[Xen-devel] [PATCH RFC 50/59] libxl: Fix Bitmap.Max(), make Test() / Clear() more robust

[Ronald Rojas <ronladred@xxxxxxxxx>]

From: George Dunlap <george.dunlap@xxxxxxxxxx>

Bitmap.Max() should return the largest currently addressable bit; at the
moment it returns the total number of bits (which is one greater than
the largest addressable bit).

This also implicitly fixes a bug in Test() and Clear() which would cause
an out-of-range error when testing a bit equal to Max().

While we're here, allow Test() and Clear() to handle null bitmaps, the
same way Set() can.

Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
---
 libxl.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libxl.go b/libxl.go
index dfe4f40..bfcaf0d 100644
--- a/libxl.go
+++ b/libxl.go
@@ -270,7 +270,7 @@ func bitmapGotoC(gbm Bitmap) (cbm C.libxl_bitmap) {
 
 func (bm *Bitmap) Test(bit int) (bool) {
        ubit := uint(bit)
-       if (bit > bm.Max()) {
+       if (bit > bm.Max() || bm.bitmap == nil) {
                return false
        }
        
@@ -294,7 +294,7 @@ func (bm *Bitmap) SetRange(start int, end int) {
 
 func (bm *Bitmap) Clear(bit int) {
        ubit := uint(bit)
-       if (bit > bm.Max()) {
+       if (bit > bm.Max() || bm.bitmap == nil) {
                return
        }
        
@@ -308,7 +308,7 @@ func (bm *Bitmap) ClearRange(start int, end int) {
 }
 
 func (bm *Bitmap) Max() (int) {
-       return len(bm.bitmap) * 8
+       return len(bm.bitmap) * 8 - 1
 }
 
 func (bm *Bitmap) IsEmpty() (bool) {
-- 
2.7.4


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