Source file src/internal/poll/fd_windows.go

Documentation: internal/poll

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package poll
     6  
     7  import (
     8  	"errors"
     9  	"internal/race"
    10  	"internal/syscall/windows"
    11  	"io"
    12  	"sync"
    13  	"sync/atomic"
    14  	"syscall"
    15  	"unicode/utf16"
    16  	"unicode/utf8"
    17  	"unsafe"
    18  )
    19  
    20  var (
    21  	initErr error
    22  	ioSync  uint64
    23  )
    24  
    25  // This package uses the SetFileCompletionNotificationModes Windows
    26  // API to skip calling GetQueuedCompletionStatus if an IO operation
    27  // completes synchronously. There is a known bug where
    28  // SetFileCompletionNotificationModes crashes on some systems (see
    29  // https://support.microsoft.com/kb/2568167 for details).
    30  
    31  var socketCanUseSetFileCompletionNotificationModes bool // determines is SetFileCompletionNotificationModes is present and sockets can safely use it
    32  
    33  // checkSetFileCompletionNotificationModes verifies that
    34  // SetFileCompletionNotificationModes Windows API is present
    35  // on the system and is safe to use.
    36  // See https://support.microsoft.com/kb/2568167 for details.
    37  func checkSetFileCompletionNotificationModes() {
    38  	err := syscall.LoadSetFileCompletionNotificationModes()
    39  	if err != nil {
    40  		return
    41  	}
    42  	protos := [2]int32{syscall.IPPROTO_TCP, 0}
    43  	var buf [32]syscall.WSAProtocolInfo
    44  	len := uint32(unsafe.Sizeof(buf))
    45  	n, err := syscall.WSAEnumProtocols(&protos[0], &buf[0], &len)
    46  	if err != nil {
    47  		return
    48  	}
    49  	for i := int32(0); i < n; i++ {
    50  		if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
    51  			return
    52  		}
    53  	}
    54  	socketCanUseSetFileCompletionNotificationModes = true
    55  }
    56  
    57  // InitWSA initiates the use of the Winsock DLL by the current process.
    58  // It is called from the net package at init time to avoid
    59  // loading ws2_32.dll when net is not used.
    60  var InitWSA = sync.OnceFunc(func() {
    61  	var d syscall.WSAData
    62  	e := syscall.WSAStartup(uint32(0x202), &d)
    63  	if e != nil {
    64  		initErr = e
    65  	}
    66  	checkSetFileCompletionNotificationModes()
    67  })
    68  
    69  // operation contains superset of data necessary to perform all async IO.
    70  type operation struct {
    71  	// Used by IOCP interface, it must be first field
    72  	// of the struct, as our code relies on it.
    73  	o syscall.Overlapped
    74  
    75  	// fields used by runtime.netpoll
    76  	runtimeCtx uintptr
    77  	mode       int32
    78  
    79  	// fields used only by net package
    80  	fd     *FD
    81  	buf    syscall.WSABuf
    82  	msg    windows.WSAMsg
    83  	sa     syscall.Sockaddr
    84  	rsa    *syscall.RawSockaddrAny
    85  	rsan   int32
    86  	handle syscall.Handle
    87  	flags  uint32
    88  	qty    uint32
    89  	bufs   []syscall.WSABuf
    90  }
    91  
    92  func (o *operation) setEvent() {
    93  	h, err := windows.CreateEvent(nil, 0, 0, nil)
    94  	if err != nil {
    95  		// This shouldn't happen when all CreateEvent arguments are zero.
    96  		panic(err)
    97  	}
    98  	// Set the low bit so that the external IOCP doesn't receive the completion packet.
    99  	o.o.HEvent = h | 1
   100  }
   101  
   102  func (o *operation) close() {
   103  	if o.o.HEvent != 0 {
   104  		syscall.CloseHandle(o.o.HEvent)
   105  	}
   106  }
   107  
   108  func (o *operation) overlapped() *syscall.Overlapped {
   109  	if o.fd.isBlocking {
   110  		// Don't return the overlapped object if the file handle
   111  		// doesn't use overlapped I/O. It could be used, but
   112  		// that would then use the file pointer stored in the
   113  		// overlapped object rather than the real file pointer.
   114  		return nil
   115  	}
   116  	return &o.o
   117  }
   118  
   119  func (o *operation) InitBuf(buf []byte) {
   120  	o.buf.Len = uint32(len(buf))
   121  	o.buf.Buf = nil
   122  	if len(buf) != 0 {
   123  		o.buf.Buf = &buf[0]
   124  	}
   125  }
   126  
   127  func (o *operation) InitBufs(buf *[][]byte) {
   128  	if o.bufs == nil {
   129  		o.bufs = make([]syscall.WSABuf, 0, len(*buf))
   130  	} else {
   131  		o.bufs = o.bufs[:0]
   132  	}
   133  	for _, b := range *buf {
   134  		if len(b) == 0 {
   135  			o.bufs = append(o.bufs, syscall.WSABuf{})
   136  			continue
   137  		}
   138  		for len(b) > maxRW {
   139  			o.bufs = append(o.bufs, syscall.WSABuf{Len: maxRW, Buf: &b[0]})
   140  			b = b[maxRW:]
   141  		}
   142  		if len(b) > 0 {
   143  			o.bufs = append(o.bufs, syscall.WSABuf{Len: uint32(len(b)), Buf: &b[0]})
   144  		}
   145  	}
   146  }
   147  
   148  // ClearBufs clears all pointers to Buffers parameter captured
   149  // by InitBufs, so it can be released by garbage collector.
   150  func (o *operation) ClearBufs() {
   151  	for i := range o.bufs {
   152  		o.bufs[i].Buf = nil
   153  	}
   154  	o.bufs = o.bufs[:0]
   155  }
   156  
   157  func (o *operation) InitMsg(p []byte, oob []byte) {
   158  	o.InitBuf(p)
   159  	o.msg.Buffers = &o.buf
   160  	o.msg.BufferCount = 1
   161  
   162  	o.msg.Name = nil
   163  	o.msg.Namelen = 0
   164  
   165  	o.msg.Flags = 0
   166  	o.msg.Control.Len = uint32(len(oob))
   167  	o.msg.Control.Buf = nil
   168  	if len(oob) != 0 {
   169  		o.msg.Control.Buf = &oob[0]
   170  	}
   171  }
   172  
   173  // waitIO waits for the IO operation o to complete.
   174  func waitIO(o *operation) error {
   175  	if o.fd.isBlocking {
   176  		panic("can't wait on blocking operations")
   177  	}
   178  	fd := o.fd
   179  	if !fd.pollable() {
   180  		// The overlapped handle is not added to the runtime poller,
   181  		// the only way to wait for the IO to complete is block until
   182  		// the overlapped event is signaled.
   183  		_, err := syscall.WaitForSingleObject(o.o.HEvent, syscall.INFINITE)
   184  		return err
   185  	}
   186  	// Wait for our request to complete.
   187  	err := fd.pd.wait(int(o.mode), fd.isFile)
   188  	switch err {
   189  	case nil, ErrNetClosing, ErrFileClosing, ErrDeadlineExceeded:
   190  		// No other error is expected.
