prepare sharing C++ class instances across lua-interpreters

in particular: lua-lifefime (!) C++ instances.
This allows for dynamic allocation of custom user-data, bound to
the lifetime of the allocating lua-context.

5 files changed, 217 insertions, 1 deletions

diff --git a/libs/ardour/ardour/lua_api.h b/libs/ardour/ardour/lua_api.h
index 9ae6bf2ff6..9af9649620 100644
--- a/libs/ardour/ardour/lua_api.h
+++ b/libs/ardour/ardour/lua_api.h
@@ -181,6 +181,46 @@ namespace ARDOUR { namespace LuaOSC {
 			lo_address _addr;
 	};
 
-} } /* namespace */
+}
+
+class LuaTableRef {
+	public:
+		LuaTableRef ();
+		~LuaTableRef ();
+
+		int get (lua_State* L);
+		int set (lua_State* L);
+
+	private:
+		struct LuaTableEntry {
+			LuaTableEntry (int kt, int vt)
+				: keytype (kt)
+				, valuetype (vt)
+			{ }
+
+			int keytype;
+			std::string k_s;
+			unsigned int k_n;
+
+			int valuetype;
+			// LUA_TUSERDATA
+			const void* c;
+			void* p;
+			// LUA_TBOOLEAN
+			bool b;
+			// LUA_TSTRING:
+			std::string s;
+			// LUA_TNUMBER:
+			double n;
+		};
+
+		std::vector<LuaTableEntry> _data;
+
+		static void* findclasskey (lua_State *L, const void* key);
+		template<typename T>
+		static void assign (luabridge::LuaRef* rv, T key, const LuaTableEntry& s);
+};
+
+} /* namespace */
 
 #endif // _ardour_lua_api_h_
diff --git a/libs/ardour/lua_api.cc b/libs/ardour/lua_api.cc
index 94b3f816c3..edee3a34a9 100644
--- a/libs/ardour/lua_api.cc
+++ b/libs/ardour/lua_api.cc
@@ -345,3 +345,153 @@ ARDOUR::LuaAPI::hsla_to_rgba (lua_State *L)
 	luabridge::Stack<double>::push (L, a);
 	return 4;
 }
+
+luabridge::LuaRef::Proxy&
+luabridge::LuaRef::Proxy::clone_instance (const void* classkey, void* p) {
+  lua_rawgeti (m_L, LUA_REGISTRYINDEX, m_tableRef);
+  lua_rawgeti (m_L, LUA_REGISTRYINDEX, m_keyRef);
+
+	luabridge::UserdataPtr::push_raw (m_L, p, classkey);
+
+  lua_rawset (m_L, -3);
+  lua_pop (m_L, 1);
+  return *this;
+}
+
+LuaTableRef::LuaTableRef () {}
+LuaTableRef::~LuaTableRef () {}
+
+int
+LuaTableRef::get (lua_State* L)
+{
+	luabridge::LuaRef rv (luabridge::newTable (L));
+	for (std::vector<LuaTableEntry>::const_iterator i = _data.begin (); i != _data.end (); ++i) {
+		switch ((*i).keytype) {
+			case LUA_TSTRING:
+				assign(&rv, i->k_s, *i);
+				break;
+			case LUA_TNUMBER:
+				assign(&rv, i->k_n, *i);
+				break;
+		}
+	}
+	luabridge::push (L, rv);
+	return 1;
+}
+
+int
+LuaTableRef::set (lua_State* L)
+{
+	if (!lua_istable (L, -1)) { return luaL_error (L, "argument is not a table"); }
+	_data.clear ();
+
+	lua_pushvalue (L, -1);
+	lua_pushnil (L);
+	while (lua_next (L, -2)) {
+		lua_pushvalue (L, -2);
+
+		LuaTableEntry s (lua_type(L, -1), lua_type(L, -2));
+		switch (lua_type(L, -1)) {
+			case LUA_TSTRING:
+				s.k_s = luabridge::Stack<std::string>::get (L, -1);
+				break;
+				;
+			case LUA_TNUMBER:
+				s.k_n = luabridge::Stack<unsigned int>::get (L, -1);
+				break;
+			default:
+				// invalid key
+				lua_pop (L, 2);
+				continue;
+		}
+
+		switch(lua_type(L, -2)) {
+			case LUA_TSTRING:
+				s.s = luabridge::Stack<std::string>::get (L, -2);
+				break;
+			case LUA_TBOOLEAN:
+				s.b = lua_toboolean (L, -2);
+				break;
+			case LUA_TNUMBER:
+				s.n = lua_tonumber (L, -2);
+				break;
+			case LUA_TUSERDATA:
+				{
+					bool ok = false;
+					lua_getmetatable (L, -2);
+					lua_rawgetp (L, -1, luabridge::getIdentityKey ());
+					if (lua_isboolean (L, -1)) {
+						lua_pop (L, 1);
+						const void* key = lua_topointer (L, -1);
+						lua_pop (L, 1);
+						void const* classkey = findclasskey (L, key);
+
+						if (classkey) {
+							ok = true;
+							s.c = classkey;
+							s.p = luabridge::Userdata::get_ptr (L, -2);
+						}
+					}  else {
+						lua_pop (L, 2);
+					}
+
+					if (ok) {
+						break;
+					}
+					// invalid userdata -- fall through
+				}
+				// no break
+			case LUA_TFUNCTION: // no support -- we could... string.format("%q", string.dump(value, true))
+			case LUA_TTABLE: // no nested tables, sorry.
+			case LUA_TNIL: // fallthrough
+			default:
+				// invalid value
+				lua_pop (L, 2);
+				continue;
+		}
+
+		_data.push_back(s);
+		lua_pop (L, 2);
+	}
+	return 0;
+}
+
+void*
+LuaTableRef::findclasskey (lua_State *L, const void* key)
+{
+	lua_pushvalue(L, LUA_REGISTRYINDEX);
+	lua_pushnil (L);
+	while (lua_next (L, -2)) {
+		lua_pushvalue (L, -2);
+		if (lua_topointer(L, -2) == key) {
+			void* rv = lua_touserdata (L, -1);
+			lua_pop (L, 4);
+			return rv;
+		}
+		lua_pop (L, 2);
+	}
+	lua_pop (L, 1);
+	return NULL;
+}
+
+template<typename T>
+void LuaTableRef::assign (luabridge::LuaRef* rv, T key, const LuaTableEntry& s)
+{
+	switch (s.valuetype) {
+		case LUA_TSTRING:
+			(*rv)[key] = s.s;
+			break;
+		case LUA_TBOOLEAN:
+			(*rv)[key] = s.b;
+			break;
+		case LUA_TNUMBER:
+			(*rv)[key] = s.n;
+			break;
+		case LUA_TUSERDATA:
+			(*rv)[key].clone_instance (s.c, s.p);
+			break;
+		default:
+			assert (0);
+			break;
+	}
+}
diff --git a/libs/ardour/luabindings.cc b/libs/ardour/luabindings.cc
index 393389c5ff..1ff2f39987 100644
--- a/libs/ardour/luabindings.cc
+++ b/libs/ardour/luabindings.cc
@@ -169,6 +169,7 @@ CLASSKEYS(ARDOUR::Session);
 CLASSKEYS(ARDOUR::BufferSet);
 CLASSKEYS(ARDOUR::ChanMapping);
 CLASSKEYS(ARDOUR::DSP::DspShm);
+CLASSKEYS(ARDOUR::LuaTableRef);
 CLASSKEYS(PBD::ID);
 CLASSKEYS(ARDOUR::Location);
 CLASSKEYS(ARDOUR::PluginInfo);
@@ -1373,6 +1374,12 @@ LuaBindings::dsp (lua_State* L)
 		.endClass ()
 
