TSAXParser.cxx

// @(#)root/xmlparser:$Id$
// Author: Jose Lo   12/1/2005

/*************************************************************************
 * Copyright (C) 1995-2005, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

//////////////////////////////////////////////////////////////////////////
//                                                                      //
// TSAXParser                                                           //
//                                                                      //
// TSAXParser is a subclass of TXMLParser, it is a wraper class to      //
// libxml library.                                                      //
//                                                                      //
// SAX (Simple API for XML) is an event based interface, which doesn't  //
// maintain the DOM tree in memory, in other words, it's much more      //
// efficient for large document.                                        //
//                                                                      //
// TSAXParserCallback contains a number of callback routines to the     //
// parser in a xmlSAXHandler structure. The parser will then parse the  //
// document and call the appropriate callback when certain conditions   //
// occur.                                                               //
//                                                                      //
//////////////////////////////////////////////////////////////////////////


/*************************************************************************
  This source is based on libxml++, a C++ wrapper for the libxml XML
  parser library.Copyright (C) 2000 by Ari Johnson

  libxml++ are copyright (C) 2000 by Ari Johnson, and are covered by the
  GNU Lesser General Public License, which should be included with
  libxml++ as the file COPYING.
 *************************************************************************/

#include "TSAXParser.h"
#include "TXMLAttr.h"
#include "Varargs.h"
#include "TObjString.h"
#include "TList.h"
#include "TClass.h"

#include <libxml/parser.h>
#include <libxml/parserInternals.h>


class TSAXParserCallback {
public:
   static void StartDocument(void *fParser);
   static void EndDocument(void *fParser);
   static void StartElement(void *fParser, const xmlChar *name, const xmlChar **p);
   static void EndElement(void *fParser, const xmlChar *name);
   static void Characters(void *fParser, const xmlChar *ch, Int_t len);
   static void Comment(void *fParser, const xmlChar *value);
   static void CdataBlock(void *fParser, const xmlChar *value, Int_t len);
   static void Warning(void *fParser, const char *fmt, ...);
   static void Error(void *fParser, const char *fmt, ...);
   static void FatalError(void *fParser, const char *fmt, ...);
};


ClassImp(TSAXParser)

//______________________________________________________________________________
TSAXParser::TSAXParser()
{
   // Create SAX parser.

   fSAXHandler = new xmlSAXHandler;
   memset(fSAXHandler, 0, sizeof(xmlSAXHandler));

   fSAXHandler->startDocument =
                   (startDocumentSAXFunc)TSAXParserCallback::StartDocument;
   fSAXHandler->endDocument   =
                   (endDocumentSAXFunc)TSAXParserCallback::EndDocument;
   fSAXHandler->startElement  =
                   (startElementSAXFunc)TSAXParserCallback::StartElement;
   fSAXHandler->endElement    =
                   (endElementSAXFunc)TSAXParserCallback::EndElement;
   fSAXHandler->characters    =
                   (charactersSAXFunc)TSAXParserCallback::Characters;
   fSAXHandler->comment       =
                   (commentSAXFunc)TSAXParserCallback::Comment;
   fSAXHandler->cdataBlock    =
                   (cdataBlockSAXFunc)TSAXParserCallback::CdataBlock;
   fSAXHandler->warning       =
                   (warningSAXFunc)TSAXParserCallback::Warning;
   fSAXHandler->error         =
                   (errorSAXFunc)TSAXParserCallback::Error;
   fSAXHandler->fatalError    =
                   (fatalErrorSAXFunc)TSAXParserCallback::FatalError;
}

//______________________________________________________________________________
TSAXParser::~TSAXParser()
{
   // TSAXParser desctructor

   ReleaseUnderlying();

   delete fSAXHandler;
}

//______________________________________________________________________________
void TSAXParser::OnStartDocument()
{
   // Emit a signal for OnStartDocument.

   Emit("OnStartDocument()");
}

//______________________________________________________________________________
void TSAXParser::OnEndDocument()
{
   // Emit a signal for OnEndDocument.

   Emit("OnEndDocument()");
}

//______________________________________________________________________________
void TSAXParser::OnStartElement(const char *name, const TList *attributes)
{
   // Emit a signal for OnStarElement, where name is the Element's name and
   // attribute is a TList of (TObjString*, TObjString *) TPair's.
   // The TPair's key is the attribute's name and value is the attribute's
   // value.

   Long_t args[2];
   args[0] = (Long_t)name;
   args[1] = (Long_t)attributes;

   Emit("OnStartElement(const char *, const TList *)", args);
}

//______________________________________________________________________________
void TSAXParser::OnEndElement(const char *name)
{
   //Emit a signal for OnEndElement, where name is the Element's name.

