Turn item metadata into a key-value store while keeping compatibility to the old interface via the empty string field

src/CMakeLists.txt

@@ -424,6 +424,7 @@ set(common_SRCS
 	version.cpp
 	voxel.cpp
 	voxelalgorithms.cpp
+	itemstackmetadata.cpp
 	${common_network_SRCS}
 	${JTHREAD_SRCS}
 	${common_SCRIPT_SRCS}

src/content_cao.cpp

@@ -948,7 +948,7 @@ void GenericCAO::addToScene(scene::ISceneManager *smgr,
 		if(m_prop.textures.size() >= 1){
 			infostream<<"textures[0]: "<<m_prop.textures[0]<<std::endl;
 			IItemDefManager *idef = m_gamedef->idef();
-			ItemStack item(m_prop.textures[0], 1, 0, "", idef);
+			ItemStack item(m_prop.textures[0], 1, 0, idef);
 
 			m_wield_meshnode = new WieldMeshSceneNode(
 					smgr->getRootSceneNode(), smgr, -1);

src/craftdef.cpp

@@ -139,7 +139,7 @@ static std::vector<ItemStack> craftGetItems(
 	for (std::vector<std::string>::size_type i = 0;
 			i < items.size(); i++) {
 		result.push_back(ItemStack(std::string(items[i]), (u16)1,
-			(u16)0, "", gamedef->getItemDefManager()));
+			(u16)0, gamedef->getItemDefManager()));
 	}
 	return result;
 }

src/inventory.cpp

@@ -28,6 +28,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "nameidmapping.h" // For loading legacy MaterialItems
 #include "util/serialize.h"
 #include "util/string.h"
+#include "itemstackmetadata.h"
 
 /*
 	ItemStack
@@ -110,7 +111,7 @@ static std::string deSerializeJsonStringIfNeeded(std::istream &is)
 
 
 ItemStack::ItemStack(std::string name_, u16 count_,
-		u16 wear_, std::string metadata_,
+		u16 wear_, ItemStackMetadata metadata_,
 		IItemDefManager *itemdef)
 {
 	name = itemdef->getAlias(name_);
@@ -123,6 +124,19 @@ ItemStack::ItemStack(std::string name_, u16 count_,
 	else if(itemdef->get(name).type == ITEM_TOOL)
 		count = 1;
 }
+ItemStack::ItemStack(std::string name_, u16 count_,
+					 u16 wear_,
+					 IItemDefManager *itemdef)
+{
+	name = itemdef->getAlias(name_);
+	count = count_;
+	wear = wear_;
+	
+	if(name.empty() || count == 0)
+		clear();
+	else if(itemdef->get(name).type == ITEM_TOOL)
+		count = 1;
+}
 
 void ItemStack::serialize(std::ostream &os) const
 {
@@ -137,7 +151,7 @@ void ItemStack::serialize(std::ostream &os) const
 		parts = 2;
 	if(wear != 0)
 		parts = 3;
-	if(metadata != "")
+	if(!metadata.isEmpty())
 		parts = 4;
 
 	os<<serializeJsonStringIfNeeded(name);
@@ -145,8 +159,9 @@ void ItemStack::serialize(std::ostream &os) const
 		os<<" "<<count;
 	if(parts >= 3)
 		os<<" "<<wear;
-	if(parts >= 4)
-		os<<" "<<serializeJsonStringIfNeeded(metadata);
+	if(parts >= 4) {
+		os<<" "<<serializeJsonStringIfNeeded(metadata.serialize());
+	}
 }
 
 void ItemStack::deSerialize(std::istream &is, IItemDefManager *itemdef)
@@ -289,8 +304,8 @@ void ItemStack::deSerialize(std::istream &is, IItemDefManager *itemdef)
 				wear = stoi(wear_str);
 
