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/**
* 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 xpath1.res ; rm xpath1.tmp
* 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
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