Generate key string for field cache at compile time

By providing a template that returns the right field name for each enum
value as a QtJniTypes::String we can create the cache key entirely at
compile time.

The key string will still be copied once, as the QHash operates on a
QByteArray as the key.

Change-Id: I611b94e0ff65d71e5cb5a63d487324b9cf485b6b
Reviewed-by: Juha Vuolle <juha.vuolle@insta.fi>
(cherry picked from commit 4f9ad7da4c4e9a0d45e501edf1db3db67cec2638)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

5 files changed, 86 insertions, 124 deletions

diff --git a/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp b/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp
index f481d47f..67678c12 100644
--- a/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp
+++ b/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp
@@ -356,9 +356,9 @@ quint8 resolveAndroidMinorClass(QBluetoothDeviceInfo::MajorDeviceClass major, ji
 
 DeviceDiscoveryBroadcastReceiver::DeviceDiscoveryBroadcastReceiver(QObject* parent): AndroidBroadcastReceiver(parent)
 {
-    addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionFound));
-    addAction(valueForStaticField(JavaNames::BluetoothAdapter, JavaNames::ActionDiscoveryStarted));
-    addAction(valueForStaticField(JavaNames::BluetoothAdapter, JavaNames::ActionDiscoveryFinished));
+    addAction(valueForStaticField<QtJniTypes::BluetoothDevice, JavaNames::ActionFound>());
+    addAction(valueForStaticField<QtJniTypes::BluetoothAdapter, JavaNames::ActionDiscoveryStarted>());
+    addAction(valueForStaticField<QtJniTypes::BluetoothAdapter, JavaNames::ActionDiscoveryFinished>());
 }
 
 // Runs in Java thread
@@ -372,17 +372,17 @@ void DeviceDiscoveryBroadcastReceiver::onReceive(JNIEnv *env, jobject context, j
 
     qCDebug(QT_BT_ANDROID) << "DeviceDiscoveryBroadcastReceiver::onReceive() - event:" << action;
 
-    if (action == valueForStaticField(JavaNames::BluetoothAdapter,
-                                      JavaNames::ActionDiscoveryFinished).toString()) {
+    if (action == valueForStaticField<QtJniTypes::BluetoothAdapter,
+                                      JavaNames::ActionDiscoveryFinished>().toString()) {
         emit finished();
-    } else if (action == valueForStaticField(JavaNames::BluetoothAdapter,
-                                             JavaNames::ActionDiscoveryStarted).toString()) {
+    } else if (action == valueForStaticField<QtJniTypes::BluetoothAdapter,
+                                             JavaNames::ActionDiscoveryStarted>().toString()) {
         emit discoveryStarted();
-    } else if (action == valueForStaticField(JavaNames::BluetoothDevice,
-                                             JavaNames::ActionFound).toString()) {
+    } else if (action == valueForStaticField<QtJniTypes::BluetoothDevice,
+                                             JavaNames::ActionFound>().toString()) {
         //get BluetoothDevice
-        QJniObject keyExtra = valueForStaticField(JavaNames::BluetoothDevice,
-                                                         JavaNames::ExtraDevice);
+        QJniObject keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                                  JavaNames::ExtraDevice>();
         const QJniObject bluetoothDevice =
                 intentObject.callMethod<QtJniTypes::Parcelable>("getParcelableExtra",
                                                                 keyExtra.object<jstring>());
@@ -390,8 +390,8 @@ void DeviceDiscoveryBroadcastReceiver::onReceive(JNIEnv *env, jobject context, j
         if (!bluetoothDevice.isValid())
             return;
 
