/** * 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 $(srcdir)/reader3.res * 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 xmlDocPtrextractFile(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);} #elseint main(void) {    fprintf(stderr, "Reader, Pattern or output support not compiled in\n");    exit(1);}#endif