   Emit("OnEndElement(const char *)", name);
}

//______________________________________________________________________________
void TSAXParser::OnCharacters(const char *characters)
{
   // Emit a signal for OnCharacters, where characters are the characters
   // outside of tags.

   Emit("OnCharacters(const char *)", characters);
}

//______________________________________________________________________________
void TSAXParser::OnComment(const char *text)
{
   // Emit a signal for OnComment, where text is the comment.

   Emit("OnComment(const char *)", text);
}

//______________________________________________________________________________
void TSAXParser::OnWarning(const char *text)
{
   // Emit a signal for OnWarning, where text is the warning.

   Emit("OnWarning(const char *)", text);
}

//______________________________________________________________________________
Int_t TSAXParser::OnError(const char *text)
{
   // Emit a signal for OnError, where text is the error and it returns the
   // Parse Error Code, see TXMLParser.

   Emit("OnError(const char *)", text);
   return -3;
}

//______________________________________________________________________________
Int_t TSAXParser::OnFatalError(const char *text)
{
   // Emit a signal for OnFactalError, where text is the error and it
   // returns the Parse Error Code, see TXMLParser.

   Emit("OnFatalError(const char *)", text);
   return -4;
}

//______________________________________________________________________________
void TSAXParser::OnCdataBlock(const char *text, Int_t len)
{
   // Emit a signal for OnCdataBlock.

   Long_t args[2];
   args[0] = (Long_t)text;
   args[1] = len;

   Emit("OnCdataBlock(const char *, Int_t)", args);
}

//______________________________________________________________________________
Int_t TSAXParser::Parse()
{
   // This function parses the xml file, by initializing the parser and checks
   // whether the parse context is created or not, it will check as well
   // whether the document is well formated.
   // It returns the parse error code, see TXMLParser.

   if (!fContext) {
      return -2;
   }

   xmlSAXHandlerPtr oldSAX = fContext->sax;
   fContext->sax = fSAXHandler;
   fContext->userData = this;

   InitializeContext();

   xmlParseDocument(fContext);

   fContext->sax = oldSAX;

   if (!fContext->wellFormed && fParseCode == 0) {
      fParseCode = -5;
   }

   ReleaseUnderlying();

   return fParseCode;
}

//______________________________________________________________________________
Int_t TSAXParser::ParseFile(const char *filename)
{
   // It creates the parse context of the xml file, where the xml file name is
   // filename. If context is created sucessfully, it will call Parse()
   // It returns parse error code, see TXMLParser.

   // Attempt to parse a second file while a parse is in progress.
   if (fContext) {
      return -1;
   }

   fContext = xmlCreateFileParserCtxt(filename);
   return Parse();
}

//______________________________________________________________________________
Int_t TSAXParser::ParseBuffer(const char *contents, Int_t len)
{
   // It parse the contents, instead of a file.
   // It will return error if is attempted to parse a second file while
   // a parse is in progres.
   // It returns parse code error, see TXMLParser.

   // Attempt to parse a second file while a parse is in progress.
   if (fContext) {
      return -1;
   }

   fContext = xmlCreateMemoryParserCtxt(contents, len);
   return Parse();
}


//--- TSAXParserCallback -------------------------------------------------------

//______________________________________________________________________________
void TSAXParserCallback::StartDocument(void *fParser)
{
   // StartDocument Callback function.

   TSAXParser *parser = (TSAXParser*)fParser;
   parser->OnStartDocument();
}

//______________________________________________________________________________
void TSAXParserCallback::EndDocument(void *fParser)
{
   // EndDocument callback function.

   TSAXParser *parser = (TSAXParser*)fParser;
   parser->OnEndDocument();
}

//______________________________________________________________________________
void TSAXParserCallback::StartElement(void *fParser, const xmlChar *name,
                                      const xmlChar **p)
{
   // StartElement callback function, where name is the name of the element
   // and p contains the attributes for the start tag.

   TSAXParser *parser = (TSAXParser*)fParser;
   TList *attributes = new TList;

   if (p) {
      for (const xmlChar **cur = p; cur && *cur; cur += 2) {
         attributes->Add(new TXMLAttr((const char*)*cur,
                                      (const char*)*(cur + 1)));
      }
   }

   parser->OnStartElement((const char*) name, attributes);

   attributes->Delete();
   delete attributes;
}

//______________________________________________________________________________
void TSAXParserCallback::EndElement(void *fParser, const xmlChar *name)
{
   // EndElement callback function, where name is the name of the element.