-        keyExtra = valueForStaticField(JavaNames::BluetoothDevice,
-                                       JavaNames::ExtraRssi);
+        keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                       JavaNames::ExtraRssi>();
         int rssi = intentObject.callMethod<jshort>("getShortExtra",
                                                    keyExtra.object<jstring>(), jshort(0));
 
diff --git a/src/bluetooth/android/jni_android.cpp b/src/bluetooth/android/jni_android.cpp
index b01bbff6..27b64f98 100644
--- a/src/bluetooth/android/jni_android.cpp
+++ b/src/bluetooth/android/jni_android.cpp
@@ -17,94 +17,12 @@ Q_DECLARE_LOGGING_CATEGORY(QT_BT_ANDROID)
 typedef QHash<QByteArray, QJniObject> JCachedStringFields;
 Q_GLOBAL_STATIC(JCachedStringFields, cachedStringFields)
 
-//Java field names
-static const char * const javaActionAclConnected = "ACTION_ACL_CONNECTED";
-static const char * const javaActionAclDisconnected = "ACTION_ACL_DISCONNECTED";
-static const char * const javaActionBondStateChanged = "ACTION_BOND_STATE_CHANGED";
-static const char * const javaActionDiscoveryStarted = "ACTION_DISCOVERY_STARTED";
-static const char * const javaActionDiscoveryFinished = "ACTION_DISCOVERY_FINISHED";
-static const char * const javaActionFound = "ACTION_FOUND";
-static const char * const javaActionScanModeChanged = "ACTION_SCAN_MODE_CHANGED";
-static const char * const javaActionUuid = "ACTION_UUID";
-static const char * const javaExtraBondState = "EXTRA_BOND_STATE";
-static const char * const javaExtraDevice = "EXTRA_DEVICE";
-static const char * const javaExtraPairingKey = "EXTRA_PAIRING_KEY";
-static const char * const javaExtraPairingVariant = "EXTRA_PAIRING_VARIANT";
-static const char * const javaExtraRssi = "EXTRA_RSSI";
-static const char * const javaExtraScanMode = "EXTRA_SCAN_MODE";
-static const char * const javaExtraUuid = "EXTRA_UUID";
-
 /*
  * This function operates on the assumption that each
  * field is of type java/lang/String.
  */
-inline QByteArray classNameForStaticField(JavaNames javaName)
-{
-    switch (javaName) {
-    case JavaNames::BluetoothAdapter: {
-        constexpr auto cn = QtJniTypes::className<QtJniTypes::BluetoothAdapter>();
-        return QByteArray(cn.data(), cn.size());
-    }
-    case JavaNames::BluetoothDevice: {
-        constexpr auto cn = QtJniTypes::className<QtJniTypes::BluetoothDevice>();
-        return QByteArray(cn.data(), cn.size());
-    }
-    default:
-        break;
-    }
-    return {};
-}
-
-QJniObject valueForStaticField(JavaNames javaName, JavaNames javaFieldName)
+QJniObject valueFromStaticFieldCache(const char *key, const char *className, const char *fieldName)
 {
-    //construct key
-    //the switch statements are used to reduce the number of duplicated strings
-    //in the library
-
-    const char *fieldName;
-    switch (javaFieldName) {
-    case JavaNames::ActionAclConnected:
-        fieldName = javaActionAclConnected; break;
-    case JavaNames::ActionAclDisconnected:
-        fieldName = javaActionAclDisconnected; break;
-    case JavaNames::ActionBondStateChanged:
-        fieldName = javaActionBondStateChanged; break;
-    case JavaNames::ActionDiscoveryStarted:
-        fieldName = javaActionDiscoveryStarted; break;
-    case JavaNames::ActionDiscoveryFinished:
-        fieldName = javaActionDiscoveryFinished; break;
-    case JavaNames::ActionFound:
-        fieldName = javaActionFound; break;
-    case JavaNames::ActionScanModeChanged:
-        fieldName = javaActionScanModeChanged; break;
-    case JavaNames::ActionUuid:
-        fieldName = javaActionUuid; break;
-    case JavaNames::ExtraBondState:
-        fieldName = javaExtraBondState; break;
-    case JavaNames::ExtraDevice:
-        fieldName = javaExtraDevice; break;
-    case JavaNames::ExtraPairingKey:
-        fieldName = javaExtraPairingKey; break;
-    case JavaNames::ExtraPairingVariant:
-        fieldName = javaExtraPairingVariant; break;
-    case JavaNames::ExtraRssi:
-        fieldName = javaExtraRssi; break;
-    case JavaNames::ExtraScanMode:
-        fieldName = javaExtraScanMode; break;
-    case JavaNames::ExtraUuid:
-        fieldName = javaExtraUuid; break;
-    default:
-        qCWarning(QT_BT_ANDROID) << "Unknown java field name passed to valueForStaticField():" << javaFieldName;
-        return QJniObject();
-    }
-
-    const QByteArray className = classNameForStaticField(javaName);
-    if (className.isEmpty()) {
-        qCWarning(QT_BT_ANDROID) << "Unknown java class name passed to valueForStaticField():" << javaName;
-        return QJniObject();
-    }
-
-    const QByteArray key = className + fieldName;
     JCachedStringFields::iterator it = cachedStringFields()->find(key);
     if (it == cachedStringFields()->end()) {
         QJniEnvironment env;
diff --git a/src/bluetooth/android/jni_android_p.h b/src/bluetooth/android/jni_android_p.h
index e172f637..c51b14e7 100644
--- a/src/bluetooth/android/jni_android_p.h
+++ b/src/bluetooth/android/jni_android_p.h
@@ -88,7 +88,50 @@ enum JavaNames {
     ExtraUuid
 };
 
