nanopb_usb.cpp

    case CTRL_REQUEST_WIFI_SCAN: {
        // Allocate buffer
        system_ctrl_alloc_reply_data(req, 1024, nullptr);
        pb_ostream_t stream = pb_ostream_from_buffer((uint8_t*)req->reply_data, req->reply_size);
        // Message
        particle_usb_WiFiScanResult res = {0};
        // Because aps is a repeated field, a custom encoding callback is required
        {
            res.aps.funcs.encode = [](pb_ostream_t* stream, const pb_field_t* field, void* const* arg) -> bool {
                // We need to pass all three fields, so create a temp state struct
                struct state {
                    pb_ostream_t* stream;
                    const pb_field_t* field;
                    bool result;
                };
                // Fill in
                state s = {0};
                s.stream = stream;
                s.field = field;
                s.result = true;
                // Scan
                int ret = wlan_scan([](WiFiAccessPoint* sap, void* ptr) {
                    state* s = (state*)ptr;
                    if (s->result == false) {
                        // Some error has already occured
                        return;
                    }
                    particle_usb_WiFiAccessPoint ap = {0};
                    // Fill in fields
                    strncpy(ap.ssid, sap->ssid, sizeof(sap->ssid));
                    memcpy(ap.bssid, sap->bssid, sizeof(sap->bssid));
                    ap.security = (particle_usb_WiFiSecurityType)sap->security;
                    ap.cipher = (particle_usb_WiFiSecurityCipher)sap->cipher;
                    ap.channel = sap->channel;
                    ap.maxDataRate = sap->maxDataRate;
                    ap.rssi = sap->rssi;
                    // Encode tag
                    if (!pb_encode_tag_for_field(s->stream, s->field)) {
                        s->result = false;
                        return;
                    }
                    // Encode submessage
                    if (!pb_encode_submessage(s->stream, particle_usb_WiFiAccessPoint_fields, &ap)) {
                        s->result = false;
                        return;
                    }
                }, &s);
                if (ret != 0) {
                    s.result = false;
                }
                return s.result;
            };
        }
        // Encode
        bool r = pb_encode(&stream, particle_usb_WiFiScanResult_fields, &res);
        // Set result
        setResult(req, r == true ? SYSTEM_ERROR_NONE : SYSTEM_ERROR_UNKNOWN);
        break;
    }