added copy optimization ; type check; and code cleanup

roaring/roaring.go

@@ -441,6 +441,39 @@ func (b *Bitmap) Difference(other *Bitmap) *Bitmap {
 	return output
 }
 
+// Xor returns the bitwise exclusive or of b and other.
+func (b *Bitmap) Xor(other *Bitmap) *Bitmap {
+	output := &Bitmap{}
+
+	ki, ci := b.keys, b.containers
+	kj, cj := other.keys, other.containers
+
+	for {
+		var key uint64
+		var container *container
+
+		ni, nj := len(ki), len(kj)
+		if ni == 0 && nj == 0 { // eof(i,j)
+			break
+		} else if ni == 0 || (nj != 0 && ki[0] > kj[0]) { // eof(i) or i > j
+			key, container = kj[0], cj[0].clone()
+			kj, cj = kj[1:], cj[1:]
+		} else if nj == 0 || (ki[0] < kj[0]) { // eof(j) or i < j
+			key, container = ki[0], ci[0].clone()
+			ki, ci = ki[1:], ci[1:]
+		} else { // i == j
+			key, container = ki[0], xor(ci[0], cj[0])
+			ki, ci = ki[1:], ci[1:]
+			kj, cj = kj[1:], cj[1:]
+		}
+
+		output.keys = append(output.keys, key)
+		output.containers = append(output.containers, container)
+	}
+
+	return output
+}
+
 // removeEmptyContainers deletes all containers that have a count of zero.
 func (b *Bitmap) removeEmptyContainers() {
 	for i := 0; i < len(b.containers); {
@@ -1563,37 +1596,6 @@ func differenceBitmapBitmap(a, b *container) *container {
 	}
 	return output
 }
-func (b *Bitmap) Xor(other *Bitmap) *Bitmap {
-	output := &Bitmap{}
-
-	ki, ci := b.keys, b.containers
-	kj, cj := other.keys, other.containers
-
-	for {
-		var key uint64
-		var container *container
-
-		ni, nj := len(ki), len(kj)
-		if ni == 0 && nj == 0 { // eof(i,j)
-			break
-		} else if ni == 0 || (nj != 0 && ki[0] > kj[0]) { // eof(i) or i > j
-			key, container = kj[0], cj[0].clone()
-			kj, cj = kj[1:], cj[1:]
-		} else if nj == 0 || (ki[0] < kj[0]) { // eof(j) or i < j
-			key, container = ki[0], ci[0].clone()
-			ki, ci = ki[1:], ci[1:]
-		} else { // i == j
-			key, container = ki[0], xor(ci[0], cj[0])
-			ki, ci = ki[1:], ci[1:]
-			kj, cj = kj[1:], cj[1:]
-		}
-
-		output.keys = append(output.keys, key)
-		output.containers = append(output.containers, container)
-	}
-
-	return output
-}
 
 func xor(a, b *container) *container {
 	if a.isArray() {
@@ -1643,32 +1645,20 @@ func xorArrayArray(a, b *container) *container {
 }
 
 func xorArrayBitmap(a, b *container) *container {
-	output := &container{}
-	itr := newBufIterator(newBitmapIterator(b.bitmap))
-	for i := 0; ; {
-		vb, eof := itr.next()
-		if i >= len(a.array) && eof {
-			break
-		} else if i >= len(a.array) {
-			output.add(vb)
-			continue
-		} else if eof {
-			output.add(a.array[i])
-			i++
-			continue
-		}
-
-		va := a.array[i]
-		if va < vb {
-			output.add(va)
-			i++
-			itr.unread()
-		} else if va > vb {
-			output.add(vb)
+	output := b.clone()
+	for _, v := range a.array {
+		if b.bitmapContains(v) {
+			output.remove(v)
 		} else {
-			i++
+
+			output.add(v)
 		}
 	}
+
+	if output.count() < ArrayMaxSize {
+		output.convertToArray()
+	}
+
 	return output
 }
 
@@ -1682,6 +1672,10 @@ func xorBitmapBitmap(a, b *container) *container {
 		output.bitmap[i] = v
 		output.n += int(popcnt(v))
 	}
+
+	if output.count() < ArrayMaxSize {
+		output.convertToArray()
+	}
 	return output
 }