🚀 go-pugleaf

libxml2
1 ����ָ�룺                              �ĵ�ָ��(xmlDocPtr)�����ָ��(xmlNodePtr)��
2 �õ��ĵ�doc:         xmlReadFile
3 �õ�����root_node�� xmlDocGetRootElement
4 ��������
1)��õ����ֵ��                 xmlNodeGetContent(��Ӧ��xmlFree)
2)����
ָ����һ����㣺           xmlNodePtr ->children
���ֵ��                            xmlNodePtr->name,
����ڱ���                   xmlNodePtr->next
5 �ͷ��ڴ棺                            xmlFreeDoc��xmlFree

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����ʹ�õ�xml�ĵ�Ϊ:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<node1>content of node 1</node1>
<node3 attribute="yes">node has attributes</node3>
<node4>other way to create content</node>
</root>

���������룺
#include <iostream>
#include <libxml/parser.h>
#include <libxml/tree.h>
using namespace std;

int main(int argc,char** argv)
{
xmlDocPtr doc=NULL;
xmlNodePtr cur=NULL;
char* name=NULL;
char* value=NULL;

xmlKeepBlanksDefault (0);

if(argc<2)
{
cout<<"argc must be 2 or above."<<endl;
return -1;
}

doc=xmlParseFile(argv[1]);//����Dom��
if(doc==NULL)
{
cout<<"Loading xml file failed."<<endl;
exit(1);
}

cur=xmlDocGetRootElement(doc);//��ȡ��ڵ�
if(cur==NULL)
{
cout<<"empty file"<<endl;
xmlFreeDoc(doc);
exit(2);
}

//walk the tree
cur=cur->xmlChildrenNode;//get sub node
while(cur !=NULL)
{
name=(char*)(cur->name);
value=(char*)xmlNodeGetContent(cur);
cout<<"name is: "<<name<<", value is: "<<value<<endl;
xmlFree(value);
cur=cur->next; 
}

xmlFreeDoc(doc);//�ͷ�xml������������Դ
xmlCleanupParser();
return 0;
}

˵����
1. ��ʹ��dom��������xml�ĵ�ʱ������Ĭ�ϵķ�ʽ�ǰѽڵ��Ŀհ׵�����һ���ӽ� �㣬����Ϊ���ܺͳ�˵�ĵ�һ���ӽڵ���������xmlKeepBlanksDefault (0)�������������ֿհס�
2. ����ʹ��xmlChar* xmlNodeGetContent(xmlNodePtr cur)�����ȡ�ڵ����ݺ󣬱������xmlFree()�����������ڴ�����ͷš�

ʹ��Xpath��ȡ�ض��������ݣ�
#include <iostream>
#include <string>
using namespace std;

#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>

int main(int argc,char** argv)
{
xmlDocPtr doc;
xmlXPathContextPtr xpathCtx;
xmlXPathObjectPtr xpathObj;
xmlNodeSetPtr nodeset;
string xpathExpr;
char* val=NULL;
int size,i;

if(argc<2)
{
cout<<"argc must be 2 or above."<<endl;
return -1;
}

doc = xmlParseFile(argv[1]);
if (doc == NULL)
{
cout<<"Error: unable to parse file: "<<argv[1]<<endl;   
return -1;
}

xpathCtx = xmlXPathNewContext(doc);
if(xpathCtx == NULL)
{
cout<<"Error: unable to create new XPath context"<<endl;
xmlXPathFreeContext(xpathCtx);
xmlFreeDoc(doc);
return -2;
}

xpathExpr="/root/node3";
xpathObj = xmlXPathexpression_r_r((const xmlChar*)(xpathExpr.c_str()), xpathCtx);
if(xpathObj == NULL)
{
cout<<"Error: unable to uate xpath expression_r_r"<<xpathExpr<<endl;
xmlXPathFreeContext(xpathCtx);
xmlFreeDoc(doc);
return -3;
}

nodeset=xpathObj->nodesetval;
if(xmlXPathNodeSetIsEmpty(nodeset))
{
cout<<"No such nodes."<<endl;
xmlXPathFreeObject(xpathObj);
xmlXPathFreeContext(xpathCtx);
xmlFreeDoc(doc);
return -4;
}

//get the value   
size = (nodeset) ? nodeset->nodeNr : 0;
for(i = 0; i <size; i++)
{
val=(char*)xmlNodeListGetString(doc, nodeset->nodeTab[i]->xmlChildrenNode, 1);       
cout<<"the results are: "<<val<<endl;
xmlFree(val);
}

//Cleanup of XPath data
xmlXPathFreeObject(xpathObj);
xmlXPathFreeContext(xpathCtx);  

xmlFreeDoc(doc);
xmlCleanupParser();
return 0;
}

����ʹ�õĹ���У����˴���û��ʹ��xmlFree(val)��Ҳû��ʹ��xmlCleanupParser()����Ȼ��û��ʹ��xmlKeepBlanksDefault (0)�������ʹ����valgrind����λ�ڴ�й¶����!

��ʾ��xmlCleanupParser()��Ҫ�������Σ�����ͻ����coredump;
# gdb -c core.18659 
.. ...
Program terminated with signal 6, Aborted.
.. ...
(gdb) bt
#0  0x0000003aeec30265 in ?? ()
#1  0x0000003aeec31d10 in ?? ()
.. ...
btҲ�������κ����õ���Ϣ����ʵֻ���ڴ���ظ��ͷ���ɣ�
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ת�ԣ�http://hi.baidu.com/goggle1/blog/item/5a381ef2cca48dc00a46e0d5.html
--
Happy XMLing


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