libdeng2|FS: ArchiveFeed observes source file for deletion

If the source file is deleted, any changes to the archive are first
saved.

doomsday/libdeng2/src/filesys/archivefeed.cpp

@@ -29,9 +29,10 @@
 namespace de {
 
 DENG2_PIMPL(ArchiveFeed)
+, DENG2_OBSERVES(File, Deletion)
 {
     /// File where the archive is stored (in a serialized format).
-    File &file;
+    File *file;
 
     /// The archive can be physically stored here, as Archive doesn't make a
     /// copy of the buffer.
@@ -45,9 +46,9 @@ DENG2_PIMPL(ArchiveFeed)
     /// The feed whose archive this feed is using.
     ArchiveFeed *parentFeed;
 
-    Instance(Public *feed, File &f) : Base(feed), file(f), arch(0), parentFeed(0)
+    Instance(Public *feed, File &f) : Base(feed), file(&f), arch(0), parentFeed(0)
     {
-        /// @todo Observe the file for deletion.
+        file->audienceForDeletion += this;
 
         // If the file happens to be a byte array file, we can use it
         // directly to store the Archive.
@@ -73,29 +74,53 @@ DENG2_PIMPL(ArchiveFeed)
 
     Instance(Public *feed, ArchiveFeed &parentFeed, String const &path)
         : Base(feed), file(parentFeed.d->file), arch(0), basePath(path), parentFeed(&parentFeed)
-    {}
+    {
+        file->audienceForDeletion += this;
+    }
 
     ~Instance()
     {
+        if(file)
+        {
+            file->audienceForDeletion -= this;
+        }
+
         if(arch)
         {
-            // If modified, the archive is written back to the file.
-            if(arch->modified())
-            {
-                LOG_RES_MSG("Updating archive in ") << file.description();
+            writeIfModified();
+            delete arch;
+        }
+    }
 
-                // Make sure we have either a compressed or uncompressed version of
-                // each entry in memory before destroying the source file.
-                arch->cache();
+    void writeIfModified()
+    {
+        if(!file || !arch) return;
 
-                file.clear();
-                Writer(file) << *arch;
-            }
-            else
-            {
-                LOG_RES_VERBOSE("Not updating archive in %s (not changed)") << file.description();
-            }
-            delete arch;
+        // If modified, the archive is written back to the file.
+        if(arch->modified())
+        {
+            LOG_RES_MSG("Updating archive in ") << file->description();
+
+            // Make sure we have either a compressed or uncompressed version of
+            // each entry in memory before destroying the source file.
+            arch->cache();
+
+            file->clear();
+            Writer(*file) << *arch;
+        }
+        else
+        {
+            LOG_RES_VERBOSE("Not updating archive in %s (not changed)") << file->description();
+        }
+    }
+
+    void fileBeingDeleted(File const &deleted)
+    {
+        if(file == &deleted)
+        {
+            // Ensure that changes are saved and detach from the file.
+            writeIfModified();
+            file = 0;
         }
     }
 
@@ -125,18 +150,19 @@ DENG2_PIMPL(ArchiveFeed)
             String entry = basePath / *i;
 
             std::auto_ptr<ArchiveEntryFile> archFile(new ArchiveEntryFile(*i, archive(), entry));
+
             // Use the status of the entry within the archive.
             archFile->setStatus(archive().entryStatus(entry));
 
             // Create a new file that accesses this feed's archive and interpret the contents.
-            File *file = folder.fileSystem().interpret(archFile.release());
-            folder.add(file);
+            File *f = folder.fileSystem().interpret(archFile.release());
+            folder.add(f);
 
             // We will decide on pruning this.
-            file->setOriginFeed(&self);
+            f->setOriginFeed(&self);
 
             // Include the file in the main index.
-            folder.fileSystem().index(*file);
+            folder.fileSystem().index(*f);
         }
 
         // Also populate subfolders.
@@ -165,7 +191,11 @@ ArchiveFeed::~ArchiveFeed()
 
 String ArchiveFeed::description() const
 {
-    return "archive in " + d->file.description();
+    if(d->file)
+    {
+        return "archive in " + d->file->description();
+    }
+    return "archive in (no file)";
 }
 
 void ArchiveFeed::populate(Folder &folder)