Diff: services/URIBeaconConfigService.h

Revision:

286:898ff71b9502

Parent:

285:984353e66610

Child:

287:cca148e535b1

--- a/services/URIBeaconConfigService.h	Fri Feb 13 13:00:41 2015 +0000
+++ b/services/URIBeaconConfigService.h	Fri Feb 13 16:37:42 2015 +0000
@@ -14,282 +14,280 @@
  * limitations under the License.
  */
 
-#ifndef SERVICES_URIBEACONCONFIGSERVICE_H_
-#define SERVICES_URIBEACONCONFIGSERVICE_H_
+#ifndef __BLE_URI_BEACON_CONFIG_SERVICE_H__
+#define __BLE_URI_BEACON_CONFIG_SERVICE_H__
 
-#define UUID_URI_BEACON(FIRST, SECOND) { \
+#include "BLEDevice.h"
+
+#define URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(FIRST, SECOND) { \
         0xee, 0x0c, FIRST, SECOND, 0x87, 0x86, 0x40, 0xba,       \
         0xab, 0x96, 0x99, 0xb9, 0x1a, 0xc9, 0x81, 0xd8,          \
 }
-
-static const uint8_t UUID_URI_BEACON_SERVICE[]    = UUID_URI_BEACON(0x20, 0x80);
-static const uint8_t UUID_LOCK_STATE_CHAR[]       = UUID_URI_BEACON(0x20, 0x81);
-static const uint8_t UUID_LOCK_CHAR[]             = UUID_URI_BEACON(0x20, 0x82);
-static const uint8_t UUID_UNLOCK_CHAR[]           = UUID_URI_BEACON(0x20, 0x83);
-static const uint8_t UUID_URI_DATA_CHAR[]         = UUID_URI_BEACON(0x20, 0x84);
-static const uint8_t UUID_FLAGS_CHAR[]            = UUID_URI_BEACON(0x20, 0x85);
-static const uint8_t UUID_ADV_POWER_LEVELS_CHAR[] = UUID_URI_BEACON(0x20, 0x86);
-static const uint8_t UUID_TX_POWER_MODE_CHAR[]    = UUID_URI_BEACON(0x20, 0x87);
-static const uint8_t UUID_BEACON_PERIOD_CHAR[]    = UUID_URI_BEACON(0x20, 0x88);
-static const uint8_t UUID_RESET_CHAR[]            = UUID_URI_BEACON(0x20, 0x89);
-static const uint8_t BEACON_UUID[] = {0xD8, 0xFE};
+static const uint8_t URIBeacon2ControlServiceUUID[] = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x80);
+static const uint8_t lockedStateCharUUID[]          = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x81);
+static const uint8_t lockCharUUID[]                 = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x82);
+static const uint8_t unlockCharUUID[]               = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x83);
+static const uint8_t uriDataCharUUID[]              = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x84);
+static const uint8_t flagsCharUUID[]                = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x85);
+static const uint8_t txPowerLevelsCharUUID[]        = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x86);
+static const uint8_t txPowerModeCharUUID[]          = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x87);
+static const uint8_t beaconPeriodCharUUID[]         = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x88);
+static const uint8_t resetCharUUID[]                = URI_BEACON_CONFIG_UUID_INITIALIZER_LIST(0x20, 0x89);
 
 /**
 * @class URIBeaconConfigService
 * @brief UriBeacon Configuration Service. Can be used to set URL, adjust power levels, and set flags.
-* See http://uribeacon.org
-*
 */
 class URIBeaconConfigService {
-  public:
+public:
     /**
+     * @enum TXPowerModes_t
      * @brief Transmission Power Modes for UriBeacon
      */
-    static const uint8_t TX_POWER_MODE_LOWEST = 0; /*!< Lowest TX power mode */
-    static const uint8_t TX_POWER_MODE_LOW    = 1; /*!< Low TX power mode */
-    static const uint8_t TX_POWER_MODE_MEDIUM = 2; /*!< Medium TX power mode */
-    static const uint8_t TX_POWER_MODE_HIGH   = 3; /*!< High TX power mode */
-    static const unsigned int NUM_POWER_MODES = 4; /*!< Number of Power Modes defined */
-
-
-    typedef uint8_t Lock_t[16];               /* 128 bits */
-    typedef int8_t PowerLevels_t[NUM_POWER_MODES];
-
-    static const int URI_DATA_MAX = 18;
-    typedef uint8_t  UriData_t[URI_DATA_MAX];
-
-    struct Params_t {
-        Lock_t              lock;
-        uint8_t             uriDataLength;
-        UriData_t           uriData;
-        uint8_t             flags;
-        // Current value of AdvertisedPowerLevels
-        PowerLevels_t       advPowerLevels;
-        // Firmware power levels used with setTxPower()
-        uint8_t             txPowerMode;
-        uint16_t            beaconPeriod;
+    enum TXPowerModes_t {
+        TX_POWER_MODE_LOWEST = 0, /*!< Lowest TX power mode */
+        TX_POWER_MODE_LOW    = 1, /*!< Low TX power mode */
+        TX_POWER_MODE_MEDIUM = 2, /*!< Medium TX power mode */
+        TX_POWER_MODE_HIGH   = 3, /*!< High TX power mode */
+        NUM_POWER_MODES           /*!< Number of Power Modes defined */
     };
 
