Golang syscall.Dup函數代碼示例

func main() {
	// I assume that in is 0
	in2, err := syscall.Dup(0)
	if err != nil {
		log.Fatal("dupping 0", err)
	}

	out2, err := syscall.Dup(1)
	if err != nil {
		log.Fatal("dupping 1", err)
	}

	os.Stdin.Close()
	os.Stdout.Close()
	os.Stdout = os.NewFile(uintptr(2), "/dev/stdout")

	/* Connections to the application. */
	cin := os.NewFile(uintptr(in2), "fromapp")
	cout := os.NewFile(uintptr(out2), "toapp")

	modifyEnvironment()

	// Fire up a new devdraw here
	devdraw, err := drawfcall.New()
	if err != nil {
		log.Fatal("making a Conn", err)
	}

	// There is probably a nicer way to do this.
	// TODO(rjkroege): do it the nicer way.
	var app App
	app.o = cout
	app.i = cin

	json := NewJsonRecorder()

	for {
		// read crap from cin
		log.Print("about to read from host")
		inbuffy, err := drawfcall.ReadMsg(cin)
		log.Print("read from host")
		if err != nil {
			devdraw.Close()
			break
		}
		go marshalsxtx(inbuffy, &app, devdraw, json)
	}

	log.Print("waiting on completion")
	json.WaitToComplete()
}

func (k *PosixKernel) Dup(oldFd co.Fd) uint64 {
	if newFd, err := syscall.Dup(int(oldFd)); err != nil {
		return Errno(err)
	} else {
		return uint64(newFd)
	}
}

func (t *FlushErrorTest) Dup() {
	var err error

	// Open the file.
	t.f1, err = os.OpenFile(path.Join(t.Dir, "foo"), os.O_WRONLY, 0)
	AssertEq(nil, err)

	fd1 := t.f1.Fd()

	// Use dup(2) to get another copy.
	fd2, err := syscall.Dup(int(fd1))
	AssertEq(nil, err)

	t.f2 = os.NewFile(uintptr(fd2), t.f1.Name())

	// Close by the first handle. On OS X, where the semantics of file handles
	// are different (cf. https://github.com/osxfuse/osxfuse/issues/199), this
	// does not result in an error.
	err = t.f1.Close()
	t.f1 = nil

	if isDarwin {
		AssertEq(nil, err)
	} else {
		ExpectThat(err, Error(HasSubstr("no such file")))
	}

	// Close by the second handle.
	err = t.f2.Close()
	t.f2 = nil

	ExpectThat(err, Error(HasSubstr("no such file")))
}

func (fd *netFD) file(f *os.File, s string) (*os.File, error) {
	dfd, err := syscall.Dup(int(f.Fd()), -1)
	if err != nil {
		return nil, os.NewSyscallError("dup", err)
	}
	return os.NewFile(uintptr(dfd), s), nil
}

func (sf *StateFile) Lock(create bool) (*Lock, error) {
	sf.lockFdMutex.Lock()
	defer sf.lockFdMutex.Unlock()

	if sf.lockFd != nil {
		return &Lock{sf.lockFd}, nil
	}

	flags := os.O_RDWR
	if create {
		flags |= os.O_CREATE | os.O_EXCL
	}
	file, err := os.OpenFile(sf.Path, flags, 0600)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	fd := int(file.Fd())
	newFd, err := syscall.Dup(fd)
	if err != nil {
		return nil, err
	}
	if syscall.Flock(newFd, syscall.LOCK_EX|syscall.LOCK_NB) != nil {
		syscall.Close(newFd)
		return nil, nil
	}
	sf.lockFd = &newFd
	return &Lock{sf.lockFd}, nil
}

func CaptureStream(file *os.File) (*os.File, func(), error) {
	pipeR, pipeW, err := os.Pipe()
	if err != nil {
		return nil, nil, err
	}

	bkupFD, err := syscall.Dup(int(file.Fd()))
	if err != nil {
		pipeW.Close()
		pipeR.Close()
		return nil, nil, err
	}

	err = syscall.Dup2(int(pipeW.Fd()), int(file.Fd()))
	if err != nil {
		syscall.Close(bkupFD)
		pipeW.Close()
		pipeR.Close()
	}

	cleanFunc := func() {
		syscall.Dup2(bkupFD, int(file.Fd()))
		syscall.Close(bkupFD)
		pipeW.Close()
		pipeR.Close()
	}

	return pipeR, cleanFunc, nil
}

func mount(mountPoint string, opts *MountOptions, ready chan<- error) (fd int, err error) {
	f, err := openFUSEDevice()
	if err != nil {
		return 0, err
	}

