/** * section: XPath * synopsis: Evaluate XPath expression and prints result node set. * purpose: Shows how to evaluate XPath expression and register * known namespaces in XPath context. * usage: xpath1 <xml-file> <xpath-expr> [<known-ns-list>] * test: xpath1 test3.xml '//child2' > xpath1.tmp && diff xpath1.tmp $(srcdir)/xpath1.res * author: Aleksey Sanin * copy: see Copyright for the status of this software. */ #include <stdlib.h> #include <stdio.h> #include <string.h> #include <assert.h> #include <libxml/tree.h> #include <libxml/parser.h> #include <libxml/xpath.h> #include <libxml/xpathInternals.h> #if defined(LIBXML_XPATH_ENABLED) && defined(LIBXML_SAX1_ENABLED) static void usage(const char *name); int execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList); int register_namespaces(xmlXPathContextPtr xpathCtx, const xmlChar* nsList); void print_xpath_nodes(xmlNodeSetPtr nodes, FILE* output); int main(int argc, char **argv) { /* Parse command line and process file */ if((argc < 3) || (argc > 4)) { fprintf(stderr, "Error: wrong number of arguments.\n"); usage(argv[0]); return(-1); } /* Init libxml */ xmlInitParser(); LIBXML_TEST_VERSION /* Do the main job */ if(execute_xpath_expression(argv[1], BAD_CAST argv[2], (argc > 3) ? BAD_CAST argv[3] : NULL) < 0) { usage(argv[0]); return(-1); } /* Shutdown libxml */ xmlCleanupParser(); /* * this is to debug memory for regression tests */ xmlMemoryDump(); return 0; } /** * usage: * @name: the program name. * * Prints usage information. */ static void usage(const char *name) { assert(name); fprintf(stderr, "Usage: %s <xml-file> <xpath-expr> [<known-ns-list>]\n", name); fprintf(stderr, "where <known-ns-list> is a list of known namespaces\n"); fprintf(stderr, "in \"<prefix1>=<href1> <prefix2>=href2> ...\" format\n"); } /** * execute_xpath_expression: * @filename: the input XML filename. * @xpathExpr: the xpath expression for evaluation. * @nsList: the optional list of known namespaces in * "<prefix1>=<href1> <prefix2>=href2> ..." format. * * Parses input XML file, evaluates XPath expression and prints results. * * Returns 0 on success and a negative value otherwise. */ int execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList) { xmlDocPtr doc; xmlXPathContextPtr xpathCtx; xmlXPathObjectPtr xpathObj; assert(filename); assert(xpathExpr); /* Load XML document */ doc = xmlParseFile(filename); if (doc == NULL) { fprintf(stderr, "Error: unable to parse file \"%s\"\n", filename); return(-1); } /* Create xpath evaluation context */ xpathCtx = xmlXPathNewContext(doc); if(xpathCtx == NULL) { fprintf(stderr,"Error: unable to create new XPath context\n"); xmlFreeDoc(doc); return(-1); } /* Register namespaces from list (if any) */ if((nsList != NULL) && (register_namespaces(xpathCtx, nsList) < 0)) { fprintf(stderr,"Error: failed to register namespaces list \"%s\"\n", nsList); xmlXPathFreeContext(xpathCtx); xmlFreeDoc(doc); return(-1); } /* Evaluate xpath expression */ xpathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx); if(xpathObj == NULL) { fprintf(stderr,"Error: unable to evaluate xpath expression \"%s\"\n", xpathExpr); xmlXPathFreeContext(xpathCtx); xmlFreeDoc(doc); return(-1); } /* Print results */ print_xpath_nodes(xpathObj->nodesetval, stdout); /* Cleanup */ xmlXPathFreeObject(xpathObj); xmlXPathFreeContext(xpathCtx); xmlFreeDoc(doc); return(0); } /** * register_namespaces: * @xpathCtx: the pointer to an XPath context. * @nsList: the list of known namespaces in * "<prefix1>=<href1> <prefix2>=href2> ..." format. * * Registers namespaces from @nsList in @xpathCtx. * * Returns 0 on success and a negative value otherwise. */ int register_namespaces(xmlXPathContextPtr xpathCtx, const xmlChar* nsList) { xmlChar* nsListDup; xmlChar* prefix; xmlChar* href; xmlChar* next; assert(xpathCtx); assert(nsList); nsListDup = xmlStrdup(nsList); if(nsListDup == NULL) { fprintf(stderr, "Error: unable to strdup namespaces list\n"); return(-1); } next = nsListDup; while(next != NULL) { /* skip spaces */ while((*next) == ' ') next++; if((*next) == '\0') break; /* find prefix */ prefix = next; next = (xmlChar*)xmlStrchr(next, '='); if(next == NULL) { fprintf(stderr,"Error: invalid namespaces list format\n"); xmlFree(nsListDup); return(-1); } *(next++) = '\0'; /* find href */ href = next; next = (xmlChar*)xmlStrchr(next, ' '); if(next != NULL) { *(next++) = '\0'; } /* do register namespace */ if(xmlXPathRegisterNs(xpathCtx, prefix, href) != 0) { fprintf(stderr,"Error: unable to register NS with prefix=\"%s\" and href=\"%s\"\n", prefix, href); xmlFree(nsListDup); return(-1); } } xmlFree(nsListDup); return(0); } /** * print_xpath_nodes: * @nodes: the nodes set. * @output: the output file handle. * * Prints the @nodes content to @output. */ void print_xpath_nodes(xmlNodeSetPtr nodes, FILE* output) { xmlNodePtr cur; int size; int i; assert(output); size = (nodes) ? nodes->nodeNr : 0; fprintf(output, "Result (%d nodes):\n", size); for(i = 0; i < size; ++i) { assert(nodes->nodeTab[i]); if(nodes->nodeTab[i]->type == XML_NAMESPACE_DECL) { xmlNsPtr ns; ns = (xmlNsPtr)nodes->nodeTab[i]; cur = (xmlNodePtr)ns->next; if(cur->ns) { fprintf(output, "= namespace \"%s\"=\"%s\" for node %s:%s\n", ns->prefix, ns->href, cur->ns->href, cur->name); } else { fprintf(output, "= namespace \"%s\"=\"%s\" for node %s\n", ns->prefix, ns->href, cur->name); } } else if(nodes->nodeTab[i]->type == XML_ELEMENT_NODE) { cur = nodes->nodeTab[i]; if(cur->ns) { fprintf(output, "= element node \"%s:%s\"\n", cur->ns->href, cur->name); } else { fprintf(output, "= element node \"%s\"\n", cur->name); } } else { cur = nodes->nodeTab[i]; fprintf(output, "= node \"%s\": type %d\n", cur->name, cur->type); } } } #else int main(void) { fprintf(stderr, "XPath support not compiled in\n"); exit(1); } #endif