Mbed OS Reference | GapAdvertisingData.h Source File

 /* mbed Microcontroller Library
  * Copyright (c) 2006-2013 ARM Limited
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 
 #ifndef MBED_GAP_ADVERTISING_DATA__LEGACY_H__
 #define MBED_GAP_ADVERTISING_DATA__LEGACY_H__
 
 #include <stdint.h>
 #include <string.h>
 
 #include "blecommon.h"
 
 /**
  * @addtogroup ble
  * @{
  * @addtogroup gap
  * @{
  */
 
 #define GAP_ADVERTISING_DATA_MAX_PAYLOAD        (31)
 
 /**
  * GAP advertising data builder.
  *
  * Advertising data are used by broadcaster or peripheral to advertise state
  * about the device. This class offers the function to add and update states present
  * in an advertisement payload.
  *
  * After construction, the advertising payload contained in the instance of
  * GapAdvertisingData is empty. Adding new states and named fields can be
  * achieved by invoking the function addData(), and updating existing state
  * involves calling the function updateData().
  *
  * Fields present in the payload can be retrieved by a call to the function
  * findField.
  *
  * This class includes shorthand for the most common fields:
  *   - FLAGS: addFlags().
  *   - APPEARANCE: addAppearance().
  *   - TX_POWER_LEVEL: addTxPower().
  *
  * @code
  *
  * Gap &gap;
  *
  * static const uint8_t device_name[] = "HRM";
  *
  * // construct an empty advertising payload
  * GapAdvertisingData advertising_data;
  *
  * // set the flags of the advertising device
  * advertising_data.addFlags(
  *    GapAdvertisingData::LE_GENERAL_DISCOVERABLE |
  *    GapAdvertisingData::BREDR_NOT_SUPPORTED
  * );
  *
  * // set the advertised name of the device
  * advertising_data.addData(
  *     GapAdvertisingData::COMPLETE_LOCAL_NAME,
  *     device_name,
  *     sizeof(device_name)
  * );
  *
  * // update the advertising data of the gap payload
  * gap.setAdvertisingPayload(advertising_data);
  *
  * @endcode
  *
  * @note See Bluetooth Specification 4.0 (Vol. 3), Part C, Sections 11 and 18
  * for further information on advertising and scan response data.
  *
  * @par Advertising and Scan Response Payloads
  * Advertising data and scan response data are organized around a set of
  * data types called 'AD types' in Bluetooth 4.0 (see the Bluetooth Core
  * Specification v4.0, Vol. 3, Part C, Sections 11 and 18).
  *
  * @par
  * Each AD type has its own standardized assigned number, as
  * the Bluetooth SIG defines:
  * https://www.bluetooth.org/en-us/specification/assigned-numbers/generic-access-profile.
  *
  * @par
  * For convenience, all appropriate AD types are encapsulated in
  * GapAdvertisingData::DataType.
  *
  * @par
  * Before the AD Types and their payload (if any) can be inserted into
  * the advertising or scan response frames, they need to be formatted as
  * follows:
  *
  * @li @c Record length (1 byte).
  * @li @c AD Type (1 byte).
  * @li @c AD payload (optional; only present if record length > 1).
  *
  * @par
  * This class takes care of properly formatting the payload, performs
  * some basic checks on the payload length and tries to avoid common
  * errors such as adding an exclusive AD field twice in the advertising
  * or scan response payload.
  *
  * @deprecated Use AdvertisingData instead.
  * This version provides the buffer backing for the advertising data
  * but it's only big enough for legacy advertising.
  */
 class GapAdvertisingData
 {
 public:
     /*!
      * List of standard Advertising Data types.
      *
      * These AD types are used to describe the capabilities of the peripheral
      * and are inserted inside the advertising or scan response payloads.
      *
      * @par Source
      *
      * @li @c Bluetooth Core Specification 4.0 (Vol. 3), Part C, Section 11, 18.
      * @li @c https://www.bluetooth.org/en-us/specification/assigned-numbers/generic-access-profile.
      */
     enum DataType_t {
         /**
          * Flags, refer to GapAdvertisingData::Flags_t.
          */
         FLAGS = 0x01,
 
         /**
          * Incomplete list of 16-bit Service IDs.
          */
         INCOMPLETE_LIST_16BIT_SERVICE_IDS = 0x02,
 
         /**
          * Complete list of 16-bit Service IDs.
          */
         COMPLETE_LIST_16BIT_SERVICE_IDS = 0x03,
 