+    static const size_t SIZEOF_LOCK_BITS = 16;                /* uint128 */
+    typedef uint8_t     LockBits_t[SIZEOF_LOCK_BITS];
 
     /**
-     * @param[ref]    ble
-     *                    BLEDevice object for the underlying controller.
-     * @param[in/out] paramsIn
-     *                    Reference to application-visible beacon state, loaded
-     *                    from persistent storage at startup.
-     * @param[in]     resetToDefaultsFlag
-     *                    reset params state to the defaults.
-     * @param[in]     defaultUriDataIn
-     *                    Default encoded URIData; applies only if the resetToDefaultsFlag is true.
-     * @param[in]     defaultUriDataLengthIn
-     *                    Length of the default encoded URIData (from above); applies only if the resetToDefaultsFlag is true.
-     * @param[in]     defaultAdvPowerLevelsIn
-     *                    Default power-levels array; applies only if the resetToDefaultsFlag is true.
+     * @param[ref] ble
+     *                 BLEDevice object for the underlying controller.
+     * @param[in]  uridata
+     *                 URI as a null-terminated string.
+     * @param[in]  flagsIn
+     *                 UriBeacon Flags.
+     * @param[in]  powerLevels[]
+     *                 Table of UriBeacon Tx Power Levels in dBm.
+     * @param[in]  powerMode
+     *                 Currently effective power mode.
+     * @param[in]  beaconPeriodIn
+     *                 The period in milliseconds that a UriBeacon packet is
+     *                 transmitted. A value of zero disables UriBeacon
+     *                 transmissions.
      */
-    URIBeaconConfigService(BLEDevice     &bleIn,
-                           Params_t      &paramsIn,
-                           bool          resetToDefaultsFlag,
-                           UriData_t     &defaultUriDataIn,
-                           int           defaultUriDataLengthIn,
-                           PowerLevels_t &defaultAdvPowerLevelsIn) :
+    URIBeaconConfigService(BLEDevice      &bleIn,
+                           const char     *uriDataIn,
+                           uint8_t         flagsIn                        = 0,
+                           const int8_t    powerLevelsIn[NUM_POWER_MODES] = NULL,
+                           TXPowerModes_t  powerModeIn                    = TX_POWER_MODE_LOW,
+                           uint16_t        beaconPeriodIn                 = 1000) :
         ble(bleIn),
-        params(paramsIn),
-        defaultUriDataLength(defaultUriDataLengthIn),
-        defaultUriData(defaultUriDataIn),
-        defaultAdvPowerLevels(defaultAdvPowerLevelsIn),
+        payloadIndex(0),
+        serviceDataPayload(),
         initSucceeded(false),
-        lockedStateChar(UUID_LOCK_STATE_CHAR, &lockedState),
-        lockChar(UUID_LOCK_CHAR, &params.lock),
-        uriDataChar(UUID_URI_DATA_CHAR, params.uriData, URI_DATA_MAX, params.uriDataLength,
-                    GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE),
-        unlockChar(UUID_UNLOCK_CHAR, &params.lock),
-        flagsChar(UUID_FLAGS_CHAR, &params.flags),
-        advPowerLevelsChar(UUID_ADV_POWER_LEVELS_CHAR, &params.advPowerLevels),
-        txPowerModeChar(UUID_TX_POWER_MODE_CHAR, &params.txPowerMode),
-        beaconPeriodChar(UUID_BEACON_PERIOD_CHAR, &params.beaconPeriod),
-        resetChar(UUID_RESET_CHAR, &resetFlag) {
-        if (defaultUriDataLengthIn > URI_DATA_MAX) {
+        lockedState(false),
+        lockBits(),
+        uriDataLength(0),
+        uriData(),
+        flags(flagsIn),
+        powerLevels(),
+        beaconPeriod(beaconPeriodIn),
+        lockedStateChar(lockedStateCharUUID, &lockedState),
+        lockChar(lockCharUUID, lockBits),
+        unlockChar(unlockCharUUID, lockBits),
+        uriDataChar(uriDataCharUUID, uriData),
+        flagsChar(flagsCharUUID, &flags),
+        txPowerLevelsChar(txPowerLevelsCharUUID, powerLevels),
+        txPowerModeChar(txPowerModeCharUUID, &txPowerMode),
+        beaconPeriodChar(beaconPeriodCharUUID, &beaconPeriod),
+        resetChar(resetCharUUID, &resetFlag)
+    {
+        if ((uriDataIn == NULL) || ((uriDataLength = strlen(uriDataIn)) == 0) || (uriDataLength > MAX_SIZE_URI_DATA_CHAR_VALUE)) {
             return;
         }
+        strcpy(reinterpret_cast<char *>(uriData), uriDataIn);
 
