Re: [Xen-devel] [PATCH 09/24] golang/xenlight: define MsVmGenid builtin type

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 10/7/19 4:12 PM, Nick Rosbrook wrote:
> From: Nick Rosbrook <rosbrookn@xxxxxxxxxxxx>
> 
> Define MsVmGenid as [int(C.LIBXL_MS_VM_GENID_LEN)]byte and implement fromC 
> and toC functions.
> 
> Signed-off-by: Nick Rosbrook <rosbrookn@xxxxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> 
>  tools/golang/xenlight/xenlight.go | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/tools/golang/xenlight/xenlight.go 
> b/tools/golang/xenlight/xenlight.go
> index 3b7824b284..6aca5b89c0 100644
> --- a/tools/golang/xenlight/xenlight.go
> +++ b/tools/golang/xenlight/xenlight.go
> @@ -216,6 +216,29 @@ func (mac *Mac) toC() (C.libxl_mac, error) {
>       return cmac, nil
>  }
>  
> +// MsVmGenid represents a libxl_ms_vm_genid.
> +type MsVmGenid [int(C.LIBXL_MS_VM_GENID_LEN)]byte
> +
> +func (mvg *MsVmGenid) fromC(cmvg *C.libxl_ms_vm_genid) error {
> +     b := 
> (*[int(C.LIBXL_MS_VM_GENID_LEN)]C.uint8_t)(unsafe.Pointer(&cmvg.bytes[0]))
> +
> +     for i, v := range b {
> +             mvg[i] = byte(v)
> +     }

It's slightly annoying to have to do this loop, but I guess given that
we have to technically cast each element of the array.  Hopefully the
compiler will eventually be able to figure out what's going on here and
just do a memcpy.

> +
> +     return nil
> +}
> +
> +func (mvg *MsVmGenid) toC() (C.libxl_ms_vm_genid, error) {

Hmm, I guess we want a pointer receiver here to make sure we don't end
up doing a 16-byte copy.

Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>

 -George

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