c语言解析json数据

http://buluzhai.iteye.com/blog/845404

我使用的是cJSON: http://sourceforge.net/projects/cjson/ 

先看json的数据结构 
c中没有对象，所以json数据是采用链表存储的 

 typedef struct cJSON {
     struct cJSON *next,*prev;   // 数组 对象数据中用到
     struct cJSON *child;        // 数组 和对象中指向子数组对象或值

     int type;           // 元素的类型，如是对象还是数组

     char *valuestring;          // 如果是字符串
     int valueint;               // 如果是数值
     double valuedouble;         // 如果类型是cJSON_Number

     char *string;               // The item's name string, if this item is the child of, or is in the list of subitems of an object.
 } cJSON;

比如你有一个json数据 

 {
     "name": "Jack (\"Bee\") Nimble",
     "format": {
         "type":       "rect",
         "width":      1920,
         "height":     1080,
         "interlace":  false,
         "frame rate": 24
     }
 }

那么你可以 
1：讲字符串解析成json结构体。 

 cJSON *root = cJSON_Parse(my_json_string);

2:获取某个元素 

 cJSON *format = cJSON_GetObjectItem(root,"format");
 int framerate = cJSON_GetObjectItem(format,"frame rate")->valueint;

3:讲json结构体转换成字符串 

 char *rendered=cJSON_Print(root);

4：删除 

 cJSON_Delete(root);

5：构建一个json结构体 

 cJSON *root,*fmt;
 root=cJSON_CreateObject();
 cJSON_AddItemToObject(root, "name", cJSON_CreateString("Jack (\"Bee\") Nimble"));
 cJSON_AddItemToObject(root, "format", fmt=cJSON_CreateObject());
 cJSON_AddStringToObject(fmt,"type",     "rect");
 cJSON_AddNumberToObject(fmt,"width",        1920);
 cJSON_AddNumberToObject(fmt,"height",       1080);
 cJSON_AddFalseToObject (fmt,"interlace");
 cJSON_AddNumberToObject(fmt,"frame rate",   24);