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Expat+SCEW-操弄XML的瑞士刀

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Expat+SCEW-操弄XML的瑞士刀

作者: Joey 日期: 2008-09-04 18:38

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之前处理XML文件时,就是用这套工具横行江湖,Expat提供细致的函式读写xml文件,SCEW则是把Expat函式包装成亮丽的界面供使用者更方便的存取xml,个人觉的,这两套函式库实在不输给.net System.xml下的API

首先下载expat library和scew library,这两套软体的使用方式很简单,执行configure,make,make install后,就可以使用它们的library,而我这边的范例编译时用static link,所以我都直接连接它们的.a函式库档

Makefile的范例如下

ALL:example
example:example.c
$(CC)-I./scew-0.4.0/scew/ -oexampleexample.clibscew.alibexpat.a
clean:
rmexample

SCEW write xml的方法大概就五组API如下
(1)创造xml tree: tree = scew_tree_create();
(2)加入root element: scew_tree_add_root(scew_tree*,char*);
(3)加入root element的子element: scew_element_add(scew_element*,char*);
(4)加入element attribute: scew_element_add_attr_pair(scew_element*,char*,char*);;
(5)加入element content: scew_element_set_contents(scew_element*,char *);

写入xml文件的范例如下

intCreateXML()
{
scew_tree*tree=NULL;
scew_element*root=NULL;
scew_element*element=NULL;
scew_element*sub_element=NULL;
scew_element*sub_sub_element=NULL;
scew_attribute*attribute=NULL;
tree=scew_tree_create();
root=scew_tree_add_root(tree,"scew_test");
/* Add an element and set element contents. */
element=scew_element_add(root,0)">"element1");
scew_element_set_contents(element,0)">"element contents.");
/* Add an element with an attribute pair (name,value). */
element=scew_element_add(root,0)">"element2");
scew_element_add_attr_pair(element,0)">"attribute",0)">"value");
element=scew_element_add(root,0)">"element3"attribute1"value1");
/**
* Another way to add an attribute. You loose attribute ownership,
* so there is no need to free it.
*/
attribute=scew_attribute_create("attribute2"value2");
scew_element_add_attr(element,attribute);
element=scew_element_add(root,0)">"element4");
sub_element=scew_element_add(element,0)">"sub_element1");
scew_element_add_attr_pair(sub_element,0)">");
sub_element=scew_element_add(element,0)">"sub_element2");
sub_sub_element=scew_element_add(sub_element,0)">"sub_sub_element1");
scew_element_add_attr_pair(sub_sub_element,0)">"attribute3"value3");
/* Check attribute2 replacement. */
scew_element_add_attr_pair(sub_sub_element,0)">"new_value2");
scew_element_set_contents(sub_sub_element,0)">");
scew_writer_tree_file(tree,0)">"example.xml");
scew_tree_free(tree);
return0;
}

执行范例会制造出如下内容的xml

<?xmlversion="1.0"encoding="UTF-8"standalone="no"?>
<scew_test>
<element1>elementcontents.</element1>
<element2attribute="/>
<element3attribute1="attribute2="/>
<element4>
<sub_element1attribute="/>
<sub_element2attribute1=">
<sub_sub_element1attribute1="attribute3=">elementcontents.</sub_sub_element1>
</sub_element2>
</element4>
</scew_test>

而SCEW读取xml的方法大约有6组API
(1)创造xml parser: parser = scew_parser_create;
(2)读入xml档案: scew_parser_load_file(scew_parser*,char*)
(3)读出element name: scew_element_name(scew_element*)
(4)读出element attribute: scew_attribute_next(scew_element*,scew_attribute*)
(5)读出element content: scew_element_contents(scew_element*)
(6)寻找子element: scew_element_next(scew_element*,scew_element*)

读取xml文件的范例如下

voidprint_attributes(scew_element*element)
{
scew_attribute*attribute=NULL;
if(element!=NULL)
{
/**
* Iterates through the element's attribute list,printing the
* pair name-value.
*/
attribute=NULL;
while((attribute=scew_attribute_next(element,attribute))!=NULL)
printf("%s=\"%s\"",scew_attribute_name(attribute),scew_attribute_value(attribute));
}
}
intPrintElement(scew_element*element)
{
scew_element*child=NULL;
XML_Charconst*contents=NULL;
printf("element name: %sscew_element_name(element));
print_attributes(element);
contents=scew_element_contents(element);
if(contents==NULL)
printf("\n\n");
elseprintf("\n%s content:%s\n\nscew_element_name(element),contents);
/**
* Call print_element function again for each child of the
* current element.
*/
while((child=scew_element_next(element,child))!=NULL)
PrintElement(child);
return0;
}
intReadXML()
{
scew_tree*tree=NULL;
scew_parser*parser=NULL;
scew_element*element=NULL,*parent=NULL;
/**
* Creates an SCEW parser. This is the first function to call.
*/
parser=scew_parser_create();
scew_parser_ignore_whitespaces(parser,1);
if(!scew_parser_load_file(parser,0)">"))return0;
tree=scew_parser_tree(parser);
PrintElement(scew_tree_root(tree));//traverse all child and siblings of tree
/* Remember to free tree (scew_parser_free does not free it) */
scew_tree_free(tree);
/* Frees the SCEW parser */
scew_parser_free(parser);
return0;