j = delta
	}
	if x.before != magic64 || x.after != magic64 {
		t.Fatalf("wrong magic: %#x _ %#x != %#x _ %#x", x.before, x.after, magic64, magic64)
	}
}

func TestSwapUint64(t *testing.T) {
	var x struct {
		before uint64
		i      uint64
		after  uint64
	}
	magic64 := uint64(magic64)
	x.before = magic64
	x.after = magic64
	var j uint64
	for delta := uint64(1); delta+delta > delta; delta += delta {

}

// Plan 9 symbol table entries.
type sym struct {
	value uint64
	typ   byte
	name  []byte
}

const (
	Magic64 = 0x8000 // 64-bit expanded header

	Magic386   = (4*11+0)*11 + 7
	MagicAMD64 = (4*26+0)*26 + 7 + Magic64
	MagicARM   = (4*20+0)*20 + 7

	if len(b) < len(magic64) || string(b[:len(magic64)]) != magic64 {
		return errors.New("hash/fnv: invalid hash state identifier")
	}
	if len(b) != marshaledSize64 {
		return errors.New("hash/fnv: invalid hash state size")
	}
	*s = sum64(byteorder.BeUint64(b[4:]))
	return nil
}

func (s *sum64a) UnmarshalBinary(b []byte) error {
	if len(b) < len(magic64a) || string(b[:len(magic64a)]) != magic64a {

func NewFile(r io.ReaderAt) (*File, error) {
	f := new(File)
	sr := io.NewSectionReader(r, 0, 1<<63-1)

	// Read and decode Mach magic to determine byte order, size.
	// Magic32 and Magic64 differ only in the bottom bit.
	var ident [4]byte
	if _, err := r.ReadAt(ident[0:], 0); err != nil {
		return nil, err
	}
	be := binary.BigEndian.Uint32(ident[0:])
	le := binary.LittleEndian.Uint32(ident[0:])

	if _, err := io.Copy(outf, exef); err != nil {
		return err
	}

	// Locate the portion of the binary containing the load commands.
	cmdOffset := unsafe.Sizeof(exem.FileHeader)
	if is64bit := exem.Magic == macho.Magic64; is64bit {
		// mach_header_64 has one extra uint32.
		cmdOffset += unsafe.Sizeof(exem.Magic)
	}
	if _, err := outf.Seek(int64(cmdOffset), 0); err != nil {
		return err
	}

		// must be converted to little endian first though.
		var buf [4]byte
		binary.BigEndian.PutUint32(buf[:], ff.Magic)
		leMagic := binary.LittleEndian.Uint32(buf[:])
		if leMagic == Magic32 || leMagic == Magic64 {
			return nil, ErrNotFat
		} else {
			return nil, &FormatError{0, "invalid magic number", nil}
		}
	}
	offset := int64(4)

	// Read the number of FatArchHeaders that come after the fat_header.

	SubCpu uint32
	Type   Type
	Ncmd   uint32
	Cmdsz  uint32
	Flags  uint32
}

const (
	fileHeaderSize32 = 7 * 4
	fileHeaderSize64 = 8 * 4
)

const (
	Magic32  uint32 = 0xfeedface
	Magic64  uint32 = 0xfeedfacf
	MagicFat uint32 = 0xcafebabe
)

// A Type is the Mach-O file type, e.g. an object file, executable, or dynamic library.
type Type uint32

const (
	TypeObj    Type = 1
	TypeExec   Type = 2

	f := &File{FileHeader: FileHeader{
		Magic:       ph.Magic,
		Bss:         ph.Bss,
		Entry:       uint64(ph.Entry),
		PtrSize:     4,
		LoadAddress: 0x1000,
		HdrSize:     4 * 8,
	}}

	if ph.Magic&Magic64 != 0 {
		if err := binary.Read(sr, binary.BigEndian, &f.Entry); err != nil {
			return nil, err
		}
		f.PtrSize = 8
		f.LoadAddress = 0x200000
		f.HdrSize += 8
	}

	var sects = []struct {

	machoMagicLittle := binary.LittleEndian.Uint32(header[:])
	machoMagicBig := binary.BigEndian.Uint32(header[:])

	if machoMagicLittle == macho.Magic32 || machoMagicLittle == macho.Magic64 ||
		machoMagicBig == macho.Magic32 || machoMagicBig == macho.Magic64 {
		f, err := b.openMachO(name, start, limit, offset)
		if err != nil {
			return nil, fmt.Errorf("error reading Mach-O file %s: %v", name, err)
		}
		return f, nil
	}

	textsect := exem.Section("__text")
	if textsect == nil {
		return fmt.Errorf("missing __text section")
	}

	cmdOffset := unsafe.Sizeof(exem.FileHeader)
	if is64bit := exem.Magic == macho.Magic64; is64bit {
		// mach_header_64 has one extra uint32.
		cmdOffset += unsafe.Sizeof(exem.Magic)
	}
	dwarfCmdOffset := uint32(cmdOffset) + exem.FileHeader.Cmdsz
	availablePadding := textsect.Offset - dwarfCmdOffset