-QJniObject valueForStaticField(JavaNames javaName, JavaNames javaFieldName);
+QJniObject valueFromStaticFieldCache(const char *key, const char *className, const char *fieldName);
+
+
+template<typename Klass, JavaNames Field>
+QJniObject valueForStaticField()
+{
+    constexpr auto className = QtJniTypes::className<Klass>();
+    constexpr auto fieldName = []() -> auto {
+        if constexpr (Field == JavaNames::ActionAclConnected)
+            return QtJniTypes::String("ACTION_ACL_CONNECTED");
+        else if constexpr (Field == ActionAclDisconnected)
+            return QtJniTypes::String("ACTION_ACL_DISCONNECTED");
+        else if constexpr (Field == ActionBondStateChanged)
+            return QtJniTypes::String("ACTION_BOND_STATE_CHANGED");
+        else if constexpr (Field == ActionDiscoveryStarted)
+            return QtJniTypes::String("ACTION_DISCOVERY_STARTED");
+        else if constexpr (Field == ActionDiscoveryFinished)
+            return QtJniTypes::String("ACTION_DISCOVERY_FINISHED");
+        else if constexpr (Field == ActionFound)
+            return QtJniTypes::String("ACTION_FOUND");
+        else if constexpr (Field == ActionScanModeChanged)
+            return QtJniTypes::String("ACTION_SCAN_MODE_CHANGED");
+        else if constexpr (Field == ActionUuid)
+            return QtJniTypes::String("ACTION_UUID");
+        else if constexpr (Field == ExtraBondState)
+            return QtJniTypes::String("EXTRA_BOND_STATE");
+        else if constexpr (Field == ExtraDevice)
+            return QtJniTypes::String("EXTRA_DEVICE");
+        else if constexpr (Field == ExtraPairingKey)
+            return QtJniTypes::String("EXTRA_PAIRING_KEY");
+        else if constexpr (Field == ExtraPairingVariant)
+            return QtJniTypes::String("EXTRA_PAIRING_VARIANT");
+        else if constexpr (Field == ExtraRssi)
+            return QtJniTypes::String("EXTRA_RSSI");
+        else if constexpr (Field == ExtraScanMode)
+            return QtJniTypes::String("EXTRA_SCAN_MODE");
+        else if constexpr (Field == ExtraUuid)
+            return QtJniTypes::String("EXTRA_UUID");
+        else
+            QtJniTypes::staticAssertTypeMismatch();
+    }();
+
+    return valueFromStaticFieldCache(className + fieldName, className.data(), fieldName.data());
+}
 
