fname    Pointer to the filepath of the file to be parsed.
 //!
 //! @param  enc      Pointer to the encoding specification. When nil, UTF-8 is
 //!                  used. Currently, this parameter is ignored.
 //!
 //! @param  impl     Pointer to the desired implementation. When nil, the
 //!                  default implementation, tinyxml, is used. The following
 //!                  are supported
 //!
 //!                  tinyxml   - builtin xml reader. Each instance is independent
 //!                              Since it builds a full DOM tree in memory, it
 //!                              is only good for small amounts of xml. Certain
 //!                              esoteric xml features are not supported.
 //!
 //!                  libxml2   - full-fledged xml reader. Instances are not
 //!                              independent if multiple uses involve setting
 //!                              callbacks, allocators, or I/O overrides. For
 //!                              MT-safeness, it must be initialized in the
 //!                              main thread (see Init() below). It is used in
 //!                              streaming mode and is good for large documents.
 //!
 //!
 //! @return !0       Pointer to an XML reader object.
 //! @return =0       An XML reader object could not be created; errno holds
 //!                  the error code of the reason.
 //-----------------------------------------------------------------------------
 static
 XrdXmlReader   *GetReader(const char *fname,
                           const char *enc=0, const char *impl=0);
 
 //-----------------------------------------------------------------------------
 //! Get the text portion of an XML tag element. GetText() should only be called
 //! after a successful call to GetElement() with a possibly intervening call
 //! to GetAttributes().
 //!
 //! @param  ename    Pointer to the corresponding tag name.
 //!
 //! @param  reqd     When true text must exist and not be null. Otherwise, an
 //!                  error is generated if the text is missing or null.
 //!
 //! @return =0       No text found.
 //! @return !0       Pointer  to the tag's text field. It must be free using
 //!                  free().
 //-----------------------------------------------------------------------------
 
 virtual char   *GetText(const char *ename, bool reqd=false)=0;
 
 //-----------------------------------------------------------------------------
 //! Preinitialze the desired implementation for future use. This is meant to be
 //! used in multi-threaded applications, as some implementation must be
 //! initialized using the main thread before spawning other threads. An exmaple
 //! is libxml2 which is generally MT-unsafe unles preinitialized.
 //!
 //! @param  impl     Pointer to the desired implementation. When nil, the
 //!                  default implementation is used. Currently, only "libxml2"
 //!                  and "tinyxml" are supported.
 //!
 //! @return true     Initialization suceeded.
 //! @return false    Initialization failed, errno has the reason.
 //-----------------------------------------------------------------------------
 
 static bool     Init(const char *impl=0);
 
 //-----------------------------------------------------------------------------
 //! Constructor & Destructor
 //-----------------------------------------------------------------------------
 
                 XrdXmlReader() {}
 virtual        ~XrdXmlReader() {}
 
 private:
 
 };
 #endif

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