         /**
          * Incomplete list of 32-bit Service IDs (not relevant for Bluetooth 4.0).
          */
         INCOMPLETE_LIST_32BIT_SERVICE_IDS = 0x04,
 
         /**
          * Complete list of 32-bit Service IDs (not relevant for Bluetooth 4.0).
          */
         COMPLETE_LIST_32BIT_SERVICE_IDS = 0x05,
 
         /**
          * Incomplete list of 128-bit Service IDs.
          */
         INCOMPLETE_LIST_128BIT_SERVICE_IDS = 0x06,
 
         /**
          * Complete list of 128-bit Service IDs.
          */
         COMPLETE_LIST_128BIT_SERVICE_IDS = 0x07,
 
         /**
          * Shortened Local Name.
          */
         SHORTENED_LOCAL_NAME = 0x08,
 
         /**
          * Complete Local Name.
          */
         COMPLETE_LOCAL_NAME = 0x09,
 
         /**
          * TX Power Level (in dBm).
          */
         TX_POWER_LEVEL = 0x0A,
 
         /**
          * Device ID.
          */
         DEVICE_ID = 0x10,
 
         /**
          * Slave Connection Interval Range.
          */
         SLAVE_CONNECTION_INTERVAL_RANGE = 0x12,
 
         /**
          * List of 128-bit service UUIDs the device is looking for.
          */
         LIST_128BIT_SOLICITATION_IDS = 0x15,
 
         /**
          * Service Data.
          */
         SERVICE_DATA = 0x16,
 
         /**
          * Appearance, refer to GapAdvertisingData::Appearance_t.
          */
         APPEARANCE = 0x19,
 
         /**
          * Advertising Interval.
          */
         ADVERTISING_INTERVAL = 0x1A,
 
         /**
          * Manufacturer Specific Data.
          */
         MANUFACTURER_SPECIFIC_DATA = 0xFF
 
     };
 
     /**
      * Alias for GapAdvertisingData::DataType_t.
      *
      * @deprecated Future releases will drop this type alias.
      */
     typedef enum DataType_t DataType;
 
     /**
      *  Enumeration of allowed flags for DataType_t::FLAGS.
      *
      *  @note DataType_t::FLAGS may contain several flags that the bitwise
      * and operator (ex.LE_GENERAL_DISCOVERABLE & BREDR_NOT_SUPPORTED) assembled.
      *
      *  @par Source
      *
      *  @li @c Bluetooth Core Specification 4.0 (Vol. 3), Part C, Section 18.1.
      */
     enum Flags_t {
         /**
          * Peripheral device is discoverable for a limited period of time.
          */
         LE_LIMITED_DISCOVERABLE = 0x01,
 
         /**
          * Peripheral device is discoverable at any moment.
          */
         LE_GENERAL_DISCOVERABLE = 0x02,
 
         /**
          * Peripheral device is LE only and does not support Bluetooth Enhanced
          * DataRate.
          */
         BREDR_NOT_SUPPORTED = 0x04,
 
         /**
          * Not relevant - dual mode only.
          */
         SIMULTANEOUS_LE_BREDR_C = 0x08,
 
         /**
          * Not relevant - dual mode only.
          */
         SIMULTANEOUS_LE_BREDR_H = 0x10
 
     };
 
     /**
      * Alias for GapAdvertisingData::Flags_t.
      *
      * @deprecated  Future releases will drop this type alias.
      */
     typedef enum Flags_t Flags;
 
     /**
      *  Enumeration of values for the DataType_t::APPEARANCE.
      *
      *  These values describe the physical shape or appearance of the device.
      *
      *  @par Source
      *
      *  @li @c Bluetooth Core Specification Supplement, Part A, Section 1.12.
      *  @li @c Bluetooth Core Specification 4.0 (Vol. 3), Part C, Section 12.2.
      *  @li @c https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.gap.appearance.xml.
      */
     enum Appearance_t {
         /**
          * Unknown or unspecified appearance type.
          */
         UNKNOWN = 0,
 
         /**
          * Generic Phone.
          */
         GENERIC_PHONE = 64,
 
         /**
          * Generic Computer.
          */
         GENERIC_COMPUTER = 128,
 
         /**
          * Generic Watch.
          */
         GENERIC_WATCH = 192,
 
         /**
          * Sports Watch.
          */
         WATCH_SPORTS_WATCH = 193,
 
         /**
          * Generic Clock.
          */
         GENERIC_CLOCK = 256,
 
         /**
          * Generic Display.
          */
         GENERIC_DISPLAY = 320,
 
         /**
          * Generic Remote Control.
          */
         GENERIC_REMOTE_CONTROL = 384,
 
