Re: Feature request: userdata slice
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- Subject: Re: Feature request: userdata slice
- From: Sean Conner <sean@...>
- Date: 2015年8月20日 01:02:15 -0400
It was thus said that the Great 云风 Cloud Wu once stated:
>
> Let me try to explain one of real user case.
>
> In my MMO game server, I create about 10K lua vm in one process. The
> average size of them is about 10M. (So it needs more than 100G altogether,
> I run it on a 128G RAM server) They works together like erlang's processes.
>
> We have a large tree based document read from a large xml or json file.
> About 10M size and more than 100K records. It's immutable and shared among
> all of the lua vm.
>
> We can't load this document in each lua vm because of size (And parsing
> time of the document is also a problem), so I must use a C object to store
> this document, and share the pointer.
>
> My problem is how to traverse this C object as lua tables efficiently.
I can think of several ways, but they all depend upon how the data is
stored internally (external to Lua). Assuming a pointer to a node is
self-describing (or the data pointed to by the pointer is self-describing so
you know what you are pointing to, if you get my drift), then you might be
best served using lightuserdata (a direct pointer to the shared data) and a
custom metatable for lightuserdata (which would be shared across all
lightuserdata). So, as long as you "know" where you are based on a pointer,
then you save the overhead of allocating memory from Lua.
static int lightusedata___index(lua_State *L)
{
struct datanode *node = lua_touserdata(L,1);
const char *idx = lua_tostring(L,2);
struct datanode *new;
new = find(node,idx);
if (new)
{
if (new->type == NODE)
lua_pushlightuserdata(L,new);
else if (new->type == STRING)
lua_pushstring(L,new->val.string);
else if (new->type == NUMBER)
lua_pushnumber(L,new->val.number);
/* ... */
}
else
/* handle appropriately */
return 1;
}
-spc (That's about as lightweight as I can imagine it being)