-        if (params.uriDataLength > URI_DATA_MAX) {
-            resetToDefaultsFlag = true;
+        if (powerLevelsIn != NULL) {
+            memcpy(powerLevels, powerLevelsIn, sizeof(powerLevels));
+            updateTxPowerLevelsCharacteristic();
         }
 
-        lockedState = isLocked();
+        configureGAP();
 
-        if (resetToDefaultsFlag) {
-            resetToDefaults();
-        } else {
-            updateCharacteristicValues();
-        }
+        // enable the following for debugging the state of the lock
+        // lockedStateChar.setReadAuthorizationCallback(this, &URIBeaconConfigService::lockedStateAuthorizationCallback);
 
         lockChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::lockAuthorizationCallback);
         unlockChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::unlockAuthorizationCallback);
         uriDataChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::uriDataWriteAuthorizationCallback);
         flagsChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::flagsAuthorizationCallback);
-        advPowerLevelsChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::denyGATTWritesIfLocked);
-        txPowerModeChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::denyGATTWritesIfLocked);
+        txPowerLevelsChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::denyGATTWritesIfLocked);
+        txPowerModeChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::powerModeAuthorizationCallback);
         beaconPeriodChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::denyGATTWritesIfLocked);
         resetChar.setWriteAuthorizationCallback(this, &URIBeaconConfigService::denyGATTWritesIfLocked);
 
-        static GattCharacteristic *charTable[] = {
-            &lockedStateChar, &lockChar, &unlockChar, &uriDataChar,
-            &flagsChar, &advPowerLevelsChar, &txPowerModeChar, &beaconPeriodChar, &resetChar
-        };
+        GattCharacteristic *charTable[] = {&lockedStateChar,
+                                           &lockChar,
+                                           &unlockChar,
+                                           &uriDataChar,
+                                           &flagsChar,
+                                           &txPowerLevelsChar,
+                                           &beaconPeriodChar,
+                                           &resetChar};
+        GattService         beaconControlService(URIBeacon2ControlServiceUUID, charTable, sizeof(charTable) / sizeof(GattCharacteristic *));
+        ble.addService(beaconControlService);
 
-        GattService configService(UUID_URI_BEACON_SERVICE, charTable, sizeof(charTable) / sizeof(GattCharacteristic *));
-
-        ble.addService(configService);
-        ble.onDataWritten(this, &URIBeaconConfigService::onDataWrittenCallback);
-
-        initSucceeded = true;
+        ble.onDataWritten(this, &URIBeaconConfigService::onDataWritten);
     }
 
     bool configuredSuccessfully(void) const {
         return initSucceeded;
     }
 
-
-  private:
-    // True if the lock bits are non-zero
-    bool isLocked() {
-        Lock_t testLock;
-        memset(testLock, 0, sizeof(Lock_t));
-        return memcmp(params.lock, testLock, sizeof(Lock_t));
+    /**
+     * Please note that the following public APIs are offered to allow modifying
+     * the service programmatically. It is also possible to do so over BLE GATT
+     * transactions.
+     */
+public:
+    /**
+     * Update flags of the URIBeacon dynamically.
+     *
+     * @param[in] flagsIn
+     * @verbatim
+     *     ### UriBeacon Flags
+     *     Bit   | Description
+     *     :---- | :----------
+     *     0     | Invisible Hint
+     *     1..7  | Reserved for future use. Must be zero.
+     * @endverbatim
+     *     The `Invisible Hint` flag is a command for the user-agent that tells
+     *     it not to access or display the UriBeacon. This is a guideline only,
+     *     and is not a blocking method. User agents may, with user approval,
+     *     display invisible beacons.
+     */
+    void setFlags(uint8_t flagsIn) {
+        flags = flagsIn;
+        configureGAP();
+        updateFlagsCharacteristic();
     }
 