         /**
          * Generic Eye Glasses.
          */
         GENERIC_EYE_GLASSES = 448,
 
         /**
          * Generic Tag.
          */
         GENERIC_TAG = 512,
 
         /**
          * Generic Keyring.
          */
         GENERIC_KEYRING = 576,
 
         /**
          * Generic Media Player.
          */
         GENERIC_MEDIA_PLAYER = 640,
 
         /**
          * Generic Bar Code Scanner.
          */
         GENERIC_BARCODE_SCANNER = 704,
 
         /**
          * Generic Thermometer.
          */
         GENERIC_THERMOMETER = 768,
 
         /**
          * Ear Thermometer.
          */
         THERMOMETER_EAR = 769,
 
         /**
          * Generic Heart Rate Sensor.
          */
         GENERIC_HEART_RATE_SENSOR = 832,
 
         /**
          * Belt Heart Rate Sensor.
          */
         HEART_RATE_SENSOR_HEART_RATE_BELT = 833,
 
         /**
          * Generic Blood Pressure.
          */
         GENERIC_BLOOD_PRESSURE = 896,
 
         /**
          * Arm Blood Pressure.
          */
         BLOOD_PRESSURE_ARM = 897,
 
         /**
          * Wrist Blood Pressure.
          */
         BLOOD_PRESSURE_WRIST = 898,
 
         /**
          * Human Interface Device (HID).
          */
         HUMAN_INTERFACE_DEVICE_HID = 960,
 
         /**
          * Keyboard.
          */
         KEYBOARD = 961,
 
         /**
          * Mouse.
          */
         MOUSE = 962,
 
         /**
          * Joystick.
          */
         JOYSTICK = 963,
 
         /**
          * Gamepad.
          */
         GAMEPAD = 964,
 
         /**
          * Digitizer Tablet.
          */
         DIGITIZER_TABLET = 965,
 
         /**
          * Card Reader.
          */
         CARD_READER = 966,
 
         /**
          * Digital Pen.
          */
         DIGITAL_PEN = 967,
 
         /**
          * Bar Code Scanner.
          */
         BARCODE_SCANNER = 968,
 
         /**
          * Generic Glucose Meter.
          */
         GENERIC_GLUCOSE_METER = 1024,
 
         /**
          * Generic Running/Walking Sensor.
          */
         GENERIC_RUNNING_WALKING_SENSOR = 1088,
 
         /**
          * In Shoe Running/Walking Sensor.
          */
         RUNNING_WALKING_SENSOR_IN_SHOE = 1089,
 
         /**
          * On Shoe Running/Walking Sensor.
          */
         RUNNING_WALKING_SENSOR_ON_SHOE = 1090,
 
         /**
          * On Hip Running/Walking Sensor.
          */
         RUNNING_WALKING_SENSOR_ON_HIP = 1091,
 
         /**
          * Generic Cycling.
          */
         GENERIC_CYCLING = 1152,
 
         /**
          * Cycling Computer.
          */
         CYCLING_CYCLING_COMPUTER = 1153,
 
         /**
          * Cycling Speed Sensor.
          */
         CYCLING_SPEED_SENSOR = 1154,
 
         /**
          * Cycling Cadence Sensor.
          */
         CYCLING_CADENCE_SENSOR = 1155,
 
         /**
          * Cycling Power Sensor.
          */
         CYCLING_POWER_SENSOR = 1156,
 
         /**
          * Cycling Speed and Cadence Sensor.
          */
         CYCLING_SPEED_AND_CADENCE_SENSOR = 1157,
 
         /**
          * Generic Pulse Oximeter.
          */
         PULSE_OXIMETER_GENERIC = 3136,
 
         /**
          * Fingertip Pulse Oximeter.
          */
         PULSE_OXIMETER_FINGERTIP = 3137,
 
         /**
          * Wrist Worn Pulse Oximeter.
          */
         PULSE_OXIMETER_WRIST_WORN = 3138,
 
         /**
          * Generic Weight Scale.
          */
         GENERIC_WEIGHT_SCALE = 3200,
 
         /**
          * Generic Outdoor.
          */
         OUTDOOR_GENERIC = 5184,
 
         /**
          * Outdoor Location Display Device.
          */
         OUTDOOR_LOCATION_DISPLAY_DEVICE = 5185,
 