 		.endNamespace () // DSP
+
+		.beginClass <LuaTableRef> ("LuaTableRef")
+		.addCFunction ("get", &LuaTableRef::get)
+		.addCFunction ("set", &LuaTableRef::set)
+		.endClass ()
+
 		.endNamespace (); // ARDOUR
 }
 
diff --git a/libs/lua/LuaBridge/detail/LuaRef.h b/libs/lua/LuaBridge/detail/LuaRef.h
index 8fae1c038a..46c756445e 100644
--- a/libs/lua/LuaBridge/detail/LuaRef.h
+++ b/libs/lua/LuaBridge/detail/LuaRef.h
@@ -180,6 +180,11 @@ private:
       return *this;
     }
 
+    // the implementation needs UserdataPtr, which
+    // is not yet defined here.
+    // -> libs/ardour/lua_api.cc
+    Proxy& clone_instance (const void* key, void* p);
+
     //--------------------------------------------------------------------------
     /**
         Assign a new value to this table key.
diff --git a/libs/lua/LuaBridge/detail/Userdata.h b/libs/lua/LuaBridge/detail/Userdata.h
index e832ef2dc1..feab28f132 100644
--- a/libs/lua/LuaBridge/detail/Userdata.h
+++ b/libs/lua/LuaBridge/detail/Userdata.h
@@ -302,6 +302,11 @@ ud __parent (nil)
 public:
   virtual ~Userdata () { }
 
+  static void* get_ptr (lua_State* L, int index) {
+    Userdata* ud = static_cast <Userdata*> (lua_touserdata (L, index));
+    return ud->m_p;
+  }
+
   //--------------------------------------------------------------------------
   /**
     Returns the Userdata* if the class on the Lua stack matches.
@@ -457,6 +462,15 @@ private:
     assert (m_p != 0);
   }
 
+  friend class LuaRef;
+  static inline void push_raw (lua_State* const L, void* p, const void* classkey)
+  {
+    new (lua_newuserdata (L, sizeof (UserdataPtr))) UserdataPtr (p);
+    lua_rawgetp (L, LUA_REGISTRYINDEX, classkey);
+    assert (lua_istable (L, -1));
+    lua_setmetatable (L, -2);
+  }
+
 public:
   /** Push non-const pointer to object.
   */