   191  	default:
   192  		panic("unexpected runtime.netpoll error: " + err.Error())
   193  	}
   194  	return err
   195  }
   196  
   197  // cancelIO cancels the IO operation o and waits for it to complete.
   198  func cancelIO(o *operation) {
   199  	fd := o.fd
   200  	if !fd.pollable() {
   201  		return
   202  	}
   203  	// Cancel our request.
   204  	err := syscall.CancelIoEx(fd.Sysfd, &o.o)
   205  	// Assuming ERROR_NOT_FOUND is returned, if IO is completed.
   206  	if err != nil && err != syscall.ERROR_NOT_FOUND {
   207  		// TODO(brainman): maybe do something else, but panic.
   208  		panic(err)
   209  	}
   210  	fd.pd.waitCanceled(int(o.mode))
   211  }
   212  
   213  // execIO executes a single IO operation o.
   214  // It supports both synchronous and asynchronous IO.
   215  // o.qty and o.flags are set to zero before calling submit
   216  // to avoid reusing the values from a previous call.
   217  func execIO(o *operation, submit func(o *operation) error) (int, error) {
   218  	fd := o.fd
   219  	// Notify runtime netpoll about starting IO.
   220  	err := fd.pd.prepare(int(o.mode), fd.isFile)
   221  	if err != nil {
   222  		return 0, err
   223  	}
   224  	// Start IO.
   225  	if !fd.isBlocking && o.o.HEvent == 0 && !fd.pollable() {
   226  		// If the handle is opened for overlapped IO but we can't
   227  		// use the runtime poller, then we need to use an
   228  		// event to wait for the IO to complete.
   229  		o.setEvent()
   230  	}
   231  	o.qty = 0
   232  	o.flags = 0
   233  	err = submit(o)
   234  	var waitErr error
   235  	// Blocking operations shouldn't return ERROR_IO_PENDING.
   236  	// Continue without waiting if that happens.
   237  	if !o.fd.isBlocking && (err == syscall.ERROR_IO_PENDING || (err == nil && !o.fd.skipSyncNotif)) {
   238  		// IO started asynchronously or completed synchronously but
   239  		// a sync notification is required. Wait for it to complete.
   240  		waitErr = waitIO(o)
   241  		if waitErr != nil {
   242  			// IO interrupted by "close" or "timeout".
   243  			cancelIO(o)
   244  			// We issued a cancellation request, but the IO operation may still succeeded
   245  			// before the cancellation request runs.
   246  		}
   247  		if fd.isFile {
   248  			err = windows.GetOverlappedResult(fd.Sysfd, &o.o, &o.qty, false)
   249  		} else {
   250  			err = windows.WSAGetOverlappedResult(fd.Sysfd, &o.o, &o.qty, false, &o.flags)
   251  		}
   252  	}
   253  	switch err {
   254  	case syscall.ERROR_OPERATION_ABORTED:
   255  		// ERROR_OPERATION_ABORTED may have been caused by us. In that case,
   256  		// map it to our own error. Don't do more than that, each submitted
   257  		// function may have its own meaning for each error.
   258  		if waitErr != nil {
   259  			// IO canceled by the poller while waiting for completion.
   260  			err = waitErr
   261  		} else if fd.kind == kindPipe && fd.closing() {
   262  			// Close uses CancelIoEx to interrupt concurrent I/O for pipes.
   263  			// If the fd is a pipe and the Write was interrupted by CancelIoEx,
   264  			// we assume it is interrupted by Close.
   265  			err = errClosing(fd.isFile)
   266  		}
   267  	case windows.ERROR_IO_INCOMPLETE:
   268  		// waitIO couldn't wait for the IO to complete.
   269  		if waitErr != nil {
   270  			// The wait error will be more informative.
   271  			err = waitErr
   272  		}
   273  	}
   274  	return int(o.qty), err
   275  }
   276  
   277  // FD is a file descriptor. The net and os packages embed this type in
   278  // a larger type representing a network connection or OS file.
   279  type FD struct {
   280  	// Lock sysfd and serialize access to Read and Write methods.
   281  	fdmu fdMutex
   282  
   283  	// System file descriptor. Immutable until Close.
   284  	Sysfd syscall.Handle
   285  
   286  	// Read operation.
   287  	rop operation
   288  	// Write operation.
   289  	wop operation
   290  
   291  	// I/O poller.
   292  	pd pollDesc
   293  
   294  	// Used to implement pread/pwrite.
   295  	l sync.Mutex
   296  
   297  	// The file offset for the next read or write.
   298  	// Overlapped IO operations don't use the real file pointer,
   299  	// so we need to keep track of the offset ourselves.
   300  	offset int64
   301  
   302  	// For console I/O.
   303  	lastbits       []byte   // first few bytes of the last incomplete rune in last write
   304  	readuint16     []uint16 // buffer to hold uint16s obtained with ReadConsole
   305  	readbyte       []byte   // buffer to hold decoding of readuint16 from utf16 to utf8
   306  	readbyteOffset int      // readbyte[readOffset:] is yet to be consumed with file.Read
   307  
   308  	// Semaphore signaled when file is closed.
   309  	csema uint32
   310  
   311  	skipSyncNotif bool
   312  
   313  	// Whether this is a streaming descriptor, as opposed to a
   314  	// packet-based descriptor like a UDP socket.
   315  	IsStream bool
   316  
   317  	// Whether a zero byte read indicates EOF. This is false for a
   318  	// message based socket connection.
   319  	ZeroReadIsEOF bool
   320  
   321  	// Whether the handle is owned by os.File.
   322  	isFile bool
   323  
   324  	// The kind of this file.
   325  	kind fileKind
   326  
   327  	// Whether FILE_FLAG_OVERLAPPED was not set when opening the file.
   328  	isBlocking bool
   329  
   330  	disassociated atomic.Bool
   331  }
   332  
   333  // setOffset sets the offset fields of the overlapped object
   334  // to the given offset. The fd.l lock must be held.
   335  //
   336  // Overlapped IO operations don't update the offset fields
   337  // of the overlapped object nor the file pointer automatically,
   338  // so we do that manually here.
   339  // Note that this is a best effort that only works if the file
   340  // pointer is completely owned by this operation. We could
   341  // call seek to allow other processes or other operations on the
   342  // same file to see the updated offset. That would be inefficient
   343  // and won't work for concurrent operations anyway. If concurrent
   344  // operations are needed, then the caller should serialize them
   345  // using an external mechanism.
   346  func (fd *FD) setOffset(off int64) {
   347  	fd.offset = off
   348  	fd.rop.o.OffsetHigh, fd.rop.o.Offset = uint32(off>>32), uint32(off)
   349  	fd.wop.o.OffsetHigh, fd.wop.o.Offset = uint32(off>>32), uint32(off)
   350  }
   351  
   352  // addOffset adds the given offset to the current offset.
   353  func (fd *FD) addOffset(off int) {
   354  	fd.setOffset(fd.offset + int64(off))
   355  }
   356  
   357  // pollable should be used instead of fd.pd.pollable(),
   358  // as it is aware of the disassociated state.
   359  func (fd *FD) pollable() bool {
   360  	return fd.pd.pollable() && !fd.disassociated.Load()
   361  }
   362  
   363  // fileKind describes the kind of file.