         /**
          * Outdoor Location and Navigation Display Device.
          */
         OUTDOOR_LOCATION_AND_NAVIGATION_DISPLAY_DEVICE = 5186,
 
         /**
          * Outdoor Location Pod.
          */
         OUTDOOR_LOCATION_POD = 5187,
 
         /**
          * Outdoor Location and Navigation Pod.
          */
         OUTDOOR_LOCATION_AND_NAVIGATION_POD = 5188
 
     };
 
     /**
      * Alias for GapAdvertisingData::Appearance_t.
      *
      * @deprecated Future releases will drop this type alias.
      */
     typedef enum Appearance_t Appearance;
 
     /**
      * Construct a GapAdvertising instance with an empty payload.
      */
     GapAdvertisingData(void) :
         _payload(),
         _payloadLen(0),
         _appearance(GENERIC_TAG) {
     }
 
     /**
      * Adds a new field into the payload.
      *
      * If the supplied advertising data type is already present in the
      * advertising payload, then the value is updated.
      *
      * @param[in] advDataType The type of the field to add.
      * @param[in] payload Pointer to the value of the field to add.
      * @param[in] len Size in bytes of the value to add.
      *
      * @return BLE_ERROR_NONE on success.
      * @return BLE_ERROR_BUFFER_OVERFLOW if the new value causes the advertising
      * buffer to overflow.
      *
      * @note When the specified data type is INCOMPLETE_LIST_16BIT_SERVICE_IDS,
      * COMPLETE_LIST_16BIT_SERVICE_IDS, INCOMPLETE_LIST_32BIT_SERVICE_IDS,
      * COMPLETE_LIST_32BIT_SERVICE_IDS, INCOMPLETE_LIST_128BIT_SERVICE_IDS,
      * COMPLETE_LIST_128BIT_SERVICE_IDS or LIST_128BIT_SOLICITATION_IDS, the
      * supplied value is appended to the values present in the payload.
      */
     ble_error_t addData(DataType_t advDataType, const uint8_t *payload, uint8_t len)
     {
         /* Find field */
         uint8_t* field = findField(advDataType);
 
         if (field) {
             /* Field type already exists, either add to field or replace */
             return addField(advDataType, payload, len, field);
         } else {
             /* Field doesn't exist, insert new */
             return appendField(advDataType, payload, len);
         }
     }
 
     /**
      * Update a specific field in the advertising payload.
      *
      * @param[in] advDataType The type of the field to update.
      * @param[in] payload Pointer to the updated value of the field.
      * @param[in] len Size of the new value in bytes.
      *
      * @return BLE_ERROR_NONE returned on success.
      * @return BLE_ERROR_UNSPECIFIED if the specified field is not found,
      * @return BLE_ERROR_BUFFER_OVERFLOW if the new value causes the
      * advertising buffer to overflow.
      */
     ble_error_t updateData(DataType_t advDataType, const uint8_t *payload, uint8_t len)
     {
         /* Find field */
         uint8_t* field = findField(advDataType);
 
         if (field) {
             /* Field type already exists, replace field contents */
             return updateField(advDataType, payload, len, field);
         } else {
             /* field doesn't exist, return an error */
             return BLE_ERROR_UNSPECIFIED;
         }
     }
 
     /**
      * Add device appearance in the advertising payload.
      *
      * @param[in] appearance The appearance to advertise.
      *
      * @return BLE_ERROR_NONE on success.
      * @return BLE_ERROR_BUFFER_OVERFLOW if the specified data would cause the
      * advertising buffer to overflow.
      *
      * @note This call is equivalent to calling addData() with
      * GapAdvertisingData::APPEARANCE as the field type.
      */
     ble_error_t addAppearance(Appearance appearance = GENERIC_TAG)
     {
         _appearance = appearance;
         return addData(GapAdvertisingData::APPEARANCE, (uint8_t *)&appearance, 2);
     }
 
     /**
      * Add BLE flags in the advertising payload.
      *
      * @param[in] flags Bitfield describing the capability of the device. See
      * allowed flags in Flags_t.
      *
      * @return BLE_ERROR_NONE on success.
      * @return BLE_ERROR_BUFFER_OVERFLOW if the specified data would cause the
      * advertising buffer to overflow.
      *
      * @note This call is equivalent to calling addData() with
      * GapAdvertisingData::FLAGS as the field type.
      */
     ble_error_t addFlags(uint8_t flags = LE_GENERAL_DISCOVERABLE)
     {
         return addData(GapAdvertisingData::FLAGS, &flags, 1);
     }
 
