使用libxml2在XML中統計具有相同名稱的標記

Question

我想使用libxml2在完整的xml中對具有相同名稱的標記進行計數。請建議libxml2中是否有任何內置函數直接返回計數。

Answer 1

使用XPath很容易。見XPath examples。一旦你獲得的xmlXPathEvalExpression的結果，只要簡單的寫：

xpathObj->nodesetval->nodeNr 

這裏給出XPath syntax。例如//elem，統計所有elem元素。

以及基於xpath1.c例如完整的功能：

int count(xmlDocPtr doc, const char* path) 
{ 
    int count; 
    xmlXPathContextPtr xpathCtx; 
    xmlXPathObjectPtr xpathObj; 

     /* Create xpath evaluation context */ 
    xpathCtx = xmlXPathNewContext(doc); 
    if(xpathCtx == NULL) { 
     fprintf(stderr,"Error: unable to create new XPath context\n"); 
     return(-1); 
    } 

    /* Evaluate xpath expression */ 
    xpathObj = xmlXPathEvalExpression(path, xpathCtx); 
    if(xpathObj == NULL) { 
     fprintf(stderr,"Error: unable to evaluate xpath expression \"%s\"\n", path); 
     xmlXPathFreeContext(xpathCtx); 
     return(-1); 
    } 

    count = xpathObj->nodesetval->nodeNr; 
    printf("count of %s: %d\n", path, count); 

    xmlXPathFreeObject(xpathObj); 
    xmlXPathFreeContext(xpathCtx); 

    return count; 
}