refs #460 CDataCache for dynamic (downloaded/generated) data with file-based distribution among processes.

src/blackmisc/dictionary.h

@@ -220,6 +220,17 @@ namespace BlackMisc
             removeByValueIf(BlackMisc::Predicates::MemberEqual(membFunc, returnValue));
         }
 
+        //! Remove elements for which the same key/value pair is present in an other dictionary.
+        void removeDuplicates(const CDictionary &other)
+        {
+            for (auto it = begin(); it != end();)
+            {
+                auto it2 = other.find(it.key());
+                if (it2 != other.end() && it.value() == it2.value()) { it = erase(it); }
+                else { ++it; }
+            }
+        }
+
         //! \copydoc CValueObject::toJson
         QJsonObject toJson() const
         {

src/blackmisc/identifier.cpp

@@ -35,6 +35,17 @@ namespace BlackMisc
         return id;
     }
 
+    QUuid CIdentifier::toUuid() const
+    {
+        static const QUuid ns = QUuid::createUuid();
+        QByteArray baseData;
+        baseData.append(getMachineId());
+        baseData.append(reinterpret_cast<const char *>(&m_processId), sizeof(m_processId));
+        baseData.append(reinterpret_cast<const char *>(&m_timestampMSecsSinceEpoch), sizeof(m_timestampMSecsSinceEpoch));
+        baseData.append(getName());
+        return QUuid::createUuidV5(ns, baseData);
+    }
+
     QByteArray CIdentifier::getMachineId() const
     {
         return QByteArray::fromBase64(m_machineIdBase64.toLocal8Bit());

src/blackmisc/identifier.h

@@ -49,6 +49,9 @@ namespace BlackMisc
         //! Returns an anonymous identifier.
         static CIdentifier anonymous();
 
+        //! Produces a UUID generated from the identifier.
+        QUuid toUuid() const;
+
         //! Name
         QString getName() const { return m_name; }
 

src/blackmisc/valuecache.cpp

@@ -146,7 +146,14 @@ namespace BlackMisc
 
     CStatusMessage CValueCache::saveToFiles(const QString &dir, const QString &keyPrefix) const
     {
+        QMutexLocker lock(&m_mutex);
         auto values = getAllValues(keyPrefix);
+        return saveToFiles(dir, values);
+    }
+
+    CStatusMessage CValueCache::saveToFiles(const QString &dir, const CVariantMap &values) const
+    {
+        QMutexLocker lock(&m_mutex);
         QMap<QString, CVariantMap> namespaces;
         for (auto it = values.cbegin(); it != values.cend(); ++it)
         {
@@ -182,10 +189,21 @@ namespace BlackMisc
 
     CStatusMessage CValueCache::loadFromFiles(const QString &dir)
     {
+        QMutexLocker lock(&m_mutex);
+        CVariantMap values;
+        auto status = loadFromFiles(dir, values);
+        insertValues(values);
+        return status;
+    }
+
+    CStatusMessage CValueCache::loadFromFiles(const QString &dir, CVariantMap &o_values) const
+    {
+        QMutexLocker lock(&m_mutex);
         if (! QDir(dir).isReadable())
         {
             return CLogMessage(this).error("Failed to read directory %1") << dir;
         }
+        auto currentValues = getAllValues();
         for (const auto &filename : QDir(dir).entryList({ "*.json" }, QDir::Files))
         {
             QFile file(dir + "/" + filename);
@@ -198,7 +216,10 @@ namespace BlackMisc
             {
                 return CLogMessage(this).error("Invalid JSON format in %1") << file.fileName();
             }
-            loadFromJson(json.object());
+            CVariantMap temp;
+            temp.convertFromJson(json.object());
+            temp.removeDuplicates(currentValues);
+            o_values.insert(temp);
         }
         return {};
     }

src/blackmisc/valuecache.h

@@ -91,13 +91,22 @@ namespace BlackMisc
         //! of CValueCache instances in all processes including this one. The slot will do its own round-trip detection.
         void valuesChangedByLocal(const BlackMisc::CVariantMap &values);
 
+    protected:
+        //! Save specific values to Json files in a given directory.
+        CStatusMessage saveToFiles(const QString &directory, const CVariantMap &values) const;
+
+        //! Load from Json files in a given directory any values which differ from the current ones, and insert them in o_values.
+        CStatusMessage loadFromFiles(const QString &directory, CVariantMap &o_values) const;
+
+        //! Mutex protecting operations which are critical on m_elements.
+        mutable QMutex m_mutex { QMutex::Recursive };
+
     private:
         friend class Private::CValuePage;
         struct Element;
         using ElementPtr = QSharedPointer<Element>; // QMap doesn't support move-only types
 
         QMap<QString, ElementPtr> m_elements;
-        mutable QMutex m_mutex { QMutex::Recursive };
 
         Element &getElement(const QString &key);
         Element &getElement(const QString &key, QMap<QString, ElementPtr>::const_iterator pos);