     /**
      * Add the advertising TX in the advertising payload.
      *
      * @param[in] txPower Transmission power level in dB.
      *
      * @return BLE_ERROR_NONE on success.
      * @return BLE_ERROR_BUFFER_OVERFLOW if the specified data would cause the
      * advertising buffer to overflow.
      *
      * @note This call is equivalent to calling addData() with
      * GapAdvertisingData::TX_POWER_LEVEL as the field type.
      */
     ble_error_t addTxPower(int8_t txPower)
     {
         /* To Do: Basic error checking to make sure txPower is in range. */
         return addData(GapAdvertisingData::TX_POWER_LEVEL, (uint8_t *)&txPower, 1);
     }
 
     /**
      * Clears the advertising data payload.
      *
      * @post getPayloadLen() returns 0.
      */
     void clear(void)
     {
         memset(&_payload, 0, GAP_ADVERTISING_DATA_MAX_PAYLOAD);
         _payloadLen = 0;
     }
 
     /**
      * Get the pointer to the advertising payload bytes.
      *
      * @return A pointer to the payload.
      */
     const uint8_t *getPayload(void) const
     {
         return _payload;
     }
 
     /**
      * Get the payload length.
      *
      * @return The payload length in bytes.
      */
     uint8_t getPayloadLen(void) const
     {
         return _payloadLen;
     }
 
     /**
      * Get the appearance set.
      *
      * If no value has been set, this function returns GENERIC_TAG.
      *
      * @return The appearance value set for this device.
      */
     uint16_t getAppearance(void) const
     {
         return (uint16_t)_appearance;
     }
 
     /**
      * Search advertisement data for a specific field.
      *
      * @param[in] type The type of the field to find.
      *
      * @return A pointer to the first element in the field if found. The first
      * element being the length of the field followed by the value of the field.
      * @return NULL if the field is not present in the payload.
      */
     const uint8_t* findField(DataType_t type) const
     {
         /* Scan through advertisement data */
         for (uint8_t idx = 0; idx < _payloadLen; ) {
             uint8_t fieldType = _payload[idx + 1];
 
             if (fieldType == type) {
                 return &_payload[idx];
             }
 
             /* Advance to next field */
             idx += _payload[idx] + 1;
         }
 
         /* Field not found */
         return NULL;
     }
 
 private:
     /**
      * Append advertising data based on the specified type.
      *
      * @param[in] advDataType Type of the new data.
      * @param[in] payload Pointer to the data to be appended to the advertising
      * payload.
      * @param[in] len Length of the data pointed to by @p payload.
      *
      * @return BLE_ERROR_NONE on success.
      * @return BLE_ERROR_BUFFER_OVERFLOW if the specified data would cause the
      * advertising buffer to overflow.
      */
     ble_error_t appendField(DataType advDataType, const uint8_t *payload, uint8_t len)
     {
         /* Make sure we don't exceed the 31-byte payload limit */
         if (_payloadLen + len + 2 > GAP_ADVERTISING_DATA_MAX_PAYLOAD) {
             return BLE_ERROR_BUFFER_OVERFLOW;
         }
 
         /* Field length. */
         memset(&_payload[_payloadLen], len + 1, 1);
         _payloadLen++;
 
         /* Field ID. */
         memset(&_payload[_payloadLen], (uint8_t)advDataType, 1);
         _payloadLen++;
 
         /* Payload. */
         memcpy(&_payload[_payloadLen], payload, len);
         _payloadLen += len;
 
         return BLE_ERROR_NONE;
     }
 
     /**
      * Search advertisement data for a specific field.
      *
      * @param[in] type The type of the field to find.
      *
      * @return A pointer to the first element in the field if found. The first
      * element being the length of the field followed by the value of the field.
      * @return NULL if the field is not present in the payload.
      */
     uint8_t* findField(DataType_t type)
     {
         return const_cast<uint8_t*>(
             static_cast<const GapAdvertisingData*>(this)->findField(type)
         );
     }
 
