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Diffstat (limited to 'doc/examples/xpath1.c')
-rw-r--r-- | doc/examples/xpath1.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/doc/examples/xpath1.c b/doc/examples/xpath1.c new file mode 100644 index 0000000..0e49737 --- /dev/null +++ b/doc/examples/xpath1.c @@ -0,0 +1,249 @@ +/** + * 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>] + * 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> + +#ifdef LIBXML_XPATH_ENABLED + + +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. + */ +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 |