Adding a unit case to verify rollover

Signed-off-by: Abhinandan Prativadi <abhi@docker.com>

bitseq/sequence_test.go

@@ -608,6 +608,7 @@ func TestSetUnset(t *testing.T) {
 			t.Fatal(err)
 		}
 	}
+
 	if _, err := hnd.SetAny(); err != ErrNoBitAvailable {
 		t.Fatal("Expected error. Got success")
 	}
@@ -908,6 +909,7 @@ func TestAllocateRandomDeallocate(t *testing.T) {
 			t.Fatalf("Unexpected failure on allocation %d: %v\n%s", i, err, hnd)
 		}
 	}
+
 	if hnd.Unselected() != uint64(numBits/2) {
 		t.Fatalf("Expected full sequence. Instead found %d free bits. %s", hnd.unselected, hnd)
 	}
@@ -1133,3 +1135,76 @@ func TestIsCorrupted(t *testing.T) {
 		}
 	}
 }
+
+func TestSetRollover(t *testing.T) {
+	ds, err := randomLocalStore()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	numBlocks := uint32(8)
+	numBits := int(numBlocks * blockLen)
+	hnd, err := NewHandle("bitseq-test/data/", ds, "test1", uint64(numBits))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Allocate first half of the bits
+	for i := 0; i < numBits/2; i++ {
+		_, err := hnd.SetAny()
+		if err != nil {
+			t.Fatalf("Unexpected failure on allocation %d: %v\n%s", i, err, hnd)
+		}
+	}
+
+	if hnd.Unselected() != uint64(numBits/2) {
+		t.Fatalf("Expected full sequence. Instead found %d free bits. %s", hnd.unselected, hnd)
+	}
+
+	seed := time.Now().Unix()
+	rand.Seed(seed)
+
+	// Deallocate half of the allocated bits following a random pattern
+	pattern := rand.Perm(numBits / 2)
+	for i := 0; i < numBits/4; i++ {
+		bit := pattern[i]
+		err := hnd.Unset(uint64(bit))
+		if err != nil {
+			t.Fatalf("Unexpected failure on deallocation of %d: %v.\nSeed: %d.\n%s", bit, err, seed, hnd)
+		}
+	}
+	if hnd.Unselected() != uint64(3*numBits/4) {
+		t.Fatalf("Expected full sequence. Instead found %d free bits.\nSeed: %d.\n%s", hnd.unselected, seed, hnd)
+	}
+
+	//request to allocate for remaining half of the bits
+	for i := 0; i < numBits/2; i++ {
+		_, err := hnd.SetAny()
+		if err != nil {
+			t.Fatalf("Unexpected failure on allocation %d: %v\nSeed: %d\n%s", i, err, seed, hnd)
+		}
+	}
+
+	//At this point all the bits must be allocated except the randomly unallocated bits
+	//which were unallocated in the first half of the bit sequence
+	if hnd.Unselected() != uint64(numBits/4) {
+		t.Fatalf("Unexpected number of unselected bits %d, Expected %d", hnd.Unselected(), numBits/4)
+	}
+
+	for i := 0; i < numBits/4; i++ {
+		_, err := hnd.SetAny()
+		if err != nil {
+			t.Fatalf("Unexpected failure on allocation %d: %v\nSeed: %d\n%s", i, err, seed, hnd)
+		}
+	}
+	//Now requesting to allocate the unallocated random bits (qurter of the number of bits) should
+	//leave no more bits that can be allocated.
+	if hnd.Unselected() != 0 {
+		t.Fatalf("Unexpected number of unselected bits %d, Expected %d", hnd.Unselected(), numBits/4)
+	}
+
+	err = hnd.Destroy()
+	if err != nil {
+		t.Fatal(err)
+	}
+}