   TSAXParser *parser = (TSAXParser*)fParser;
   parser->OnEndElement((const char*) name);
}

//______________________________________________________________________________
void TSAXParserCallback::Characters(void *fParser, const xmlChar *ch,
                                    Int_t len)
{
   // Character callback function. It is called when there are characters that
   // are outside of tags get parsed and the context will be stored in ch,
   // len is the length of ch.

   TSAXParser *parser = (TSAXParser*)fParser;

   char *str = new char[len+1];
   strlcpy(str, (const char*) ch, len+1);
   str[len] = '\0';

   parser->OnCharacters(str);

   delete [] str;
}

//______________________________________________________________________________
void TSAXParserCallback::Comment(void *fParser, const xmlChar *value)
{
   // Comment callback function.
   // Comment of the xml file will be parsed to value.

   TSAXParser *parser = (TSAXParser*)fParser;
   parser->OnComment((const char*) value);
}

//______________________________________________________________________________
void TSAXParserCallback::Warning(void * fParser, const char *va_(fmt), ...)
{
   // Warning callback function. Warnings while parsing a xml file will
   // be stored at fmt.

   TSAXParser *parser = (TSAXParser*)fParser;

   va_list arg;
   char buffer[2048];

   va_start(arg, va_(fmt));
   vsnprintf(buffer, 2048, va_(fmt), arg);
   va_end(arg);

   TString buff(buffer);

   parser->OnWarning(buff.Data());
}

//______________________________________________________________________________
void TSAXParserCallback::Error(void *fParser, const char *va_(fmt), ...)
{
   // Error callback function. Errors while parsing a xml file will be stored
   // at fmt.

   Int_t errorcode;
   TSAXParser *parser = (TSAXParser*)fParser;

   va_list arg;
   char buffer[2048];

   va_start(arg, va_(fmt));
   vsnprintf(buffer, 2048, va_(fmt), arg);
   va_end(arg);

   TString buff(buffer);

   errorcode = parser->OnError(buff.Data());
   if (errorcode < 0) { //When error occurs, write fErrorCode
      parser->SetParseCode(errorcode);
   }

   if (errorcode < 0 && parser->GetStopOnError()) {
      //When GetStopOnError is enabled, stop the parse when an error occurs
      parser->StopParser();
   }
}

//______________________________________________________________________________
void TSAXParserCallback::FatalError(void *fParser, const char *va_(fmt), ...)
{
   // FactalError callback function. Factal errors while parsing a xml file
   // will be stored at fmt.

   Int_t errorcode;
   TSAXParser *parser = (TSAXParser*)fParser;

   va_list arg;
   char buffer[2048];

   va_start(arg, va_(fmt));
   vsnprintf(buffer, 2048, va_(fmt), arg);
   va_end(arg);

   TString buff(buffer);

   errorcode = parser->OnFatalError(buff);
   if (errorcode < 0) {
      parser->SetParseCode(errorcode);
      parser->StopParser();
   }
}

//______________________________________________________________________________
void TSAXParserCallback::CdataBlock(void *fParser, const xmlChar *value,
                                    Int_t len)
{
   // CdataBlock Callback function.

   TSAXParser *parser = (TSAXParser*)fParser;
   parser->OnCdataBlock((const char*)value, len);
}

//______________________________________________________________________________
void TSAXParser::ConnectToHandler(const char *handlerName, void *handler)
{
   // A default TSAXParser to a user-defined Handler connection function.
   // This function makes connection between various function from TSAXParser
   // with the user-define SAX Handler, whose functions has to be exactly the
   // same as in TSAXParser.
   //
   // handlerName is the user-defined SAX Handler class name
   // handler is the pointer to the user-defined SAX Handler
   //
   // See SAXHandler.C tutorial.

   const TString kFunctionsName [] = {
      "OnStartDocument()",
      "OnEndDocument()",
      "OnStartElement(const char *, const TList *)",
      "OnEndElement(const char *)",
      "OnCharacters(const char *)",
      "OnComment(const char *)",
      "OnWarning(const char *)",
      "OnError(const char *)",
      "OnFatalError(const char *)",
      "OnCdataBlock(const char *, Int_t)"
   };

   TClass *cl = TClass::GetClass(handlerName);

   for (Int_t i = 0; i < 10; i++) {
      if (CheckConnectArgs(this, this->IsA(), kFunctionsName[i],
                           cl, kFunctionsName[i]) != -1)
         Connect(kFunctionsName[i], handlerName, handler, kFunctionsName[i]);
   }
}