1 files changed, 25 insertions, 0 deletions

diff --git a/src/uniquekey.h b/src/uniquekey.h
new file mode 100644
index 0000000..c90d09a
--- /dev/null
+++ b/src/uniquekey.h
@@ -0,0 +1,25 @@
+#if !defined __LANES_UNIQUEKEY_H__
+#define __LANES_UNIQUEKEY_H__ 1
+
+#include "lualib.h"
+
+// Lua light userdata can hold a pointer.
+struct s_UniqueKey
+{
+        void* value;
+};
+typedef struct s_UniqueKey UniqueKey;
+
+#if defined(LUA_JITLIBNAME) && (defined(__x86_64__) || defined(_M_X64)) // building against LuaJIT headers, light userdata is restricted to 47 significant bits.
+#define MAKE_UNIQUE_KEY( p_) ((void*)(p_) & 0x7fffffffffffull)
+#else // LUA_JITLIBNAME
+#define MAKE_UNIQUE_KEY( p_) ((void*) p_)
+#endif // LUA_JITLIBNAME
+
+#define DECLARE_UNIQUE_KEY( name_) UniqueKey name_
+#define DECLARE_CONST_UNIQUE_KEY( name_, p_) UniqueKey const name_ = { MAKE_UNIQUE_KEY( p_)}
+
+#define push_unique_key( L, key_) lua_pushlightuserdata( L, key_.value)
+#define equal_unique_key( L, i, key_) (lua_touserdata( L, i) == key_.value)
+
+#endif // __LANES_UNIQUEKEY_H__