libxml庫之xmlParseMemory和xmlDocDumpFormatMemory函數

兩個函數，怎麼在記憶體中處理xml檔案。有個疑問，xmlChar *xmlbuff;這樣系統第一次配置設定了xmlbuff的大小以後。對xml做修改，可以成功嗎。

有空試試。

函數原型：

xmlParseMemory

xmlDocPtr	xmlParseMemory		(const char * buffer, 
					 int size)

parse an XML in-memory block and build a tree.

buffer:	an pointer to a char array
size:	the size of the array
Returns:	the resulting document tree
Function: xmlParserAddNodeIn
           

代碼示例：

解析xml字元串
xmlDocPtr doc = xmlParseMemory(pXml, length);
 
//根據xmldoc獲得xml的根節點
xmlNodePtr cur = xmlDocGetRootElement(doc);
 
//獲得子節點:->children獲得不是第一個子節點，必須用next才能獲得第一個子節點
cur = cur->children;
cur = cur->next;

// 獲得節點資訊中的内容: 注意釋放資源
xmlChar* key = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
xmlFree(key);

//獲得節點資訊屬性的值：屬性name，注意釋放資源
xmlChar* fversion = xmlGetProp(cur, "version");
xmlFree(fversion);



//根節點相關函數
xmlNodePtr xmlDocGetRootElement (xmlDocPtr doc) //擷取文檔根節點
xmlNodePtr xmlDocSetRootElement (xmlDocPtr doc, xmlNodePtr root) //設定文檔根節點

//建立子節點相關函數
xmlNodePtr xmlNewNode (xmlNsPtr ns, const xmlChar * name) //建立新節點
xmlNodePtr xmlNewChild (xmlNodePtr parent, xmlNsPtr ns, const xmlChar * name, const xmlChar * content) //建立新的子節點
xmlNodePtr xmlCopyNode (const xmlNodePtr node, int extended) //複制目前節點

//添加子節點相關函數
xmlNodePtr xmlAddChild (xmlNodePtr parent, xmlNodePtr cur) //給指定節點添加子節點
xmlNodePtr xmlAddNextSibling (xmlNodePtr cur, xmlNodePtr elem) //添加後一個兄弟節點
xmlNodePtr xmlAddPrevSibling (xmlNodePtr cur, xmlNodePtr elem) //添加前一個兄弟節點
xmlNodePtr xmlAddSibling (xmlNodePtr cur, xmlNodePtr elem) //添加兄弟節點

//屬性相關函數
xmlAttrPtr    xmlNewProp (xmlNodePtr node, const xmlChar * name, const xmlChar * value) //建立新節點屬性
xmlChar *    xmlGetProp (xmlNodePtr node, const xmlChar * name) //讀取節點屬性
xmlAttrPtr    xmlSetProp (xmlNodePtr node, const xmlChar * name, const xmlChar * value) //設定節點屬性

=xmlNodeListGetstring(doc, cur->xmlChildrenNode, 1);
=xmlNodeContent(cur);
           

===========================================================================================

函數原型：

Function: xmlDocDumpFormatMemory

void	xmlDocDumpFormatMemory		(xmlDocPtr cur, 
					 xmlChar ** mem, 
					 int * size, 
					 int format)

Dump an XML document in memory and return the #xmlChar * and it's size. It's up to the caller to free the memory with xmlFree(). Note that @format = 1 provide node indenting only if xmlIndentTreeOutput = 1 or xmlKeepBlanksDefault(0) was called

cur:	the document
mem:	OUT: the memory pointer
size:	OUT: the memory length
format:	should formatting spaces been added
           

程式示例：

/**
 * section: InputOutput
 * synopsis: Output to char buffer
 * purpose: Demonstrate the use of xmlDocDumpMemory
 *          to output document to a character buffer
 * usage: io2
 * test: io2 > io2.tmp ; diff io2.tmp io2.res ; rm -f io2.tmp
 * author: John Fleck
 * copy: see Copyright for the status of this software.
 */

#include <libxml/parser.h>

#if defined(LIBXML_TREE_ENABLED) && defined(LIBXML_OUTPUT_ENABLED)
int
main(void)
{

    xmlNodePtr n;
    xmlDocPtr doc;
    xmlChar *xmlbuff;
    int buffersize;

    /*
     * Create the document.
     */
    doc = xmlNewDoc(BAD_CAST "1.0");
    n = xmlNewNode(NULL, BAD_CAST "root");
    xmlNodeSetContent(n, BAD_CAST "content");
    xmlDocSetRootElement(doc, n);

    /*
     * Dump the document to a buffer and print it
     * for demonstration purposes.
     */
    xmlDocDumpFormatMemory(doc, &xmlbuff, &buffersize, 1);
    printf("%s", (char *) xmlbuff);

    /*
     * Free associated memory.
     */
    xmlFree(xmlbuff);
    xmlFreeDoc(doc);

    return (0);

}
#else
#include <stdio.h>

int
main(void)
{
    fprintf(stderr,
            "library not configured with tree and output support\n");
    return (1);
}
#endif
           

來源：

http://xmlsoft.org/examples/io2.c           //libxml官方網站

http://blog.163.com/miky_sun/blog/static/3369405201041942853395/