Re: Fast metamethods for Userdata types

[Javier Guerra Giraldez <javier@...>]

On Tue, Apr 7, 2015 at 3:50 PM, Dibyendu Majumdar
<mobile@majumdar.org.uk> wrote:
> Now if you think of
> Ravi where the [] operator on an array is specialized - and executed
> inline for gets, then the cost of a hash table lookup and then going
> through the mechanism for a function call is enormous.


In LuaJIT, methametods are added to ffi objects using the
`ffi.metatype(ct, metatable)`, where `ct` is the ffi type and
`metatable` is compatible with the plain Lua metatable.  But the user
is not allowed to modify the metatable, its contents, or it's __index
contents after the call to metatype().

I guess that allows LuaJIT to statically set all the function
bindings, and the result is that adding simple methods to ffi objects
is _very_ efficient, and typically gets fully compiled.


-- 
Javier