-    /*
-     * This callback is invoked when a GATT client attempts to modify any of the
-     * characteristics of this service. Attempts to do so are also applied to
-     * the internal state of this service object.
+    /**
+     * @brief Update the txPowerLevels table.
+     *
+     * @param[in] powerLevelsIn
+     *              Array of power levels
      */
-    void onDataWrittenCallback(const GattCharacteristicWriteCBParams *writeParams) {
-        uint16_t handle = writeParams->charHandle;
+    void setTxPowerLevels(const int8_t powerLevelsIn[NUM_POWER_MODES]) {
+        memcpy(powerLevels, powerLevelsIn, sizeof(powerLevels));
+        configureGAP();
+        updateTxPowerLevelsCharacteristic();
+    }
 
-        if (handle == lockChar.getValueHandle()) {
-            // Validated earlier
-            memcpy(params.lock, writeParams->data, sizeof(Lock_t));
-            // use isLocked() in case bits are being set to all 0's
-            lockedState = isLocked();
-        } else if (handle == unlockChar.getValueHandle()) {
-            // Validated earlier
-            memset(params.lock, 0, sizeof(Lock_t));
-            lockedState = false;
-        } else if (handle == uriDataChar.getValueHandle()) {
-            params.uriDataLength = writeParams->len;
-            memcpy(params.uriData, writeParams->data, params.uriDataLength);
-        } else if (handle == flagsChar.getValueHandle()) {
-            params.flags = *(writeParams->data);
-        } else if (handle == advPowerLevelsChar.getValueHandle()) {
-            memcpy(params.advPowerLevels, writeParams->data, sizeof(PowerLevels_t));
-        } else if (handle == txPowerModeChar.getValueHandle()) {
-            params.txPowerMode = *(writeParams->data);
-        } else if (handle == beaconPeriodChar.getValueHandle()) {
-            params.beaconPeriod = *((uint16_t *)(writeParams->data));
-        } else if (handle == resetChar.getValueHandle()) {
-            resetToDefaults();
+    /**
+     * @brief Set the effective power mode from one of the values in the powerLevels tables.
+     *
+     * @param[in] mode
+     *              Set the TX Power Mode.
+     */
+    void setTxPowerMode(TXPowerModes_t mode) {
+        txPowerMode = mode;
+        configureGAP();
+        updateTxPowerModeCharacteristic();
+    }
+
+    /**
+     * The period in milliseconds that a UriBeacon packet is transmitted.
+     *
+     * @note A value of zero disables UriBeacon transmissions.
+     *
+     * @param beaconPeriodIn
+     *              Beacon advertising period in milliseconds
+     */
+    void setBeaconPeriod(uint16_t beaconPeriodIn) {
+        beaconPeriod = beaconPeriodIn;
+        configureGAP();
+        updateBeaconPeriodCharacteristic();
+    }
+
+protected:
+    void updateLockBits(const LockBits_t lockBitsIn) {
+        static const uint8_t allZeroes[SIZEOF_LOCK_BITS] = {0, 0, 0, 0, 0, 0, 0, 0,
+                                                            0, 0, 0, 0, 0, 0, 0, 0};
+
+        memcpy(lockBits, lockBitsIn, SIZEOF_LOCK_BITS);
+        if (memcmp(lockBits, allZeroes, SIZEOF_LOCK_BITS)) {
+            lockedState = true;
         }
     }
 
