From 2182534cc732fd946bb5cf94121a172066a9bde0 Mon Sep 17 00:00:00 2001
From: Todd Gruben <tgruben@umbel.com>
Date: Mon, 22 May 2017 16:51:53 -0500
Subject: [PATCH] added xor support to roaring

---
 roaring/roaring.go      | 121 ++++++++++++++++++++++++++++++++++++++++
 roaring/roaring_test.go |  40 +++++++++++++
 2 files changed, 161 insertions(+)

diff --git a/roaring/roaring.go b/roaring/roaring.go
index 86d810450..bb27a4143 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -1563,6 +1563,127 @@ 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() {
+		if b.isArray() {
+			return xorArrayArray(a, b)
+		} else {
+			return xorArrayBitmap(a, b)
+		}
+	} else {
+		if b.isArray() {
+			return xorArrayBitmap(b, a)
+		} else {
+			return xorBitmapBitmap(a, b)
+		}
+	}
+}
+
+func xorArrayArray(a, b *container) *container {
+	output := &container{}
+	na, nb := len(a.array), len(b.array)
+	for i, j := 0, 0; ; {
+		if i >= na && j >= nb {
+			break
+		} else if i < na && j >= nb {
+			output.add(a.array[i])
+			i++
+			continue
+		} else if i >= na && j < nb {
+			output.add(b.array[j])
+			j++
+			continue
+		}
+
+		va, vb := a.array[i], b.array[j]
+		if va < vb {
+			output.add(va)
+			i++
+		} else if va > vb {
+			output.add(vb)
+			j++
+		} else { //==
+			i++
+			j++
+		}
+	}
+	return output
+}
+
+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)
+		} else {
+			i++
+		}
+	}
+	return output
+}
+
+func xorBitmapBitmap(a, b *container) *container {
+	output := &container{
+		bitmap: make([]uint64, bitmapN),
+	}
+
+	for i := 0; i < bitmapN; i++ {
+		v := a.bitmap[i] ^ b.bitmap[i]
+		output.bitmap[i] = v
+		output.n += int(popcnt(v))
+	}
+	return output
+}
 
 // opType represents a type of operation.
 type opType uint8
diff --git a/roaring/roaring_test.go b/roaring/roaring_test.go
index d28e72354..32492d870 100644
--- a/roaring/roaring_test.go
+++ b/roaring/roaring_test.go
@@ -130,6 +130,46 @@ func TestBitmap_Union(t *testing.T) {
 	}
 }
 
+func TestBitmap_Xor_ArrayArray(t *testing.T) {
+	bm0 := roaring.NewBitmap(0, 1000001, 1000002, 1000003)
+	bm1 := roaring.NewBitmap(0, 50000, 1000001, 1000002)
+	result := bm0.Xor(bm1)
+	if n := result.Count(); n != 2 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
+
+func TestBitmap_Xor_ArrayBitmap(t *testing.T) {
+	bm0 := roaring.NewBitmap(1, 70, 200, 4097, 4098)
+	bm1 := roaring.NewBitmap()
+	for i := uint64(0); i < 10000; i += 2 {
+		bm1.Add(i)
+	}
+
+	result := bm0.Xor(bm1)
+	if n := result.Count(); n != 4999 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
+
+func TestBitmap_Xor_BitmapBitmap(t *testing.T) {
+	bm0 := roaring.NewBitmap()
+	bm1 := roaring.NewBitmap()
+	for i := uint64(0); i < 10000; i += 2 {
+		bm1.Add(i)
+	}
+	for i := uint64(1); i < 10000; i += 2 {
+		bm0.Add(i)
+	}
+
+	result := bm0.Xor(bm1)
+	if n := result.Count(); n != 10000 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
+
+
+
 // Ensure bitmap can return the number of intersecting bits in two bitmaps.
 func TestBitmap_IntersectionCount_ArrayArray(t *testing.T) {
 	bm0 := roaring.NewBitmap(0, 1000001, 1000002, 1000003)