Re: [Xen-devel] [PATCH RFC 6/8] golang/xenlight: Implement libxl_bitmap and helper operations

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 23/01/17 16:43, Ronald Rojas wrote:
> Implement Bitmap type, along with helper functions.
> 
> The Bitmap type is implemented interllay in a way which makes it
> easy to copy into and out of the C libxl_bitmap type.
> 
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> Signed-off-by: Ronald Rojas <ronladred@xxxxxxxxx>
> ---
>  tools/golang/xenlight/xenlight.go | 166 
> ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 166 insertions(+)
> 
> diff --git a/tools/golang/xenlight/xenlight.go 
> b/tools/golang/xenlight/xenlight.go
> index dd6893c..54692fd 100644
> --- a/tools/golang/xenlight/xenlight.go
> +++ b/tools/golang/xenlight/xenlight.go
> @@ -131,6 +131,19 @@ func (chwcap C.libxl_hwcap)CToGo() (ghwcap Hwcap) {
>       return
>  }
>  
> +// typedef struct {
> +//     uint32_t size;          /* number of bytes in map */
> +//     uint8_t *map;
> +// } libxl_bitmap;
> +
> +// Implement the Go bitmap type such that the underlying data can
> +// easily be copied in and out.  NB that we still have to do copies
> +// both directions, because cgo runtime restrictions forbid passing to
> +// a C function a pointer to a Go-allocated structure which contains a
> +// pointer.
> +type Bitmap struct {
> +     bitmap []C.uint8_t
> +}
>  
>  /*
>   * Types: IDL
> @@ -199,6 +212,159 @@ type Dominfo struct {
>  }
>  
>  /*
> + * Bitmap operations
> + */
> +
> +// Return a Go bitmap which is a copy of the referred C bitmap.
> +func (cbm C.libxl_bitmap) CToGo() (gbm Bitmap) {

Probably just toGo()...

> +     // Alloc a Go slice for the bytes
> +     size := int(cbm.size)
> +     gbm.bitmap = make([]C.uint8_t, size)
> +
> +     // Make a slice pointing to the C array
> +     mapslice := (*[1 << 30]C.uint8_t)(unsafe.Pointer(cbm._map))[:size:size]
> +
> +     // And copy the C array into the Go array
> +     copy(gbm.bitmap, mapslice)
> +
> +     return
> +}
> +
> +// Must be C.libxl_bitmap_dispose'd of afterwards
> +func (gbm Bitmap)GoToC() (cbm C.libxl_bitmap) {

...and toC (lower case so they're not visible outside the package).

Also 'go fmt'.

> +     C.libxl_bitmap_init(&cbm)
> +
> +     size := len(gbm.bitmap)
> +     cbm._map = (*C.uint8_t)(C.malloc(C.size_t(size)))
> +     cbm.size = C.uint32_t(size)
> +     if cbm._map == nil {
> +             panic("C.calloc failed!")

malloc  (This is probably my typo).

Other than that, looks good.

 -George


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