Yes, it does a copy. ccall is meant to be a super-simple interface, but because of that it adds overhead. So it can receive a JS array, which compiled code can't see, and it copies it to a place that that code can.
If you have large arrays or do many calls, it's better to malloc a buffer and read/write to it directly, and just pass a pointer to it in the call. On Sat, Nov 4, 2017 at 4:16 PM, Dannii Willis <curiousdan...@gmail.com> wrote: > What are the performance considerations of passing large arrays (up to a > few MB) to ccall? > > If the data is ever copied, I think I can change what I'm doing to stop > passing the array. (I realised I'm passing it in only to pass it > immediately out again through custom library functions.) > > -- > You received this message because you are subscribed to the Google Groups > "emscripten-discuss" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to emscripten-discuss+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "emscripten-discuss" group. To unsubscribe from this group and stop receiving emails from it, send an email to emscripten-discuss+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
