🔡 C JSON

Epitech C JSON tool

Usage

Prerequisties

In order to use CJSON functions you have to include cjson.h header file.

#include "cjson.h"

int main(void)
{
    return 1;
}

Load JSON file to CJSON type

cjson_t *cjson = cjson_parse_file(filename); // Parse given file

Get property of object

To get a property there are severals methods to do it.

Follwing fake file will be used in next examples :

{
    "id": 3,
    "price": 1.90,
    "name": "John",
    "enabled": true,
    "notes": [2, 4.5, 78, 12]
}

Get property value directly to type expected

You need to know the type that you want to get.

This method is not recommanded because if an error occured you'll not be able to know it

//Example in order to get int property 'id'

int integer = cjson_get_prop_int_unsafe(cjson, "id");
//integer = 3

float price = cjson_get_prop_float_unsafe(cjson, "price");
//price = "1.90"

char *str = cjson_get_prop_string_unsafe(cjson, "name");
//str = "John"

bool enabled = cjson_get_prop_bool_unsafe(cjson, "enabled");
//enabled = true

cjson_array_t *notes = cjson_get_prop_array_unsafe(cjson, "notes");
//notes = [2, 4.5, 78, 12] (linked list system)

Get property value with error handling

You need to know the type that you want to get.

This method is recommanded because if an error occured you will able to know it

//Example in order to get int property 'id'

int integer = 0;
if (!cjson_get_prop_int(cjson, "id", &integer))
    printf("An error occured on integer\n");
//integer = 3

float price = 0;
if (!cjson_get_prop_float(cjson, "price", &price))
    printf("An error occured on float\n");
//price = "1.90"

char *str = NULL;
if (!cjson_get_prop_string(cjson, "name", &str))
    printf("An error occured on string\n");
//str = "John"

bool enabled = false;
if (!cjson_get_prop_string(cjson, "enabled", &enabled))
    printf("An error occured on boolean\n");
//bool = true

cjson_array_t *notes = NULL;
if (!cjson_get_prop_array(cjson, "notes", &notes))
    printf("An error occured on array\n");
//notes = [2, 4.5, 78, 12] (linked list system)

Get property CJSON element

This method get CJSON element that is directly editable, with this maneer you'll be able to:

• Edit its key
• Edit its value
• Display it
• Export it

// Get a CJSON element representing a float -> "price" : 1.90
cjson_t *price = cjson_get_prop(cjson, "price");

//To edit key you can do as follwing
cjson_set_prop_key(price, "MyNewPriceKey"); //Now price is : "MyNewPriceKey" : 1.90

//To edit value you can do as follwing
cjson_set_prop_value(price, CJSON(34.7), CJSON_NUMBER_T); //Now price is : "MyNewPriceKey" : 34.7

//Or you can do as follwing
cjson_set_prop_value(price, CJSON(false), CJSON_BOOL_T); //Now price is : "MyNewPriceKey" : false

Get array of items in primitive C types

CJSON lib offer you possibility to convert directly in expected primitive C type.

Convert to int array

cjson_array_t *notes = NULL;
if (!cjson_get_prop_array(cjson, "notes", &notes)) {
    printf("An error occured on array\n");
    exit(1);
}

size_t len = 0;
int *converted = cjson_array_to_int_array(notes, &len);

if (!converted) {
    printf("An error occured on array conversion\n");
    exit(1);
}
for (size_t i = 0; i < len; i++) {
    printf("notes[%zu] = %d\n", i, converted[i]);
}
//len = 4
//converted = [2, 4, 78, 12]

//Display:
//notes[0] = 2
//notes[1] = 4
//notes[2] = 78
//notes[3] = 12

Made by Flavien Chenu