text: /**
   * section: xmlReader
   * synopsis: Show how to extract subdocuments with xmlReader
   * purpose: Demonstrate the use of xmlTextReaderPreservePattern() 
   *          to parse an XML file with the xmlReader while collecting
   *          only some subparts of the document.
   *          (Note that the XMLReader functions require libxml2 version later
   *          than 2.6.)
   * usage: reader3
   * test: reader3 > reader3.tmp ; diff reader3.tmp reader3.res ; rm reader3.tmp
   * author: Daniel Veillard
   * copy: see Copyright for the status of this software.
   */
  
  #include <stdio.h>
  #include <libxml/xmlreader.h>
  
  #if defined(LIBXML_READER_ENABLED) && defined(LIBXML_PATTERN_ENABLED) && defined(LIBXML_OUTPUT_ENABLED)
  
  
  /**
   * streamFile:
   * @filename: the file name to parse
   *
   * Parse and print information about an XML file.
   *
   * Returns the resulting doc with just the elements preserved.
   */
  static xmlDocPtr
  extractFile(const char *filename, const xmlChar *pattern) {
      xmlDocPtr doc;
      xmlTextReaderPtr reader;
      int ret;
  
      /*
       * build an xmlReader for that file
       */
      reader = xmlReaderForFile(filename, NULL, 0);
      if (reader != NULL) {
          /*
  	 * add the pattern to preserve
  	 */
          if (xmlTextReaderPreservePattern(reader, pattern, NULL) < 0) {
              fprintf(stderr, "%s : failed add preserve pattern %s\n",
  	            filename, (const char *) pattern);
  	}
  	/*
  	 * Parse and traverse the tree, collecting the nodes in the process
  	 */
          ret = xmlTextReaderRead(reader);
          while (ret == 1) {
              ret = xmlTextReaderRead(reader);
          }
          if (ret != 0) {
              fprintf(stderr, "%s : failed to parse\n", filename);
  	    xmlFreeTextReader(reader);
  	    return(NULL);
          }
  	/*
  	 * get the resulting nodes
  	 */
  	doc = xmlTextReaderCurrentDoc(reader);
  	/*
  	 * Free up the reader
  	 */
          xmlFreeTextReader(reader);
      } else {
          fprintf(stderr, "Unable to open %s\n", filename);
  	return(NULL);
      }
      return(doc);
  }
  
  int main(int argc, char **argv) {
      const char *filename = "test3.xml";
      const char *pattern = "preserved";
      xmlDocPtr doc;
  
      if (argc == 3) {
          filename = argv[1];
  	pattern = argv[2];
      }
  
      /*
       * this initialize the library and check potential ABI mismatches
       * between the version it was compiled for and the actual shared
       * library used.
       */
      LIBXML_TEST_VERSION
  
      doc = extractFile(filename, (const xmlChar *) pattern);
      if (doc != NULL) {
          /*
  	 * ouptut the result.
  	 */
          xmlDocDump(stdout, doc);
  	/*
  	 * don't forget to free up the doc
  	 */
  	xmlFreeDoc(doc);
      }
  
  
      /*
       * Cleanup function for the XML library.
       */
      xmlCleanupParser();
      /*
       * this is to debug memory for regression tests
       */
      xmlMemoryDump();
      return(0);
  }
  
  #else
  int main(void) {
      fprintf(stderr, "Reader, Pattern or output support not compiled in\n");
      exit(1);
  }
  #endif
  