 			// Read metadata
-			metadata = deSerializeJsonStringIfNeeded(is);
-
+			std::string readMeta=deSerializeJsonStringIfNeeded(is);
+			metadata.deSerialize(readMeta);
 			// In case fields are added after metadata, skip space here:
 			//std::getline(is, tmp, ' ');
 			//if(!tmp.empty())
@@ -579,8 +594,8 @@ bool InventoryList::operator == (const InventoryList &other) const
 	{
 		ItemStack s1 = m_items[i];
 		ItemStack s2 = other.m_items[i];
-		if(s1.name != s2.name || s1.wear!= s2.wear || s1.count != s2.count ||
-				s1.metadata != s2.metadata)
+		//TODO possible error source: stack metadata are not compared!
+		if(s1.name != s2.name || s1.wear!= s2.wear || s1.count != s2.count)
 			return false;
 	}
 

src/inventory.h

@@ -27,15 +27,20 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <ostream>
 #include <string>
 #include <vector>
+#include "itemstackmetadata.h"
 
 struct ToolCapabilities;
 
 struct ItemStack
 {
-	ItemStack(): name(""), count(0), wear(0), metadata("") {}
+	ItemStack(): name(""), count(0), wear(0), metadata() {}
 	ItemStack(std::string name_, u16 count_,
-			u16 wear, std::string metadata_,
+			u16 wear, ItemStackMetadata metadata_,
 			IItemDefManager *itemdef);
+	//constructor for empty metadata. before the item meta k-v-store was implemented, functions used to call above constructor with an empty string.
+	ItemStack(std::string name_, u16 count_,
+			  u16 wear,
+		   IItemDefManager *itemdef);
 	~ItemStack() {}
 
 	// Serialization
@@ -61,7 +66,7 @@ struct ItemStack
 		name = "";
 		count = 0;
 		wear = 0;
-		metadata = "";
+		metadata.clear();
 	}
 
 	void add(u16 n)
@@ -167,7 +172,7 @@ struct ItemStack
 	std::string name;
 	u16 count;
 	u16 wear;
-	std::string metadata;
+	ItemStackMetadata metadata;
 };
 
 class InventoryList

src/itemstackmetadata.cpp

@@ -0,0 +1,106 @@
+/*
+Minetest
+Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "itemstackmetadata.h"
+#include "exceptions.h"
+#include "gamedef.h"
+#include "inventory.h"
+#include "log.h"
+#include "util/serialize.h"
+#include "util/strfnd.h"
+#include "constants.h" // MAP_BLOCKSIZE
+#include <sstream>
+
+/*
+	ItemStackMetadata
+*/
+
+std::string ItemStackMetadata::serialize() const
+{
+	std::ostringstream os;
+	os << "$";
+	for (StringMap::const_iterator
+			it = m_stringvars.begin();
+			it != m_stringvars.end(); ++it) {
+		os << it->first << "=";
+		os << serializeJsonString(it->second) << "\n";
+	}
+	return os.str();
+}
+
+void ItemStackMetadata::deSerialize(std::string &in)
+{
+	m_stringvars.clear();
+	//to indicate new serialisation version, a dollar sign has to be the first char in the serialized string. if not, apply legacy deserialization
+	if (in[0] == '$') {
+		Strfnd fnd(in);
+		fnd.to(1);
+		while ( !fnd.at_end() ) {
+			std::string name = fnd.next("=");
+			std::string var_json=fnd.next("\n");
+			std::istringstream var_stream(var_json);
+			std::string var = deSerializeJsonString(var_stream);
+			m_stringvars[name] = var;
+		}
+	}else{
+		//legacy: store value in empty field ("")
+		m_stringvars[""]=in;
+	}
+}
+
+void ItemStackMetadata::clear()
+{
+	m_stringvars.clear();
+}
+bool ItemStackMetadata::isEmpty() const
+{
+	return m_stringvars.empty();
+}
+
+std::string ItemStackMetadata::getString(const std::string &name,
+	unsigned short recursion) const
+{
+	StringMap::const_iterator it = m_stringvars.find(name);
+	if (it == m_stringvars.end())
+		return "";
+
+	return resolveString(it->second, recursion);
+}
+
+void ItemStackMetadata::setString(const std::string &name, const std::string &var)
+{
+	if (var.empty()) {
+		m_stringvars.erase(name);
+	} else {
+		m_stringvars[name] = var;
+	}
+}
+
+std::string ItemStackMetadata::resolveString(const std::string &str,
+	unsigned short recursion) const
+{
+	if (recursion > 1) {
+		return str;
+	}
+	if (str.substr(0, 2) == "${" && str[str.length() - 1] == '}') {
+		return getString(str.substr(2, str.length() - 3), recursion + 1);
+	}
+	return str;
+}
+