-    /*
-     * Reset the default values.
+    void copyLockBitsInto(LockBits_t lockBitsOut) const {
+        memcpy(lockBitsOut, lockBits, SIZEOF_LOCK_BITS);
+    }
+
+    void resetLockBits(void) {
+        lockedState = false;
+        memset(lockBits, 0, SIZEOF_LOCK_BITS);
+        storage_saveLockBits();
+    }
+
+    /**
+     * APIs around making lockBits persistent.
+     */
+private:
+    /**
+     * Have we previously saved lockedBits? Once set, this state is expected to persist.
+     * @return true if we've previously saved locked bits.
+     */
+    virtual bool storage_haveSavedLockBits() const {
+        /* Expecting to be overridden. Left empty to allow the default URIBeacon to be instantiated if persistence isn't required. */
+        return false;
+    }
+
+    /**
+     * Save the current value of lockBits into persistent storage; this value is then retrievable by lockLockBits() until a subsequent call to saveLockBits().
      */
-    void resetToDefaults(void) {
-        lockedState      = false;
-        memset(params.lock, 0, sizeof(Lock_t));
-        memcpy(params.uriData, defaultUriData, URI_DATA_MAX);
-        params.uriDataLength    = defaultUriDataLength;
-        params.flags            = 0;
-        memcpy(params.advPowerLevels, defaultAdvPowerLevels, sizeof(PowerLevels_t));
-        params.txPowerMode      = TX_POWER_MODE_LOW;
-        params.beaconPeriod     = 1000;
-        updateCharacteristicValues();
+    virtual void storage_saveLockBits() {
+        /* Expecting to be overridden. Left empty to allow the default URIBeacon to be instantiated if persistence isn't required. */
+    }
+
+    /**
+     * Retrieve the saved lockBits from persistent storage and update the class member 'lockBits'.
+     */
+    virtual void storage_loadLockBits() {
+        /* Expecting to be overridden. Left empty to allow the default URIBeacon to be instantiated if persistence isn't required. */
+    }
+
+private:
+    /*
+     * Setup the advertisement payload and GAP settings.
+     */
+    void configureGAP(void) {
+        const uint8_t BEACON_UUID[] = {0xD8, 0xFE};
+
+        payloadIndex                       = 0;
+        serviceDataPayload[payloadIndex++] = BEACON_UUID[0];
+        serviceDataPayload[payloadIndex++] = BEACON_UUID[1];
+        serviceDataPayload[payloadIndex++] = flags;
+        serviceDataPayload[payloadIndex++] = powerLevels[txPowerMode];
+
+        const char *urlData       = reinterpret_cast<char *>(uriData);
+        size_t      sizeofURLData = uriDataLength;
+        size_t      encodedBytes  = encodeURISchemePrefix(urlData, sizeofURLData) + encodeURI(urlData, sizeofURLData);
+
+        ble.clearAdvertisingPayload();
+        ble.accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LIST_16BIT_SERVICE_IDS, BEACON_UUID, sizeof(BEACON_UUID));
+        ble.accumulateAdvertisingPayload(GapAdvertisingData::SERVICE_DATA, serviceDataPayload, encodedBytes + 4);
+
+        ble.setAdvertisingInterval(Gap::MSEC_TO_ADVERTISEMENT_DURATION_UNITS(beaconPeriod));
+        ble.setTxPower(powerLevels[txPowerMode]);
     }
 
     /*
-     * Internal helper function used to update the GATT database following any
-     * change to the internal state of the service object.
+     *  Encode the URI Prefix to a single byte if possible.
      */
-    void updateCharacteristicValues(void) {
-        ble.updateCharacteristicValue(lockedStateChar.getValueHandle(), &lockedState, 1);
-        ble.updateCharacteristicValue(uriDataChar.getValueHandle(), params.uriData, params.uriDataLength);
-        ble.updateCharacteristicValue(flagsChar.getValueHandle(), &params.flags, 1);
-        ble.updateCharacteristicValue(beaconPeriodChar.getValueHandle(),
-                                      reinterpret_cast<uint8_t *>(&params.beaconPeriod), sizeof(uint16_t));
-        ble.updateCharacteristicValue(txPowerModeChar.getValueHandle(), &params.txPowerMode, 1);
-        ble.updateCharacteristicValue(advPowerLevelsChar.getValueHandle(),
-                                      reinterpret_cast<uint8_t *>(params.advPowerLevels), sizeof(PowerLevels_t));
-    }
-
-  private:
-    void lockAuthorizationCallback(GattCharacteristicWriteAuthCBParams *authParams) {
-        authParams->authorizationReply = (authParams->len == sizeof(Lock_t)) && !lockedState;
-    }
-
-
-    void unlockAuthorizationCallback(GattCharacteristicWriteAuthCBParams *authParams) {
-        if (!lockedState || (authParams->len == sizeof(Lock_t) && (memcmp(authParams->data, params.lock, sizeof(Lock_t)) == 0))) {
-            authParams->authorizationReply = true;
-        } else {
-            authParams->authorizationReply = false;
-        }
-    }
-
-    void uriDataWriteAuthorizationCallback(GattCharacteristicWriteAuthCBParams *authParams) {
-        if (lockedState || (authParams->offset != 0) || (authParams->len > URI_DATA_MAX)) {
-            authParams->authorizationReply = false;
-        }
-    }
-
-    void flagsAuthorizationCallback(GattCharacteristicWriteAuthCBParams *authParams) {
-        if (lockedState || authParams->len != 1) {
-            authParams->authorizationReply = false;
-        }
-    }
-
-    void denyGATTWritesIfLocked(GattCharacteristicWriteAuthCBParams *authParams) {
-        if (lockedState) {
-            authParams->authorizationReply = false;
-        }
-    }
-
-    BLEDevice     &ble;
-    Params_t      &params;
-    // Default value that is restored on reset
-    uint16_t      defaultUriDataLength;
-    UriData_t     &defaultUriData;
-    // Default value that is restored on reset
-    PowerLevels_t &defaultAdvPowerLevels;
-    uint8_t       lockedState;
-    bool          initSucceeded;
-    uint8_t       resetFlag;
-
-    ReadOnlyGattCharacteristic<uint8_t>        lockedStateChar;
-    WriteOnlyGattCharacteristic<Lock_t>        lockChar;
-    GattCharacteristic                         uriDataChar;
-    WriteOnlyGattCharacteristic<Lock_t>        unlockChar;
-    ReadWriteGattCharacteristic<uint8_t>       flagsChar;
-    ReadWriteGattCharacteristic<PowerLevels_t> advPowerLevelsChar;
-    ReadWriteGattCharacteristic<uint8_t>       txPowerModeChar;
-    ReadWriteGattCharacteristic<uint16_t>      beaconPeriodChar;
-    WriteOnlyGattCharacteristic<uint8_t>       resetChar;
-
-  public:
-    /*
-     *  Encode a human-readable URI into the binary format defined by URIBeacon spec (https://github.com/google/uribeacon/tree/master/specification).
-     */
-    static void encodeURI(const char *uriDataIn, UriData_t uriDataOut, size_t &sizeofURIDataOut) {
-        sizeofURIDataOut = 0;
-        memset(uriDataOut, 0, sizeof(UriData_t));
-
-        if ((uriDataIn == NULL) || (strlen(uriDataIn) == 0)) {
-            return;
+    size_t encodeURISchemePrefix(const char *&urldata, size_t &sizeofURLData) {
+        if (!sizeofURLData) {
+            return 0;
         }
 
