From 02cba542e8cebdde0de2850b822cdfd01b2d9858 Mon Sep 17 00:00:00 2001
From: Todd Gruben <tgruben@umbel.com>
Date: Fri, 16 Jun 2017 16:27:54 -0500
Subject: [PATCH] bug in CountRange

---
 roaring/roaring.go      |  2 +-
 roaring/roaring_test.go | 43 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/roaring/roaring.go b/roaring/roaring.go
index 80ac665f5..7aeab1e3f 100644
--- a/roaring/roaring.go
+++ b/roaring/roaring.go
@@ -196,7 +196,7 @@ func (b *Bitmap) CountRange(start, end uint64) (n uint64) {
 	j := search64(b.keys, highbits(end))
 
 	// If range is entirely in one container then just count that range.
-	if i > 0 && i == j {
+	if i >= 0 && i == j {
 		return uint64(b.containers[i].countRange(lowbits(start), lowbits(end)))
 	}
 
diff --git a/roaring/roaring_test.go b/roaring/roaring_test.go
index 580829450..9ab63c748 100644
--- a/roaring/roaring_test.go
+++ b/roaring/roaring_test.go
@@ -127,6 +127,29 @@ func TestBitmap_Max(t *testing.T) {
 		}
 	}
 }
+func TestBitmap_CountRange(t *testing.T) {
+	bm0 := roaring.NewBitmap(0, 2683177)
+	for i := uint64(628); i < 2683301; i++ {
+		bm0.Add(i)
+	}
+	bm0.Add(2683307)
+	if n := bm0.CountRange(1, 2683311); n != 2682674 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+
+	if n := bm0.CountRange(2683177, 2683310); n != 125 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+
+	if n := bm0.CountRange(2683301, 3000000); n != 1 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+
+	if n := bm0.CountRange(0, 1); n != 1 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+
+}
 
 func TestBitmap_Intersection(t *testing.T) {
 	bm0 := roaring.NewBitmap(0, 2683177)
@@ -140,6 +163,16 @@ func TestBitmap_Intersection(t *testing.T) {
 		t.Fatalf("unexpected n: %d", n)
 	}
 
+}
+func TestBitmap_Intersection_Empty(t *testing.T) {
+	bm0 := roaring.NewBitmap(0, 2683177)
+	bm1 := roaring.NewBitmap()
+
+	result := bm0.Intersect(bm1)
+	if n := result.Count(); n != 0 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+
 }
 
 func TestBitmap_Difference(t *testing.T) {
@@ -149,11 +182,18 @@ func TestBitmap_Difference(t *testing.T) {
 		bm1.Add(i)
 	}
 	result := bm0.Difference(bm1)
-	//expect to have just 0
 	if n := result.Count(); n != 1 {
 		t.Fatalf("unexpected n: %d", n)
 	}
 }
+func TestBitmap_Difference_Empty(t *testing.T) {
+	bm0 := roaring.NewBitmap(0, 2683177)
+	bm1 := roaring.NewBitmap()
+	result := bm0.Difference(bm1)
+	if n := result.Count(); n != 2 {
+		t.Fatalf("unexpected n: %d", n)
+	}
+}
 
 func TestBitmap_Union(t *testing.T) {
 	bm0 := roaring.NewBitmap(0, 1000001, 1000002, 1000003)
@@ -417,7 +457,6 @@ func testBitmapQuick(t *testing.T, n int, min, max uint64) {
 	})
 }
 
-
 func TestBitmap_Marshal_Quick_Array1(t *testing.T)  { testBitmapMarshalQuick(t, 1000, 1000, 2000, false) }
 func TestBitmap_Marshal_Quick_Array2(t *testing.T)  { testBitmapMarshalQuick(t, 10000, 0, 1000, false) }
 func TestBitmap_Marshal_Quick_Bitmap1(t *testing.T) { testBitmapMarshalQuick(t, 10000, 0, 10000, false) }