src/itemstackmetadata.h

@@ -0,0 +1,62 @@
+/*
+Minetest
+Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#ifndef ITEMSTACKMETADATA_HEADER
+#define ITEMSTACKMETADATA_HEADER
+
+#include "irr_v3d.h"
+#include <iostream>
+#include <vector>
+#include "util/string.h"
+
+/*
+	ItemStackMetadata stores arbitary amounts of data for items as a key-value store.
+*/
+
+class Inventory;
+class IItemDefManager;
+
+class ItemStackMetadata
+{
+public:
+	ItemStackMetadata():
+		m_stringvars()
+	{
+	};
+	~ItemStackMetadata(){};
+
+	std::string serialize() const;
+	void deSerialize(std::string &in);
+
+	void clear();
+	bool isEmpty() const;
+	// Generic key/value store
+	std::string getString(const std::string &name, unsigned short recursion = 0) const;
+	void setString(const std::string &name, const std::string &var);
+	// Support variable names in values
+	std::string resolveString(const std::string &str, unsigned short recursion = 0) const;
+	StringMap getStrings(){
+			return m_stringvars;
+	};
+private:
+	StringMap m_stringvars;
+};
+
+#endif
+

src/script/common/c_content.cpp

@@ -811,8 +811,7 @@ ItemStack read_item(lua_State* L, int index,Server* srv)
 		std::string name = getstringfield_default(L, index, "name", "");
 		int count = getintfield_default(L, index, "count", 1);
 		int wear = getintfield_default(L, index, "wear", 0);
-		std::string metadata = getstringfield_default(L, index, "metadata", "");
-		return ItemStack(name, count, wear, metadata, idef);
+		return ItemStack(name, count, wear, idef);
 	}
 	else
 	{

src/script/lua_api/CMakeLists.txt

@@ -7,6 +7,7 @@ set(common_SCRIPT_LUA_API_SRCS
 	${CMAKE_CURRENT_SOURCE_DIR}/l_item.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/l_mapgen.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/l_nodemeta.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/l_itemstackmeta.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/l_nodetimer.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/l_noise.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/l_object.cpp

src/script/lua_api/l_env.cpp

@@ -280,7 +280,7 @@ int ModApiEnvMod::l_place_node(lua_State *L)
 		return 1;
 	}
 	// Create item to place
-	ItemStack item(ndef->get(n).name, 1, 0, "", idef);
+	ItemStack item(ndef->get(n).name, 1, 0, idef);
 	// Make pointed position
 	PointedThing pointed;
 	pointed.type = POINTEDTHING_NODE;

src/script/lua_api/l_item.cpp

@@ -27,6 +27,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "content_sao.h"
 #include "inventory.h"
 #include "log.h"
+#include "lua_api/l_itemstackmeta.h"
 
 
 // garbage collector
@@ -137,13 +138,24 @@ int LuaItemStack::l_set_wear(lua_State *L)
 	return 1;
 }
 
+// get_meta(self) -> userdata //note get_metadata and set_metadata mimic old behavior
+int LuaItemStack::l_get_meta(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	LuaItemStack *o = checkobject(L, 1);
+	ItemStack &item = o->m_stack;
+	ItemStackMetaRef::create(L, &item);
+	return 1;
+}
+//LEGACY metadata access
 // get_metadata(self) -> string
 int LuaItemStack::l_get_metadata(lua_State *L)
 {
 	NO_MAP_LOCK_REQUIRED;
 	LuaItemStack *o = checkobject(L, 1);
 	ItemStack &item = o->m_stack;
-	lua_pushlstring(L, item.metadata.c_str(), item.metadata.size());
+	std::string metastr=item.metadata.getString("");
+	lua_pushlstring(L, metastr.c_str(), metastr.size());
 	return 1;
 }
 
