C语言使用JSON，cJSON库的使用

21 December 2013

学习了点socket编程，发现通过TCP/UDP进行通信接收到的是连续的字节内容，于是想要传输有结构的数据，就想到了JSON，上网查了下，找到了从cJSON库，这个库简单易用，很不错。

结构体：

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typedef struct cJSON {
    struct cJSON *next,*prev;   /* next/prev allow you to walk array/object chains. Alternatively, use GetArraySize/GetArrayItem/GetObjectItem */
    struct cJSON *child;        /* An array or object item will have a child pointer pointing to a chain of the items in the array/object. */
 
    int type;                   /* The type of the item, as above. */
 
    char *valuestring;          /* The item's string, if type==cJSON_String */
    int valueint;               /* The item's number, if type==cJSON_Number */
    double valuedouble;         /* The item's number, if type==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;

示例：

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#include<stdio.h>

#include<string.h>

#include "cJSON/cJSON.h"
#include "cJSON/cJSON.c"

int main() {
    char *json = "{\"name\":\"me\"}";
    cJSON *name = cJSON_Parse(json);
    printf("%s\n", cJSON_GetObjectItem(name, "name")->valuestring);
    
    cJSON *user_list = cJSON_CreateObject();
    cJSON *u = cJSON_CreateObject();
    cJSON_AddStringToObject(u, "username", "kun");
    cJSON_AddItemToObject(user_list, "kun",u);
    u = cJSON_CreateObject();
    cJSON_AddStringToObject(u, "username", "liang");
    cJSON_AddItemToObject(user_list, "liang", u);

    int length = cJSON_GetArraySize(user_list);
    printf("%d\n", length);
    int i;
    for (i=0; i<length; i++) {
        cJSON *item = cJSON_GetArrayItem(user_list, i);
        printf("%s\n", cJSON_GetObjectItem(item, "username")->valuestring);
    }
    printf("%s\n", cJSON_PrintUnformatted(user_list));

    cJSON_Delete(name);
    cJSON_Delete(user_list);

    return 0;
}

输出：
demo

C库 1