>>> Flow 2 (server to client)
00000000  16 03 01 00 5d 02 00 00  59 03 01 6f 48 26 41 da  |....]...Y..oH&A.|
00000010  73 82 d1 cf 84 ad 06 e9  76 39 dc e4 c8 34 af 53  |s.......v9...4.S|
00000020  06 ed ed 68 56 5f 76 11  4e f6 ff 20 55 fd 29 c5  |...hV_v.N.. U.).|
00000030  aa 56 af bd 5d 67 74 4f  08 8a 52 a1 7e cd b9 ac  |.V..]gtO..R.~...|
00000040  31 a0 2f 45 25 1f b2 24  71 26 80 17 c0 09 00 00  |1./E%..$q&......|

	SYSCALL	$SYS_open
	BVC	2(PC)
	MOVW	$-1, R3
	MOVW	R3, ret+16(FP)
	RET

TEXT runtime·closefd(SB),NOSPLIT|NOFRAME,$0-12
	MOVW	fd+0(FP), R3
	SYSCALL	$SYS_close
	BVC	2(PC)
	MOVW	$-1, R3
	MOVW	R3, ret+8(FP)
	RET

TEXT runtime·write1(SB),NOSPLIT|NOFRAME,$0-28
	MOVD	fd+0(FP), R3
	MOVD	p+8(FP), R4
	MOVW	n+16(FP), R5
	SYSCALL	$SYS_write
	BVC	2(PC)
	NEG	R3	// caller expects negative errno
	MOVW	R3, ret+24(FP)

		// atomic sequences (e.g., write barrier) and nosplit
		// functions (except at calls).
		return false, 0
	}
	if fd := funcdata(f, abi.FUNCDATA_LocalsPointerMaps); fd == nil || f.flag&abi.FuncFlagAsm != 0 {
		// This is assembly code. Don't assume it's well-formed.
		// TODO: Empirically we still need the fd == nil check. Why?
		//
		// TODO: Are there cases that are safe but don't have a

//
//go:nosplit
func write1(fd uintptr, buf unsafe.Pointer, n int32) int32 {
	const (
		_STD_OUTPUT_HANDLE = ^uintptr(10) // -11
		_STD_ERROR_HANDLE  = ^uintptr(11) // -12
	)
	var handle uintptr
	switch fd {
	case 1:
		handle = stdcall1(_GetStdHandle, _STD_OUTPUT_HANDLE)
	case 2:
		handle = stdcall1(_GetStdHandle, _STD_ERROR_HANDLE)
	default:
		// assume fd is real windows handle.
		handle = fd
	}

while(<>) {
	chomp;
	s/\s+/ /g;
	s/^\s+//;
	s/\s+$//;
	my $nonblock = /^\/\/sysnb /;
	next if !/^\/\/sys / && !$nonblock;

	# Line must be of the form
	#	func Open(path string, mode int, perm int) (fd int, errno error)
	# Split into name, in params, out params.
	if(!/^\/\/sys(nb)? (\w+)\(([^()]*)\)\s*(?:\(([^()]+)\))?\s*(?:=\s*((?i)_?SYS_[A-Z0-9_]+))?$/) {
		print STDERR "$ARGV:$.: malformed //sys declaration\n";

				if err != nil {
					return written, err
				}
				nw = int64(n)
			}

			// Disable O_DIRECT on fd's on unaligned buffer
			// perform an amortized Fdatasync(fd) on the fd at
			// the end, this is performed by the caller before
			// closing 'w'.
			if err = disk.DisableDirectIO(file); err != nil {
				return written, err
			}

	// but in line with the uploader, log to a file in debug
	// only if that directory was created by the user.
	fd, err := os.Stat(telemetry.Default.DebugDir())
	if err != nil {
		if !os.IsNotExist(err) {
			log.Fatalf("failed to stat debug directory: %v", err)
		}
	} else if fd.IsDir() {
		// local/debug exists and is a directory. Set stderr to a log file path
		// in local/debug.

00000280  cd f4 05 84 db 8b 0b 22  e3 50 1b e7 6d 02 42 01  |.......".P..m.B.|
00000290  fd 1e bc 64 8b 01 3f a0  f8 8b 41 be 4d 97 07 6c  |...d..?...A.M..l|
000002a0  3b 09 74 d6 00 76 b3 a0  c0 d0 92 d0 78 24 d7 b2  |;.t..v......x$..|
000002b0  1f c0 86 90 59 3a fb a8  e1 f6 80 23 db f7 90 93  |....Y:.....#....|
000002c0  95 fd 37 14 8c 34 f3 07  10 f8 dd e3 66 28 1c b2  |..7..4......f(..|

// back from uintptr to pointer.
//
// If a pointer argument must be converted to uintptr for use as an argument,
// that conversion must appear in the call expression itself:
//
//	syscall.Syscall(SYS_READ, uintptr(fd), uintptr(unsafe.Pointer(p)), uintptr(n))
//
// The compiler handles a Pointer converted to a uintptr in the argument list of
// a call to a function implemented in assembly by arranging that the referenced

	if err != nil {
		return err
	}

	linkp := syscall.StringToUTF16(link)
	fd, err := syscall.CreateFile(&linkp[0], syscall.GENERIC_WRITE, 0, nil, syscall.OPEN_EXISTING,
		syscall.FILE_FLAG_OPEN_REPARSE_POINT|syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
	if err != nil {
		return err
	}
	defer syscall.CloseHandle(fd)

	buflen := uint32(rdb.header.ReparseDataLength) + uint32(unsafe.Sizeof(rdb.header))