Merge pull request #592 from tgruben/flip

add support for bit flip (negate) in roaring

roaring/roaring.go

@@ -101,7 +101,6 @@ func (b *Bitmap) Add(a ...uint64) (changed bool, err error) {
 
 	return changed, nil
 }
-
 func (b *Bitmap) add(v uint64) bool {
 	hb := highbits(v)
 	i := search64(b.keys, hb)
@@ -706,6 +705,34 @@ func (b *Bitmap) Check() error {
 	return a
 }
 
+//Perform a logical negate of the bits in the range [start,end].
+func (b *Bitmap) Flip(start, end uint64) *Bitmap {
+	result := NewBitmap()
+	itr := b.Iterator()
+	v, eof := itr.Next()
+	//copy over previous bits.
+	for v < start && !eof {
+		result.add(v)
+		v, eof = itr.Next()
+	}
+	//flip bits in range .
+	for i := start; i <= end; i++ {
+		if eof {
+			result.add(i)
+		} else if v == i {
+			v, eof = itr.Next()
+		} else {
+			result.add(i)
+		}
+	}
+	//add remaining.
+	for !eof {
+		result.add(v)
+		v, eof = itr.Next()
+	}
+	return result
+}
+
 // BitmapInfo represents a point-in-time snapshot of bitmap stats.
 type BitmapInfo struct {
 	OpN        int

roaring/roaring_test.go

@@ -15,8 +15,8 @@
 package roaring_test
 
 import (
-	"bytes"
 	"fmt"
+	"bytes"
 	"math"
 	"math/rand"
 	"reflect"
@@ -199,6 +199,69 @@ func TestBitmap_Xor_BitmapBitmap(t *testing.T) {
 	}
 }
 
+// Ensure bitmap contents alternate.
+func TestBitmap_Flip_Empty(t *testing.T) {
+	bm := roaring.NewBitmap()
+	results := bm.Flip(0, 10)
+	if n := results.Count(); n != 11 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+	results = results.Flip(0, 10)
+	if n := results.Count(); n != 0 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
+
+// Test Subrange Flip should not affect bits outside of Range
+func TestBitmap_Flip_Array(t *testing.T) {
+	bm := roaring.NewBitmap(0, 1, 2, 3, 4, 8, 16, 32, 64, 128, 256, 512, 1024)
+	results := bm.Flip(0, 4)
+	if !reflect.DeepEqual(results.Slice(), []uint64{8, 16, 32, 64, 128, 256, 512, 1024}) {
+		t.Fatalf("unexpected %v ", results.Slice())
+	}
+	results = results.Flip(0, 4)
+	if !reflect.DeepEqual(results.Slice(), []uint64{0, 1, 2, 3, 4, 8, 16, 32, 64, 128, 256, 512, 1024}) {
+		t.Fatalf("unexpected %v ", results.Slice())
+	}
+
+}
+
+// Ensure  Flip works with underlying Bitmap container.
+func TestBitmap_Flip_Bitmap(t *testing.T) {
+	bm := roaring.NewBitmap()
+	size := uint64(10000)
+	for i := uint64(0); i < size; i += 2 {
+		bm.Add(i)
+	}
+	results := bm.Flip(0, size-1)
+	if n := results.Count(); n != size/2 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+	results = results.Flip(0, size-1) //flipping back should be the same
+	if n := results.Count(); n != size/2 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
+
+// Verify Flip works correctly with in different regions of bitmap, beginning, middle, and end.
+func TestBitmap_Flip_After(t *testing.T) {
+	bm := roaring.NewBitmap(0, 2, 4, 8)
+	results := bm.Flip(9, 10)
+
+	if !reflect.DeepEqual(results.Slice(), []uint64{0, 2, 4, 8, 9, 10}) {
+		t.Fatalf("unexpected %v ", results.Slice())
+	}
+	results = results.Flip(0, 1)
+	if !reflect.DeepEqual(results.Slice(), []uint64{1, 2, 4, 8, 9, 10}) {
+		t.Fatalf("unexpected %v ", results.Slice())
+	}
+	results = results.Flip(4, 8)
+	if !reflect.DeepEqual(results.Slice(), []uint64{1, 2, 5, 6, 7, 9, 10}) {
+		t.Fatalf("unexpected %v ", results.Slice())
+	}
+
+}
+
 // 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)