Merge pull request #205 from whisk/fix/popcnt-empty

fixed UnionCardinality panic on empty bitsets

Author: lemire

bitset_test.go

@@ -1302,6 +1302,14 @@ func TestUnion(t *testing.T) {
 	}
 }
 
+func TestEmptyUnionCardinality(t *testing.T) {
+	a := New(0)
+	b := New(0)
+	if a.UnionCardinality(b) != 0 {
+		t.Error("UnionCardinality should be zero")
+	}
+}
+
 func TestInPlaceUnion(t *testing.T) {
 	a := New(100)
 	b := New(200)
@@ -1353,6 +1361,14 @@ func TestIntersection(t *testing.T) {
 	}
 }
 
+func TestEmptyIntersectionCardinality(t *testing.T) {
+	a := New(0)
+	b := New(0)
+	if a.IntersectionCardinality(b) != 0 {
+		t.Error("IntersectionCardinality should be zero")
+	}
+}
+
 func TestInplaceIntersection(t *testing.T) {
 	a := New(100)
 	b := New(200)
@@ -1408,6 +1424,14 @@ func TestDifference(t *testing.T) {
 	}
 }
 
+func TestEmptyDifferenceCardinality(t *testing.T) {
+	a := New(0)
+	b := New(0)
+	if a.DifferenceCardinality(b) != 0 {
+		t.Error("DifferenceCardinality should be zero")
+	}
+}
+
 func TestInPlaceDifference(t *testing.T) {
 	a := New(100)
 	b := New(200)
@@ -1463,6 +1487,14 @@ func TestSymmetricDifference(t *testing.T) {
 	}
 }
 
+func TestEmptySymmetricDifferenceCardinality(t *testing.T) {
+	a := New(0)
+	b := New(0)
+	if a.SymmetricDifferenceCardinality(b) != 0 {
+		t.Error("SymmetricDifferenceCardinality should be zero")
+	}
+}
+
 func TestInPlaceSymmetricDifference(t *testing.T) {
 	a := New(100)
 	b := New(200)

popcnt.go

@@ -10,31 +10,27 @@ func popcntSlice(s []uint64) (cnt uint64) {
 }
 
 func popcntMaskSlice(s, m []uint64) (cnt uint64) {
-	_ = m[len(s)-1] // BCE
 	for i := range s {
 		cnt += uint64(bits.OnesCount64(s[i] &^ m[i]))
 	}
 	return
 }
 
 func popcntAndSlice(s, m []uint64) (cnt uint64) {
-	_ = m[len(s)-1] // BCE
 	for i := range s {
 		cnt += uint64(bits.OnesCount64(s[i] & m[i]))
 	}
 	return
 }
 
 func popcntOrSlice(s, m []uint64) (cnt uint64) {
-	_ = m[len(s)-1] // BCE
 	for i := range s {
 		cnt += uint64(bits.OnesCount64(s[i] | m[i]))
 	}
 	return
 }
 
 func popcntXorSlice(s, m []uint64) (cnt uint64) {
-	_ = m[len(s)-1] // BCE
 	for i := range s {
 		cnt += uint64(bits.OnesCount64(s[i] ^ m[i]))
 	}