// before
static int output_json_one_sensor(
    bool first, float value, const char* name,
    char* buffer, size_t size, int offset)
{
    // 中略
    new_offset += snprintf(
        buffer + new_offset, size - new_offset,
        "{\"name\":\"%s\",\"value\":%.2f}", name,
        value);
    // 中略
}