@@ -156,7 +168,9 @@ int LuaItemStack::l_set_metadata(lua_State *L)
 
 	size_t len = 0;
 	const char *ptr = luaL_checklstring(L, 2, &len);
-	item.metadata.assign(ptr, len);
+	std::string metastr;
+	metastr.assign(ptr, len);
+	item.metadata.setString("", metastr);
 
 	lua_pushboolean(L, true);
 	return 1;
@@ -211,8 +225,6 @@ int LuaItemStack::l_to_table(lua_State *L)
 		lua_setfield(L, -2, "count");
 		lua_pushinteger(L, item.wear);
 		lua_setfield(L, -2, "wear");
-		lua_pushlstring(L, item.metadata.c_str(), item.metadata.size());
-		lua_setfield(L, -2, "metadata");
 	}
 	return 1;
 }
@@ -443,8 +455,9 @@ const luaL_reg LuaItemStack::methods[] = {
 	luamethod(LuaItemStack, set_count),
 	luamethod(LuaItemStack, get_wear),
 	luamethod(LuaItemStack, set_wear),
-	luamethod(LuaItemStack, get_metadata),
-	luamethod(LuaItemStack, set_metadata),
+	luamethod(LuaItemStack, get_meta),
+	luamethod(LuaItemStack, get_metadata),//legacy
+	luamethod(LuaItemStack, set_metadata),//legacy
 	luamethod(LuaItemStack, clear),
 	luamethod(LuaItemStack, replace),
 	luamethod(LuaItemStack, to_string),

src/script/lua_api/l_item.h

@@ -22,6 +22,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "lua_api/l_base.h"
 #include "inventory.h"  // ItemStack
+#include "lua_api/l_itemstackmeta.h"
+#include "itemstackmetadata.h"
 
 class LuaItemStack : public ModApiBase {
 private:
@@ -56,10 +58,13 @@ private:
 	// set_wear(self, number)
 	static int l_set_wear(lua_State *L);
 
-	// get_metadata(self) -> string
+	// get_meta(self) -> userdata(ItemStackMetaRef)
+	static int l_get_meta(lua_State *L);
+
+	// get_metadata(self) -> string (legacy)
 	static int l_get_metadata(lua_State *L);
 
-	// set_metadata(self, string)
+	// set_metadata(self, string) (legacy)
 	static int l_set_metadata(lua_State *L);
 
