Hi Bryan But the returned uintptr from syscall is as far as i know a pointer to a struct which has been created by the C API, so go runtime won't touch it or do I miss something?
Am Freitag, 15. Dezember 2017 00:48:51 UTC+1 schrieb Bryan Mills: > > In this case, the vet tool is correct if you're making the syscall with > Go-allocated memory. > The Go runtime is allowed to move values around: the address of a Go > variable is only pinned for the duration of the syscall itself. > > If you've got C-allocated memory (or statically-allocated memory), > https://golang.org/issue/13656#issuecomment-303216308 has a solution that > avoids copying and is more robust to large sizes. > > > On Thursday, December 14, 2017 at 5:27:57 AM UTC-5, snmed wrote: >> >> Okay I found a way, this seems to work: >> >> ca := (*[1000000]byte) (unsafe.Pointer(certctx.pbCertEncoded))[:certctx. >> cbCertEncoded] >> >> or >> >> mm := make([]byte, certctx.cbCertEncoded) >> for i := uint32(0) ; i < certctx.cbCertEncoded; i++ { >> mm[i] = *((*byte)(unsafe.Pointer(certctx.pbCertEncoded + uintptr( >> i) * unsafe.Sizeof(new(byte))))) >> } >> >> >> >> Anyway, the vet tool is complaining: >> >> main.go:106: possible misuse of unsafe.Pointer >> main.go:109: possible misuse of unsafe.Pointer >> >> This is the code fragment: >> >> 104 certctx := new(CERT_CONTEXT) >> 105 >> 106 certctx = (*CERT_CONTEXT) (unsafe.Pointer(pccert_context)) >> 107 >> 108 >> 109 ca := (*[1000000]byte) (unsafe.Pointer(certctx.pbCertEncoded))[: >> certctx.cbCertEncoded] >> >> Is there another way to use syscall return values uintptr without vet >> warnings? And which solution should I prefer? I think the later one should >> be more safe, isn't it? >> >> Cheers >> >> >> Am Donnerstag, 14. Dezember 2017 09:29:38 UTC+1 schrieb snmed: >>> >>> Hi Miki >>> >>> I'm using syscall package and no C import, but maybe it is possible to >>> use this function as well? >>> >>> Am Donnerstag, 14. Dezember 2017 09:18:26 UTC+1 schrieb Miki Tebeka: >>>> >>>> Do you mean >>>> >>>> func C.GoBytes(unsafe.Pointer, C.int) []byte >>>> >>>> ? >>>> >>>> On Thursday, December 14, 2017 at 9:05:32 AM UTC+2, snmed wrote: >>>>> >>>>> Hi all >>>>> >>>>> I'm trying to map a C structure to an equivalent go struct, but I >>>>> bumped into a problem with a pointer to byte that is actually an array of >>>>> bytes. >>>>> >>>>> Here is the C struct: >>>>> >>>>> typedef struct _CERT_CONTEXT { >>>>> DWORD dwCertEncodingType; >>>>> BYTE *pbCertEncoded; >>>>> DWORD cbCertEncoded; >>>>> PCERT_INFO pCertInfo; >>>>> HCERTSTORE hCertStore; >>>>> } CERT_CONTEXT, *PCERT_CONTEXT; >>>>> >>>>> >>>>> and this is my go struct: >>>>> >>>>> type CERT_CONTEXT struct { >>>>> dwCertEncodingType uint32 >>>>> pbCertEncoded uintptr >>>>> cbCertEncoded uint32 >>>>> pCertInfo uintptr >>>>> hCertStore uintptr >>>>> } >>>>> >>>>> for my case I need only the first 3 fields and I do not have any >>>>> problem to get 1 and 3, but I can't remember how to translate the second >>>>> field to a slice of bytes. >>>>> This is how I map the struct from an uintptr and print it to the >>>>> console: >>>>> >>>>> certctx = (*CERT_CONTEXT) (unsafe.Pointer(pccert_context)) >>>>> fmt.Printf("%v\n", certctx) >>>>> >>>>> >&{1 807520 674 833008 789360} >>>>> >>>>> Any advise is warmly welcome. >>>>> >>>>> Cheers, >>>>> Sandro >>>>> >>>> -- 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.