   364  type fileKind byte
   365  
   366  const (
   367  	kindNet fileKind = iota
   368  	kindFile
   369  	kindConsole
   370  	kindPipe
   371  	kindFileNet
   372  )
   373  
   374  // Init initializes the FD. The Sysfd field should already be set.
   375  // This can be called multiple times on a single FD.
   376  // The net argument is a network name from the net package (e.g., "tcp"),
   377  // or "file" or "console" or "dir".
   378  // Set pollable to true if fd should be managed by runtime netpoll.
   379  // Pollable must be set to true for overlapped fds.
   380  func (fd *FD) Init(net string, pollable bool) error {
   381  	if initErr != nil {
   382  		return initErr
   383  	}
   384  
   385  	switch net {
   386  	case "file":
   387  		fd.kind = kindFile
   388  	case "console":
   389  		fd.kind = kindConsole
   390  	case "pipe":
   391  		fd.kind = kindPipe
   392  	case "file+net":
   393  		fd.kind = kindFileNet
   394  	default:
   395  		// We don't actually care about the various network types.
   396  		fd.kind = kindNet
   397  	}
   398  	fd.isFile = fd.kind != kindNet
   399  	fd.isBlocking = !pollable
   400  	fd.rop.mode = 'r'
   401  	fd.wop.mode = 'w'
   402  	fd.rop.fd = fd
   403  	fd.wop.fd = fd
   404  
   405  	// It is safe to add overlapped handles that also perform I/O
   406  	// outside of the runtime poller. The runtime poller will ignore
   407  	// I/O completion notifications not initiated by us.
   408  	err := fd.pd.init(fd)
   409  	if err != nil {
   410  		return err
   411  	}
   412  	fd.rop.runtimeCtx = fd.pd.runtimeCtx
   413  	fd.wop.runtimeCtx = fd.pd.runtimeCtx
   414  	if fd.kind != kindNet || socketCanUseSetFileCompletionNotificationModes {
   415  		// Non-socket handles can use SetFileCompletionNotificationModes without problems.
   416  		err := syscall.SetFileCompletionNotificationModes(fd.Sysfd,
   417  			syscall.FILE_SKIP_SET_EVENT_ON_HANDLE|syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS,
   418  		)
   419  		fd.skipSyncNotif = err == nil
   420  	}
   421  	return nil
   422  }
   423  
   424  // DisassociateIOCP disassociates the file handle from the IOCP.
   425  // The disassociate operation will not succeed if there is any
   426  // in-progress IO operation on the file handle.
   427  func (fd *FD) DisassociateIOCP() error {
   428  	if err := fd.incref(); err != nil {
   429  		return err
   430  	}
   431  	defer fd.decref()
   432  
   433  	if fd.isBlocking || !fd.pollable() {
   434  		// Nothing to disassociate.
   435  		return nil
   436  	}
   437  
   438  	info := windows.FILE_COMPLETION_INFORMATION{}
   439  	if err := windows.NtSetInformationFile(fd.Sysfd, &windows.IO_STATUS_BLOCK{}, unsafe.Pointer(&info), uint32(unsafe.Sizeof(info)), windows.FileReplaceCompletionInformation); err != nil {
   440  		return err
   441  	}
   442  	fd.disassociated.Store(true)
   443  	// Don't call fd.pd.close(), it would be too racy.
   444  	// There is no harm on leaving fd.pd open until Close is called.
   445  	return nil
   446  }
   447  
   448  func (fd *FD) destroy() error {
   449  	if fd.Sysfd == syscall.InvalidHandle {
   450  		return syscall.EINVAL
   451  	}
   452  	fd.rop.close()
   453  	fd.wop.close()
   454  	// Poller may want to unregister fd in readiness notification mechanism,
   455  	// so this must be executed before fd.CloseFunc.
   456  	fd.pd.close()
   457  	var err error
   458  	switch fd.kind {
   459  	case kindNet, kindFileNet:
   460  		// The net package uses the CloseFunc variable for testing.
   461  		err = CloseFunc(fd.Sysfd)
   462  	default:
   463  		err = syscall.CloseHandle(fd.Sysfd)
   464  	}
   465  	fd.Sysfd = syscall.InvalidHandle
   466  	runtime_Semrelease(&fd.csema)
   467  	return err
   468  }
   469  
   470  // Close closes the FD. The underlying file descriptor is closed by
   471  // the destroy method when there are no remaining references.
   472  func (fd *FD) Close() error {
   473  	if !fd.fdmu.increfAndClose() {
   474  		return errClosing(fd.isFile)
   475  	}
   476  
   477  	if fd.kind == kindPipe {
   478  		syscall.CancelIoEx(fd.Sysfd, nil)
   479  	}
   480  	// unblock pending reader and writer
   481  	fd.pd.evict()
   482  	err := fd.decref()
   483  	// Wait until the descriptor is closed. If this was the only
   484  	// reference, it is already closed.
   485  	runtime_Semacquire(&fd.csema)
   486  	return err
   487  }
   488  
   489  // Windows ReadFile and WSARecv use DWORD (uint32) parameter to pass buffer length.
   490  // This prevents us reading blocks larger than 4GB.
   491  // See golang.org/issue/26923.
   492  const maxRW = 1 << 30 // 1GB is large enough and keeps subsequent reads aligned
   493  
   494  // Read implements io.Reader.
   495  func (fd *FD) Read(buf []byte) (int, error) {
   496  	if err := fd.readLock(); err != nil {
   497  		return 0, err
   498  	}
   499  	defer fd.readUnlock()
   500  	if fd.kind == kindFile {
   501  		fd.l.Lock()
   502  		defer fd.l.Unlock()
   503  	}
   504  
   505  	if len(buf) > maxRW {
   506  		buf = buf[:maxRW]
   507  	}
   508  
   509  	var n int
   510  	var err error
   511  	switch fd.kind {
   512  	case kindConsole:
   513  		n, err = fd.readConsole(buf)
   514  	case kindFile, kindPipe:
   515  		o := &fd.rop
   516  		o.InitBuf(buf)
   517  		n, err = execIO(o, func(o *operation) error {
   518  			return syscall.ReadFile(o.fd.Sysfd, unsafe.Slice(o.buf.Buf, o.buf.Len), &o.qty, o.overlapped())
   519  		})
   520  		fd.addOffset(n)
   521  		switch err {
   522  		case syscall.ERROR_HANDLE_EOF:
   523  			err = io.EOF
   524  		case syscall.ERROR_BROKEN_PIPE:
   525  			// ReadFile only documents ERROR_BROKEN_PIPE for pipes.
   526  			if fd.kind == kindPipe {
   527  				err = io.EOF
   528  			}
   529  		}
   530  	case kindNet:
   531  		o := &fd.rop
   532  		o.InitBuf(buf)
   533  		n, err = execIO(o, func(o *operation) error {
   534  			return syscall.WSARecv(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
   535  		})
   536  		if race.Enabled {
   537  			race.Acquire(unsafe.Pointer(&ioSync))
   538  		}
   539  	}
   540  	if len(buf) != 0 {
   541  		err = fd.eofError(n, err)
   542  	}
   543  	return n, err
   544  }
   545  
   546  var ReadConsole = syscall.ReadConsole // changed for testing
   547  
   548  // readConsole reads utf16 characters from console File,
   549  // encodes them into utf8 and stores them in buffer b.