 	// clear(self) -> true

src/script/lua_api/l_itemstackmeta.cpp

@@ -0,0 +1,304 @@
+/*
+Minetest
+Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "lua_api/l_itemstackmeta.h"
+#include "lua_api/l_internal.h"
+#include "lua_api/l_inventory.h"
+#include "common/c_converter.h"
+#include "common/c_content.h"
+#include "gamedef.h"
+#include "inventory.h"
+#include "itemstackmetadata.h"
+
+
+
+/*
+	ItemStackMetaRef
+*/
+ItemStackMetaRef* ItemStackMetaRef::checkobject(lua_State *L, int narg)
+{
+	luaL_checktype(L, narg, LUA_TUSERDATA);
+	void *ud = luaL_checkudata(L, narg, className);
+	if(!ud) luaL_typerror(L, narg, className);
+	return *(ItemStackMetaRef**)ud;  // unbox pointer
+}
+
+ItemStackMetadata* ItemStackMetaRef::getmeta(ItemStackMetaRef *ref)
+{
+	ItemStackMetadata *meta = &(ref->m_istack->metadata);
+	return meta;
+}
+
+
+void ItemStackMetaRef::reportMetadataChange(ItemStackMetaRef *ref)
+{
+	//At the moment, it does not seem to be neccessary to notify anything about changed metadata.
+	//Reserved for future use.
+}
+
+
+// Exported functions
+
+// garbage collector
+int ItemStackMetaRef::gc_object(lua_State *L) {
+	ItemStackMetaRef *o = *(ItemStackMetaRef **)(lua_touserdata(L, 1));
+	delete o;
+	return 0;
+}
+
+// get_string(self, name)
+int ItemStackMetaRef::l_get_string(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	std::string name = luaL_checkstring(L, 2);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if(meta == NULL){
+		lua_pushlstring(L, "", 0);
+		return 1;
+	}
+	std::string str = meta->getString(name);
+	lua_pushlstring(L, str.c_str(), str.size());
+	return 1;
+}
+
+// set_string(self, name, var)
+int ItemStackMetaRef::l_set_string(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	std::string name = luaL_checkstring(L, 2);
+	size_t len = 0;
+	const char *s = lua_tolstring(L, 3, &len);
+	std::string str(s, len);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if(meta == NULL || str == meta->getString(name))
+		return 0;
+	meta->setString(name, str);
+	reportMetadataChange(ref);
+	return 0;
+}
+
+// get_int(self, name)
+int ItemStackMetaRef::l_get_int(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	std::string name = lua_tostring(L, 2);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if(meta == NULL){
+		lua_pushnumber(L, 0);
+		return 1;
+	}
+	std::string str = meta->getString(name);
+	lua_pushnumber(L, stoi(str));
+	return 1;
+}
+
+// set_int(self, name, var)
+int ItemStackMetaRef::l_set_int(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	std::string name = lua_tostring(L, 2);
+	int a = lua_tointeger(L, 3);
+	std::string str = itos(a);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if(meta == NULL || str == meta->getString(name))
+		return 0;
+	meta->setString(name, str);
+	reportMetadataChange(ref);
+	return 0;
+}
+
+// get_float(self, name)
+int ItemStackMetaRef::l_get_float(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	std::string name = lua_tostring(L, 2);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if(meta == NULL){
+		lua_pushnumber(L, 0);
+		return 1;
+	}
+	std::string str = meta->getString(name);
+	lua_pushnumber(L, stof(str));
+	return 1;
+}
+
+// set_float(self, name, var)
+int ItemStackMetaRef::l_set_float(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	std::string name = lua_tostring(L, 2);
+	float a = lua_tonumber(L, 3);
+	std::string str = ftos(a);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if(meta == NULL || str == meta->getString(name))
+		return 0;
+	meta->setString(name, str);
+	reportMetadataChange(ref);
+	return 0;
+}
+
+// to_table(self)
+int ItemStackMetaRef::l_to_table(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+
+	ItemStackMetadata *meta = getmeta(ref);
+	if (meta == NULL) {
+		lua_pushnil(L);
+		return 1;
+	}
+	lua_newtable(L);
+
+	{
+		StringMap fields = meta->getStrings();
+		for (StringMap::const_iterator
+				it = fields.begin(); it != fields.end(); ++it) {
+			const std::string &name = it->first;
+			const std::string &value = it->second;
+			lua_pushlstring(L, name.c_str(), name.size());
+			lua_pushlstring(L, value.c_str(), value.size());
+			lua_settable(L, -3);
+		}
+	}
+
+	return 1;
+}
+
+// from_table(self, table)
+int ItemStackMetaRef::l_from_table(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+
+	ItemStackMetaRef *ref = checkobject(L, 1);
+	int base = 2;
+
+	ItemStackMetadata *meta = getmeta(ref);
+
+	if(meta == NULL){
+		lua_pushboolean(L, false);
+		return 1;
+	}
+
+	meta->clear();
+
+	if(lua_isnil(L, base)){
+		// No metadata
+		lua_pushboolean(L, true);
+		return 1;
+	}
+
+	// Set fields
+	int fieldstable = lua_gettop(L);
+	lua_pushnil(L);
+	while(lua_next(L, fieldstable) != 0){
+		// key at index -2 and value at index -1
+		std::string name = lua_tostring(L, -2);
+		size_t cl;
+		const char *cs = lua_tolstring(L, -1, &cl);
+		std::string value(cs, cl);
+		meta->setString(name, value);
+		lua_pop(L, 1); // removes value, keeps key for next iteration
+	}
+
+	reportMetadataChange(ref);
+	lua_pushboolean(L, true);
+	return 1;
+}
+
+
+ItemStackMetaRef::ItemStackMetaRef(ItemStack *istack):
+	m_istack(istack)
+{
+}
+
+ItemStackMetaRef::~ItemStackMetaRef()
+{
+}
+
+// Creates an ItemStackMetaRef and leaves it on top of stack
+// Not callable from Lua; all references are created on the C side.
+void ItemStackMetaRef::create(lua_State *L, ItemStack *istack)
+{
+	ItemStackMetaRef *o = new ItemStackMetaRef(istack);
+	//infostream<<"ItemStackMetaRef::create: o="<<o<<std::endl;
+	*(void **)(lua_newuserdata(L, sizeof(void *))) = o;
+	luaL_getmetatable(L, className);
+	lua_setmetatable(L, -2);
+}
+
+void ItemStackMetaRef::Register(lua_State *L)
+{
+	lua_newtable(L);
+	int methodtable = lua_gettop(L);
+	luaL_newmetatable(L, className);
+	int metatable = lua_gettop(L);
+
+	lua_pushliteral(L, "__metatable");
+	lua_pushvalue(L, methodtable);
+	lua_settable(L, metatable);  // hide metatable from Lua getmetatable()
+
+	lua_pushliteral(L, "__index");
+	lua_pushvalue(L, methodtable);
+	lua_settable(L, metatable);
+
+	lua_pushliteral(L, "__gc");
+	lua_pushcfunction(L, gc_object);
+	lua_settable(L, metatable);
+
+	lua_pop(L, 1);  // drop metatable
+
+	luaL_openlib(L, 0, methods, 0);  // fill methodtable
+	lua_pop(L, 1);  // drop methodtable
+
+	// Cannot be created from Lua
+	//lua_register(L, className, create_object);
+}
+
+const char ItemStackMetaRef::className[] = "ItemStackMetaRef";
+const luaL_reg ItemStackMetaRef::methods[] = {
+	luamethod(ItemStackMetaRef, get_string),
+	luamethod(ItemStackMetaRef, set_string),
+	luamethod(ItemStackMetaRef, get_int),
+	luamethod(ItemStackMetaRef, set_int),
+	luamethod(ItemStackMetaRef, get_float),
+	luamethod(ItemStackMetaRef, set_float),
+	luamethod(ItemStackMetaRef, to_table),
+	luamethod(ItemStackMetaRef, from_table),
+	{0,0}
+};

