Allow checking tag position

Only implemented for MP4 so far

CMakeLists.txt

@@ -159,8 +159,8 @@ set(META_APP_AUTHOR "Martchus")
 set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
 set(META_APP_DESCRIPTION "C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags")
 set(META_VERSION_MAJOR 6)
-set(META_VERSION_MINOR 0)
+set(META_VERSION_MINOR 1)
-set(META_VERSION_PATCH 1)
+set(META_VERSION_PATCH 0)
 set(META_PUBLIC_SHARED_LIB_DEPENDS c++utilities)
 set(META_PUBLIC_STATIC_LIB_DEPENDS c++utilities_static)
 set(META_PRIVATE_COMPILE_DEFINITIONS LEGACY_API)

abstractcontainer.cpp

@@ -315,6 +315,16 @@ bool AbstractContainer::removeTag(Tag *)
 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.
+ */
+ElementPosition AbstractContainer::determineTagPosition() const
+{
+    return ElementPosition::Keep;
+}
+
 /*!
  * \brief Returns the track with the specified \a index.
  *

abstractcontainer.h

@@ -13,10 +13,8 @@
 #include <iostream>
 
 namespace IoUtilities {
-
 class BinaryReader;
 class BinaryWriter;
-
 }
 
 namespace Media {
@@ -26,6 +24,13 @@ class AbstractTrack;
 class AbstractChapter;
 class AbstractAttachment;
 
+enum class ElementPosition
+{
+    BeforeData, /**< the element is positioned before the actual data */
+    AfterData, /**< the element is positioned after the actual data */
+    Keep /**< the element is placed where it was before */
+};
+
 class TAG_PARSER_EXPORT AbstractContainer : public StatusProvider
 {
 public:
@@ -55,6 +60,7 @@ public:
     virtual std::size_t tagCount() const;
     virtual bool removeTag(Tag *tag);
     virtual void removeAllTags();
+    virtual ElementPosition determineTagPosition() const;
 
     virtual AbstractTrack *track(std::size_t index);
     virtual std::size_t trackCount() const;

matroska/matroskacontainer.cpp

@@ -332,6 +332,11 @@ generateRandomId:
     return attachment.get();
 }
 
+ElementPosition MatroskaContainer::determineTagPosition() const
+{
+    return ElementPosition::Keep; // TODO
+}
+
 void MatroskaContainer::internalParseHeader()
 {
     static const string context("parsing header of Matroska container");

matroska/matroskacontainer.h

@@ -41,6 +41,7 @@ public:
     MatroskaAttachment *createAttachment();
     MatroskaAttachment *attachment(std::size_t index);
     std::size_t attachmentCount() const;
+    ElementPosition determineTagPosition() const;
 
     virtual bool supportsTitle() const;
     virtual std::size_t segmentCount() const;

mediafileinfo.h

@@ -37,13 +37,6 @@ enum class TagUsage
     Never /**< tags of the type are never used; a possibly existing tag of the type is removed */
 };
 
-enum class ElementPosition
-{
-    BeforeData, /**< the element is positioned before the actual data */
-    AfterData, /**< the element is positioned after the actual data */
-    Keep /**< the element is placed at its previous position */
-};
-
 /*!
  * \brief The ParsingStatus enum specifies whether a certain part of the file (tracks, tags, ...) has
  *        been parsed yet and if what the parsing result is.

mp4/mp4container.cpp

@@ -45,6 +45,18 @@ void Mp4Container::reset()
     m_fragmented = false;
 }
 
+ElementPosition Mp4Container::determineTagPosition() const
+{
+    if(m_firstElement) {
+        Mp4Atom *mediaDataAtom = m_firstElement->siblingById(Mp4AtomIds::MediaData);
+        Mp4Atom *userDataAtom = m_firstElement->subelementByPath({Mp4AtomIds::Movie, Mp4AtomIds::UserData});
+        if(mediaDataAtom && userDataAtom) {
+            return userDataAtom->startOffset() < mediaDataAtom->startOffset() ? ElementPosition::BeforeData : ElementPosition::AfterData;
+        }
+    }
+    return ElementPosition::Keep;
+}
+
 void Mp4Container::internalParseHeader()
 {
     //const string context("parsing header of MP4 container"); will be used when generating notifications

mp4/mp4container.h

@@ -25,6 +25,7 @@ public:
     bool supportsTrackModifications() const;
     bool isFragmented() const;
     void reset();
+    ElementPosition determineTagPosition() const;
 
 protected:
     void internalParseHeader();