	cmd := exec.Command(bin, "-o", strings.Join(opts.optionsStrings(), ","), "-o", fmt.Sprintf("iosize=%d", opts.MaxWrite), "3", mountPoint)
	cmd.ExtraFiles = []*os.File{f}
	cmd.Env = append(os.Environ(), "MOUNT_FUSEFS_CALL_BY_LIB=", "MOUNT_OSXFUSE_CALL_BY_LIB=",
		"MOUNT_OSXFUSE_DAEMON_PATH="+os.Args[0],
		"MOUNT_FUSEFS_DAEMON_PATH="+os.Args[0])

	var out, errOut bytes.Buffer
	cmd.Stdout = &out
	cmd.Stderr = &errOut

	if err := cmd.Start(); err != nil {
		f.Close()
		return 0, err
	}
	go func() {
		err := cmd.Wait()
		if err != nil {
			err = fmt.Errorf("mount_osxfusefs failed: %v. Stderr: %s, Stdout: %s", err, errOut.String(), out.String())
		}

		ready <- err
		close(ready)
	}()

	// The finalizer for f will close its fd so we return a dup.
	defer f.Close()
	return syscall.Dup(int(f.Fd()))
}

func TestSendErrorFromChild(t *testing.T) {
	pipe, err := NewSyncPipe()
	if err != nil {
		t.Fatal(err)
	}
	defer func() {
		if err := pipe.Close(); err != nil {
			t.Fatal(err)
		}
	}()

	childfd, err := syscall.Dup(int(pipe.Child().Fd()))
	if err != nil {
		t.Fatal(err)
	}
	childPipe, _ := NewSyncPipeFromFd(0, uintptr(childfd))

	pipe.CloseChild()
	pipe.SendToChild(nil)

	expected := "something bad happened"
	childPipe.ReportChildError(fmt.Errorf(expected))

	childError := pipe.ReadFromChild()
	if childError == nil {
		t.Fatal("expected an error to be returned but did not receive anything")
	}

	if childError.Error() != expected {
		t.Fatalf("expected %q but received error message %q", expected, childError.Error())
	}
}

// NewBufferFile maps a file to shared memory and returns a handle to the shared memory buffer
func NewBufferFile(file *os.File, size, prot int) (Buffer, error) {
	fi, err := file.Stat()
	if err != nil {
		return nil, err
	}
	sys := fi.Sys().(*syscall.Stat_t)
	if sys.Size != int64(size) {
		return nil, errWrongSize
	}

	// Dup to allow file parameter to be closed regardless
	fd, err := syscall.Dup(int(file.Fd()))
	if err != nil {
		return nil, err
	}
	const flags = syscall.MAP_SHARED
	b, err := syscall.Mmap(fd, 0, size, prot, flags)
	if err != nil {
		return nil, err
	}

	// localFile is nil because fd is from somewhere else
	buf := &sharedBuffer{os.NewFile(uintptr(fd), ""), nil, b, stackToKeep()}
	runtime.SetFinalizer(buf, (*sharedBuffer).finalize)

	return buf, nil
}

// Get topology data using blkid APIs. In case of an error getting any of the
// topology properties the field will be set to 0
func getBlockDeviceTopology(file File) (DeviceTopology, error) {
	var res DeviceTopology

	probe := C.blkid_new_probe()
	if probe == nil {
		return res, fmt.Errorf("Could not probe device")
	}
	C.blkid_reset_probe(probe)

	fd, err := syscall.Dup(int(file.Fd()))
	if err != nil {
		return res, fmt.Errorf("Could not dup FD as part of device probing: %s", err)
	}

	rv := C.blkid_probe_set_device(probe, C.int(fd), 0, 0)
	if rv != 0 {
		syscall.Close(fd)
	}

	defer C.blkid_free_probe(probe)

	topology := C.blkid_probe_get_topology(probe)
	if topology == nil {
		return res, fmt.Errorf("Could not get topology for device")
	}

	res.AlignmentOffset = uint64(C.blkid_topology_get_alignment_offset(topology))
	res.MinimumIOSize = uint64(C.blkid_topology_get_minimum_io_size(topology))
	res.OptimalIOSize = uint64(C.blkid_topology_get_optimal_io_size(topology))
	res.LogicalSectorSize = uint64(C.blkid_topology_get_logical_sector_size(topology))
	res.PhysicalSectorSize = uint64(C.blkid_topology_get_physical_sector_size(topology))
	return res, nil
}

func dup(file *os.File, name string) (newfile *os.File, err error) {
	fd, err := syscall.Dup(int(file.Fd()))
	if err != nil {
		return nil, err
	}

