LE peripheral manager - warn about value length limit (iOS)

Apparently, it cannot exceed the 512-octets limit on iOS.
Also, warn about notifications - the value is truncated for
a connected peripheral, we are limited by a central.maximumUpdateValueLength.

Change-Id: Ia3d09fe0306a2514cf2c6f391cc57e6d300b75fd
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

4 files changed, 34 insertions, 2 deletions

diff --git a/src/bluetooth/osx/osxbtperipheralmanager.mm b/src/bluetooth/osx/osxbtperipheralmanager.mm
index 03b95667..9c443cf6 100644
--- a/src/bluetooth/osx/osxbtperipheralmanager.mm
+++ b/src/bluetooth/osx/osxbtperipheralmanager.mm
@@ -187,6 +187,7 @@ bool qt_validate_value_range(const QLowEnergyCharacteristicData &data)
         state = PeripheralState::idle;
         nextServiceToAdd = {};
         connectedCentrals.reset([[NSMutableSet alloc] init]);
+        maxNotificationValueLength = std::numeric_limits<NSUInteger>::max();
     }
 
     return self;
@@ -353,8 +354,13 @@ bool qt_validate_value_range(const QLowEnergyCharacteristicData &data)
     }
 
     const auto & range = valueRanges[charHandle];
-    if (value.size() < int(range.first) || value.size() > int(range.second)) {
-        qCWarning(QT_BT_OSX) << "ignoring value of invalid length" << value.count();
+    if (value.size() < int(range.first) || value.size() > int(range.second)
+#ifdef Q_OS_IOS
+        || value.size() > OSXBluetooth::maxValueLength) {
+#else
+       ) {
+#endif
+        qCWarning(QT_BT_OSX) << "ignoring value of invalid length" << value.size();
         return;
     }
 
@@ -630,6 +636,12 @@ bool qt_validate_value_range(const QLowEnergyCharacteristicData &data)
     while (updateQueue.size()) {
         const auto &request = updateQueue.front();
         if (charMap.contains(request.charHandle)) {
+            if ([connectedCentrals count]
+                && maxNotificationValueLength < [request.value length]) {
+                qCWarning(QT_BT_OSX) << "value of length" << [request.value length]
+                                     << "will possibly be truncated to"
+                                     << maxNotificationValueLength;
+            }
             const BOOL res = [manager updateValue:request.value
                               forCharacteristic:static_cast<CBMutableCharacteristic *>(charMap[request.charHandle])
                               onSubscribedCentrals:nil];
@@ -655,6 +667,9 @@ bool qt_validate_value_range(const QLowEnergyCharacteristicData &data)
         return;
     }
 
+    maxNotificationValueLength = std::min(maxNotificationValueLength,
+                                          central.maximumUpdateValueLength);
+
     QT_BT_MAC_AUTORELEASEPOOL
 
     if (state == PeripheralState::advertising) {
@@ -683,6 +698,9 @@ bool qt_validate_value_range(const QLowEnergyCharacteristicData &data)
         state = PeripheralState::idle;
         emit notifier->disconnected();
     }
+
+    if (![connectedCentrals count])
+        maxNotificationValueLength = std::numeric_limits<NSUInteger>::max();
 }
 
 - (CBService *)findIncludedService:(const QBluetoothUuid &)qtUUID
@@ -749,6 +767,16 @@ bool qt_validate_value_range(const QLowEnergyCharacteristicData &data)
             continue;
         }
 
+#ifdef Q_OS_IOS
+        if (ch.value().length() > OSXBluetooth::maxValueLength) {
+            qCWarning(QT_BT_OSX) << "addCharacteristicsAndDescritptors: "
+                                    "value exceeds the maximal permitted "
+                                    "value length (" << OSXBluetooth::maxValueLength
+                                    << "octets) on the platform";
+            continue;
+        }
+#endif
+
         const auto cbChar(create_characteristic(ch));
         if (!cbChar) {
             qCWarning(QT_BT_OSX) << "addCharacteristicsAndDescritptors: "
diff --git a/src/bluetooth/osx/osxbtperipheralmanager_p.h b/src/bluetooth/osx/osxbtperipheralmanager_p.h
index b6021fb8..3fee7537 100644
--- a/src/bluetooth/osx/osxbtperipheralmanager_p.h
+++ b/src/bluetooth/osx/osxbtperipheralmanager_p.h
@@ -137,6 +137,7 @@ using ValueRange = QPair<NSUInteger, NSUInteger>;
     ObjCScopedPointer<NSMutableSet> connectedCentrals;
 
     PeripheralState state;
+    NSUInteger maxNotificationValueLength;
 }
 
 - (id)initWith:(LECBManagerNotifier *)notifier;
diff --git a/src/bluetooth/osx/osxbtutility.mm b/src/bluetooth/osx/osxbtutility.mm
index 139ccc54..1508c89f 100644
--- a/src/bluetooth/osx/osxbtutility.mm
+++ b/src/bluetooth/osx/osxbtutility.mm
@@ -72,6 +72,8 @@ Q_LOGGING_CATEGORY(QT_BT_OSX, "qt.bluetooth.ios")
 namespace OSXBluetooth {
 
 const int defaultLEScanTimeoutMS = 25000;
+// We use it only on iOS for now:
+const int maxValueLength = 512;
 
 QString qt_address(NSString *address)
 {
diff --git a/src/bluetooth/osx/osxbtutility_p.h b/src/bluetooth/osx/osxbtutility_p.h
index 3c0e05e7..148ebc0b 100644
--- a/src/bluetooth/osx/osxbtutility_p.h
+++ b/src/bluetooth/osx/osxbtutility_p.h
@@ -304,6 +304,7 @@ ObjCStrongReference<NSMutableData> mutable_data_from_bytearray(const QByteArray
 dispatch_queue_t qt_LE_queue();
 
 extern const int defaultLEScanTimeoutMS;
+extern const int maxValueLength;
 
 } // namespace OSXBluetooth