 QT_END_NAMESPACE
 
diff --git a/src/bluetooth/android/localdevicebroadcastreceiver.cpp b/src/bluetooth/android/localdevicebroadcastreceiver.cpp
index 61ed4336..6e2ccf7a 100644
--- a/src/bluetooth/android/localdevicebroadcastreceiver.cpp
+++ b/src/bluetooth/android/localdevicebroadcastreceiver.cpp
@@ -16,10 +16,10 @@ const char *bondModes[] = {"BOND_NONE", "BOND_BONDING", "BOND_BONDED"};
 LocalDeviceBroadcastReceiver::LocalDeviceBroadcastReceiver(QObject *parent) :
     AndroidBroadcastReceiver(parent), previousScanMode(0)
 {
-    addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionBondStateChanged));
-    addAction(valueForStaticField(JavaNames::BluetoothAdapter, JavaNames::ActionScanModeChanged));
-    addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionAclConnected));
-    addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionAclDisconnected));
+    addAction(valueForStaticField<QtJniTypes::BluetoothDevice, JavaNames::ActionBondStateChanged>());
+    addAction(valueForStaticField<QtJniTypes::BluetoothAdapter, JavaNames::ActionScanModeChanged>());
+    addAction(valueForStaticField<QtJniTypes::BluetoothDevice, JavaNames::ActionAclConnected>());
+    addAction(valueForStaticField<QtJniTypes::BluetoothDevice, JavaNames::ActionAclDisconnected>());
 
     //cache integer values for host & bonding mode
     //don't use the java fields directly but refer to them by name
@@ -45,13 +45,13 @@ void LocalDeviceBroadcastReceiver::onReceive(JNIEnv *env, jobject context, jobje
     const QString action = intentObject.callMethod<jstring>("getAction").toString();
     qCDebug(QT_BT_ANDROID) << QStringLiteral("LocalDeviceBroadcastReceiver::onReceive() - event: %1").arg(action);
 
-    if (action == valueForStaticField(JavaNames::BluetoothAdapter,
-                                      JavaNames::ActionScanModeChanged).toString()) {
+    if (action == valueForStaticField<QtJniTypes::BluetoothAdapter,
+                                      JavaNames::ActionScanModeChanged>().toString()) {
 
         const QJniObject extrasBundle =
                 intentObject.callMethod<QtJniTypes::Bundle>("getExtras");
-        const QJniObject keyExtra = valueForStaticField(JavaNames::BluetoothAdapter,
-                                                               JavaNames::ExtraScanMode);
+        const QJniObject keyExtra = valueForStaticField<QtJniTypes::BluetoothAdapter,
+                                                        JavaNames::ExtraScanMode>();
 
         int extra = extrasBundle.callMethod<jint>("getInt", keyExtra.object<jstring>());
 
@@ -67,17 +67,18 @@ void LocalDeviceBroadcastReceiver::onReceive(JNIEnv *env, jobject context, jobje
             else
                 qCWarning(QT_BT_ANDROID) << "Unknown Host State";
         }
-    } else if (action == valueForStaticField(JavaNames::BluetoothDevice,
-                                             JavaNames::ActionBondStateChanged).toString()) {
+    } else if (action == valueForStaticField<QtJniTypes::BluetoothDevice,
+                                                        JavaNames::ActionBondStateChanged>().toString()) {
         //get BluetoothDevice
-        QJniObject keyExtra = valueForStaticField(JavaNames::BluetoothDevice,
-                                                         JavaNames::ExtraDevice);
+        QJniObject keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                                  JavaNames::ExtraDevice>();
         const QJniObject bluetoothDevice =
                 intentObject.callMethod<QtJniTypes::Parcelable>("getParcelableExtra",
                                                                 keyExtra.object<jstring>());
 