   550  // It returns the number of utf8 bytes read and an error, if any.
   551  func (fd *FD) readConsole(b []byte) (int, error) {
   552  	if len(b) == 0 {
   553  		return 0, nil
   554  	}
   555  
   556  	if fd.readuint16 == nil {
   557  		// Note: syscall.ReadConsole fails for very large buffers.
   558  		// The limit is somewhere around (but not exactly) 16384.
   559  		// Stay well below.
   560  		fd.readuint16 = make([]uint16, 0, 10000)
   561  		fd.readbyte = make([]byte, 0, 4*cap(fd.readuint16))
   562  	}
   563  
   564  	for fd.readbyteOffset >= len(fd.readbyte) {
   565  		n := cap(fd.readuint16) - len(fd.readuint16)
   566  		if n > len(b) {
   567  			n = len(b)
   568  		}
   569  		var nw uint32
   570  		err := ReadConsole(fd.Sysfd, &fd.readuint16[:len(fd.readuint16)+1][len(fd.readuint16)], uint32(n), &nw, nil)
   571  		if err != nil {
   572  			return 0, err
   573  		}
   574  		uint16s := fd.readuint16[:len(fd.readuint16)+int(nw)]
   575  		fd.readuint16 = fd.readuint16[:0]
   576  		buf := fd.readbyte[:0]
   577  		for i := 0; i < len(uint16s); i++ {
   578  			r := rune(uint16s[i])
   579  			if utf16.IsSurrogate(r) {
   580  				if i+1 == len(uint16s) {
   581  					if nw > 0 {
   582  						// Save half surrogate pair for next time.
   583  						fd.readuint16 = fd.readuint16[:1]
   584  						fd.readuint16[0] = uint16(r)
   585  						break
   586  					}
   587  					r = utf8.RuneError
   588  				} else {
   589  					r = utf16.DecodeRune(r, rune(uint16s[i+1]))
   590  					if r != utf8.RuneError {
   591  						i++
   592  					}
   593  				}
   594  			}
   595  			buf = utf8.AppendRune(buf, r)
   596  		}
   597  		fd.readbyte = buf
   598  		fd.readbyteOffset = 0
   599  		if nw == 0 {
   600  			break
   601  		}
   602  	}
   603  
   604  	src := fd.readbyte[fd.readbyteOffset:]
   605  	var i int
   606  	for i = 0; i < len(src) && i < len(b); i++ {
   607  		x := src[i]
   608  		if x == 0x1A { // Ctrl-Z
   609  			if i == 0 {
   610  				fd.readbyteOffset++
   611  			}
   612  			break
   613  		}
   614  		b[i] = x
   615  	}
   616  	fd.readbyteOffset += i
   617  	return i, nil
   618  }
   619  
   620  // Pread emulates the Unix pread system call.
   621  func (fd *FD) Pread(b []byte, off int64) (int, error) {
   622  	if fd.kind == kindPipe {
   623  		// Pread does not work with pipes
   624  		return 0, syscall.ESPIPE
   625  	}
   626  	// Call incref, not readLock, because since pread specifies the
   627  	// offset it is independent from other reads.
   628  	if err := fd.incref(); err != nil {
   629  		return 0, err
   630  	}
   631  	defer fd.decref()
   632  
   633  	if len(b) > maxRW {
   634  		b = b[:maxRW]
   635  	}
   636  
   637  	fd.l.Lock()
   638  	defer fd.l.Unlock()
   639  	if fd.isBlocking {
   640  		curoffset, err := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent)
   641  		if err != nil {
   642  			return 0, err
   643  		}
   644  		defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart)
   645  		defer fd.setOffset(curoffset)
   646  	} else {
   647  		// Overlapped handles don't have the file pointer updated
   648  		// when performing I/O operations, so there is no need to
   649  		// call Seek to reset the file pointer.
   650  		// Also, some overlapped file handles don't support seeking.
   651  		// See https://go.dev/issues/74951.
   652  		curoffset := fd.offset
   653  		defer fd.setOffset(curoffset)
   654  	}
   655  	o := &fd.rop
   656  	o.InitBuf(b)
   657  	fd.setOffset(off)
   658  	n, err := execIO(o, func(o *operation) error {
   659  		return syscall.ReadFile(o.fd.Sysfd, unsafe.Slice(o.buf.Buf, o.buf.Len), &o.qty, &o.o)
   660  	})
   661  	if err == syscall.ERROR_HANDLE_EOF {
   662  		err = io.EOF
   663  	}
   664  	if len(b) != 0 {
   665  		err = fd.eofError(n, err)
   666  	}
   667  	return n, err
   668  }
   669  
   670  // ReadFrom wraps the recvfrom network call.
   671  func (fd *FD) ReadFrom(buf []byte) (int, syscall.Sockaddr, error) {
   672  	if len(buf) == 0 {
   673  		return 0, nil, nil
   674  	}
   675  	if len(buf) > maxRW {
   676  		buf = buf[:maxRW]
   677  	}
   678  	if err := fd.readLock(); err != nil {
   679  		return 0, nil, err
   680  	}
   681  	defer fd.readUnlock()
   682  	o := &fd.rop
   683  	o.InitBuf(buf)
   684  	n, err := execIO(o, func(o *operation) error {
   685  		if o.rsa == nil {
   686  			o.rsa = new(syscall.RawSockaddrAny)
   687  		}
   688  		o.rsan = int32(unsafe.Sizeof(*o.rsa))
   689  		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
   690  	})
   691  	err = fd.eofError(n, err)
   692  	if err != nil {
   693  		return n, nil, err
   694  	}
   695  	sa, _ := o.rsa.Sockaddr()
   696  	return n, sa, nil
   697  }
   698  
   699  // ReadFromInet4 wraps the recvfrom network call for IPv4.
   700  func (fd *FD) ReadFromInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) {
   701  	if len(buf) == 0 {
   702  		return 0, nil
   703  	}
   704  	if len(buf) > maxRW {
   705  		buf = buf[:maxRW]
   706  	}
   707  	if err := fd.readLock(); err != nil {
   708  		return 0, err
   709  	}
   710  	defer fd.readUnlock()
   711  	o := &fd.rop
   712  	o.InitBuf(buf)
   713  	n, err := execIO(o, func(o *operation) error {
   714  		if o.rsa == nil {
   715  			o.rsa = new(syscall.RawSockaddrAny)
   716  		}
   717  		o.rsan = int32(unsafe.Sizeof(*o.rsa))
   718  		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
   719  	})
   720  	err = fd.eofError(n, err)
   721  	if err != nil {
   722  		return n, err
   723  	}
   724  	rawToSockaddrInet4(o.rsa, sa4)
   725  	return n, err
   726  }
   727  
   728  // ReadFromInet6 wraps the recvfrom network call for IPv6.
