Generic history for battery and the sensors

[Kampi]

The idea is to write a generic history manager to provide an option to store sensor data as a history for a given time (like the current battery app).

Current idea

Use of a history object like this

typedef struct
{
    uint16_t first_sample_index;
    uint16_t length;
    void* samples;
} zsw_history_t;

and a sensor specific sample object like this

typedef struct {
    uint8_t mv_with_decimals;
    uint8_t percent;
} zsw_battery_sample_t;

typedef struct {
    float temperature;
    float humidity;
    float pressure;
} zsw_env_sample_t;

Then you can initialize it in the code as follows:

static battery_sample_t samples[MAX_SAMPLES];
static zsw_history_t battery_context;

...

void Init(void) {
    zsw_history_init(&battery_context);
    battery_context.samples = samples;
    battery_context.length = MAX_SAMPLES;
    ...
}

Current issue

Loading from the settings is done via Zephyr settings API

static int battery_load_state(const char *p_key, size_t len,
                              settings_read_cb read_cb, void *p_cb_arg, void *p_param)
{
    zsw_history_t* history = (zsw_history_t*) p_param;

    ARG_UNUSED(p_key);

    if (len != sizeof(zsw_history_t)) {
        return -EINVAL;
    }

    int num_bytes_read = read_cb(p_cb_arg, &battery_context, len);
    LOG_DBG("Read %d bytes", num_bytes_read);

    LOG_DBG("Number samples: %d", battery_context.num_samples);

    if (num_bytes_read == 0) {
        LOG_ERR("Currupt battery settings data");
    } else if (num_bytes_read != sizeof(zsw_history_t)) {
        LOG_WRN("No battery settings data read");
        return -ENODATA;
    }

    LOG_DBG("Loaded battery history data");

    return 0;
}

...

if (settings_load_subtree_direct(Key, battery_load_state, &battery_context)) {
    LOG_ERR("Error during settings_load_subtree!");
    return -EFAULT;
}

But read_cb(p_cb_arg, &battery_context, len) requires a pointer to a data structure and a length. Because battery_context contains a pointer to data the data doesn´t get loaded correctly, because the samples pointer inside of battery_context doesn´t get dereferenced correctly. So the saved data contain the memory address of the samples array and not the data.

Ideas to solve it

• Switch to C++ to have classes

Doesn´t make sense for one code file imo