On 23 September 2013 21:40, Igor Stasenko <siguc...@gmail.com> wrote:
> > > > On 23 September 2013 16:23, Camillo Bruni <camillobr...@gmail.com> wrote: > >> Hi Jan, >> >> I think I will add the ByteArray accessor to NBExternalAddress today >> or tomorrow since I need it as well for another project. >> >> hmm, reading from memory into bytearray can be done with memory copy: > > inputs: address , offset , size to read > > newAddress := NBExternalAddress value: address value + offset. > buffer := ByteArray new: size. > NativeBoost memCopy: newAddress to: buffer size: size. > > same way, writing, just swap the source and destination: > > newAddress := NBExternalAddress value: address value + offset. > buffer "is given from somewhere". > NativeBoost memCopy: buffer to: newAddress size: size. > > but as Jan noted, you cannot tell to write starting at specified offset > from/to bytearray, e.g.: > > copy from: address to: buffer + someOffset > neither: > copy from: buffer + someOffset to: someAddress > > this where we need to introduce special 'field address' type, so you can > construct it like this: > > offsetAddress := buffer nbAddressAt: offset. > > so then you can use it to pass to any function, which expects address, > like memory copy > or any foreign function. > > Since objects are moving in memory, we cannot calculate address of field > before hand: > > address := NBExternalAddress value: someObject address + offset. > > because if GC will happen, after computing such address and its actual use, > you will read/write to wrong location. > ** after computing and *before* actual use ** > Thus we should keep oop + offset up to the point of passing it to external > function, under > controllable conditions, that guarantee there's no GC is possible. > > > Things would be much simpler if we could have pinning, isnt? :) > -- > Best regards, > Igor Stasenko. > -- Best regards, Igor Stasenko.
