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- Subject: Re: avoiding copy - Luajit FFI
- From: Fabio Kaminski <fabiokaminski@...>
- Date: Tue, 7 Jun 2011 13:12:50 -0300
im answeraring myself.. rsrs
i think my solution will be a bytebuffer that can be handled in lua
itself but with a ffi ctype
that ctype(pointer) would be feeded in the C space, and in the lua context ..
you would call functions to do this copy defered .. or lazy as possible..
(but i guess this thread could be a food of thought.. about some concerns)
On Tue, Jun 7, 2011 at 12:58 PM, Fabio Kaminski <firstname.lastname@example.org> wrote:
> On Tue, Jun 7, 2011 at 12:53 PM, Justin Cormack
> <email@example.com> wrote:
>> On Tue, Jun 7, 2011 at 3:54 PM, Fabio Kaminski <firstname.lastname@example.org>
>>> Hi Folks,
>>> Im trying to get less memory copy as possible with luajit FFI, and in
>>> the api to get your hands in a (void *) or (char *) pointer
>>> is copying it through "ffi.string()" wich in turns, will create a lua
>>> my first question: why cant ffi.string() reuse the given pointer.. vm
>>> design? avoid concurrency races from the C side?
>>> the c api "lua_pushlstring()" works the same way?
>>> When you simply need to push a string or even a file buffer thats
>>> fine, but if whe are talking about things like byte buffers over a
>>> those copy would make it loose a lot of performance in the long run..
>>> even creating a bytebuffer on the C side and passing only the
>>> requested byte string on the lua api side..
>>> Anyone has found a way (writing c logic or not) to avoid those copies?
>> Only call ffi.string when you absolutely need to, the rest of the time you
>> can just pass around the raw buffers. You can just allocate them with
> Yeah, thats the way to go.. create more C abstraction (and black
> boxes from lua app perspective) and try to switch C/Lua VM the least
> as possible..
> no skinny C interface for now..