Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1321 insertions, 0 deletions

diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go
new file mode 100644
index 0000000..3a4a74f
--- /dev/null
+++ b/src/internal/poll/fd_windows.go
@@ -0,0 +1,1321 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package poll
+
+import (
+	"errors"
+	"internal/race"
+	"internal/syscall/windows"
+	"io"
+	"sync"
+	"syscall"
+	"unicode/utf16"
+	"unicode/utf8"
+	"unsafe"
+)
+
+var (
+	initErr error
+	ioSync  uint64
+)
+
+// This package uses the SetFileCompletionNotificationModes Windows
+// API to skip calling GetQueuedCompletionStatus if an IO operation
+// completes synchronously. There is a known bug where
+// SetFileCompletionNotificationModes crashes on some systems (see
+// https://support.microsoft.com/kb/2568167 for details).
+
+var useSetFileCompletionNotificationModes bool // determines is SetFileCompletionNotificationModes is present and safe to use
+
+// checkSetFileCompletionNotificationModes verifies that
+// SetFileCompletionNotificationModes Windows API is present
+// on the system and is safe to use.
+// See https://support.microsoft.com/kb/2568167 for details.
+func checkSetFileCompletionNotificationModes() {
+	err := syscall.LoadSetFileCompletionNotificationModes()
+	if err != nil {
+		return
+	}
+	protos := [2]int32{syscall.IPPROTO_TCP, 0}
+	var buf [32]syscall.WSAProtocolInfo
+	len := uint32(unsafe.Sizeof(buf))
+	n, err := syscall.WSAEnumProtocols(&protos[0], &buf[0], &len)
+	if err != nil {
+		return
+	}
+	for i := int32(0); i < n; i++ {
+		if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
+			return
+		}
+	}
+	useSetFileCompletionNotificationModes = true
+}
+
+func init() {
+	var d syscall.WSAData
+	e := syscall.WSAStartup(uint32(0x202), &d)
+	if e != nil {
+		initErr = e
+	}
+	checkSetFileCompletionNotificationModes()
+}
+
+// operation contains superset of data necessary to perform all async IO.
+type operation struct {
+	// Used by IOCP interface, it must be first field
+	// of the struct, as our code rely on it.
+	o syscall.Overlapped
+
+	// fields used by runtime.netpoll
+	runtimeCtx uintptr
+	mode       int32
+	errno      int32
+	qty        uint32
+
+	// fields used only by net package
+	fd     *FD
+	buf    syscall.WSABuf
+	msg    windows.WSAMsg
+	sa     syscall.Sockaddr
+	rsa    *syscall.RawSockaddrAny
+	rsan   int32
+	handle syscall.Handle
+	flags  uint32
+	bufs   []syscall.WSABuf
+}
+
+func (o *operation) InitBuf(buf []byte) {
+	o.buf.Len = uint32(len(buf))
+	o.buf.Buf = nil
+	if len(buf) != 0 {
+		o.buf.Buf = &buf[0]
+	}
+}
+
+func (o *operation) InitBufs(buf *[][]byte) {
+	if o.bufs == nil {
+		o.bufs = make([]syscall.WSABuf, 0, len(*buf))
+	} else {
+		o.bufs = o.bufs[:0]
+	}
+	for _, b := range *buf {
+		if len(b) == 0 {
+			o.bufs = append(o.bufs, syscall.WSABuf{})
+			continue
+		}
+		for len(b) > maxRW {
+			o.bufs = append(o.bufs, syscall.WSABuf{Len: maxRW, Buf: &b[0]})
+			b = b[maxRW:]
+		}
+		if len(b) > 0 {
+			o.bufs = append(o.bufs, syscall.WSABuf{Len: uint32(len(b)), Buf: &b[0]})
+		}
+	}
+}
+
+// ClearBufs clears all pointers to Buffers parameter captured
+// by InitBufs, so it can be released by garbage collector.
+func (o *operation) ClearBufs() {
+	for i := range o.bufs {
+		o.bufs[i].Buf = nil
+	}
+	o.bufs = o.bufs[:0]
+}
+
+func (o *operation) InitMsg(p []byte, oob []byte) {
+	o.InitBuf(p)
+	o.msg.Buffers = &o.buf
+	o.msg.BufferCount = 1
+
+	o.msg.Name = nil
+	o.msg.Namelen = 0
+
+	o.msg.Flags = 0
+	o.msg.Control.Len = uint32(len(oob))
+	o.msg.Control.Buf = nil
+	if len(oob) != 0 {
+		o.msg.Control.Buf = &oob[0]
+	}
+}
+
+// execIO executes a single IO operation o. It submits and cancels
+// IO in the current thread for systems where Windows CancelIoEx API
+// is available. Alternatively, it passes the request onto
+// runtime netpoll and waits for completion or cancels request.
+func execIO(o *operation, submit func(o *operation) error) (int, error) {
+	if o.fd.pd.runtimeCtx == 0 {
+		return 0, errors.New("internal error: polling on unsupported descriptor type")
+	}
+
+	fd := o.fd
+	// Notify runtime netpoll about starting IO.
