if err == nil && p >= 0 {
			directoryEndOffset = p
			err = readDirectory64End(r, p, d)
		}
		if err != nil {
			return nil, 0, err
		}
	}

	maxInt64 := uint64(1<<63 - 1)
	if d.directorySize > maxInt64 || d.directoryOffset > maxInt64 {
		return nil, 0, ErrFormat
	}

	baseOffset = directoryEndOffset - int64(d.directorySize) - int64(d.directoryOffset)

		wantSize  int64
		wantName  string
		wantErr   error
	}{{
		inputHdrs: nil,
		wantErr:   nil,
	}, {
		inputHdrs: map[string]string{
			paxGNUSparseNumBlocks: strconv.FormatInt(math.MaxInt64, 10),
			paxGNUSparseMap:       "0,1,2,3",
		},
		wantErr: ErrHeader,
	}, {
		inputHdrs: map[string]string{
			paxGNUSparseNumBlocks: "4\x00",
			paxGNUSparseMap:       "0,1,2,3",
		},

		return false
	}
	var pre sparseEntry
	for _, cur := range sp {
		switch {
		case cur.Offset < 0 || cur.Length < 0:
			return false // Negative values are never okay
		case cur.Offset > math.MaxInt64-cur.Length:
			return false // Integer overflow with large length
		case cur.endOffset() > size:
			return false // Region extends beyond the actual size
		case pre.endOffset() > cur.Offset:

		}
		if _, err := io.Copy(io.Discard, r); err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
	}
}

func TestBaseOffsetPlusOverflow(t *testing.T) {
	// directoryOffset > maxInt64 && size-directoryOffset < 0
	data := []byte{
		0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
		0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,
		0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20,

pkg math, const Log2E ideal-float
pkg math, const MaxFloat32 ideal-float
pkg math, const MaxFloat64 ideal-float
pkg math, const MaxInt16 ideal-int
pkg math, const MaxInt32 ideal-int
pkg math, const MaxInt64 ideal-int
pkg math, const MaxInt8 ideal-int
pkg math, const MaxUint16 ideal-int
pkg math, const MaxUint32 ideal-int
pkg math, const MaxUint64 ideal-int
pkg math, const MaxUint8 ideal-int

pkg math, const MaxInt16 = 32767
pkg math, const MaxInt32 = 2147483647
pkg math, const MaxInt64 = 9223372036854775807
pkg math, const MaxInt8 = 127
pkg math, const MaxUint16 = 65535
pkg math, const MaxUint32 = 4294967295
pkg math, const MaxUint64 = 18446744073709551615
pkg math, const MaxUint8 = 255