   729  func (fd *FD) ReadFromInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) {
   730  	if len(buf) == 0 {
   731  		return 0, nil
   732  	}
   733  	if len(buf) > maxRW {
   734  		buf = buf[:maxRW]
   735  	}
   736  	if err := fd.readLock(); err != nil {
   737  		return 0, err
   738  	}
   739  	defer fd.readUnlock()
   740  	o := &fd.rop
   741  	o.InitBuf(buf)
   742  	n, err := execIO(o, func(o *operation) error {
   743  		if o.rsa == nil {
   744  			o.rsa = new(syscall.RawSockaddrAny)
   745  		}
   746  		o.rsan = int32(unsafe.Sizeof(*o.rsa))
   747  		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
   748  	})
   749  	err = fd.eofError(n, err)
   750  	if err != nil {
   751  		return n, err
   752  	}
   753  	rawToSockaddrInet6(o.rsa, sa6)
   754  	return n, err
   755  }
   756  
   757  // Write implements io.Writer.
   758  func (fd *FD) Write(buf []byte) (int, error) {
   759  	if err := fd.writeLock(); err != nil {
   760  		return 0, err
   761  	}
   762  	defer fd.writeUnlock()
   763  	if fd.kind == kindFile {
   764  		fd.l.Lock()
   765  		defer fd.l.Unlock()
   766  	}
   767  
   768  	var ntotal int
   769  	for {
   770  		max := len(buf)
   771  		if max-ntotal > maxRW {
   772  			max = ntotal + maxRW
   773  		}
   774  		b := buf[ntotal:max]
   775  		var n int
   776  		var err error
   777  		switch fd.kind {
   778  		case kindConsole:
   779  			n, err = fd.writeConsole(b)
   780  		case kindPipe, kindFile:
   781  			o := &fd.wop
   782  			o.InitBuf(b)
   783  			n, err = execIO(o, func(o *operation) error {
   784  				return syscall.WriteFile(o.fd.Sysfd, unsafe.Slice(o.buf.Buf, o.buf.Len), &o.qty, o.overlapped())
   785  			})
   786  			fd.addOffset(n)
   787  		case kindNet:
   788  			if race.Enabled {
   789  				race.ReleaseMerge(unsafe.Pointer(&ioSync))
   790  			}
   791  			o := &fd.wop
   792  			o.InitBuf(b)
   793  			n, err = execIO(o, func(o *operation) error {
   794  				return syscall.WSASend(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, &o.o, nil)
   795  			})
   796  		}
   797  		ntotal += n
   798  		if ntotal == len(buf) || err != nil {
   799  			return ntotal, err
   800  		}
   801  		if n == 0 {
   802  			return ntotal, io.ErrUnexpectedEOF
   803  		}
   804  	}
   805  }
   806  
   807  // writeConsole writes len(b) bytes to the console File.
   808  // It returns the number of bytes written and an error, if any.
   809  func (fd *FD) writeConsole(b []byte) (int, error) {
   810  	n := len(b)
   811  	runes := make([]rune, 0, 256)
   812  	if len(fd.lastbits) > 0 {
   813  		b = append(fd.lastbits, b...)
   814  		fd.lastbits = nil
   815  
   816  	}
   817  	for len(b) >= utf8.UTFMax || utf8.FullRune(b) {
   818  		r, l := utf8.DecodeRune(b)
   819  		runes = append(runes, r)
   820  		b = b[l:]
   821  	}
   822  	if len(b) > 0 {
   823  		fd.lastbits = make([]byte, len(b))
   824  		copy(fd.lastbits, b)
   825  	}
   826  	// syscall.WriteConsole seems to fail, if given large buffer.
   827  	// So limit the buffer to 16000 characters. This number was
   828  	// discovered by experimenting with syscall.WriteConsole.
   829  	const maxWrite = 16000
   830  	for len(runes) > 0 {
   831  		m := len(runes)
   832  		if m > maxWrite {
   833  			m = maxWrite
   834  		}
   835  		chunk := runes[:m]
   836  		runes = runes[m:]
   837  		uint16s := utf16.Encode(chunk)
   838  		for len(uint16s) > 0 {
   839  			var written uint32
   840  			err := syscall.WriteConsole(fd.Sysfd, &uint16s[0], uint32(len(uint16s)), &written, nil)
   841  			if err != nil {
   842  				return 0, err
   843  			}
   844  			uint16s = uint16s[written:]
   845  		}
   846  	}
   847  	return n, nil
   848  }
   849  
   850  // Pwrite emulates the Unix pwrite system call.
   851  func (fd *FD) Pwrite(buf []byte, off int64) (int, error) {
   852  	if fd.kind == kindPipe {
   853  		// Pwrite does not work with pipes
   854  		return 0, syscall.ESPIPE
   855  	}
   856  	// Call incref, not writeLock, because since pwrite specifies the
   857  	// offset it is independent from other writes.
   858  	if err := fd.incref(); err != nil {
   859  		return 0, err
   860  	}
   861  	defer fd.decref()
   862  
   863  	fd.l.Lock()
   864  	defer fd.l.Unlock()
   865  	if fd.isBlocking {
   866  		curoffset, err := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent)
   867  		if err != nil {
   868  			return 0, err
   869  		}
   870  		defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart)
   871  		defer fd.setOffset(curoffset)
   872  	} else {
   873  		// Overlapped handles don't have the file pointer updated
   874  		// when performing I/O operations, so there is no need to
   875  		// call Seek to reset the file pointer.
   876  		// Also, some overlapped file handles don't support seeking.
   877  		// See https://go.dev/issues/74951.
   878  		curoffset := fd.offset
   879  		defer fd.setOffset(curoffset)
   880  	}
   881  
   882  	var ntotal int
   883  	for {
   884  		max := len(buf)
   885  		if max-ntotal > maxRW {
   886  			max = ntotal + maxRW
   887  		}
   888  		b := buf[ntotal:max]
   889  		o := &fd.wop
   890  		o.InitBuf(b)
   891  		fd.setOffset(off + int64(ntotal))
   892  		n, err := execIO(o, func(o *operation) error {
   893  			return syscall.WriteFile(o.fd.Sysfd, unsafe.Slice(o.buf.Buf, o.buf.Len), &o.qty, &o.o)
   894  		})
   895  		if n > 0 {
   896  			ntotal += n
   897  		}
   898  		if ntotal == len(buf) || err != nil {
   899  			return ntotal, err
   900  		}
   901  		if n == 0 {
   902  			return ntotal, io.ErrUnexpectedEOF
   903  		}
   904  	}
   905  }
   906  
   907  // Writev emulates the Unix writev system call.
   908  func (fd *FD) Writev(buf *[][]byte) (int64, error) {
   909  	if len(*buf) == 0 {
   910  		return 0, nil
   911  	}
   912  	if err := fd.writeLock(); err != nil {
   913  		return 0, err
   914  	}
   915  	defer fd.writeUnlock()
   916  	if race.Enabled {
   917  		race.ReleaseMerge(unsafe.Pointer(&ioSync))
   918  	}
   919  	o := &fd.wop
   920  	o.InitBufs(buf)
   921  	n, err := execIO(o, func(o *operation) error {
   922  		return syscall.WSASend(o.fd.Sysfd, &o.bufs[0], uint32(len(o.bufs)), &o.qty, 0, &o.o, nil)
   923  	})
   924  	o.ClearBufs()
   925  	TestHookDidWritev(n)
   926  	consume(buf, int64(n))
   927  	return int64(n), err
   928  }
   929  
   930  // WriteTo wraps the sendto network call.
