refs #644 Add method CCached::save, like setAndSave but using the currently set value.

Implemented with a flag in CValueCachePacket to indicate a request to save only.

src/blackmisc/datacache.h

@@ -268,6 +268,9 @@ namespace BlackMisc
 
         //! Data cache doesn't support setAndSave (because set() already causes save anyway).
         CStatusMessage setAndSave(const typename Trait::type &value, qint64 timestamp = 0) = delete;
+
+        //! Data cache doesn't support save (because currently set value is saved already).
+        CStatusMessage save() = delete;
     };
 
     /*!

src/blackmisc/valuecache.cpp

@@ -33,8 +33,8 @@ namespace BlackMisc
     // CValueCachePacket
     ////////////////////////////////
 
-    CValueCachePacket::CValueCachePacket(const CVariantMap &values, qint64 timestamp, bool saved) :
-        m_saved(saved)
+    CValueCachePacket::CValueCachePacket(const CVariantMap &values, qint64 timestamp, bool saved, bool valuesChanged) :
+        m_saved(saved), m_valuesChanged(valuesChanged)
     {
         for (auto it = values.cbegin(); it != values.cend(); ++it)
         {
@@ -182,13 +182,16 @@ namespace BlackMisc
             while (out != end && out.key() < in.key()) { ++out; }
             auto &element = getElement(in.key(), out);
 
-            Q_ASSERT(isSafeToIncrement(element.m_pendingChanges));
-            element.m_pendingChanges++;
-            element.m_value = in.value();
-            element.m_timestamp = in.timestamp();
+            if (values.valuesChanged())
+            {
+                Q_ASSERT(isSafeToIncrement(element.m_pendingChanges));
+                element.m_pendingChanges++;
+                element.m_value = in.value();
+                element.m_timestamp = in.timestamp();
+            }
             element.m_saved = values.isSaved();
         }
-        emit valuesChanged(values, sender());
+        if (values.valuesChanged()) { emit valuesChanged(values, sender()); }
         emit valuesChangedByLocal(values);
     }
 
@@ -196,6 +199,11 @@ namespace BlackMisc
     {
         QMutexLocker lock(&m_mutex);
         if (values.empty()) { return; }
+        if (! values.valuesChanged())
+        {
+            if (values.isSaved()) { emit valuesSaveRequested(values); }
+            return;
+        }
         CValueCachePacket ratifiedChanges(values.isSaved());
         auto out = m_elements.lowerBound(values.cbegin().key());
         auto end = m_elements.upperBound((values.cend() - 1).key());
@@ -453,17 +461,24 @@ namespace BlackMisc
         return element.m_value.read();
     }
 
-    CStatusMessage CValuePage::setValue(Element &element, const CVariant &value, qint64 timestamp, bool save)
+    CStatusMessage CValuePage::setValue(Element &element, CVariant value, qint64 timestamp, bool save, bool ignoreValue)
     {
         Q_ASSERT(QThread::currentThread() == thread());
 
         if (timestamp == 0) { timestamp = QDateTime::currentMSecsSinceEpoch(); }
-        if (element.m_value.read() == value && element.m_timestamp == timestamp) { return {}; }
+        if (element.m_value.read() == value && element.m_timestamp == timestamp && ! ignoreValue) { return {}; }
+
+        if (ignoreValue) { value = element.m_value.read(); }
 
         auto status = validate(element, value, CStatusMessage::SeverityError);
         if (status.isSuccess())
         {
-            if (m_batchMode > 0)
+            if (ignoreValue)
+            {
+                element.m_saved = save;
+                emit valuesWantToCache({ { { element.m_key, {} } }, 0, save, false });
+            }
+            else if (m_batchMode > 0)
             {
                 m_batchedValues[element.m_key] = value;
             }
@@ -505,6 +520,7 @@ namespace BlackMisc
     void CValuePage::setValuesFromCache(const CValueCachePacket &values, QObject *changedBy)
     {
         Q_ASSERT(QThread::currentThread() == thread());
+        Q_ASSERT_X(values.valuesChanged(), Q_FUNC_INFO, "packet with unchanged values should not reach here");
 
         QList<NotifySlot> notifySlots;
 

src/blackmisc/valuecache.h

@@ -35,10 +35,13 @@ namespace BlackMisc
         using base_type = CDictionary;
 
         //! Constructor.
-        CValueCachePacket(bool saved = false) : m_saved(saved) {}
+        CValueCachePacket(bool saved = false, bool valuesChanged = true) : m_saved(saved), m_valuesChanged(valuesChanged) {}
 
         //! Construct from CVariantMap and a timestamp.
-        CValueCachePacket(const CVariantMap &values, qint64 timestamp, bool saved = false);
+        CValueCachePacket(const CVariantMap &values, qint64 timestamp, bool saved = false, bool valuesChanged = true);
+
+        //! Values have been changed.
+        bool valuesChanged() const { return m_valuesChanged; }
 
         //! Values are to be saved.
         //! @{
@@ -90,10 +93,12 @@ namespace BlackMisc
 
     private:
         bool m_saved = false;
+        bool m_valuesChanged = true;
 
         BLACK_METACLASS(
             CValueCachePacket,
-            BLACK_METAMEMBER(saved)
+            BLACK_METAMEMBER(saved),
+            BLACK_METAMEMBER(valuesChanged)
         );
     };
 
@@ -304,6 +309,9 @@ namespace BlackMisc
         //! Write and save in the same step. Must be called from the thread in which the owner lives.
         CStatusMessage setAndSave(const T &value, qint64 timestamp = 0) { return m_page.setValue(m_element, CVariant::from(value), timestamp, true); }
 
+        //! Save using the currently set value. Must be called from the thread in which the owner lives.
+        CStatusMessage save() { return m_page.setValue(m_element, {}, 0, true, true); }
+
         //! Is current thread the owner thread, so CCached::set is safe
         bool isOwnerThread() const { return QThread::currentThread() == m_page.thread(); }
 

src/blackmisc/valuecacheprivate.h

@@ -69,7 +69,7 @@ namespace BlackMisc
             CVariant getValueCopy(const Element &element) const;
 
             //! Write the value corresponding to the element's key and begin synchronizing it to any other pages.
-            CStatusMessage setValue(Element &element, const CVariant &value, qint64 timestamp, bool save = false);
+            CStatusMessage setValue(Element &element, CVariant value, qint64 timestamp, bool save = false, bool ignoreValue = false);
 
             //! Get the key string corresponding to the element.
             const QString &getKey(const Element &element) const;