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:

  lion
  bunny
  cat
  

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;
}