func ARM64RegisterShift(reg, op, count int16) (int64, error) {
	// the base register of shift operations must be general register.
	if reg > arm64.REG_R31 || reg < arm64.REG_R0 {
		return 0, errors.New("invalid register for shift operation")
	}
	return int64(reg&31)<<16 | int64(op)<<22 | int64(uint16(count)), nil
}

			}, nil},
			testWrite{"", 0, nil},

			testClose{nil},
		},
	}, {
		// The truncated test file was produced using these commands:
		//   dd if=/dev/zero bs=1048576 count=16384 > /tmp/16gig.txt
		//   tar -b 1 -c -f- /tmp/16gig.txt | dd bs=512 count=8 > writer-big.tar
		file: "testdata/writer-big.tar",
		tests: []testFnc{
			testHeader{Header{
				Typeflag: TypeReg,
				Name:     "tmp/16gig.txt",
				Size:     16 << 30,