Rewrite DirManager::EnsureSafeFileName without downcasts...

... weakening but not yet eliminating dependency on BlockFile subclasses

src/BlockFile.cpp

@@ -133,6 +133,16 @@ void BlockFile::SetFileName(wxFileNameWrapper &&name)
    mFileName=std::move(name);
 }
 
+const wxFileNameWrapper &BlockFile::GetExternalFileName() const
+{
+   static wxFileNameWrapper empty;
+   return empty;
+}
+
+void BlockFile::SetExternalFileName( wxFileNameWrapper && )
+{
+   wxASSERT( false );
+}
 
 /// Marks this BlockFile as "locked."  A locked BlockFile may not
 /// be moved or deleted, only copied.  Locking a BlockFile prevents
@@ -724,6 +734,16 @@ AliasBlockFile::~AliasBlockFile()
 {
 }
 
+const wxFileNameWrapper &AliasBlockFile::GetExternalFileName() const
+{
+   return GetAliasedFileName();
+}
+
+void AliasBlockFile::SetExternalFileName( wxFileNameWrapper &&newName )
+{
+   ChangeAliasedFileName( std::move( newName ) );
+}
+
 /// Read the summary of this alias block from disk.  Since the audio data
 /// is elsewhere, this consists of reading the entire summary file.
 /// Fill with zeroes and return false if data are unavailable for any reason.

src/BlockFile.h

@@ -114,6 +114,12 @@ class PROFILE_DLL_API BlockFile /* not final, abstract */ {
    virtual GetFileNameResult GetFileName() const;
    virtual void SetFileName(wxFileNameWrapper &&name);
 
+   // Managing an external file dependency
+   // Default always returns empty
+   virtual const wxFileNameWrapper &GetExternalFileName() const;
+   // Default does nothing (and gives assertion violation in debug)
+   virtual void SetExternalFileName( wxFileNameWrapper &&newName );
+
    size_t GetLength() const { return mLen; }
    void SetLength(size_t newLen) { mLen = newLen; }
 
@@ -278,10 +284,13 @@ class AliasBlockFile /* not final */ : public BlockFile
    //
    // These methods are for advanced use only!
    //
-   const wxFileName &GetAliasedFileName() const { return mAliasedFileName; }
+   const wxFileNameWrapper &GetAliasedFileName() const { return mAliasedFileName; }
    void ChangeAliasedFileName(wxFileNameWrapper &&newAliasedFile);
    bool IsAlias() const override { return true; }
 
+   const wxFileNameWrapper &GetExternalFileName() const override;
+   void SetExternalFileName( wxFileNameWrapper &&newName ) override;
+
  protected:
    // Introduce a NEW virtual.
    /// Write the summary to disk, using the derived ReadData() to get the data

src/DirManager.cpp

@@ -1581,25 +1581,11 @@ bool DirManager::EnsureSafeFilename(const wxFileName &fName)
    {
       BlockFilePtr b = iter->second.lock();
       if (b) {
-         // don't worry, we don't rely on this cast unless IsAlias is true
+         if (fName.IsOk() && b->GetExternalFileName() == fName) {
-         auto ab = static_cast< AliasBlockFile * > ( &*b );
-
-         // don't worry, we don't rely on this cast unless ISDataAvailable is false
-         // which means that it still needs to access the file.
-         auto db = static_cast< ODDecodeBlockFile * > ( &*b );
-
-         if (b->IsAlias() && ab->GetAliasedFileName() == fName) {
             needToRename = true;
 
             //ODBlocks access the aliased file on another thread, so we need to pause them before this continues.
-            readLocks.push_back( ab->LockForRead() );
+            readLocks.push_back( b->LockForRead() );
-         }
-         //now for encoded OD blocks  (e.g. flac)
-         else if (!b->IsDataAvailable() && db->GetEncodedAudioFilename() == fName) {
-            needToRename = true;
-
-            //ODBlocks access the aliased file on another thread, so we need to pause them before this continues.
-            readLocks.push_back( db->LockForRead() );
          }
       }
       ++iter;
@@ -1631,19 +1617,12 @@ bool DirManager::EnsureSafeFilename(const wxFileName &fName)
          {
             BlockFilePtr b = iter2->second.lock();
             if (b) {
-               auto ab = static_cast< AliasBlockFile * > ( &*b );
+               if (fName.IsOk() && b->GetExternalFileName() == fName) {
-               auto db = static_cast< ODDecodeBlockFile * > ( &*b );
+                  b->SetExternalFileName(wxFileNameWrapper{ renamedFileName });
-
-               if (b->IsAlias() && ab->GetAliasedFileName() == fName)
-               {
-                  ab->ChangeAliasedFileName(wxFileNameWrapper{ renamedFileName });
                   wxPrintf(_("Changed block %s to new alias name\n"),
                            b->GetFileName().name.GetFullName());
 
                }
-               else if (!b->IsDataAvailable() && db->GetEncodedAudioFilename() == fName) {
-                  db->ChangeAudioFile(wxFileNameWrapper{ renamedFileName });
-               }
             }
             ++iter2;
          }

src/blockfile/ODDecodeBlockFile.cpp

@@ -502,6 +502,18 @@ void ODDecodeBlockFile::UnlockRead() const
    mReadDataMutex.Unlock();
 }
 
+const wxFileNameWrapper &ODDecodeBlockFile::GetExternalFileName() const
+{
+   if ( !IsDataAvailable() )
+      return GetEncodedAudioFilename();
+   return SimpleBlockFile::GetExternalFileName();
+}
+
+void ODDecodeBlockFile::SetExternalFileName( wxFileNameWrapper &&newName )
+{
+   ChangeAudioFile( std::move( newName ) );
+}
+
 /// Modify this block to point at a different file.  This is generally
 /// looked down on, but it is necessary in one case: see
 /// DirManager::EnsureSafeFilename().

src/blockfile/ODDecodeBlockFile.h

@@ -56,6 +56,9 @@ class ODDecodeBlockFile final : public SimpleBlockFile
    /// Returns TRUE if the summary has not yet been written, but is actively being computed and written to disk
    bool IsSummaryBeingComputed() override { return false; }
 
+   const wxFileNameWrapper &GetExternalFileName() const override;
+   void SetExternalFileName( wxFileNameWrapper &&newName ) override;
+
    //Calls that rely on summary files need to be overidden
    DiskByteCount GetSpaceUsage() const override;
    /// Gets extreme values for the specified region
@@ -138,7 +141,7 @@ class ODDecodeBlockFile final : public SimpleBlockFile
 
    ///// Get the name of the file where the audio data for this block is
    /// stored.
-   const wxFileName &GetEncodedAudioFilename()
+   const wxFileNameWrapper &GetEncodedAudioFilename() const
    {
       return mAudioFileName;
    }