glib 学习笔记4，解析xml文件

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xml的用处越来越广泛了，解析xml得库也非常多，总的来说分为两种，一种是把xml当作一个“树”来进行解析，一种是基于事件类型的

glib就是使用事件类型解析xml。
有5种不同的事件类型
1）一个element的开始
2）一个element的结束
3）element得文本
4）一些stuff
5) 错误
There are five kinds of event which can happen:

• The start of an element
• The end of an element
• Some text (inside an element)
• Some other stuff (processing instructions, mainly, including comments and doctypes)
• An error

下面是一个简单的xml

simple.xml :

<zoo>

  <animal noise="roar">lion</animal>

  <animal noise="sniffle">bunny</animal>

  <animal noise="lol">cat</animal>

  <keeper/>

</zoo>

被解析成以下的动作

• Start of “zoo”.
• Start of “animal”, with a “noise” attribute of “roar”.
• The text “lion”.
• End of “animal”.
• Start of “animal”, with a “noise” attribute of “sniffle”.
• The text “bunny”.
• End of “animal”.
• Start of “animal”, with a “noise” attribute of “lol”.
• The text “cat”.
• End of “animal”.
• Start of “keeper”.
• End of “keeper”.
• End of “zoo”.

程序运行结果
I am a lion and I go roar. Can you do it?
I am a bunny and I go sniffle. Can you do it?
I am a cat and I go lol. Can you do it?

# include < stdio. h>

gchar * current_animal_noise = NULL ;

static void start( GMarkupParseContext * context,
const gchar * element_name,
const gchar * * attribute_names,
const gchar * * attribute_values,
gpointer user_data,
GError * * error )
{
const gchar * * name_cursor = attribute_names;
const gchar * * value_cursor = attribute_values;

while ( * name_cursor) {
if ( strcmp ( * name_cursor, "noise" ) = = 0)
current_animal_noise = g_strdup ( * value_cursor) ;
name_cursor+ + ;
value_cursor+ + ;
}

}

static void end( GMarkupParseContext * context,
const gchar * element_name,
gpointer user_data,
GError * * error )
{
if ( current_animal_noise)
{
g_free ( current_animal_noise) ;
current_animal_noise = NULL ;
}
}


static void text( GMarkupParseContext * context,
const gchar * text,
gsize text_len,
gpointer user_data,
GError * * error )
{
if ( current_animal_noise)
printf ( "I am a %*s and I go %s. Can you do it?/n" ,
text_len, text, current_animal_noise) ;
printf ( "test text/n" ) ;
}



GMarkupParser parser = {
. start_element = start,
. end_element = end,
. text = text,
. passthrough = NULL ,
. error = NULL
} ;


int main( )
{
char * buf;
gsize length;
GMarkupParseContext * context;
g_file_get_contents( "test.xml" , & buf, & length, NULL ) ;
g_printf( "%s/n" , buf) ;
context = g_markup_parse_context_new( & parser, 0, NULL , NULL ) ;
if ( g_markup_parse_context_parse( context, buf, length, NULL ) = = FALSE )
{
printf ( "Couldn't load xml/n" ) ;

g_markup_parse_context_free(context);
return 0;
}