Annotation of embedaddon/libxml2/doc/examples/xpath1.c, revision 1.1
1.1 ! misho 1: /**
! 2: * section: XPath
! 3: * synopsis: Evaluate XPath expression and prints result node set.
! 4: * purpose: Shows how to evaluate XPath expression and register
! 5: * known namespaces in XPath context.
! 6: * usage: xpath1 <xml-file> <xpath-expr> [<known-ns-list>]
! 7: * test: ./xpath1 test3.xml '//child2' > xpath1.tmp ; diff xpath1.tmp xpath1.res ; rm xpath1.tmp
! 8: * author: Aleksey Sanin
! 9: * copy: see Copyright for the status of this software.
! 10: */
! 11: #include <stdlib.h>
! 12: #include <stdio.h>
! 13: #include <string.h>
! 14: #include <assert.h>
! 15:
! 16: #include <libxml/tree.h>
! 17: #include <libxml/parser.h>
! 18: #include <libxml/xpath.h>
! 19: #include <libxml/xpathInternals.h>
! 20:
! 21: #if defined(LIBXML_XPATH_ENABLED) && defined(LIBXML_SAX1_ENABLED)
! 22:
! 23:
! 24: static void usage(const char *name);
! 25: int execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList);
! 26: int register_namespaces(xmlXPathContextPtr xpathCtx, const xmlChar* nsList);
! 27: void print_xpath_nodes(xmlNodeSetPtr nodes, FILE* output);
! 28:
! 29: int
! 30: main(int argc, char **argv) {
! 31: /* Parse command line and process file */
! 32: if((argc < 3) || (argc > 4)) {
! 33: fprintf(stderr, "Error: wrong number of arguments.\n");
! 34: usage(argv[0]);
! 35: return(-1);
! 36: }
! 37:
! 38: /* Init libxml */
! 39: xmlInitParser();
! 40: LIBXML_TEST_VERSION
! 41:
! 42: /* Do the main job */
! 43: if(execute_xpath_expression(argv[1], BAD_CAST argv[2], (argc > 3) ? BAD_CAST argv[3] : NULL) < 0) {
! 44: usage(argv[0]);
! 45: return(-1);
! 46: }
! 47:
! 48: /* Shutdown libxml */
! 49: xmlCleanupParser();
! 50:
! 51: /*
! 52: * this is to debug memory for regression tests
! 53: */
! 54: xmlMemoryDump();
! 55: return 0;
! 56: }
! 57:
! 58: /**
! 59: * usage:
! 60: * @name: the program name.
! 61: *
! 62: * Prints usage information.
! 63: */
! 64: static void
! 65: usage(const char *name) {
! 66: assert(name);
! 67:
! 68: fprintf(stderr, "Usage: %s <xml-file> <xpath-expr> [<known-ns-list>]\n", name);
! 69: fprintf(stderr, "where <known-ns-list> is a list of known namespaces\n");
! 70: fprintf(stderr, "in \"<prefix1>=<href1> <prefix2>=href2> ...\" format\n");
! 71: }
! 72:
! 73: /**
! 74: * execute_xpath_expression:
! 75: * @filename: the input XML filename.
! 76: * @xpathExpr: the xpath expression for evaluation.
! 77: * @nsList: the optional list of known namespaces in
! 78: * "<prefix1>=<href1> <prefix2>=href2> ..." format.
! 79: *
! 80: * Parses input XML file, evaluates XPath expression and prints results.
! 81: *
! 82: * Returns 0 on success and a negative value otherwise.
! 83: */
! 84: int
! 85: execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList) {
! 86: xmlDocPtr doc;
! 87: xmlXPathContextPtr xpathCtx;
! 88: xmlXPathObjectPtr xpathObj;
! 89:
! 90: assert(filename);
! 91: assert(xpathExpr);
! 92:
! 93: /* Load XML document */
! 94: doc = xmlParseFile(filename);
! 95: if (doc == NULL) {
! 96: fprintf(stderr, "Error: unable to parse file \"%s\"\n", filename);
! 97: return(-1);
! 98: }
! 99:
! 100: /* Create xpath evaluation context */
! 101: xpathCtx = xmlXPathNewContext(doc);
! 102: if(xpathCtx == NULL) {
! 103: fprintf(stderr,"Error: unable to create new XPath context\n");
! 104: xmlFreeDoc(doc);
! 105: return(-1);
! 106: }
! 107:
! 108: /* Register namespaces from list (if any) */
! 109: if((nsList != NULL) && (register_namespaces(xpathCtx, nsList) < 0)) {
! 110: fprintf(stderr,"Error: failed to register namespaces list \"%s\"\n", nsList);
! 111: xmlXPathFreeContext(xpathCtx);
! 112: xmlFreeDoc(doc);
! 113: return(-1);
! 114: }
! 115:
! 116: /* Evaluate xpath expression */
! 117: xpathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx);
! 118: if(xpathObj == NULL) {
! 119: fprintf(stderr,"Error: unable to evaluate xpath expression \"%s\"\n", xpathExpr);
! 120: xmlXPathFreeContext(xpathCtx);
! 121: xmlFreeDoc(doc);
! 122: return(-1);
! 123: }
! 124:
! 125: /* Print results */
! 126: print_xpath_nodes(xpathObj->nodesetval, stdout);
! 127:
! 128: /* Cleanup */
! 129: xmlXPathFreeObject(xpathObj);
! 130: xmlXPathFreeContext(xpathCtx);
! 131: xmlFreeDoc(doc);
! 132:
! 133: return(0);
! 134: }
! 135:
! 136: /**
! 137: * register_namespaces:
! 138: * @xpathCtx: the pointer to an XPath context.
