Annotation of embedaddon/libxml2/doc/examples/xpath1.c, revision 1.1.1.1
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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