   931  func (fd *FD) WriteTo(buf []byte, sa syscall.Sockaddr) (int, error) {
   932  	if err := fd.writeLock(); err != nil {
   933  		return 0, err
   934  	}
   935  	defer fd.writeUnlock()
   936  
   937  	if len(buf) == 0 {
   938  		// handle zero-byte payload
   939  		o := &fd.wop
   940  		o.InitBuf(buf)
   941  		o.sa = sa
   942  		n, err := execIO(o, func(o *operation) error {
   943  			return syscall.WSASendto(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
   944  		})
   945  		return n, err
   946  	}
   947  
   948  	ntotal := 0
   949  	for len(buf) > 0 {
   950  		b := buf
   951  		if len(b) > maxRW {
   952  			b = b[:maxRW]
   953  		}
   954  		o := &fd.wop
   955  		o.InitBuf(b)
   956  		o.sa = sa
   957  		n, err := execIO(o, func(o *operation) error {
   958  			return syscall.WSASendto(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
   959  		})
   960  		ntotal += int(n)
   961  		if err != nil {
   962  			return ntotal, err
   963  		}
   964  		buf = buf[n:]
   965  	}
   966  	return ntotal, nil
   967  }
   968  
   969  // WriteToInet4 is WriteTo, specialized for syscall.SockaddrInet4.
   970  func (fd *FD) WriteToInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) {
   971  	if err := fd.writeLock(); err != nil {
   972  		return 0, err
   973  	}
   974  	defer fd.writeUnlock()
   975  
   976  	if len(buf) == 0 {
   977  		// handle zero-byte payload
   978  		o := &fd.wop
   979  		o.InitBuf(buf)
   980  		n, err := execIO(o, func(o *operation) error {
   981  			return windows.WSASendtoInet4(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa4, &o.o, nil)
   982  		})
   983  		return n, err
   984  	}
   985  
   986  	ntotal := 0
   987  	for len(buf) > 0 {
   988  		b := buf
   989  		if len(b) > maxRW {
   990  			b = b[:maxRW]
   991  		}
   992  		o := &fd.wop
   993  		o.InitBuf(b)
   994  		n, err := execIO(o, func(o *operation) error {
   995  			return windows.WSASendtoInet4(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa4, &o.o, nil)
   996  		})
   997  		ntotal += int(n)
   998  		if err != nil {
   999  			return ntotal, err
  1000  		}
  1001  		buf = buf[n:]
  1002  	}
  1003  	return ntotal, nil
  1004  }
  1005  
  1006  // WriteToInet6 is WriteTo, specialized for syscall.SockaddrInet6.
  1007  func (fd *FD) WriteToInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) {
  1008  	if err := fd.writeLock(); err != nil {
  1009  		return 0, err
  1010  	}
  1011  	defer fd.writeUnlock()
  1012  
  1013  	if len(buf) == 0 {
  1014  		// handle zero-byte payload
  1015  		o := &fd.wop
  1016  		o.InitBuf(buf)
  1017  		n, err := execIO(o, func(o *operation) error {
  1018  			return windows.WSASendtoInet6(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa6, &o.o, nil)
  1019  		})
  1020  		return n, err
  1021  	}
  1022  
  1023  	ntotal := 0
  1024  	for len(buf) > 0 {
  1025  		b := buf
  1026  		if len(b) > maxRW {
  1027  			b = b[:maxRW]
  1028  		}
  1029  		o := &fd.wop
  1030  		o.InitBuf(b)
  1031  		n, err := execIO(o, func(o *operation) error {
  1032  			return windows.WSASendtoInet6(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa6, &o.o, nil)
  1033  		})
  1034  		ntotal += int(n)
  1035  		if err != nil {
  1036  			return ntotal, err
  1037  		}
  1038  		buf = buf[n:]
  1039  	}
  1040  	return ntotal, nil
  1041  }
  1042  
  1043  // Call ConnectEx. This doesn't need any locking, since it is only
  1044  // called when the descriptor is first created. This is here rather
  1045  // than in the net package so that it can use fd.wop.
  1046  func (fd *FD) ConnectEx(ra syscall.Sockaddr) error {
  1047  	o := &fd.wop
  1048  	o.sa = ra
  1049  	_, err := execIO(o, func(o *operation) error {
  1050  		return ConnectExFunc(o.fd.Sysfd, o.sa, nil, 0, nil, &o.o)
  1051  	})
  1052  	return err
  1053  }
  1054  
  1055  func (fd *FD) acceptOne(s syscall.Handle, rawsa []syscall.RawSockaddrAny, o *operation) (string, error) {
  1056  	// Submit accept request.
  1057  	o.handle = s
  1058  	o.rsan = int32(unsafe.Sizeof(rawsa[0]))
  1059  	_, err := execIO(o, func(o *operation) error {
  1060  		return AcceptFunc(o.fd.Sysfd, o.handle, (*byte)(unsafe.Pointer(&rawsa[0])), 0, uint32(o.rsan), uint32(o.rsan), &o.qty, &o.o)
  1061  	})
  1062  	if err != nil {
  1063  		CloseFunc(s)
  1064  		return "acceptex", err
  1065  	}
  1066  
  1067  	// Inherit properties of the listening socket.
  1068  	err = syscall.Setsockopt(s, syscall.SOL_SOCKET, syscall.SO_UPDATE_ACCEPT_CONTEXT, (*byte)(unsafe.Pointer(&fd.Sysfd)), int32(unsafe.Sizeof(fd.Sysfd)))
  1069  	if err != nil {
  1070  		CloseFunc(s)
  1071  		return "setsockopt", err
  1072  	}
  1073  
  1074  	return "", nil
  1075  }
  1076  
  1077  // Accept handles accepting a socket. The sysSocket parameter is used
  1078  // to allocate the net socket.
  1079  func (fd *FD) Accept(sysSocket func() (syscall.Handle, error)) (syscall.Handle, []syscall.RawSockaddrAny, uint32, string, error) {
  1080  	if err := fd.readLock(); err != nil {
  1081  		return syscall.InvalidHandle, nil, 0, "", err
  1082  	}
  1083  	defer fd.readUnlock()
  1084  
  1085  	o := &fd.rop
  1086  	var rawsa [2]syscall.RawSockaddrAny
  1087  	for {
  1088  		s, err := sysSocket()
  1089  		if err != nil {
  1090  			return syscall.InvalidHandle, nil, 0, "", err
  1091  		}
  1092  
  1093  		errcall, err := fd.acceptOne(s, rawsa[:], o)
  1094  		if err == nil {
  1095  			return s, rawsa[:], uint32(o.rsan), "", nil
  1096  		}
  1097  
  1098  		// Sometimes we see WSAECONNRESET and ERROR_NETNAME_DELETED is
  1099  		// returned here. These happen if connection reset is received
  1100  		// before AcceptEx could complete. These errors relate to new
  1101  		// connection, not to AcceptEx, so ignore broken connection and
  1102  		// try AcceptEx again for more connections.
