[Xen-devel] [PATCH RFC 5/8] golang/xenlight: Implement libxl_bitmap and helper operations

[Ronald Rojas <ronladred@xxxxxxxxx>]

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 | 167 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)

diff --git a/tools/golang/xenlight/xenlight.go 
b/tools/golang/xenlight/xenlight.go
index 1e25413..8aaca6a 100644
--- a/tools/golang/xenlight/xenlight.go
+++ b/tools/golang/xenlight/xenlight.go
@@ -131,6 +131,20 @@ func hwcapCToGo(chwcap C.libxl_hwcap) (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
  *
@@ -198,6 +212,159 @@ type Dominfo struct {
 }
 
 /*
+ * Bitmap operations
+ */
+
+// Return a Go bitmap which is a copy of the referred C bitmap.
+func bitmapCToGo(cbm C.libxl_bitmap) (gbm Bitmap) {
+       // 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 bitmapGotoC(gbm Bitmap) (cbm C.libxl_bitmap) {
+       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!")
+       }
+
+       // Make a slice pointing to the C array
+       mapslice := (*[1 << 30]C.uint8_t)(unsafe.Pointer(cbm._map))[:size:size]
+
+       // And copy the Go array into the C array
+       copy(mapslice, gbm.bitmap)
+
+       return
+}
+
+func (bm *Bitmap) Test(bit int) bool {
+       ubit := uint(bit)
+       if bit > bm.Max() || bm.bitmap == nil {
+               return false
+       }
+
+       return (bm.bitmap[bit/8] & (1 << (ubit & 7))) != 0
+}
+
+func (bm *Bitmap) Set(bit int) {
+       ibit := bit / 8
+       if ibit+1 > len(bm.bitmap) {
+               bm.bitmap = append(bm.bitmap, make([]C.uint8_t, 
ibit+1-len(bm.bitmap))...)
+       }
+
+       bm.bitmap[ibit] |= 1 << (uint(bit) & 7)
+}
+
+func (bm *Bitmap) SetRange(start int, end int) {
+       for i := start; i <= end; i++ {
+               bm.Set(i)
+       }
+}
+
+func (bm *Bitmap) Clear(bit int) {
+       ubit := uint(bit)
+       if bit > bm.Max() || bm.bitmap == nil {
+               return
+       }
+
+       bm.bitmap[bit/8] &= ^(1 << (ubit & 7))
+}
+
+func (bm *Bitmap) ClearRange(start int, end int) {
+       for i := start; i <= end; i++ {
+               bm.Clear(i)
+       }
+}
+
+func (bm *Bitmap) Max() int {
+       return len(bm.bitmap)*8 - 1
+}
+
+func (bm *Bitmap) IsEmpty() bool {
+       for i := 0; i < len(bm.bitmap); i++ {
+               if bm.bitmap[i] != 0 {
+                       return false
+               }
+       }
+       return true
+}
+
+func (a Bitmap) And(b Bitmap) (c Bitmap) {
+       var max, min int
+       if len(a.bitmap) > len(b.bitmap) {
+               max = len(a.bitmap)
+               min = len(b.bitmap)
+       } else {
+               max = len(b.bitmap)
+               min = len(a.bitmap)
+       }
+       c.bitmap = make([]C.uint8_t, max)
+
+       for i := 0; i < min; i++ {
+               c.bitmap[i] = a.bitmap[i] & b.bitmap[i]
+       }
+       return
+}
+
+func (bm Bitmap) String() (s string) {
+       lastOnline := false
+       crange := false
+       printed := false
+       var i int
+       /// --x-xxxxx-x -> 2,4-8,10
+       /// --x-xxxxxxx -> 2,4-10
+       for i = 0; i <= bm.Max(); i++ {
+               if bm.Test(i) {
+                       if !lastOnline {
+                               // Switching offline -> online, print this cpu
+                               if printed {
+                                       s += ","
+                               }
+                               s += fmt.Sprintf("%d", i)
+                               printed = true
+                       } else if !crange {
+                               // last was online, but we're not in a range; 
print -
+                               crange = true
+                               s += "-"
+                       } else {
+                               // last was online, we're in a range,  nothing 
else to do
+                       }
+                       lastOnline = true
+               } else {
+                       if lastOnline {
+                               // Switching online->offline; do we need to end 
a range?
+                               if crange {
+                                       s += fmt.Sprintf("%d", i-1)
+                               }
+                       }
+                       lastOnline = false
+                       crange = false
+               }
+       }
+       if lastOnline {
+               // Switching online->offline; do we need to end a range?
+               if crange {
+                       s += fmt.Sprintf("%d", i-1)
+               }
+       }
+
+       return
+}
+
+/*
  * Context
  */
 var Ctx Context
-- 
2.7.4


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