flatten    bool
		oSizes     sizeHistogram
	}{
		{
			path:    "/",
			size:    1322310,
			flatten: true,
			objs:    8,
			oSizes:  sizeHistogram{0: 2, 1: 3, 2: 2, 4: 1},
		},
		{
			path:   "/",
			size:   20000,
			objs:   2,
			oSizes: sizeHistogram{1: 2},
		},
		{
			path:   "/dir1",
			size:   1302010,
			objs:   5,
			oSizes: sizeHistogram{0: 1, 1: 1, 2: 2, 4: 1},
		},
		{

}

func TestMigrateSizeHistogramFromV1(t *testing.T) {
	tests := []struct {
		v    sizeHistogramV1
		want sizeHistogram
	}{
		{
			v:    sizeHistogramV1{0: 10, 1: 20, 2: 3},
			want: sizeHistogram{0: 10, 5: 20, 6: 3},
		},
		{
			v:    sizeHistogramV1{0: 10, 1: 20, 2: 3, 3: 4, 4: 5, 5: 6, 6: 7},
			want: sizeHistogram{0: 10, 5: 20, 6: 3, 7: 4, 8: 5, 9: 6, 10: 7},
		},
	}
	for i, test := range tests {

type dataUsageHash string

// sizeHistogramV1 is size histogram V1, which has fewer intervals esp. between
// 1024B and 1MiB.
type sizeHistogramV1 [dataUsageBucketLenV1]uint64

// sizeHistogram is a size histogram.
type sizeHistogram [dataUsageBucketLen]uint64

// versionsHistogram is a histogram of number of versions in an object.
type versionsHistogram [dataUsageVersionLen]uint64

type dataUsageEntry struct {

	}
}

func BenchmarkMarshalMsgsizeHistogram(b *testing.B) {
	v := sizeHistogram{}
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		v.MarshalMsg(nil)
	}
}

func BenchmarkAppendMsgsizeHistogram(b *testing.B) {
	v := sizeHistogram{}
	bts := make([]byte, 0, v.Msgsize())
	bts, _ = v.MarshalMsg(bts[0:0])
	b.SetBytes(int64(len(bts)))

}

// MarshalMsg implements msgp.Marshaler
func (z *sizeHistogram) MarshalMsg(b []byte) (o []byte, err error) {
	o = msgp.Require(b, z.Msgsize())
	o = msgp.AppendArrayHeader(o, uint32(dataUsageBucketLen))
	for za0001 := range z {
		o = msgp.AppendUint64(o, z[za0001])
	}
	return
}

// UnmarshalMsg implements msgp.Unmarshaler
func (z *sizeHistogram) UnmarshalMsg(bts []byte) (o []byte, err error) {