1 files changed, 108 insertions, 0 deletions
diff --git a/source/blender/blenkernel/BKE_id_handle.h b/source/blender/blenkernel/BKE_id_handle.h
new file mode 100644
index 00000000000..ce45ccb1eb3
--- /dev/null
+++ b/source/blender/blenkernel/BKE_id_handle.h
@@ -0,0 +1,108 @@
+#ifndef __BKE_ID_HANDLE_H__
+#define __BKE_ID_HANDLE_H__
+
+#include "BLI_utildefines.h"
+
+#include "BLI_map.h"
+
+extern "C" {
+struct ID;
+struct Object;
+struct Image;
+}
+
+namespace BKE {
+
+using BLI::Map;
+
+/**
+ * This is a weak reference to an ID data-block. It does not contain a pointer to the actual data.
+ * It can happen that the IDHandle references data, that does not exist anymore. The handle does
+ * not know that.
+ */
+class IDHandle {
+ private:
+  uint32_t m_identifier;
+
+ public:
+  IDHandle() : m_identifier((uint32_t)-1)
+  {
+  }
+
+  IDHandle(struct ID *id);
+
+  friend bool operator==(IDHandle a, IDHandle b)
+  {
+    return a.m_identifier == b.m_identifier;
+  }
+
+  friend bool operator!=(IDHandle a, IDHandle b)
+  {
+    return !(a == b);
+  }
+
+  uint32_t internal_identifier() const
+  {
+    return m_identifier;
+  }
+};
+
+class ObjectIDHandle : public IDHandle {
+ public:
+  ObjectIDHandle() : IDHandle()
+  {
+  }
+
+  ObjectIDHandle(struct Object *object);
+};
+
+class ImageIDHandle : public IDHandle {
+ public:
+  ImageIDHandle() : IDHandle()
+  {
+  }
+
+  ImageIDHandle(struct Image *image);
+};
+
+class IDHandleLookup {
+ private:
+  Map<IDHandle, ID *> m_handle_to_id_map;
+
+ public:
+  void add(ID &id)
+  {
+    IDHandle handle(&id);
+    m_handle_to_id_map.add(handle, &id);
+  }
+
+  ID *lookup(IDHandle handle) const
+  {
+    return m_handle_to_id_map.lookup_default(handle, nullptr);
+  }
+
+  struct Object *lookup(ObjectIDHandle handle) const
+  {
+    return reinterpret_cast<struct Object *>(this->lookup((IDHandle)handle));
+  }
+
+  struct Image *lookup(ImageIDHandle handle) const
+  {
+    return reinterpret_cast<struct Image *>(this->lookup((IDHandle)handle));
+  }
+
+  static const IDHandleLookup &Empty();
+};
+
+}  // namespace BKE
+
+namespace BLI {
+template<> struct DefaultHash<BKE::IDHandle> {
+  uint32_t operator()(const BKE::IDHandle &value) const
+  {
+    return value.internal_identifier();
+  }
+};
+}  // namespace BLI
+
+#endif /* __BKE_ID_HANDLE_H__ */
+\ No newline at end of file