Refactored return values to ArrayBuffer

Author: EddyVerbruggen

README.md

@@ -201,8 +201,8 @@ The promise will receive an object like this:
 
 ```js
 {
-  value: <72>, // the platform-specific binary value of the characteristic
-  valueDecoded: 65, // the plugin's best effort of auto-decoding the value (for testing purposes mostly)
+  value: <ArrayBuffer>, // an ArrayBuffer which you can use to decode (see example below)
+  valueRaw: <72>, // the platform-specific binary value of the characteristic: NSData (iOS), byte[] (Android)
   characteristicUUID: '434234-234234-234234-434'
 }
 ```
@@ -215,7 +215,9 @@ bluetooth.read({
   serviceUUID: '180d',
   characteristicUUID: '3434-45234-34324-2343'
 }).then(function(result) {
-  console.log("read: " + JSON.stringify(result));
+  // fi. a heartrate monitor value (Uint8) can be retrieved like this:
+  var data = new Uint8Array(result.value);
+  console.log("Your heartrate is: " + data[1] + " bpm");  
 }).then(function(err) {
   console.log("read error: " + err);
 });
@@ -253,6 +255,7 @@ bluetooth.startNotifying({
   serviceUUID: '180d',
   characteristicUUID: '3434-45234-34324-2343',
   onNotify: function (result) {
+    // see the read example for how to decode ArrayBuffers
 	console.log("read: " + JSON.stringify(result));
   }  
 }).then(function() {
@@ -275,8 +278,12 @@ bluetooth.stopNotifying({
 });
 ```
 
+## Changelog
+* 1.1.0  To be compatible with any Bluetooth device out there, the value returned from `read` and `notify` is now an `ArrayBuffer`.
+* 1.0.0  Initial release
+
 ## Future work
-* Find a more convenient way (and document it) to read/write values.
+* Find an even better way to write values.
 * Support other properties of a characteristic.
 * Report advertising data peripherals broadcast.
-* Support interacting with multiple characteristics of the same peripheral at the same time.
+* Support interacting with multiple characteristics of the same peripheral at the same time.

bluetooth-common.js

@@ -1,3 +1,5 @@
+require('./base64');
+
 var Bluetooth = {};
 
 Bluetooth.requestCoarseLocationPermission = function () {
@@ -12,4 +14,15 @@ Bluetooth.hasCoarseLocationPermission = function () {
   });
 };
 
+Bluetooth._base64ToArrayBuffer = function (b64) {
+  var stringToArrayBuffer = function(str) {
+    var ret = new Uint8Array(str.length);
+    for (var i = 0; i < str.length; i++) {
+      ret[i] = str.charCodeAt(i);
+    }
+    return ret.buffer;
+  };
+  return stringToArrayBuffer(atob(b64));
+};
+
 module.exports = Bluetooth;

bluetooth.android.js

@@ -1,6 +1,7 @@
 var utils = require("utils/utils");
 var application = require("application");
 var Bluetooth = require("./bluetooth-common");
+
 var ACCESS_COARSE_LOCATION_PERMISSION_REQUEST_CODE = 222;
 
 var adapter,
@@ -131,14 +132,14 @@ Bluetooth._MyGattCallback = android.bluetooth.BluetoothGattCallback.extend({
    * 3: disconnecting
    */
   onConnectionStateChange: function(bluetoothGatt, status, newState) {
-    console.log("------- _MyGattCallback.onConnectionStateChange, status: " + status);
-    console.log("------- _MyGattCallback.onConnectionStateChange, newState: " + newState);
+    console.log("------- _MyGattCallback.onConnectionStateChange, status: " + status + ", new state: " + newState);
 
     // https://github.com/don/cordova-plugin-ble-central/blob/master/src/android/Peripheral.java#L191    
     if (newState == 2 /* connected */ && status === 0 /* gatt success */) {
       console.log("---- discovering services..");
       bluetoothGatt.discoverServices();
     } else {
+      // perhaps the device was manually disconnected, or in use by another device