-        /*
-         * handle prefix
-         */
+        /* These are the URI Prefixes that can be abbreviated.*/
         const char *prefixes[] = {
             "http://www.",
             "https://www.",
@@ -297,19 +295,29 @@
             "https://",
             "urn:uuid:"
         };
-        const size_t NUM_PREFIXES     = sizeof(prefixes) / sizeof(char *);
+
+        size_t       encodedBytes = 0;
+        const size_t NUM_PREFIXES = sizeof(prefixes) / sizeof(char *);
         for (unsigned i = 0; i < NUM_PREFIXES; i++) {
             size_t prefixLen = strlen(prefixes[i]);
-            if (strncmp(uriDataIn, prefixes[i], prefixLen) == 0) {
-                uriDataOut[sizeofURIDataOut++]  = i;
-                uriDataIn                      += prefixLen;
+            if (strncmp(urldata, prefixes[i], prefixLen) == 0) {
+                serviceDataPayload[payloadIndex++] = i;
+                encodedBytes                       = 1;
+
+                urldata       += prefixLen;
+                sizeofURLData -= prefixLen;
                 break;
             }
         }
 
-        /*
-         * handle suffixes
-         */
+        return encodedBytes;
+    }
+
+    /*
+     *  Encode the URI Suffix to a single byte if possible.
+     */
+    size_t encodeURI(const char *urldata, size_t sizeofURLData) {
+        /* These are the URI suffixes that can be abbreviated. */
         const char *suffixes[] = {
             ".com/",
             ".org/",
@@ -327,28 +335,212 @@
             ".gov"
         };
         const size_t NUM_SUFFIXES = sizeof(suffixes) / sizeof(char *);
-        while (*uriDataIn && (sizeofURIDataOut < URI_DATA_MAX)) {
+
+        size_t encodedBytes = 0;
+        while (sizeofURLData && (payloadIndex < MAX_SIZEOF_SERVICE_DATA_PAYLOAD)) {
             /* check for suffix match */
             unsigned i;
             for (i = 0; i < NUM_SUFFIXES; i++) {
                 size_t suffixLen = strlen(suffixes[i]);
-                if (suffixLen == 0) {
+                if ((suffixLen == 0) || (sizeofURLData < suffixLen)) {
                     continue;
                 }
 