     /**
      * Update in place the value of a field in the advertising payload.
      *
      * @param[in] advDataType Type of the new data.
      * @param[in] payload Pointer to the data to be added to the advertising
      * payload.
      * @param[in] len Length of the data pointed to by @p payload.
      * @param[in] field Pointer to the field of type @p advDataType in the
      * advertising buffer.
      *
      * @note When the specified AD type is INCOMPLETE_LIST_16BIT_SERVICE_IDS,
      * COMPLETE_LIST_16BIT_SERVICE_IDS, INCOMPLETE_LIST_32BIT_SERVICE_IDS,
      * COMPLETE_LIST_32BIT_SERVICE_IDS, INCOMPLETE_LIST_128BIT_SERVICE_IDS,
      * COMPLETE_LIST_128BIT_SERVICE_IDS or LIST_128BIT_SOLICITATION_IDS, the
      * supplied value is appended to the values previously added to the
      * payload.
      *
      * @return BLE_ERROR_NONE on success.
      */
     ble_error_t addField(
         DataType_t advDataType,
         const uint8_t *payload,
         uint8_t len,
         uint8_t* field
     ) {
         ble_error_t result = BLE_ERROR_BUFFER_OVERFLOW;
 
         switch(advDataType) {
             /* These fields have the new data appended if there is sufficient space. */
             case INCOMPLETE_LIST_16BIT_SERVICE_IDS:
             case COMPLETE_LIST_16BIT_SERVICE_IDS:
             case INCOMPLETE_LIST_32BIT_SERVICE_IDS:
             case COMPLETE_LIST_32BIT_SERVICE_IDS:
             case INCOMPLETE_LIST_128BIT_SERVICE_IDS:
             case COMPLETE_LIST_128BIT_SERVICE_IDS:
             case LIST_128BIT_SOLICITATION_IDS: {
                 /* Check if data fits */
                 if ((_payloadLen + len) <= GAP_ADVERTISING_DATA_MAX_PAYLOAD) {
                     /*
                      * Make room for new field by moving the remainder of the
                      * advertisement payload "to the right" starting after the
                      * TYPE field.
                      */
                     uint8_t* end = &_payload[_payloadLen];
 
                     while (&field[1] < end) {
                         end[len] = *end;
                         end--;
                     }
 
                     /* Insert new data */
                     for (uint8_t idx = 0; idx < len; idx++) {
                         field[2 + idx] = payload[idx];
                     }
 
                     /* Increment lengths */
                     field[0] += len;
                     _payloadLen += len;
 
                     result = BLE_ERROR_NONE;
                 }
 
                 break;
             }
             /* These fields are overwritten with the new value */
             default: {
                 result = updateField(advDataType, payload, len, field);
 
                 break;
             }
         }
 
         return result;
     }
 
     /**
      * Update in place the value of a field in the advertising payload.
      *
      * @param[in] advDataType Type of the new data.
      * @param[in] payload Pointer to the data to be added to the advertising
      * payload.
      * @param[in] len Length of the data pointed to by @p payload.
      * @param[in] field Pointer to the field of type @p advDataType in the
      * advertising buffer.
      *
      * @return BLE_ERROR_NONE on success.
      */
     ble_error_t updateField(
         DataType_t advDataType,
         const uint8_t *payload,
         uint8_t len,
         uint8_t* field
     ) {
         ble_error_t result = BLE_ERROR_BUFFER_OVERFLOW;
         uint8_t dataLength = field[0] - 1;
 
         /* New data has same length, do in-order replacement */
         if (len == dataLength) {
             for (uint8_t idx = 0; idx < dataLength; idx++) {
                 field[2 + idx] = payload[idx];
             }
 
             result = BLE_ERROR_NONE;
         } else {
             /* Check if data fits */
             if ((_payloadLen - dataLength + len) <= GAP_ADVERTISING_DATA_MAX_PAYLOAD) {
 
                 /* Remove old field */
                 while ((field + dataLength + 2) < &_payload[_payloadLen]) {
                     *field = field[dataLength + 2];
                     field++;
                 }
 
                 /* Reduce length */
                 _payloadLen -= dataLength + 2;
 
                 /* Add new field */
                 result = appendField(advDataType, payload, len);
             }
         }
 
         return result;
     }
 
     /**
      * Advertising data buffer.
      */
     uint8_t _payload[GAP_ADVERTISING_DATA_MAX_PAYLOAD];
 
     /**
      * Length of the data added to the advertising buffer.
      */
     uint8_t _payloadLen;
 
     /**
      * Appearance value.
      */
     uint16_t _appearance;
 };
 
 /**
  * @}
  * @}
  */
 
 
 #endif /* ifndef MBED_GAP_ADVERTISING_DATA__LEGACY_H__ */
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