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 $(srcdir)/xpath1.res
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
24static void usage(const char *name);
25int  execute_xpath_expression(const char* filename, const xmlChar* xpathExpr, const xmlChar* nsList);
26int  register_namespaces(xmlXPathContextPtr xpathCtx, const xmlChar* nsList);
27void print_xpath_nodes(xmlNodeSetPtr nodes, FILE* output);
28
29int
30main(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 */
64static void
65usage(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 */
84int
85execute_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 */
146int
147register_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 */
204void
205print_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
246int main(void) {
247    fprintf(stderr, "XPath support not compiled in\n");
248    exit(1);
249}
250#endif
251