-                if (strncmp(uriDataIn, suffixes[i], suffixLen) == 0) {
-                    uriDataOut[sizeofURIDataOut++] = i;
-                    uriDataIn       += suffixLen;
+                if (strncmp(urldata, suffixes[i], suffixLen) == 0) {
+                    serviceDataPayload[payloadIndex++] = i;
+                    ++encodedBytes;
+                    urldata       += suffixLen;
+                    sizeofURLData -= suffixLen;
                     break; /* from the for loop for checking against suffixes */
                 }
             }
             /* This is the default case where we've got an ordinary character which doesn't match a suffix. */
             if (i == NUM_SUFFIXES) {
-                uriDataOut[sizeofURIDataOut++] = *uriDataIn;
-                ++uriDataIn;
+                serviceDataPayload[payloadIndex++] = *urldata;
+                ++encodedBytes;
+                ++urldata;
+                --sizeofURLData;
             }
         }
+        if (sizeofURLData == 0) {
+            initSucceeded = true;
+        }
+
+        return encodedBytes;
     }
+
+    /*
+     * This callback is invoked when a GATT client attempts to modify any of the
+     * characteristics of this service. Attempts to do so are also applied to
+     * the internal state of this service object.
+     */
+    void onDataWritten(const GattCharacteristicWriteCBParams *params) {
+        uint16_t handle = params->charHandle;
+        if (handle == lockChar.getValueHandle()) {
+            updateLockBits(params->data);
+            storage_saveLockBits();
+        } else if (handle == unlockChar.getValueHandle()) {
+            memset(lockBits, 0, SIZEOF_LOCK_BITS);
+            lockedState = false;
+            storage_saveLockBits();
+        } else if (handle == uriDataChar.getValueHandle()) {
+            uriDataLength = params->len;
+            memcpy(uriData, params->data, uriDataLength);
+        } else if (handle == flagsChar.getValueHandle()) {
+            flags = *(params->data);
+        } else if (handle == txPowerLevelsChar.getValueHandle()) {
+            memcpy(powerLevels, params->data, NUM_POWER_MODES * sizeof(int8_t));
+        } else if (handle == txPowerModeChar.getValueHandle()) {
+            txPowerMode = *reinterpret_cast<const TXPowerModes_t *>(params->data);
+        } else if (handle == beaconPeriodChar.getValueHandle()) {
+            beaconPeriod = *((uint16_t *)(params->data));
+        } else if (handle == resetChar.getValueHandle()) {
+            resetDefaults();
+        }
+        configureGAP();
+        ble.setAdvertisingPayload();
+    }
+
+    /*
+     * Reset the default values.
+     */
+    void resetDefaults(void) {
+        uriDataLength    = 0;
+        memset(uriData, 0, MAX_SIZE_URI_DATA_CHAR_VALUE);
+        flags            = 0;
+        memset(powerLevels, 0, sizeof(powerLevels));
+        txPowerMode      = TX_POWER_MODE_LOW;
+        beaconPeriod     = 0;
+        resetLockBits();
+
+        updateGATT();
+    }
+
+    /*
+     * Internal helper function used to update the GATT database following any
+     * change to the internal state of the service object.
+     */
+    void updateGATT(void) {
+        updateLockedStateCharacteristic();
+        updateURIDataCharacteristic();
+        updateFlagsCharacteristic();
+        updateBeaconPeriodCharacteristic();
+        updateTxPowerLevelsCharacteristic();
+        updateTxPowerModeCharacteristic();
+    }
+
+    void updateLockedStateCharacteristic(void) {
+        ble.updateCharacteristicValue(lockedStateChar.getValueHandle(), reinterpret_cast<uint8_t *>(&lockedState), sizeof(lockedState));
+    }
+
+    void updateURIDataCharacteristic(void) {
+        ble.updateCharacteristicValue(uriDataChar.getValueHandle(), uriData, uriDataLength);
+    }
+
+    void updateFlagsCharacteristic(void) {
+        ble.updateCharacteristicValue(flagsChar.getValueHandle(), &flags, 1 /* size */);
+    }
+
+    void updateBeaconPeriodCharacteristic(void) {
+        ble.updateCharacteristicValue(beaconPeriodChar.getValueHandle(), reinterpret_cast<uint8_t *>(&beaconPeriod), sizeof(uint16_t));
+    }
+
+    void updateTxPowerModeCharacteristic(void) {
+        ble.updateCharacteristicValue(txPowerModeChar.getValueHandle(), reinterpret_cast<uint8_t *>(&txPowerMode), sizeof(uint8_t));
+    }
+
