source: vbox/trunk/src/libs/libxml2-2.6.31/doc/examples/xpath1.c@ 53411

/** 
 * 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