After I added the unsafe.Pointer conversion the code compiled: https://play.golang.org/p/QTPyhZzKZH
So my understanding is that line 15 is jut a pointer type conversion to slice that is backed by the C array, so it doesn't matter if I choose 1 << 20 entries or 1 << 22 entries, in both cases the runtime is just creating a slice? Another question, which of the two approaches (pointer arithmetic vs iterating over sliced back by C array) is more efficient to create a Go slice? This code will be invoked hundreds of times per minute to convert C arrays coming from C functions into memory safe Go slices that will then be used throughout the Go program. On Wednesday, August 31, 2016 at 5:26:27 PM UTC-5, Ian Lance Taylor wrote: > On Wed, Aug 31, 2016 at 2:06 PM, Luke Mauldin <lukem...@gmail.com > <javascript:>> wrote: > > I modified my example based on the code example you gave at the bottom > for > > the pointer arithmetic and that compiled without any go vet errors. I > > attempted to use the slice whose backing array is the C array > > https://play.golang.org/p/rJoDMu5YAQ but I get a compile error: > > main.go:14: cannot convert cArr (type *Tag) to type *[1048576]Tag > > Oh, sorry, you need to drop in another conversion to unsafe.Pointer. > > > Another question, if I update my code to use the slice whose backing > array > > is the C array, I see the slice type supports 1048576 entries. If I only > > need at most 100 entries, is there a memory penalty imposed by declaring > the > > type to support 1048576 entries? If so, how great is that penalty? > > There is no penalty. It's just a pointer type conversion. Though if > you are seeing that many entries, then I suspect that you left out the > operation that slices the pointer back down to arrLength (the > [:arrLength:arrLength] at the end of line in the code I sent). > > Ian > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