+    void updateTxPowerLevelsCharacteristic(void) {
+        ble.updateCharacteristicValue(txPowerLevelsChar.getValueHandle(), reinterpret_cast<uint8_t *>(powerLevels), NUM_POWER_MODES * sizeof(int8_t));
+    }
+
+private:
+    // enable the following for debugging the state of the lock
+    // void lockedStateAuthorizationCallback(GattCharacteristicReadAuthCBParams *params) {
+    //     printf("read authorization callback: lockedState is %u\r\n", lockedState);
+    //     params->authorizationReply = true;
+    // }
+
+    void lockAuthorizationCallback(GattCharacteristicWriteAuthCBParams *params) {
+        params->authorizationReply = !lockedState;
+    }
+
+    void unlockAuthorizationCallback(GattCharacteristicWriteAuthCBParams *params) {
+        if (lockedState && (memcmp(params->data, lockBits, SIZEOF_LOCK_BITS) == 0)) {
+            params->authorizationReply = true;
+        } else {
+            params->authorizationReply = false;
+        }
+    }
+
+    void uriDataWriteAuthorizationCallback(GattCharacteristicWriteAuthCBParams *params) {
+        if (lockedState || (params->offset != 0) || (params->len > MAX_SIZE_URI_DATA_CHAR_VALUE)) {
+            params->authorizationReply = false;
+        }
+    }
+
+    void flagsAuthorizationCallback(GattCharacteristicWriteAuthCBParams *params) {
+        if (lockedState || ((*(params->data) & 0xFE) != 0)) {
+            params->authorizationReply = false;
+        }
+    }
+
+    void powerModeAuthorizationCallback(GattCharacteristicWriteAuthCBParams *params) {
+        if (lockedState || (*(params->data) >= NUM_POWER_MODES)) {
+            params->authorizationReply = false;
+        }
+    }
+
+    void denyGATTWritesIfLocked(GattCharacteristicWriteAuthCBParams *params) {
+        if (lockedState) {
+            params->authorizationReply = false;
+        }
+    }
+
+private:
+    /**
+     * For debugging only. Print Hex representation of ServiceDataPayload to the console.
+     */
+    // void dumpEncodedSeviceData() const {
+    //     printf("encoded: '");
+    //     for (unsigned i = 0; i < payloadIndex; i++) {
+    //         printf(" %02x", serviceDataPayload[i]);
+    //     }
+    //     printf("'\r\n");
+    // }
+
+private:
+    static const size_t MAX_SIZEOF_SERVICE_DATA_PAYLOAD = 22; /* Uri Data must be between 0 and 18 bytes in length; and
+                                                               * together with the 4-byte header, the service data must
+                                                               * fit within 22 bytes. */
+    static const size_t MAX_SIZE_URI_DATA_CHAR_VALUE    = 48; /* This is chosen arbitrarily. It should be large enough
+                                                               * to hold any reasonable uncompressed URI. */
+private:
+    BLEDevice          &ble;
+
+    size_t              payloadIndex;
+    uint8_t             serviceDataPayload[MAX_SIZEOF_SERVICE_DATA_PAYLOAD];
+    bool                initSucceeded;
+
+    bool                lockedState;
+    uint8_t             lockBits[SIZEOF_LOCK_BITS];
+
+    uint16_t            uriDataLength;
+    uint8_t             uriData[MAX_SIZE_URI_DATA_CHAR_VALUE];
+    uint8_t             flags;
+    int8_t              powerLevels[NUM_POWER_MODES];
+    TXPowerModes_t      txPowerMode;
+    uint16_t            beaconPeriod;
+    bool                resetFlag;
+
+    ReadOnlyGattCharacteristic<bool>                                        lockedStateChar;
+    WriteOnlyArrayGattCharacteristic<uint8_t, SIZEOF_LOCK_BITS>             lockChar;
+    WriteOnlyArrayGattCharacteristic<uint8_t, SIZEOF_LOCK_BITS>             unlockChar;
+    ReadWriteArrayGattCharacteristic<uint8_t, MAX_SIZE_URI_DATA_CHAR_VALUE> uriDataChar;
+    ReadWriteGattCharacteristic<uint8_t>                                    flagsChar;
+    ReadWriteArrayGattCharacteristic<int8_t, NUM_POWER_MODES>               txPowerLevelsChar;
+    ReadWriteGattCharacteristic<TXPowerModes_t>                             txPowerModeChar;
+    ReadWriteGattCharacteristic<uint16_t>                                   beaconPeriodChar;
+    WriteOnlyGattCharacteristic<bool>                                       resetChar;
 };
 
-#endif  // SERVICES_URIBEACONCONFIGSERVICE_H_
\ No newline at end of file
+#endif /* #ifndef __BLE_URI_BEACON_CONFIG_SERVICE_H__*/
\ No newline at end of file