Add lua_tabletype function to improve serialization

CMakeLists.txt

@@ -3,7 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 cmake_minimum_required(VERSION 3.6 FATAL_ERROR)
-project(luasandbox VERSION 1.2.11 LANGUAGES C)
+project(luasandbox VERSION 1.3.0 LANGUAGES C)
 
 set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Generic Lua sandbox for dynamic data analysis")
 set(CPACK_PACKAGE_VERSION_MAJOR ${PROJECT_VERSION_MAJOR})

include/luasandbox/lua.h

@@ -81,6 +81,13 @@ typedef void * (*lua_Alloc) (void *ud, void *ptr, size_t osize, size_t nsize);
 #define LUA_TUSERDATA		7
 #define LUA_TTHREAD		8
 
+/*
+** table types
+*/
+#define LUA_TTEMPTY             0
+#define LUA_TTARRAY             1
+#define LUA_TTHASH              2
+#define LUA_TTMIXED             3
 
 
 /* minimum Lua stack available to a C function */
@@ -132,6 +139,7 @@ LUA_API void  (lua_xmove) (lua_State *from, lua_State *to, int n);
 ** access functions (stack -> C)
 */
 
+LUA_API int             (lua_tabletype) (lua_State *L, int idx);
 LUA_API int             (lua_isnumber) (lua_State *L, int idx);
 LUA_API int             (lua_isstring) (lua_State *L, int idx);
 LUA_API int             (lua_iscfunction) (lua_State *L, int idx);

src/lua/lapi.c

@@ -257,6 +257,18 @@ LUA_API int lua_iscfunction (lua_State *L, int idx) {
 }
 
 
+LUA_API int lua_tabletype (lua_State *L, int idx) {
+  StkId t;
+  int tt;
+  lua_lock(L);
+  t = index2adr(L, idx);
+  api_check(L, ttistable(t));
+  tt = luaH_type(hvalue(t));
+  lua_unlock(L);
+  return tt;
+}
+
+
 LUA_API int lua_isnumber (lua_State *L, int idx) {
   TValue n;
   const TValue *o = index2adr(L, idx);

src/lua/ltable.c

@@ -577,6 +577,13 @@ int luaH_getn (Table *t) {
 }
 
 
+int luaH_type (Table *t) {
+  if (t->sizearray == 0) {
+    return t->node == dummynode ? LUA_TTEMPTY : LUA_TTHASH;
+  }
+  return t->node == dummynode ? LUA_TTARRAY : LUA_TTMIXED;
+}
+
 
 #if defined(LUA_DEBUG)
 

src/lua/ltable.h

@@ -29,6 +29,7 @@ LUAI_FUNC void luaH_resizearray (lua_State *L, Table *t, int nasize);
 LUAI_FUNC void luaH_free (lua_State *L, Table *t);
 LUAI_FUNC int luaH_next (lua_State *L, Table *t, StkId key);
 LUAI_FUNC int luaH_getn (Table *t);
+LUAI_FUNC int luaH_type (Table *t);
 
 
 #if defined(LUA_DEBUG)

src/luasandbox_serialize.c

@@ -311,8 +311,13 @@ serialize_kvp(lsb_lua_sandbox *lsb, serialization_data *data, size_t parent)
       seen = add_table_ref(&data->tables, ptr, pos);
       if (seen != NULL) {
         data->keys.pos += 1;
-        fprintf(data->fh, "%s = {}\n", data->keys.buf + pos);
-        ret = serialize_table(lsb, data, pos);
+        if (lua_tabletype(lsb->lua, vindex) == LUA_TTARRAY
+            && lua_objlen(lsb->lua, vindex) == 0) {
+            fprintf(data->fh, "%s = {nil}\n", data->keys.buf + pos);
+        } else {
+          fprintf(data->fh, "%s = {}\n", data->keys.buf + pos);
+          ret = serialize_table(lsb, data, pos);
+        }
       } else {
         snprintf(lsb->error_message, LSB_ERROR_SIZE,
                  "lsb_serialize preserve table out of memory");

src/test/lua/serialize.lua

@@ -42,6 +42,13 @@ data = ud.new("ud2")
 
 dataRef = data
 
+empty_array = {nil}
+empty_array1 = {}
+empty_array1[1] = nil
+empty_object = {}
+empty_object1 = {[1] = nil}
+array = {1, "two", 3, "four", 5}
+
 function process_message ()
     return 0
 end

src/test/output/serialize.lua51.data

@@ -1,6 +1,14 @@
 if _PRESERVATION_VERSION and _PRESERVATION_VERSION ~= 0 then return end
 _G["ninf"] = -1/0
+_G["empty_object1"] = {}
 if _G["dataRef"] == nil then _G["dataRef"] = ud.new('ud2') end
+_G["array"] = {}
+_G["array"][1] = 1
+_G["array"][2] = "two"
+_G["array"][3] = 3
+_G["array"][4] = "four"
+_G["array"][5] = 5
+_G["empty_object"] = {}
 _G["rate"] = 0.12345678
 _G["kvp"] = {}
 _G["kvp"]["a"] = "foo"
@@ -12,6 +20,7 @@ _G["kvp"]["r"][4] = 92.002
 _G["kvp"]["r"][5] = 91.10001
 _G["kvp"]["r"]["key"] = "val"
 _G["kvp"]["b"] = "bar"
+_G["key with spaces"] = "kws"
 _G["uuids"] = {}
 _G["uuids"][1] = {}
 _G["uuids"][1]["type"] = "test"
@@ -20,6 +29,7 @@ _G["uuids"][2] = {}
 _G["uuids"][2]["type"] = "test1"
 _G["uuids"][2]["uuid"] = "BD48B609-8922-4E59-A358-C242075CE089"
 _G["inf"] = 1/0
+_G["empty_array"] = {nil}
 _G["data"] = _G["dataRef"]
 _G["cycleb"] = {}
 _G["cycleb"]["a"] = {}
@@ -48,7 +58,7 @@ _G["large_key"]["aaaaaaaaaaaaaaaaaaa"]["bbbbbbbbbbbbbbbbbbb"]["BD48B609-8922-4E5
 _G["large_key"]["aaaaaaaaaaaaaaaaaaa"]["BD48B609-8922-4E59-A358-C242075CE081"] = 1
 _G["count"] = 0
 _G["boolean"] = true
-_G["key with spaces"] = "kws"
+_G["empty_array1"] = {nil}
 _G["nested"] = {}
 _G["nested"]["arg2"] = 2
 _G["nested"]["nested"] = {}