json.h File Reference

Layer 6 (Presentation) - zero-heap JSON: a bounded writer and top-level reader. More...

#include "ServerConfig.h"
#include <stddef.h>
#include <stdint.h>

Go to the source code of this file.

Classes
class	JsonWriter
	Builds a JSON document into a fixed caller buffer, no heap. More...

Functions
bool	json_get_str (const char *json, const char *key, char *out, size_t out_cap)
	Read a top-level string member from a JSON object body.
bool	json_get_int (const char *json, const char *key, long *out)
	Read a top-level integer member from a JSON object body.
bool	json_get_bool (const char *json, const char *key, bool *out)
	Read a top-level boolean member (true/false) from a JSON object body.

Detailed Description

Layer 6 (Presentation) - zero-heap JSON: a bounded writer and top-level reader.

A deliberately small JSON helper for the common IoT shapes (a flat-ish object of strings / numbers / booleans, with bounded nesting). It allocates nothing: the writer formats into a caller-provided buffer, and the reader scans a NUL-terminated body in place. ArduinoJson remains the option when you need a full DOM - it heap-allocates, which this library avoids.

Writing

char buf[128];
JsonWriter w(buf, sizeof(buf));
w.begin_object();
  w.kv_str("status", "ok");
  w.kv_int("count", 3);
  w.key("items"); w.begin_array();
    w.str("a"); w.str("b");
  w.end_array();
w.end_object();
if (w.ok()) server.send(slot, 200, "application/json", w.c_str());
// -> {"status":"ok","count":3,"items":["a","b"]}

Reading (top-level keys of an object body)

char ssid[33];
if (json_get_str(req->body, "ssid", ssid, sizeof(ssid))) { ... }
long port;
if (json_get_int(req->body, "port", &port)) { ... }

Definition in file json.h.

Function Documentation

json_get_str()

bool json_get_str	(	const char *	json,
		const char *	key,
		char *	out,
		size_t	out_cap
	)

Read a top-level string member from a JSON object body.

Finds "key": "..." at the root object level (nested objects/arrays and string contents are skipped, so a same-named nested key is not matched), unescapes the value, and copies it (NUL-terminated, bounded by out_cap) into out.

Parameters

json	NUL-terminated JSON object text.
key	Member name to find.
out	Destination buffer.
out_cap	Capacity of out including the NUL.

Returns

true if a string member was found and copied; false otherwise.

Definition at line 512 of file json.cpp.

References EMITTED, and TRUNCATED.

json_get_int()

bool json_get_int	(	const char *	json,
		const char *	key,
		long *	out
	)

Read a top-level integer member from a JSON object body.

Returns

true if the member exists and parses as an integer; false otherwise.

Definition at line 552 of file json.cpp.

References det_strtol().

json_get_bool()

bool json_get_bool	(	const char *	json,
		const char *	key,
		bool *	out
	)

Read a top-level boolean member (true/false) from a JSON object body.

Returns

true if the member exists and is a JSON boolean; false otherwise.

Definition at line 567 of file json.cpp.