JSON
Zephyr provides a JSON library that can be used to encode and decode JSON data.
Usage
Defining the Data Structure
First, define the C structure that corresponds to the JSON object and the descriptor that maps the structure fields to JSON tokens.
#include <zephyr/data/json.h>
struct foo {
int bar;
const char *baz;
};
static const struct json_obj_descr foo_descr[] = {
JSON_OBJ_DESCR_PRIM(struct foo, bar, JSON_TOK_NUMBER),
JSON_OBJ_DESCR_PRIM(struct foo, baz, JSON_TOK_STRING),
};
Encoding
To encode a C structure into a JSON string, use json_obj_encode_buf().
void encode_example(void)
{
struct foo data = { .bar = 42, .baz = "hello" };
char buffer[128];
int ret;
ret = json_obj_encode_buf(foo_descr, ARRAY_SIZE(foo_descr),
&data,
buffer, sizeof(buffer));
if (ret < 0) {
/* handle error */
}
}
Decoding
To decode a JSON string into a C structure, use json_obj_parse().
void decode_example(void)
{
struct foo data;
const char *json_text = "{\"bar\": 42, \"baz\": \"hello\"}";
int ret;
ret = json_obj_parse(json_text, strlen(json_text),
foo_descr, ARRAY_SIZE(foo_descr),
&data);
if (ret < 0) {
/* handle error */
}
}
Configuration
To enable JSON support, enable the CONFIG_JSON_LIBRARY Kconfig option.