Re: How to create Lua nested namespaces in C

[Malte Thiesen <malte.thiesen@...>]

Hi,
I use the following code to create nested tables. The function takes a 
Lua-state and a string like "very.deeply.nested" and then creates all 
the subtables down to "nested" and leaves the "deepest" table on the stack.
It also makes sure that the tables aren't overwritten, so if you create 
"very.deeply.nested" and "very.deeply" already exists only "nested" is 
created. Unlike you I use std::string not C-strings so you may have to 
adapt the code a little.

bool CreateNestedTable(lua_State * L, const std::string & TableName)
{
   // The tablename is seperated at the periods and the subtables are 
created if they don't exist.
   // On success true is returned and the last subtable is on top of 
the Lua-stack.
  
   std::string::size_type PartBegin = 0;
   while (PartBegin <= TableName.size())
   {
       std::string::size_type PartEnd;
       PartEnd = TableName.find(".", PartBegin);
       if (PartEnd == std::string::npos) PartEnd = TableName.size();
       std::string SubTableName = TableName.substr(PartBegin, PartEnd - 
PartBegin);

       // Tables need to have a name (something like "a..b" occured)
       if (SubTableName.size() == 0) return false;

       // Check if a table already exists
       // At the first pass the table is searched in the global 
namespace. Later the parent-table on the stack is searched.
       if (PartBegin == 0)
       {
           lua_pushstring(L, SubTableName.c_str());
           lua_gettable(L, LUA_GLOBALSINDEX);
       }
       else
       {
           lua_pushstring(L, SubTableName.c_str());
           lua_gettable(L, -2);
           if (!lua_isnil(L, -1)) lua_remove(L, -2);
       }

       // If the table wasn't found, it has to be created
       if (lua_isnil(L, -1))
       {
           // Pop nil from the stack
           lua_pop(L, 1);

           // Create new table
           lua_newtable(L);
           lua_pushstring(L, SubTableName.c_str());
           lua_pushvalue(L, -2);
           if (PartBegin == 0)
               lua_settable(L, LUA_GLOBALSINDEX);
           else
           {
               lua_settable(L, -4);
               lua_remove(L, -2);
           }
       }

       // Skip the period
       PartBegin = PartEnd + 1;
   }

   return true;
}


Regards,
Malte