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[REBOL] Re: callbacks

From: lmecir:mbox:vol:cz at: 7-Nov-2007 6:16

Hi Max,
> I allocate nothing, its a callback. the lib calls my func. I never build a > struct except to supply the callbacks upon loading the lib, and that is > safe.
Sorry for not believing you, it looked so improbable, but you were right! Rebol indeed recycled the memory it did not allocate.
> Maybe its possible the gc could recycle in the window of time in between > change pointer address and doing the copy, but if this is the case, both > versions I guess suffer the same fatality. maybe adding a recycle/off > recycle/on pair within the func could prevent this possibility. >
There indeed is a problem with your memcopy version. The code below reliably crashes the console, when copied and pasted to it: include %peekpoke.r include %timblk.r a: #{00010203040506070809} aa: string-address? a time-block [memcopy-max aa 10] 0,05 time-block [memcopy-max aa 10] 0,05 After inserting recycle/off; recycle/on pair as follows: memcopy-max: func [ {copies a region of ram given at address with sizeof length.} address [integer!] length [integer!] /local struct-struct buffer addr ] [ recycle/off address: make struct! [address [integer!]] reduce [address] struct-struct: make struct! compose/deep [ struct [struct! [(head insert/dup copy [] [c [char]] length)]] ] none addr: copy third struct-struct change third struct-struct third address buffer: copy third struct-struct/struct address change third struct-struct third addr recycle/on buffer ] the crash was still there.
> previously, anytime the GC would pick up the struct it would crash. Delay > was no issue, the stuct really is left corrupted, my guess is that the GC > attempts a free() on the memory pointed to by address. There are a few > reasons why structs could actually be allocated manually, outside of the > normal recycling pool, and since there is a GC managing the struct rebol > wrapper anyways, the rule that everything eventually gets freed is still > applicable. > > wrt speed, my tests where within my whole environment. I'm sorry if a pure > test shows you're function almost twice as fast, and I insinuated otherwise.
+187% in speed means 287% in total ;-)
> just a question, can you add a to-binary to your memcopy and see the speed > impact that has?
to-binary is not necessary, as-binary suffices and it is faster. The speed difference between a version returning string and a version using as-binary to return a binary is almost unmeasurable. Here it is: memcopy: func [ {copy a region of memory given at address with the given size} address [integer!] size [integer!] /local s c ] [ address: make struct! [address [integer!]] reduce [address] s: make struct! compose/deep [c [char-array (size)]] none change third s third address c: s/c change third s #{00000000} as-binary c ] -L