【C++】使用libxml解析XML文件

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OpenCV中使用FileStorage创建和解析XML文件。但FileStorage不能处理节点为空的情况，且对属性也不友好。例子见这里。

libxml是C接口的处理xml文件的开源代码库。可以在这里下载。

对于一段如下的xml文件：

<?xml version="1.0"?><Message Version="1.0">  <Info evaluateType="2" mediaFile="1.avi">1</Info>  <Items>    <Item frameNum="0" scale="2" />    <Item frameNum="1" scale="2" />    <Item frameNum="2" scale="2" /><Item frameNum="2913" scale="2">      <Label type="2" l="564" t="178" r="594" b="280" id="15" />      <Label type="2" l="528" t="184" r="560" b="288" id="11" />      <Label type="2" l="490" t="182" r="522" b="288" id="16" />      <Label type="2" l="614" t="358" r="704" b="600" id="4" />    </Item>  </Items></Message>

libxml处理的函数如下：

string getLabes(char *szDocName, map<pair<int,int>,Rect > &labels){xmlDocPtr doc;          xmlNodePtr curNode;      xmlChar *szKey;          string filename="";doc = xmlReadFile(szDocName,"GB2312",XML_PARSE_RECOVER); //解析文件if (doc==NULL){  fprintf(stderr,"Document not parsed successfully.\n");     return filename; } curNode = xmlDocGetRootElement(doc); //确定文档根元素if (NULL == curNode){ fprintf(stderr,"empty document\n");xmlFreeDoc(doc); return filename; } if (xmlStrcmp(curNode->name, BAD_CAST "Message")) {fprintf(stderr,"document of the wrong type, root node != Message"); xmlFreeDoc(doc);return filename; } curNode = curNode->xmlChildrenNode;xmlNodePtr propNodePtr = curNode;xmlNodePtr itemNodePtr;  while(curNode != NULL){//取出文件名称if (xmlHasProp(curNode,BAD_CAST "mediaFile")) {propNodePtr = curNode;} if (!xmlStrcmp(curNode->name, BAD_CAST "Items")) {itemNodePtr = curNode->xmlChildrenNode;} curNode = curNode->next;}xmlAttrPtr attrPtr = propNodePtr->properties;while (attrPtr != NULL){if (!xmlStrcmp(attrPtr->name, BAD_CAST "mediaFile")){xmlChar* szAttr = xmlGetProp(propNodePtr,BAD_CAST "mediaFile");char* szAttrG = u2g((char*)szAttr);filename = string(szAttrG);//cout<<"get filename: "<<filename<<endl;xmlFree(szAttr);}attrPtr = attrPtr->next;}// Itemwhile (itemNodePtr != NULL){int frameNum = 0;int peopleID = 0;Rect rect;//<Label type="2" l="620" t="164" r="648" b="234" id="15" />xmlAttrPtr attrPtr = itemNodePtr->properties;while (attrPtr != NULL){if (!xmlStrcmp(attrPtr->name, BAD_CAST "frameNum")){xmlChar* szAttr = xmlGetProp(itemNodePtr,BAD_CAST "frameNum");frameNum = atoi((char*)szAttr);//cout<<"get frameNum: "<<frameNum<<endl;xmlFree(szAttr);}attrPtr = attrPtr->next;}// LabelxmlNodePtr childNodePtr = itemNodePtr->xmlChildrenNode;while (childNodePtr != NULL){int l=0,t=0,r=0,b=0;attrPtr = childNodePtr->properties; while(attrPtr != NULL){if (!xmlStrcmp(attrPtr->name, BAD_CAST "l")){xmlChar* szAttr = xmlGetProp(childNodePtr,BAD_CAST "l");l=atoi((char*)szAttr);xmlFree(szAttr);}if (!xmlStrcmp(attrPtr->name, BAD_CAST "t")){xmlChar* szAttr = xmlGetProp(childNodePtr,BAD_CAST "t");t=atoi((char*)szAttr);xmlFree(szAttr);}if (!xmlStrcmp(attrPtr->name, BAD_CAST "r")){xmlChar* szAttr = xmlGetProp(childNodePtr,BAD_CAST "r");r=atoi((char*)szAttr);xmlFree(szAttr);}if (!xmlStrcmp(attrPtr->name, BAD_CAST "b")){xmlChar* szAttr = xmlGetProp(childNodePtr,BAD_CAST "b");b=atoi((char*)szAttr);xmlFree(szAttr);}if (!xmlStrcmp(attrPtr->name, BAD_CAST "id")){xmlChar* szAttr = xmlGetProp(childNodePtr,BAD_CAST "id");peopleID=atoi((char*)szAttr);xmlFree(szAttr);}attrPtr = attrPtr->next;}if(!(l==0&&t==0&&b==0&&r==0)){rect.x=l;rect.y=t;rect.width=r-l;rect.height=b-t;labels[pair<int,int>(frameNum,peopleID)] = rect;//cout<<"get label: "<<l<<" "<<t<<" "<<r<<" "<<b<<" "<<" "<<peopleID<<endl;}childNodePtr = childNodePtr->next;}itemNodePtr = itemNodePtr->next;}xmlFreeDoc(doc);return filename;}

用map的iterator输出：

for(map<pair<int,int>,Rect >::iterator it=labels.begin();it!=labels.end();it++){cout<<(*it).first.first<<" "<<(*it).first.second<<" "<<(*it).second.x<<" "<<(*it).second.y<<" "<<(*it).second.width<<" "<<(*it).second.height<<endl;}

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