一、cJSON的介绍
cJSON是一个开源的JSON解析器,用于解析JSON数据。它是由纯C语言实现,因此跨平台性好,移植简单。
下载地址:
https://github.com/DaveGamble/cJSON.git
https://gitee.com/du-yueqiang/cJSON?_from=gitee_search
二、移植方法
cJSON只有一个cjson.c和cjson.h文件,可以很方便地集成到其他项目中。cJSON支持将JSON数据解析为cJSON对象,也支持将cJSON对象转换为JSON数据。cJSON的使用非常简单,只需要包含cjson.h头文件,然后调用相应的API即可完成JSON数据的解析和生成。
三、测试代码
//根据官方代码修改,创建json格式数据(字符串、整形、数组)
//增加了json数据解析功能
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "cJSON.h"
/* Used by some code below as an example datatype. */
struct record
{
const char *precision;
double lat;
double lon;
const char *address;
const char *city;
const char *state;
const char *zip;
const char *country;
};
/* Create a bunch of objects as demonstration. */
static int print_preallocated(cJSON *root)
{
/* declarations */
char *out = NULL;
char *buf = NULL;
char *buf_fail = NULL;
size_t len = 0;
size_t len_fail = 0;
/* formatted print */
out = cJSON_Print(root);
/* create buffer to succeed */
/* the extra 5 bytes are because of inaccuracies when reserving memory */
len = strlen(out) + 5;
buf = (char*)malloc(len);
if (buf == NULL)
{
printf("Failed to allocate memory.\n");
exit(1);
}
/* create buffer to fail */
len_fail = strlen(out);
buf_fail = (char*)malloc(len_fail);
if (buf_fail == NULL)
{
printf("Failed to allocate memory.\n");
exit(1);
}
/* Print to buffer */
if (!cJSON_PrintPreallocated(root, buf, (int)len, 1)) {
printf("cJSON_PrintPreallocated failed!\n");
if (strcmp(out, buf) != 0) {
printf("cJSON_PrintPreallocated not the same as cJSON_Print!\n");
printf("cJSON_Print result:\n%s\n", out);
printf("cJSON_PrintPreallocated result:\n%s\n", buf);
}
free(out);
free(buf_fail);
free(buf);
return -1;
}
/* success */
printf("%s\n", buf);
/* force it to fail */
if (cJSON_PrintPreallocated(root, buf_fail, (int)len_fail, 1)) {
printf("cJSON_PrintPreallocated failed to show error with insufficient memory!\n");
printf("cJSON_Print result:\n%s\n", out);
printf("cJSON_PrintPreallocated result:\n%s\n", buf_fail);
free(out);
free(buf_fail);
free(buf);
return -1;
}
free(out);
free(buf_fail);
free(buf);
return 0;
}
/* Create a bunch of objects as demonstration. */
static void create_objects(void)
{
/* declare a few. */
cJSON *root = NULL;
cJSON *fmt = NULL;
cJSON *img = NULL;
cJSON *thm = NULL;
cJSON *fld = NULL;
int i = 0;
int n;
/* Our "days of the week" array: */
const char *strings[7] =
{
"Sunday",
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday"
};
/* Our matrix: */
int numbers[3][3] =
{
{0, -1, 0},
{1, 0, 0},
{0 ,0, 1}
};
/* Our "gallery" item: */
int ids[4] = { 116, 943, 234, 38793 };
/* Our array of "records": */
struct record fields[2] =
{
{
"zip",
37.7668,
-1.223959e+2,
"",
"SAN FRANCISCO",
"CA",
"94107",
"US"
},
{
"zip",
37.371991,
-1.22026e+2,
"",
"SUNNYVALE",
"CA",
"94085",
"US"
}
};
volatile double zero = 0.0;
/* Here we construct some JSON standards, from the JSON site. */
/* Our "Video" datatype: */
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);
/* Print to text */
if (print_preallocated(root) != 0) {
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
cJSON *name=cJSON_GetObjectItem(root,"name");
if (cJSON_IsString(name) && (name->valuestring != NULL))
{
printf("name is \"%s\"\n", name->valuestring);
}
cJSON *format=cJSON_GetObjectItem(root,"format");
if (cJSON_IsObject(format) && (format != NULL))
{
if (print_preallocated(format) != 0)
{
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
cJSON *type=cJSON_GetObjectItem(format,"type");
if (cJSON_IsString(type) && (type->valuestring != NULL))
{
printf("type is \"%s\"\n", type->valuestring);
}
cJSON *width=cJSON_GetObjectItem(format,"width");
if (cJSON_IsNumber(width))
{
printf("width is %d\n", width->valueint);
}
cJSON *interlace=cJSON_GetObjectItem(format,"interlace");
if (cJSON_IsBool(interlace))
{
printf("interlace is %d\n", interlace->valueint);
}
}
cJSON_Delete(root);
/* Our "days of the week" array: */
root = cJSON_CreateStringArray(strings, 7);
