[VM] Add an API to fetch current number of entries in a table

Ast/src/StringUtils.cpp

@@ -7,6 +7,7 @@
 #include <vector>
 #include <string>
 #include <string.h>
+#include <cstdint>
 
 namespace Luau
 {

VM/include/lua.h

@@ -475,6 +475,7 @@ LUA_API int lua_isclosing(lua_State *L);
 LUA_API int lua_findreferences(lua_State* L);
 LUA_API void lua_clonetable(lua_State* L, int idx);
 LUA_API void lua_remaptable(lua_State* L, int idx, int mapIdx);
+LUA_API int lua_gettablesize(lua_State* L, int idx);
 
 
 /******************************************************************************

VM/src/lapi.cpp

@@ -1498,6 +1498,14 @@ void lua_cleartable(lua_State* L, int idx)
     luaH_clear(tt);
 }
 
+int lua_gettablesize(lua_State* L, int idx)
+{
+    StkId t = index2addr(L, idx);
+    api_check(L, ttistable(t));
+    Table* tt = hvalue(t);
+    return luaH_getsize(tt);
+}
+
 lua_Callbacks* lua_callbacks(lua_State* L)
 {
     return &L->global->cb;

VM/src/ltable.cpp

@@ -867,3 +867,26 @@ void luaH_clear(Table* tt)
     // back to empty -> no tag methods present
     tt->tmcache = cast_byte(~0);
 }
+
+int luaH_getsize(Table* t)
+{
+    int count=0;
+    if (t->sizearray)
+    {
+        for (int k=0;k<t->sizearray;k++) {
+            if (!ttisnil(&t->array[k]))
+                count++;
+        }
+    }
+
+    if (t->node != dummynode)
+    {
+        for (int i=0; i < sizenode(t); i++)
+        { // then hash part
+            if (!ttisnil(gval(gnode(t, i))))
+                count++;
+        }
+    }
+
+    return count;
+}

VM/src/ltable.h

@@ -30,6 +30,7 @@ LUAI_FUNC int luaH_getn(Table* t);
 LUAI_FUNC Table* luaH_clone(lua_State* L, Table* tt);
 LUAI_FUNC void luaH_remaptable(Table* t, Table *lt);
 LUAI_FUNC void luaH_clear(Table* tt);
+LUAI_FUNC int luaH_getsize(Table* tt);
 
 #define luaH_setslot(L, t, slot, key) (invalidateTMcache(t), (slot == luaO_nilobject ? luaH_newkey(L, t, key) : cast_to(TValue*, slot)))