Function __json_snprintf

dpdk/lib/telemetry/telemetry_json.h:30–72

 */
__rte_format_printf(3, 4)
static inline int
__json_snprintf(char *buf, const int len, const char *format, ...)
{
	va_list ap;
	char tmp[4];
	char *newbuf;
	int ret;

	if (len == 0)
		return 0;

	/* to ensure unmodified if we overflow, we save off any values currently in buf
	 * before we printf, if they are short enough. We restore them on error.
	 */
	if (strnlen(buf, sizeof(tmp)) < sizeof(tmp)) {
		strcpy(tmp, buf);  /* strcpy is safe as we know the length */
		va_start(ap, format);
		ret = vsnprintf(buf, len, format, ap);
		va_end(ap);
		if (ret > 0 && ret < len)
			return ret;
		strcpy(buf, tmp);  /* restore on error */
		return 0;
	}

	/* in normal operations should never hit this, but can do if buffer is
	 * incorrectly initialized e.g. in unit test cases
	 */
	newbuf = malloc(len);
	if (newbuf == NULL)
		return 0;

	va_start(ap, format);
	ret = vsnprintf(newbuf, len, format, ap);
	va_end(ap);
	if (ret > 0 && ret < len) {
		strcpy(buf, newbuf);
		free(newbuf);
		return ret;
	}
	free(newbuf);
	return 0; /* nothing written or modified */
}

static const char control_chars[0x20] = {
		['\n'] = 'n',