! 139: * @nsList: the list of known namespaces in
! 140: * "<prefix1>=<href1> <prefix2>=href2> ..." format.
! 141: *
! 142: * Registers namespaces from @nsList in @xpathCtx.
! 143: *
! 144: * Returns 0 on success and a negative value otherwise.
! 145: */
! 146: int
! 147: register_namespaces(xmlXPathContextPtr xpathCtx, const xmlChar* nsList) {
! 148: xmlChar* nsListDup;
! 149: xmlChar* prefix;
! 150: xmlChar* href;
! 151: xmlChar* next;
! 152:
! 153: assert(xpathCtx);
! 154: assert(nsList);
! 155:
! 156: nsListDup = xmlStrdup(nsList);
! 157: if(nsListDup == NULL) {
! 158: fprintf(stderr, "Error: unable to strdup namespaces list\n");
! 159: return(-1);
! 160: }
! 161:
! 162: next = nsListDup;
! 163: while(next != NULL) {
! 164: /* skip spaces */
! 165: while((*next) == ' ') next++;
! 166: if((*next) == '\0') break;
! 167:
! 168: /* find prefix */
! 169: prefix = next;
! 170: next = (xmlChar*)xmlStrchr(next, '=');
! 171: if(next == NULL) {
! 172: fprintf(stderr,"Error: invalid namespaces list format\n");
! 173: xmlFree(nsListDup);
! 174: return(-1);
! 175: }
! 176: *(next++) = '\0';
! 177:
! 178: /* find href */
! 179: href = next;
! 180: next = (xmlChar*)xmlStrchr(next, ' ');
! 181: if(next != NULL) {
! 182: *(next++) = '\0';
! 183: }
! 184:
! 185: /* do register namespace */
! 186: if(xmlXPathRegisterNs(xpathCtx, prefix, href) != 0) {
! 187: fprintf(stderr,"Error: unable to register NS with prefix=\"%s\" and href=\"%s\"\n", prefix, href);
! 188: xmlFree(nsListDup);
! 189: return(-1);
! 190: }
! 191: }
! 192:
! 193: xmlFree(nsListDup);
! 194: return(0);
! 195: }
! 196:
! 197: /**
! 198: * print_xpath_nodes:
! 199: * @nodes: the nodes set.
! 200: * @output: the output file handle.
! 201: *
! 202: * Prints the @nodes content to @output.
! 203: */
! 204: void
! 205: print_xpath_nodes(xmlNodeSetPtr nodes, FILE* output) {
! 206: xmlNodePtr cur;
! 207: int size;
! 208: int i;
! 209:
! 210: assert(output);
! 211: size = (nodes) ? nodes->nodeNr : 0;
! 212:
! 213: fprintf(output, "Result (%d nodes):\n", size);
! 214: for(i = 0; i < size; ++i) {
! 215: assert(nodes->nodeTab[i]);
! 216:
! 217: if(nodes->nodeTab[i]->type == XML_NAMESPACE_DECL) {
! 218: xmlNsPtr ns;
! 219:
! 220: ns = (xmlNsPtr)nodes->nodeTab[i];
! 221: cur = (xmlNodePtr)ns->next;
! 222: if(cur->ns) {
! 223: fprintf(output, "= namespace \"%s\"=\"%s\" for node %s:%s\n",
! 224: ns->prefix, ns->href, cur->ns->href, cur->name);
! 225: } else {
! 226: fprintf(output, "= namespace \"%s\"=\"%s\" for node %s\n",
! 227: ns->prefix, ns->href, cur->name);
! 228: }
! 229: } else if(nodes->nodeTab[i]->type == XML_ELEMENT_NODE) {
! 230: cur = nodes->nodeTab[i];
! 231: if(cur->ns) {
! 232: fprintf(output, "= element node \"%s:%s\"\n",
! 233: cur->ns->href, cur->name);
! 234: } else {
! 235: fprintf(output, "= element node \"%s\"\n",
! 236: cur->name);
! 237: }
! 238: } else {
! 239: cur = nodes->nodeTab[i];
! 240: fprintf(output, "= node \"%s\": type %d\n", cur->name, cur->type);
! 241: }
! 242: }
! 243: }
! 244:
! 245: #else
! 246: int main(void) {
! 247: fprintf(stderr, "XPath support not compiled in\n");
! 248: exit(1);
! 249: }
! 250: #endif
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