Add a getter for fallback in Collection

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

diff --git a/source/collection.h b/source/collection.h
index bbde9f904dfd3e8415ae0e0a8dc0ae8b2d9db641..06b8e348cbe3d2a7e16ce2735971802efa73a863 100644 (file)
--- a/source/collection.h
+++ b/source/collection.h
@@ -17,17 +17,14 @@ namespace DataFile {
 Helper struct to determine whether a Loader has a Collection typedef.
 */
 template<typename T>
-struct NeedsCollection
+struct NeedsCollection: public Sfinae
 {
-       struct Yes { char c[2]; };
-       struct No { char c; };
-
        template<typename U>
        static Yes f(typename U::Collection *);
        template<typename U>
        static No f(...);
 
-       enum { value = (sizeof(f<T>(0))==sizeof(Yes)) };
+       enum { value = Evaluate<sizeof(f<T>(0))>::value };
 };
 
 class CollectionItemTypeBase;
@@ -45,6 +42,11 @@ 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.
+
+As a last resort, a fallback collection can be designated for 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
 {
@@ -81,16 +83,17 @@ public:
 private:
        typedef std::map<std::string, Variant> ItemMap;
        typedef std::list<CollectionItemTypeBase *> TypeList;
-       typedef std::list<CollectionSource *> SourceList;
+       typedef std::list<const CollectionSource *> SourceList;
 
        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
@@ -252,16 +255,37 @@ private:
        template<typename T>
        CollectionItemTypeBase *get_type() const;
 
+       /// Gets a descriptor with the same type as another descriptor.
+       CollectionItemTypeBase *get_type(const CollectionItemTypeBase &) const;
+
        /// Returns the descriptor for an item, or null if it's of an unknown type.
        CollectionItemTypeBase *get_type_for_item(const Variant &) const;
 
 protected:
-       void add_source(CollectionSource &);
+       /** Adds a source for automatically loading items.  Sources are consulted
+       in the order they are added. */
+       void add_source(const CollectionSource &);
+
+public:
+       /** Opens a raw resource, without interpreting it as object data.  Null is
+       returned if no such file is found.  The caller must dispose of the returned
+       object when done with it. */
+       IO::Seekable *open_raw(const std::string &) const;
+
+protected:
+       IO::Seekable *open_from_sources(const std::string &n) { return open_raw(n); }
 
 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 *);
+
+       Collection *get_fallback() const { return fallback; }
 };
 
 template<typename T>
@@ -309,6 +333,7 @@ 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;
@@ -360,7 +385,7 @@ private:
                Creator(FuncPtr f): func(f) { }
 
                virtual T *create(Collection &coll, const std::string &name) const
-               { return (static_cast<C &>(coll).*func)(name); }
+               { return (dynamic_cast<C &>(coll).*func)(name); }
        };
 
        template<typename B>
@@ -423,6 +448,9 @@ 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> >(); }