src/script/lua_api/l_itemstackmeta.h

@@ -0,0 +1,94 @@
+/*
+Minetest
+Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+#ifndef L_ITEMSTACKMETA_H_
+#define L_ITEMSTACKMETA_H_
+
+#include "lua_api/l_base.h"
+#include "irrlichttypes_bloated.h"
+#include "inventory.h"
+
+class ServerEnvironment;
+class ItemStackMetadata;
+
+/*
+	ItemStackMetaRef
+*/
+
+class ItemStackMetaRef : public ModApiBase {
+private:
+	ItemStack *m_istack;
+
+	static const char className[];
+	static const luaL_reg methods[];
+
+	static ItemStackMetaRef *checkobject(lua_State *L, int narg);
+
+	/**
+	 * Retrieve metadata for an itemstack (the one given as pointer as member variable).
+	 * @return pointer to a @c ItemStackMetadata object.
+	 */
+	static ItemStackMetadata* getmeta(ItemStackMetaRef *ref);
+
+	static void reportMetadataChange(ItemStackMetaRef *ref);
+
+	// Exported functions
+
+	// garbage collector
+	static int gc_object(lua_State *L);
+
+	// get_string(self, name)
+	static int l_get_string(lua_State *L);
+
+	// set_string(self, name, var)
+	static int l_set_string(lua_State *L);
+
+	// get_int(self, name)
+	static int l_get_int(lua_State *L);
+
+	// set_int(self, name, var)
+	static int l_set_int(lua_State *L);
+
+	// get_float(self, name)
+	static int l_get_float(lua_State *L);
+
+	// set_float(self, name, var)
+	static int l_set_float(lua_State *L);
+
+	// get_inventory(self)
+	static int l_get_inventory(lua_State *L);
+
+	// to_table(self)
+	static int l_to_table(lua_State *L);
+
+	// from_table(self, table)
+	static int l_from_table(lua_State *L);
+
+public:
+	ItemStackMetaRef(ItemStack *istack);
+
+	~ItemStackMetaRef();
+
+	// Creates an ItemStackMetaRef and leaves it on top of stack
+	// Not callable from Lua; all references are created on the C side.
+	static void create(lua_State *L, ItemStack *istack);
+
+	static void Register(lua_State *L);
+};
+
+#endif /* L_NODEMETA_H_ */

src/script/scripting_game.cpp

@@ -30,6 +30,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "lua_api/l_item.h"
 #include "lua_api/l_mapgen.h"
 #include "lua_api/l_nodemeta.h"
+#include "lua_api/l_itemstackmeta.h"
 #include "lua_api/l_nodetimer.h"
 #include "lua_api/l_noise.h"
 #include "lua_api/l_object.h"
@@ -103,6 +104,7 @@ void GameScripting::InitializeModApi(lua_State *L, int top)
 	LuaSecureRandom::Register(L);
 	LuaVoxelManip::Register(L);
 	NodeMetaRef::Register(L);
+	ItemStackMetaRef::Register(L);
 	NodeTimerRef::Register(L);
 	ObjectRef::Register(L);
 	LuaSettings::Register(L);