  1103  		errno, ok := err.(syscall.Errno)
  1104  		if !ok {
  1105  			return syscall.InvalidHandle, nil, 0, errcall, err
  1106  		}
  1107  		switch errno {
  1108  		case syscall.ERROR_NETNAME_DELETED, syscall.WSAECONNRESET:
  1109  			// ignore these and try again
  1110  		default:
  1111  			return syscall.InvalidHandle, nil, 0, errcall, err
  1112  		}
  1113  	}
  1114  }
  1115  
  1116  // Seek wraps syscall.Seek.
  1117  func (fd *FD) Seek(offset int64, whence int) (int64, error) {
  1118  	if fd.kind == kindPipe {
  1119  		return 0, syscall.ESPIPE
  1120  	}
  1121  	if err := fd.incref(); err != nil {
  1122  		return 0, err
  1123  	}
  1124  	defer fd.decref()
  1125  
  1126  	fd.l.Lock()
  1127  	defer fd.l.Unlock()
  1128  
  1129  	if !fd.isBlocking && whence == io.SeekCurrent {
  1130  		// Windows doesn't keep the file pointer for overlapped file handles.
  1131  		// We do it ourselves in case to account for any read or write
  1132  		// operations that may have occurred.
  1133  		offset += fd.offset
  1134  	}
  1135  	n, err := syscall.Seek(fd.Sysfd, offset, whence)
  1136  	fd.setOffset(n)
  1137  	return n, err
  1138  }
  1139  
  1140  // Fchmod updates syscall.ByHandleFileInformation.Fileattributes when needed.
  1141  func (fd *FD) Fchmod(mode uint32) error {
  1142  	if err := fd.incref(); err != nil {
  1143  		return err
  1144  	}
  1145  	defer fd.decref()
  1146  
  1147  	var d syscall.ByHandleFileInformation
  1148  	if err := syscall.GetFileInformationByHandle(fd.Sysfd, &d); err != nil {
  1149  		return err
  1150  	}
  1151  	attrs := d.FileAttributes
  1152  	if mode&syscall.S_IWRITE != 0 {
  1153  		attrs &^= syscall.FILE_ATTRIBUTE_READONLY
  1154  	} else {
  1155  		attrs |= syscall.FILE_ATTRIBUTE_READONLY
  1156  	}
  1157  	if attrs == d.FileAttributes {
  1158  		return nil
  1159  	}
  1160  
  1161  	var du windows.FILE_BASIC_INFO
  1162  	du.FileAttributes = attrs
  1163  	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, unsafe.Pointer(&du), uint32(unsafe.Sizeof(du)))
  1164  }
  1165  
  1166  // Fchdir wraps syscall.Fchdir.
  1167  func (fd *FD) Fchdir() error {
  1168  	if err := fd.incref(); err != nil {
  1169  		return err
  1170  	}
  1171  	defer fd.decref()
  1172  	return syscall.Fchdir(fd.Sysfd)
  1173  }
  1174  
  1175  // GetFileType wraps syscall.GetFileType.
  1176  func (fd *FD) GetFileType() (uint32, error) {
  1177  	if err := fd.incref(); err != nil {
  1178  		return 0, err
  1179  	}
  1180  	defer fd.decref()
  1181  	return syscall.GetFileType(fd.Sysfd)
  1182  }
  1183  
  1184  // GetFileInformationByHandle wraps GetFileInformationByHandle.
  1185  func (fd *FD) GetFileInformationByHandle(data *syscall.ByHandleFileInformation) error {
  1186  	if err := fd.incref(); err != nil {
  1187  		return err
  1188  	}
  1189  	defer fd.decref()
  1190  	return syscall.GetFileInformationByHandle(fd.Sysfd, data)
  1191  }
  1192  
  1193  // RawRead invokes the user-defined function f for a read operation.
  1194  func (fd *FD) RawRead(f func(uintptr) bool) error {
  1195  	if err := fd.readLock(); err != nil {
  1196  		return err
  1197  	}
  1198  	defer fd.readUnlock()
  1199  	for {
  1200  		if f(uintptr(fd.Sysfd)) {
  1201  			return nil
  1202  		}
  1203  
  1204  		// Use a zero-byte read as a way to get notified when this
  1205  		// socket is readable. h/t https://stackoverflow.com/a/42019668/332798
  1206  		o := &fd.rop
  1207  		o.InitBuf(nil)
  1208  		_, err := execIO(o, func(o *operation) error {
  1209  			if !fd.IsStream {
  1210  				o.flags |= windows.MSG_PEEK
  1211  			}
  1212  			return syscall.WSARecv(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
  1213  		})
  1214  		if err == windows.WSAEMSGSIZE {
  1215  			// expected with a 0-byte peek, ignore.
  1216  		} else if err != nil {
  1217  			return err
  1218  		}
  1219  	}
  1220  }
  1221  
  1222  // RawWrite invokes the user-defined function f for a write operation.
  1223  func (fd *FD) RawWrite(f func(uintptr) bool) error {
  1224  	if err := fd.writeLock(); err != nil {
  1225  		return err
  1226  	}
  1227  	defer fd.writeUnlock()
  1228  
  1229  	if f(uintptr(fd.Sysfd)) {
  1230  		return nil
  1231  	}
  1232  
  1233  	// TODO(tmm1): find a way to detect socket writability
  1234  	return syscall.EWINDOWS
  1235  }
  1236  
  1237  func sockaddrInet4ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) int32 {
  1238  	*rsa = syscall.RawSockaddrAny{}
  1239  	raw := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
  1240  	raw.Family = syscall.AF_INET
  1241  	p := (*[2]byte)(unsafe.Pointer(&raw.Port))
  1242  	p[0] = byte(sa.Port >> 8)
  1243  	p[1] = byte(sa.Port)
  1244  	raw.Addr = sa.Addr
  1245  	return int32(unsafe.Sizeof(*raw))
  1246  }
  1247  
  1248  func sockaddrInet6ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) int32 {
  1249  	*rsa = syscall.RawSockaddrAny{}
  1250  	raw := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
  1251  	raw.Family = syscall.AF_INET6
  1252  	p := (*[2]byte)(unsafe.Pointer(&raw.Port))
  1253  	p[0] = byte(sa.Port >> 8)
  1254  	p[1] = byte(sa.Port)
  1255  	raw.Scope_id = sa.ZoneId
  1256  	raw.Addr = sa.Addr
  1257  	return int32(unsafe.Sizeof(*raw))
  1258  }
  1259  
  1260  func rawToSockaddrInet4(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) {
  1261  	pp := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
  1262  	p := (*[2]byte)(unsafe.Pointer(&pp.Port))
  1263  	sa.Port = int(p[0])<<8 + int(p[1])
  1264  	sa.Addr = pp.Addr
  1265  }
  1266  
  1267  func rawToSockaddrInet6(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) {
  1268  	pp := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
  1269  	p := (*[2]byte)(unsafe.Pointer(&pp.Port))
  1270  	sa.Port = int(p[0])<<8 + int(p[1])
  1271  	sa.ZoneId = pp.Scope_id
  1272  	sa.Addr = pp.Addr
  1273  }
  1274  
  1275  func sockaddrToRaw(rsa *syscall.RawSockaddrAny, sa syscall.Sockaddr) (int32, error) {
  1276  	switch sa := sa.(type) {
  1277  	case *syscall.SockaddrInet4:
  1278  		sz := sockaddrInet4ToRaw(rsa, sa)
  1279  		return sz, nil
  1280  	case *syscall.SockaddrInet6:
  1281  		sz := sockaddrInet6ToRaw(rsa, sa)
  1282  		return sz, nil
  1283  	default:
  1284  		return 0, syscall.EWINDOWS
  1285  	}
  1286  }
  1287  
  1288  // ReadMsg wraps the WSARecvMsg network call.