	return os.NewFile(uintptr(fd), "<stdin>"), nil
}

// DupFd returns the integer Unix file descriptor duplicated from Listener.
// This method can't invoke simultaneously.
func (l *Listener) DupFd() (int, error) {
	f, err := l.fileListener.File()
	if err != nil {
		return 0, err
	}

	return syscall.Dup(int(f.Fd()))
}

func newFileFD(f *os.File) (*netFD, error) {
	syscall.ForkLock.RLock()
	fd, err := syscall.Dup(int(f.Fd()))
	if err != nil {
		syscall.ForkLock.RUnlock()
		return nil, os.NewSyscallError("dup", err)
	}
	syscall.CloseOnExec(fd)
	syscall.ForkLock.RUnlock()

	sotype, err := syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_TYPE)
	if err != nil {
		closesocket(fd)
		return nil, os.NewSyscallError("getsockopt", err)
	}

	family := syscall.AF_UNSPEC
	toAddr := sockaddrToTCP
	sa, _ := syscall.Getsockname(fd)
	switch sa.(type) {
	default:
		closesocket(fd)
		return nil, syscall.EINVAL
	case *syscall.SockaddrInet4:
		family = syscall.AF_INET
		if sotype == syscall.SOCK_DGRAM {
			toAddr = sockaddrToUDP
		} else if sotype == syscall.SOCK_RAW {
			toAddr = sockaddrToIP
		}
	case *syscall.SockaddrInet6:
		family = syscall.AF_INET6
		if sotype == syscall.SOCK_DGRAM {
			toAddr = sockaddrToUDP
		} else if sotype == syscall.SOCK_RAW {
			toAddr = sockaddrToIP
		}
	case *syscall.SockaddrUnix:
		family = syscall.AF_UNIX
		toAddr = sockaddrToUnix
		if sotype == syscall.SOCK_DGRAM {
			toAddr = sockaddrToUnixgram
		} else if sotype == syscall.SOCK_SEQPACKET {
			toAddr = sockaddrToUnixpacket
		}
	}
	laddr := toAddr(sa)
	sa, _ = syscall.Getpeername(fd)
	raddr := toAddr(sa)

	netfd, err := newFD(fd, family, sotype, laddr.Network())
	if err != nil {
		closesocket(fd)
		return nil, err
	}
	netfd.setAddr(laddr, raddr)
	return netfd, nil
}

func (fd *netFD) file(f *os.File, s string) (*os.File, error) {
	syscall.ForkLock.RLock()
	dfd, err := syscall.Dup(int(f.Fd()), -1)
	syscall.ForkLock.RUnlock()
	if err != nil {
		return nil, &OpError{"dup", s, fd.laddr, err}
	}
	return os.NewFile(uintptr(dfd), s), nil
}

func newFileFD(f *os.File) (net *netFD, err error) {
	var ctl *os.File
	close := func(fd int) {
		if err != nil {
			syscall.Close(fd)
		}
	}

	path, err := syscall.Fd2path(int(f.Fd()))
	if err != nil {
		return nil, os.NewSyscallError("fd2path", err)
	}
	comp := splitAtBytes(path, "/")
	n := len(comp)
	if n < 3 || comp[0] != "net" {
		return nil, syscall.EPLAN9
	}

	name := comp[2]
	switch file := comp[n-1]; file {
	case "ctl", "clone":
		syscall.ForkLock.RLock()
		fd, err := syscall.Dup(int(f.Fd()), -1)
		syscall.ForkLock.RUnlock()
		if err != nil {
			return nil, os.NewSyscallError("dup", err)
		}
		defer close(fd)

		dir := "/net/" + comp[n-2]
		ctl = os.NewFile(uintptr(fd), dir+"/"+file)
		ctl.Seek(0, 0)
		var buf [16]byte
		n, err := ctl.Read(buf[:])
		if err != nil {
			return nil, err
		}
		name = string(buf[:n])
	default:
		if len(comp) < 4 {
			return nil, errors.New("could not find control file for connection")
		}
		dir := "/net/" + comp[1] + "/" + name
		ctl, err = os.OpenFile(dir+"/ctl", os.O_RDWR, 0)
		if err != nil {
			return nil, err
		}
		defer close(int(ctl.Fd()))
	}
	dir := "/net/" + comp[1] + "/" + name
	laddr, err := readPlan9Addr(comp[1], dir+"/local")
	if err != nil {
		return nil, err
	}
	return newFD(comp[1], name, ctl, nil, laddr, nil), nil
}