       Bluetooth._disconnect(bluetoothGatt);
     }
   },
@@ -234,14 +235,10 @@ Bluetooth._MyGattCallback = android.bluetooth.BluetoothGattCallback.extend({
     if (value === null) {
       return null;
     }
-    // TODO may be Uint16Array as well
-    var data = new Uint8Array(value);
-    for (var d in data) {
-      if (data[d] !== undefined) {
-        return data[d];
-      }
-    }
-    return value;
+
+    // value is of Java type: byte[]
+    var b = android.util.Base64.encodeToString(value, android.util.Base64.NO_WRAP);
+    return Bluetooth._base64ToArrayBuffer(b);
   },
 
   onCharacteristicRead: function(bluetoothGatt, bluetoothGattCharacteristic, status) {
@@ -257,8 +254,8 @@ Bluetooth._MyGattCallback = android.bluetooth.BluetoothGattCallback.extend({
     if (stateObject.onReadPromise) {
       var value = bluetoothGattCharacteristic.getValue();
       stateObject.onReadPromise({
-        value: value,
-        valueDecoded: this._decodeValue(value),
+        valueRaw: value,
+        value: this._decodeValue(value),
         characteristicUUID: bluetoothGattCharacteristic.getUuid()
       });
     }
@@ -276,11 +273,9 @@ Bluetooth._MyGattCallback = android.bluetooth.BluetoothGattCallback.extend({
 
     if (stateObject.onNotifyCallback) {
       var value = bluetoothGattCharacteristic.getValue();
-      var data = new Uint8Array(value);
-      console.log("------- _MyGattCallback.onCharacteristicChanged, decodedvalue: " + data[1]);
       stateObject.onNotifyCallback({
-        value: value,
-        valueDecoded: data[1],
+        valueRaw: value,
+        value: this._decodeValue(value),
         characteristicUUID: bluetoothGattCharacteristic.getUuid()
       });
     }

bluetooth.ios.js

@@ -1,5 +1,4 @@
 var Bluetooth = require("./bluetooth-common");
-require('./base64');
 
 Bluetooth._state = { 
   manager: null,
@@ -120,23 +119,14 @@ var CBPeripheralDelegateImpl = (function (_super) {
     }
   };
 
-  CBPeripheralDelegateImpl.prototype._decodeValue = function(value) {
+  CBPeripheralDelegateImpl.prototype._toArrayBuffer = function(value) {
     if (value === null) {
       return null;
     }
-    var v = atob(value.base64EncodedStringWithOptions(0));
-    var l = v.length;
-    var ret = new Uint8Array(l);
-    for (var i = 0; i < l; i++) {
-      ret[i] = v.charCodeAt(i);
-    }
-    var data = new Uint8Array(ret.buffer);
-    for (var d in data) {
-      if (data[d] !== undefined) {
-        return data[d];
-      }
-    }
-    return value;
+
+    // value is of ObjC type: NSData
+    var b = value.base64EncodedStringWithOptions(0);
+    return Bluetooth._base64ToArrayBuffer(b);
   };
 
   // this is called when a value is read from a peripheral
@@ -152,17 +142,13 @@ var CBPeripheralDelegateImpl = (function (_super) {
       return;
     }
 
-    var value = characteristic.value;
-    var valueDecoded = this._decodeValue(value);
-    console.log("value received from peripheral: " + value + ", decoded: " + valueDecoded);
-
     var result = {
       type: characteristic.isNotifying ? "notification" : "read",
       characteristicUUID: characteristic.UUID.UUIDString,
-      value: value,
-      valueDecoded: valueDecoded
+      valueRaw: characteristic.value,
+      value: this._toArrayBuffer(characteristic.value)
     };
-
+    
     if (result.type === "read") {
       if (this._onReadPromise) {
         this._onReadPromise(result);

package.json

@@ -1,6 +1,6 @@
 {
   "name": "nativescript-bluetooth",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description" : "Connect to and interact with Bluetooth LE peripherals",
   "main" : "bluetooth.js",
   "nativescript": {