Add an API to open files from a collection's sources

[libs/datafile.git] / source / collection.h

diff --git a/source/collection.h b/source/collection.h
index bbde9f904dfd3e8415ae0e0a8dc0ae8b2d9db641..0d2dc6be2fd7a6c4043ff4db18bfdc32a04bb270 100644 (file)
--- a/source/collection.h
+++ b/source/collection.h
@@ -45,6 +45,11 @@ method for details.
 
 Collections can have sources for loading objects on demand.  Automatic loading
 only works on a non-const Collection.  See class CollectionSource for details.
+
+A fallback collection can be designated as another way of loading items that
+are not present.  Items retrieted from the fallback collection are shared
+between the collections, and are only deleted when all collections in the chain
+have been destroyed.
 */
 class Collection
 {
@@ -86,11 +91,12 @@ private:
        TypeList types;
        ItemMap items;
        SourceList sources;
+       Collection *fallback;
 
        Collection(const Collection &);
        Collection &operator=(const Collection &);
 public:
-       Collection() { }
+       Collection();
        virtual ~Collection();
 
        /** Adds an object into the collection.  The name must not pre-exist.  The
@@ -258,10 +264,17 @@ private:
 protected:
        void add_source(CollectionSource &);
 
+       IO::Seekable *open_from_sources(const std::string &);
+
 private:
        void gather_names_from_sources(std::list<std::string> &, const CollectionItemTypeBase &) const;
 
        void load_items_from_sources(const CollectionItemTypeBase &);
+
+protected:
+       /** Sets a fallback collection, which will be consulted if an item is not
+       found. */
+       void set_fallback(Collection *);
 };
 
 template<typename T>
@@ -309,6 +322,7 @@ public:
        const std::string &get_keyword() const { return kwd; }
        void add_suffix(const std::string &);
        bool match_name(const std::string &) const;
+       virtual bool is_same_type(const CollectionItemTypeBase &) const = 0;
        virtual bool check_item_type(const Variant &) const = 0;
        virtual void add_to_loader(Collection::Loader &) const = 0;
        virtual bool can_create() const = 0;
@@ -423,6 +437,9 @@ public:
                return *this;
        }
 
+       virtual bool is_same_type(const CollectionItemTypeBase &other) const
+       { return dynamic_cast<const CollectionItemType<T> *>(&other); }
+
        virtual bool check_item_type(const Variant &var) const
        { return var.check_type<RefPtr<T> >(); }