+	err := fd.pd.prepare(int(o.mode), fd.isFile)
+	if err != nil {
+		return 0, err
+	}
+	// Start IO.
+	err = submit(o)
+	switch err {
+	case nil:
+		// IO completed immediately
+		if o.fd.skipSyncNotif {
+			// No completion message will follow, so return immediately.
+			return int(o.qty), nil
+		}
+		// Need to get our completion message anyway.
+	case syscall.ERROR_IO_PENDING:
+		// IO started, and we have to wait for its completion.
+		err = nil
+	default:
+		return 0, err
+	}
+	// Wait for our request to complete.
+	err = fd.pd.wait(int(o.mode), fd.isFile)
+	if err == nil {
+		// All is good. Extract our IO results and return.
+		if o.errno != 0 {
+			err = syscall.Errno(o.errno)
+			// More data available. Return back the size of received data.
+			if err == syscall.ERROR_MORE_DATA || err == windows.WSAEMSGSIZE {
+				return int(o.qty), err
+			}
+			return 0, err
+		}
+		return int(o.qty), nil
+	}
+	// IO is interrupted by "close" or "timeout"
+	netpollErr := err
+	switch netpollErr {
+	case ErrNetClosing, ErrFileClosing, ErrDeadlineExceeded:
+		// will deal with those.
+	default:
+		panic("unexpected runtime.netpoll error: " + netpollErr.Error())
+	}
+	// Cancel our request.
+	err = syscall.CancelIoEx(fd.Sysfd, &o.o)
+	// Assuming ERROR_NOT_FOUND is returned, if IO is completed.
+	if err != nil && err != syscall.ERROR_NOT_FOUND {
+		// TODO(brainman): maybe do something else, but panic.
+		panic(err)
+	}
+	// Wait for cancellation to complete.
+	fd.pd.waitCanceled(int(o.mode))
+	if o.errno != 0 {
+		err = syscall.Errno(o.errno)
+		if err == syscall.ERROR_OPERATION_ABORTED { // IO Canceled
+			err = netpollErr
+		}
+		return 0, err
+	}
+	// We issued a cancellation request. But, it seems, IO operation succeeded
+	// before the cancellation request run. We need to treat the IO operation as
+	// succeeded (the bytes are actually sent/recv from network).
+	return int(o.qty), nil
+}
+
+// FD is a file descriptor. The net and os packages embed this type in
+// a larger type representing a network connection or OS file.
+type FD struct {
+	// Lock sysfd and serialize access to Read and Write methods.
+	fdmu fdMutex
+
+	// System file descriptor. Immutable until Close.
+	Sysfd syscall.Handle
+
+	// Read operation.
+	rop operation
+	// Write operation.
+	wop operation
+
+	// I/O poller.
+	pd pollDesc
+
+	// Used to implement pread/pwrite.
+	l sync.Mutex
+
+	// For console I/O.
+	lastbits       []byte   // first few bytes of the last incomplete rune in last write
+	readuint16     []uint16 // buffer to hold uint16s obtained with ReadConsole
+	readbyte       []byte   // buffer to hold decoding of readuint16 from utf16 to utf8
+	readbyteOffset int      // readbyte[readOffset:] is yet to be consumed with file.Read
+
+	// Semaphore signaled when file is closed.
+	csema uint32
+
+	skipSyncNotif bool
+
+	// Whether this is a streaming descriptor, as opposed to a
+	// packet-based descriptor like a UDP socket.
+	IsStream bool
+
+	// Whether a zero byte read indicates EOF. This is false for a
+	// message based socket connection.
+	ZeroReadIsEOF bool
+
+	// Whether this is a file rather than a network socket.
+	isFile bool
+
+	// The kind of this file.
+	kind fileKind
+}
+
+// fileKind describes the kind of file.
+type fileKind byte
+
+const (
+	kindNet fileKind = iota
+	kindFile
+	kindConsole
+	kindPipe
+)
+
+// logInitFD is set by tests to enable file descriptor initialization logging.
+var logInitFD func(net string, fd *FD, err error)
+
+// Init initializes the FD. The Sysfd field should already be set.
+// This can be called multiple times on a single FD.
+// The net argument is a network name from the net package (e.g., "tcp"),
+// or "file" or "console" or "dir".
+// Set pollable to true if fd should be managed by runtime netpoll.
+func (fd *FD) Init(net string, pollable bool) (string, error) {
+	if initErr != nil {
+		return "", initErr
+	}
+
+	switch net {
+	case "file", "dir":
+		fd.kind = kindFile
+	case "console":
+		fd.kind = kindConsole
+	case "pipe":
+		fd.kind = kindPipe
+	case "tcp", "tcp4", "tcp6",
+		"udp", "udp4", "udp6",
+		"ip", "ip4", "ip6",
+		"unix", "unixgram", "unixpacket":
+		fd.kind = kindNet
+	default:
+		return "", errors.New("internal error: unknown network type " + net)
+	}
+	fd.isFile = fd.kind != kindNet
+
+	var err error
+	if pollable {
+		// Only call init for a network socket.
+		// This means that we don't add files to the runtime poller.
+		// Adding files to the runtime poller can confuse matters
+		// if the user is doing their own overlapped I/O.