  1289  func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.Sockaddr, error) {
  1290  	if err := fd.readLock(); err != nil {
  1291  		return 0, 0, 0, nil, err
  1292  	}
  1293  	defer fd.readUnlock()
  1294  
  1295  	if len(p) > maxRW {
  1296  		p = p[:maxRW]
  1297  	}
  1298  
  1299  	o := &fd.rop
  1300  	o.InitMsg(p, oob)
  1301  	if o.rsa == nil {
  1302  		o.rsa = new(syscall.RawSockaddrAny)
  1303  	}
  1304  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1305  	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
  1306  	o.msg.Flags = uint32(flags)
  1307  	n, err := execIO(o, func(o *operation) error {
  1308  		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
  1309  	})
  1310  	err = fd.eofError(n, err)
  1311  	var sa syscall.Sockaddr
  1312  	if err == nil {
  1313  		sa, err = o.rsa.Sockaddr()
  1314  	}
  1315  	return n, int(o.msg.Control.Len), int(o.msg.Flags), sa, err
  1316  }
  1317  
  1318  // ReadMsgInet4 is ReadMsg, but specialized to return a syscall.SockaddrInet4.
  1319  func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.SockaddrInet4) (int, int, int, error) {
  1320  	if err := fd.readLock(); err != nil {
  1321  		return 0, 0, 0, err
  1322  	}
  1323  	defer fd.readUnlock()
  1324  
  1325  	if len(p) > maxRW {
  1326  		p = p[:maxRW]
  1327  	}
  1328  
  1329  	o := &fd.rop
  1330  	o.InitMsg(p, oob)
  1331  	if o.rsa == nil {
  1332  		o.rsa = new(syscall.RawSockaddrAny)
  1333  	}
  1334  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1335  	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
  1336  	o.msg.Flags = uint32(flags)
  1337  	n, err := execIO(o, func(o *operation) error {
  1338  		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
  1339  	})
  1340  	err = fd.eofError(n, err)
  1341  	if err == nil {
  1342  		rawToSockaddrInet4(o.rsa, sa4)
  1343  	}
  1344  	return n, int(o.msg.Control.Len), int(o.msg.Flags), err
  1345  }
  1346  
  1347  // ReadMsgInet6 is ReadMsg, but specialized to return a syscall.SockaddrInet6.
  1348  func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.SockaddrInet6) (int, int, int, error) {
  1349  	if err := fd.readLock(); err != nil {
  1350  		return 0, 0, 0, err
  1351  	}
  1352  	defer fd.readUnlock()
  1353  
  1354  	if len(p) > maxRW {
  1355  		p = p[:maxRW]
  1356  	}
  1357  
  1358  	o := &fd.rop
  1359  	o.InitMsg(p, oob)
  1360  	if o.rsa == nil {
  1361  		o.rsa = new(syscall.RawSockaddrAny)
  1362  	}
  1363  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1364  	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
  1365  	o.msg.Flags = uint32(flags)
  1366  	n, err := execIO(o, func(o *operation) error {
  1367  		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
  1368  	})
  1369  	err = fd.eofError(n, err)
  1370  	if err == nil {
  1371  		rawToSockaddrInet6(o.rsa, sa6)
  1372  	}
  1373  	return n, int(o.msg.Control.Len), int(o.msg.Flags), err
  1374  }
  1375  
  1376  // WriteMsg wraps the WSASendMsg network call.
  1377  func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, error) {
  1378  	if len(p) > maxRW {
  1379  		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
  1380  	}
  1381  
  1382  	if err := fd.writeLock(); err != nil {
  1383  		return 0, 0, err
  1384  	}
  1385  	defer fd.writeUnlock()
  1386  
  1387  	o := &fd.wop
  1388  	o.InitMsg(p, oob)
  1389  	if sa != nil {
  1390  		if o.rsa == nil {
  1391  			o.rsa = new(syscall.RawSockaddrAny)
  1392  		}
  1393  		len, err := sockaddrToRaw(o.rsa, sa)
  1394  		if err != nil {
  1395  			return 0, 0, err
  1396  		}
  1397  		o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1398  		o.msg.Namelen = len
  1399  	}
  1400  	n, err := execIO(o, func(o *operation) error {
  1401  		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
  1402  	})
  1403  	return n, int(o.msg.Control.Len), err
  1404  }
  1405  
  1406  // WriteMsgInet4 is WriteMsg specialized for syscall.SockaddrInet4.
  1407  func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (int, int, error) {
  1408  	if len(p) > maxRW {
  1409  		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
  1410  	}
  1411  
  1412  	if err := fd.writeLock(); err != nil {
  1413  		return 0, 0, err
  1414  	}
  1415  	defer fd.writeUnlock()
  1416  
  1417  	o := &fd.wop
  1418  	o.InitMsg(p, oob)
  1419  	if o.rsa == nil {
  1420  		o.rsa = new(syscall.RawSockaddrAny)
  1421  	}
  1422  	len := sockaddrInet4ToRaw(o.rsa, sa)
  1423  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1424  	o.msg.Namelen = len
  1425  	n, err := execIO(o, func(o *operation) error {
  1426  		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
  1427  	})
  1428  	return n, int(o.msg.Control.Len), err
  1429  }
  1430  
  1431  // WriteMsgInet6 is WriteMsg specialized for syscall.SockaddrInet6.
  1432  func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (int, int, error) {
  1433  	if len(p) > maxRW {
  1434  		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
  1435  	}
  1436  
  1437  	if err := fd.writeLock(); err != nil {
  1438  		return 0, 0, err
  1439  	}
  1440  	defer fd.writeUnlock()
  1441  
  1442  	o := &fd.wop
  1443  	o.InitMsg(p, oob)
  1444  	if o.rsa == nil {
  1445  		o.rsa = new(syscall.RawSockaddrAny)
  1446  	}
  1447  	len := sockaddrInet6ToRaw(o.rsa, sa)
  1448  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1449  	o.msg.Namelen = len
  1450  	n, err := execIO(o, func(o *operation) error {
  1451  		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
  1452  	})
  1453  	return n, int(o.msg.Control.Len), err
  1454  }
  1455  
  1456  func DupCloseOnExec(fd int) (int, string, error) {
  1457  	proc, err := syscall.GetCurrentProcess()
  1458  	if err != nil {
  1459  		return 0, "GetCurrentProcess", err
  1460  	}
  1461  
  1462  	var nfd syscall.Handle
  1463  	const inherit = false // analogous to CLOEXEC
  1464  	if err := syscall.DuplicateHandle(proc, syscall.Handle(fd), proc, &nfd, 0, inherit, syscall.DUPLICATE_SAME_ACCESS); err != nil {
  1465  		return 0, "DuplicateHandle", err
  1466  	}
  1467  	return int(nfd), "", nil
  1468  }
  1469  

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