         //get new bond state
-        keyExtra = valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ExtraBondState);
+        keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                       JavaNames::ExtraBondState>();
         const QJniObject extrasBundle =
                 intentObject.callMethod<QtJniTypes::Bundle>("getExtras");
         int bondState = extrasBundle.callMethod<jint>("getInt", keyExtra.object<jstring>());
@@ -95,19 +96,19 @@ void LocalDeviceBroadcastReceiver::onReceive(JNIEnv *env, jobject context, jobje
         else
             qCWarning(QT_BT_ANDROID) << "Unknown BOND_STATE_CHANGED value:" << bondState;
 
-    } else if (action == valueForStaticField(JavaNames::BluetoothDevice,
-                                             JavaNames::ActionAclConnected).toString() ||
-               action == valueForStaticField(JavaNames::BluetoothDevice,
-                                             JavaNames::ActionAclDisconnected).toString()) {
+    } else if (action == valueForStaticField<QtJniTypes::BluetoothDevice,
+                                             JavaNames::ActionAclConnected>().toString() ||
+               action == valueForStaticField<QtJniTypes::BluetoothDevice,
+                                             JavaNames::ActionAclDisconnected>().toString()) {
 
-        const QString connectEvent = valueForStaticField(JavaNames::BluetoothDevice,
-                                                         JavaNames::ActionAclConnected).toString();
+        const QString connectEvent = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                                         JavaNames::ActionAclConnected>().toString();
         const bool isConnectEvent =
                 action == connectEvent ? true : false;
 
         //get BluetoothDevice
-        const QJniObject keyExtra = valueForStaticField(JavaNames::BluetoothDevice,
-                                                               JavaNames::ExtraDevice);
+        const QJniObject keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                                        JavaNames::ExtraDevice>();
         QJniObject bluetoothDevice =
                 intentObject.callMethod<QtJniTypes::Parcelable>("getParcelableExtra",
                                                                 keyExtra.object<jstring>());
diff --git a/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp b/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp
index 825e4abc..082e7247 100644
--- a/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp
+++ b/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp
@@ -15,7 +15,7 @@ Q_DECLARE_LOGGING_CATEGORY(QT_BT_ANDROID)
 
 ServiceDiscoveryBroadcastReceiver::ServiceDiscoveryBroadcastReceiver(QObject* parent): AndroidBroadcastReceiver(parent)
 {
-    addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionUuid));
+    addAction(valueForStaticField<QtJniTypes::BluetoothDevice, JavaNames::ActionUuid>());
 }
 
 void ServiceDiscoveryBroadcastReceiver::onReceive(JNIEnv *env, jobject context, jobject intent)
@@ -28,11 +28,11 @@ void ServiceDiscoveryBroadcastReceiver::onReceive(JNIEnv *env, jobject context,
 
     qCDebug(QT_BT_ANDROID) << "ServiceDiscoveryBroadcastReceiver::onReceive() - event:" << action;
 
-    if (action == valueForStaticField(JavaNames::BluetoothDevice,
-                                      JavaNames::ActionUuid).toString()) {
+    if (action == valueForStaticField<QtJniTypes::BluetoothDevice,
+                                      JavaNames::ActionUuid>().toString()) {
 
-        QJniObject keyExtra = valueForStaticField(JavaNames::BluetoothDevice,
-                                                         JavaNames::ExtraUuid);
+        QJniObject keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice,
+                                                         JavaNames::ExtraUuid>();
         QJniObject parcelableUuids = intentObject.callMethod<QtJniTypes::ParcelableArray>(
                                                 "getParcelableArrayExtra",
                                                 keyExtra.object<jstring>());
@@ -42,7 +42,7 @@ void ServiceDiscoveryBroadcastReceiver::onReceive(JNIEnv *env, jobject context,
         }
         const QList<QBluetoothUuid> result = ServiceDiscoveryBroadcastReceiver::convertParcelableArray(parcelableUuids);
 
-        keyExtra = valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ExtraDevice);
+        keyExtra = valueForStaticField<QtJniTypes::BluetoothDevice, JavaNames::ExtraDevice>();
         QJniObject bluetoothDevice =
         intentObject.callMethod<QtJniTypes::Parcelable>("getParcelableExtra",
                                   keyExtra.object<jstring>());