> On 23 Feb 2017, at 19:21, raffaello.giulie...@lifeware.ch wrote: > > On 23/02/17 19:17, Esteban Lorenzano wrote: >> >>> On 23 Feb 2017, at 19:11, raffaello.giulie...@lifeware.ch wrote: >>> >>> Hi Esteban, >>> >>> yes, I already looked at LibC's memcpy, but that doesn't help in case >>> you need to copy a *portion* of the ByteArray that does not start at >>> index 1. While one can do pointer arithmetic on ExternalAddress, this >>> does not, of course, apply to ByteArray. >>> >>> To sum up, I think Pharo 5 currently lacks an efficient way to copy >>> parts of ByteArrays to/from the C heap. One has to instantiate >>> additional temporary ByteArrays and perform copies between ByteArrays in >>> addition to LibC>>memcpy. >>> >>> But I see there's an Alien class which seems to better support such >>> copying. Thus, I wonder if it is somehow compatible with the rest of UFFI. >> >> Which Alien class? >> >> Esteban > > What do you mean? > I see it in package Alien-Core.
ah, problem is that #copyInto:from:to:in:startingAt: requires an Alien instead a ExternalAddress (and they are not the same). But I guess you can use it if you have two ByteArrays. in the times of old NativeBoost, Igor implemented a memcpy as you want it, because yes, is a problem we have… if is seriously needed, you can always compile your own library with such symbol… a memcpy with start positions. function in C is more or less trivial because you will receive two pointers and you can perform pointer arithmetic on both. Esteban > > >> >>> >>> >>> >>> >>> >>> >>> On 23/02/17 17:35, Esteban Lorenzano wrote: >>>> Sorry, I forgot to answer and now I'm in movement. >>>> Look in LibC memcpy method (is not called exactly like that) and his uses. >>>> That's the faster you can move things inside the image. >>>> >>>> And remember: an EA is a pointer and a ByteArray is an array who will be >>>> passed as pointer too. >>>> >>>> Esteban >>>> >>>>> On 23 Feb 2017, at 17:21, raffaello.giulie...@lifeware.ch wrote: >>>>> >>>>> Hi, >>>>> >>>>> browsing through ByteArray's and ExternalAddress's code, I'm getting the >>>>> impression that copying *portions* of ByteArrays from/to the C heap can >>>>> be quite costly. >>>>> >>>>> Copying *to* the C heap sometimes requires first copying the portion of >>>>> the ByteArray into a newly instantiated temporary ByteArray, then >>>>> copying the latter to the C heap. >>>>> >>>>> Copying *from* the C heap might require explicitly looping over the >>>>> single bytes. I say "might" because I still cannot find more direct way, >>>>> as using ByteArray>>replaceFrom:to:with:startingAt: doesn't seem to work. >>>>> >>>>> Any suggestion on more effective copy operations? >>>>> >>>>> Thanks >>>>> Raffaello >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>> On 22/02/17 15:08, Raffaello Giulietti wrote: >>>>>> Hi Esteban, >>>>>> >>>>>> not sure I'm understanding your snippet correctly. >>>>>> >>>>>> Below is my try. It throws a SubscriptOutOfBounds exception in the last >>>>>> line. The reason is that the implementation of ByteArray >>>>>> replaceFrom:to:with:startingAt: does not consider that ea is meant to be >>>>>> a pointer to a C byte array, not an object whose content is to be copied >>>>>> directly. >>>>>> >>>>>> >>>>>> | ea ba | >>>>>> ea := ExternalAddress gcallocate: 200. >>>>>> ba := ByteArray new: 100. >>>>>> ba replaceFrom: 1 to: 50 with: ea startingAt: 51. >>>>>> >>>>>> >>>>>> Am I missing some point? >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> On 2017-02-21 17:20, Esteban Lorenzano wrote: >>>>>>> usually, something more or less like this: >>>>>>> >>>>>>> sourceByteArrayOrExternalAddress := … some ... >>>>>>> destEnternalAddressOrByteArray >>>>>>> replaceFrom: 1 >>>>>>> to: sourceByteArrayOrExternalAddress size >>>>>>> with: sourceByteArrayOrExternalAddress >>>>>>> startingAt: 1 >>>>>>> >>>>>>> and or course you can play with the starting points and sizes. >>>>>>> >>>>>>> cheers, >>>>>>> Esteban >>>>>>> >>>>>>> >>>>>>>> On 21 Feb 2017, at 17:13, Raffaello Giulietti >>>>>>>> <raffaello.giulie...@lifeware.ch> wrote: >>>>>>>> >>>>>>>> Hi, >>>>>>>> >>>>>>>> I'm having a hard time finding documentation on how to copy a portion >>>>>>>> of a ByteArray to/from another portion of a heap allocated C byte >>>>>>>> array with UFFI. >>>>>>>> >>>>>>>> My current reference is >>>>>>>> https://ci.inria.fr/pharo-contribution/view/Books/job/PharoBookWorkInProgress/lastSuccessfulBuild/artifact/book-result/UnifiedFFI/UnifiedFFI.pdf >>>>>>>> >>>>>>>> >>>>>>>> Thanks for directing me at relevant docs or examples and sorry in >>>>>>>> advance if I missed some important point in the docs. >>>>>>>> >>>>>>>> RG