if (print_preallocated(root) != 0) {
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
n=cJSON_GetArraySize(root);
cJSON *day;
for(i=0;i<n;i++)
{
day=cJSON_GetArrayItem(root,i);
if (cJSON_IsString(day) && (day->valuestring != NULL))
{
printf("day is \"%s\"\n", day->valuestring);
}
}
cJSON_Delete(root);
/* Our matrix: */
root = cJSON_CreateArray();
for (i = 0; i < 3; i++)
{
cJSON_AddItemToArray(root, cJSON_CreateIntArray(numbers[i], 3));
}
/* cJSON_ReplaceItemInArray(root, 1, cJSON_CreateString("Replacement")); */
if (print_preallocated(root) != 0) {
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
n=cJSON_GetArraySize(root);
cJSON *num;
for(i=0;i<n;i++)
{
num=cJSON_GetArrayItem(root,i);
int m=cJSON_GetArraySize(num);
for(int k=0;k<m;k++)
{
cJSON *j=cJSON_GetArrayItem(num,k);
if (cJSON_IsNumber(j) )
{
printf("day is %d\n", j->valueint);
}
}
}
cJSON_Delete(root);
/* Our "gallery" item: */
root = cJSON_CreateObject();
cJSON_AddItemToObject(root, "Image", img = cJSON_CreateObject());
cJSON_AddNumberToObject(img, "Width", 800);
cJSON_AddNumberToObject(img, "Height", 600);
cJSON_AddStringToObject(img, "Title", "View from 15th Floor");
cJSON_AddItemToObject(img, "Thumbnail", thm = cJSON_CreateObject());
cJSON_AddStringToObject(thm, "Url", "http:/*www.example.com/image/481989943");
cJSON_AddNumberToObject(thm, "Height", 125);
cJSON_AddStringToObject(thm, "Width", "100");
cJSON_AddItemToObject(img, "IDs", cJSON_CreateIntArray(ids, 4));
if (print_preallocated(root) != 0) {
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
cJSON_Delete(root);
/* Our array of "records": */
root = cJSON_CreateArray();
for (i = 0; i < 2; i++)
{
cJSON_AddItemToArray(root, fld = cJSON_CreateObject());
cJSON_AddStringToObject(fld, "precision", fields[i].precision);
cJSON_AddNumberToObject(fld, "Latitude", fields[i].lat);
cJSON_AddNumberToObject(fld, "Longitude", fields[i].lon);
cJSON_AddStringToObject(fld, "Address", fields[i].address);
cJSON_AddStringToObject(fld, "City", fields[i].city);
cJSON_AddStringToObject(fld, "State", fields[i].state);
cJSON_AddStringToObject(fld, "Zip", fields[i].zip);
cJSON_AddStringToObject(fld, "Country", fields[i].country);
}
/* cJSON_ReplaceItemInObject(cJSON_GetArrayItem(root, 1), "City", cJSON_CreateIntArray(ids, 4)); */
if (print_preallocated(root) != 0) {
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
cJSON_Delete(root);
root = cJSON_CreateObject();
cJSON_AddNumberToObject(root, "number", 1.0 / zero);
if (print_preallocated(root) != 0) {
cJSON_Delete(root);
exit(EXIT_FAILURE);
}
cJSON_Delete(root);
}
int CJSON_CDECL main(void)
{
/* print the version */
printf("Version: %s\n", cJSON_Version());
/* Now some samplecode for building objects concisely: */
create_objects();
return 0;
}
四、实验结果
执行之后,打印如下信息
Version: 1.7.16
{
"name": "Jack (\"Bee\") Nimble",
"format": {
"type": "rect",
"width": 1920,
"height": 1080,
"interlace": false,
"frame rate": 24
}
}
name is "Jack ("Bee") Nimble"
{
"type": "rect",
"width": 1920,
"height": 1080,
"interlace": false,
"frame rate": 24
}
type is "rect"
width is 1920
interlace is 0
["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]
day is "Sunday"
day is "Monday"
day is "Tuesday"
day is "Wednesday"
day is "Thursday"
day is "Friday"
day is "Saturday"
[[0, -1, 0], [1, 0, 0], [0, 0, 1]]
day is 0
day is -1
day is 0
day is 1
day is 0
day is 0
day is 0
day is 0
day is 1
{
"Image": {
"Width": 800,
"Height": 600,
"Title": "View from 15th Floor",
"Thumbnail": {
"Url": "http:/*www.example.com/image/481989943",
"Height": 125,
"Width": "100"
},
"IDs": [116, 943, 234, 38793]
}
}
[{
"precision": "zip",
"Latitude": 37.7668,
"Longitude": -122.3959,
"Address": "",
"City": "SAN FRANCISCO",
"State": "CA",
"Zip": "94107",
"Country": "US"
}, {
"precision": "zip",
"Latitude": 37.371991,
"Longitude": -122.026,
"Address": "",
"City": "SUNNYVALE",
"State": "CA",
"Zip": "94085",
"Country": "US"
}]
{
"number": null
}
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