Implement determine tag/index pos for MKV

abstractcontainer.cpp

@@ -175,6 +175,9 @@ bool AbstractContainer::supportsTrackModifications() const
  * \brief Determines the position of the index.
  * \returns Returns ElementPosition::BeforeData or ElementPosition::AfterData if the position could
  *          be determined; otherwise returns ElementPosition::Keep.
+ * \remarks
+ * - It might be required to parse tracks before the index position can be determined.
+ * - Not be applicable for files composed of multiple segments.
  */
 ElementPosition AbstractContainer::determineIndexPosition() const
 {
@@ -329,6 +332,9 @@ void AbstractContainer::removeAllTags()
  * \brief Determines the position of the tags inside the file.
  * \returns Returns ElementPosition::BeforeData or ElementPosition::AfterData if the position could
  *          be determined; otherwise returns ElementPosition::Keep.
+ * \remarks
+ * - It might be required to parse tags before the tag position can be determined.
+ * - Not be applicable for files composed of multiple segments.
  */
 ElementPosition AbstractContainer::determineTagPosition() const
 {

matroska/matroskacontainer.cpp

@@ -332,14 +332,41 @@ generateRandomId:
     return attachment.get();
 }
 
+/*!
+ * \brief Determines the position of the element with the specified \a elementId.
+ * \sa determineTagPosition() and determineIndexPosition()
+ */
+ElementPosition MatroskaContainer::determineElementPosition(uint64 elementId) const
+{
+    if(m_firstElement && m_segmentCount == 1) {
+        if(const EbmlElement *segmentElement = m_firstElement->siblingById(MatroskaIds::Segment, true)) {
+            for(const EbmlElement *childElement = segmentElement->firstChild(); childElement; childElement = childElement->nextSibling()) {
+                if(childElement->id() == elementId) {
+                    return ElementPosition::BeforeData;
+                } else if(childElement->id() == MatroskaIds::Cluster) {
+                    for(const auto &seekInfo : m_seekInfos) {
+                        for(const auto &info : seekInfo->info()) {
+                            if(info.first == elementId) {
+                                return ElementPosition::AfterData;
+                            }
+                        }
+                    }
+                    return ElementPosition::Keep;
+                }
+            }
+        }
+    }
+    return ElementPosition::Keep;
+}
+
 ElementPosition MatroskaContainer::determineTagPosition() const
 {
-    return ElementPosition::Keep; // TODO
+    return determineElementPosition(MatroskaIds::Tags);
 }
 
 ElementPosition MatroskaContainer::determineIndexPosition() const
 {
-    return ElementPosition::Keep; // TODO
+    return determineElementPosition(MatroskaIds::Cues);
 }
 
 void MatroskaContainer::internalParseHeader()

matroska/matroskacontainer.h

@@ -41,6 +41,7 @@ public:
     MatroskaAttachment *createAttachment();
     MatroskaAttachment *attachment(std::size_t index);
     std::size_t attachmentCount() const;
+    ElementPosition determineElementPosition(uint64 elementId) const;
     ElementPosition determineTagPosition() const;
     ElementPosition determineIndexPosition() const;