+		// See issue #21172.
+		//
+		// In general the code below avoids calling the execIO
+		// function for non-network sockets. If some method does
+		// somehow call execIO, then execIO, and therefore the
+		// calling method, will return an error, because
+		// fd.pd.runtimeCtx will be 0.
+		err = fd.pd.init(fd)
+	}
+	if logInitFD != nil {
+		logInitFD(net, fd, err)
+	}
+	if err != nil {
+		return "", err
+	}
+	if pollable && useSetFileCompletionNotificationModes {
+		// We do not use events, so we can skip them always.
+		flags := uint8(syscall.FILE_SKIP_SET_EVENT_ON_HANDLE)
+		// It's not safe to skip completion notifications for UDP:
+		// https://docs.microsoft.com/en-us/archive/blogs/winserverperformance/designing-applications-for-high-performance-part-iii
+		if net == "tcp" {
+			flags |= syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS
+		}
+		err := syscall.SetFileCompletionNotificationModes(fd.Sysfd, flags)
+		if err == nil && flags&syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS != 0 {
+			fd.skipSyncNotif = true
+		}
+	}
+	// Disable SIO_UDP_CONNRESET behavior.
+	// http://support.microsoft.com/kb/263823
+	switch net {
+	case "udp", "udp4", "udp6":
+		ret := uint32(0)
+		flag := uint32(0)
+		size := uint32(unsafe.Sizeof(flag))
+		err := syscall.WSAIoctl(fd.Sysfd, syscall.SIO_UDP_CONNRESET, (*byte)(unsafe.Pointer(&flag)), size, nil, 0, &ret, nil, 0)
+		if err != nil {
+			return "wsaioctl", err
+		}
+	}
+	fd.rop.mode = 'r'
+	fd.wop.mode = 'w'
+	fd.rop.fd = fd
+	fd.wop.fd = fd
+	fd.rop.runtimeCtx = fd.pd.runtimeCtx
+	fd.wop.runtimeCtx = fd.pd.runtimeCtx
+	return "", nil
+}
+
+func (fd *FD) destroy() error {
+	if fd.Sysfd == syscall.InvalidHandle {
+		return syscall.EINVAL
+	}
+	// Poller may want to unregister fd in readiness notification mechanism,
+	// so this must be executed before fd.CloseFunc.
+	fd.pd.close()
+	var err error
+	switch fd.kind {
+	case kindNet:
+		// The net package uses the CloseFunc variable for testing.
+		err = CloseFunc(fd.Sysfd)
+	default:
+		err = syscall.CloseHandle(fd.Sysfd)
+	}
+	fd.Sysfd = syscall.InvalidHandle
+	runtime_Semrelease(&fd.csema)
+	return err
+}
+
+// Close closes the FD. The underlying file descriptor is closed by
+// the destroy method when there are no remaining references.
+func (fd *FD) Close() error {
+	if !fd.fdmu.increfAndClose() {
+		return errClosing(fd.isFile)
+	}
+	if fd.kind == kindPipe {
+		syscall.CancelIoEx(fd.Sysfd, nil)
+	}
+	// unblock pending reader and writer
+	fd.pd.evict()
+	err := fd.decref()
+	// Wait until the descriptor is closed. If this was the only
+	// reference, it is already closed.
+	runtime_Semacquire(&fd.csema)
+	return err
+}
+
+// Windows ReadFile and WSARecv use DWORD (uint32) parameter to pass buffer length.
+// This prevents us reading blocks larger than 4GB.
+// See golang.org/issue/26923.
+const maxRW = 1 << 30 // 1GB is large enough and keeps subsequent reads aligned
+
+// Read implements io.Reader.
+func (fd *FD) Read(buf []byte) (int, error) {
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
+
+	if len(buf) > maxRW {
+		buf = buf[:maxRW]
+	}
+
+	var n int
+	var err error
+	if fd.isFile {
+		fd.l.Lock()
+		defer fd.l.Unlock()
+		switch fd.kind {
+		case kindConsole:
+			n, err = fd.readConsole(buf)
+		default:
+			n, err = syscall.Read(fd.Sysfd, buf)
+			if fd.kind == kindPipe && err == syscall.ERROR_OPERATION_ABORTED {
+				// Close uses CancelIoEx to interrupt concurrent I/O for pipes.
+				// If the fd is a pipe and the Read was interrupted by CancelIoEx,
+				// we assume it is interrupted by Close.
+				err = ErrFileClosing
+			}
+		}
+		if err != nil {
+			n = 0
+		}
+	} else {
+		o := &fd.rop
+		o.InitBuf(buf)
+		n, err = execIO(o, func(o *operation) error {
+			return syscall.WSARecv(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
+		})
+		if race.Enabled {
+			race.Acquire(unsafe.Pointer(&ioSync))
+		}
+	}
+	if len(buf) != 0 {
+		err = fd.eofError(n, err)
+	}
+	return n, err
+}
+
+var ReadConsole = syscall.ReadConsole // changed for testing
+
+// readConsole reads utf16 characters from console File,
+// encodes them into utf8 and stores them in buffer b.
+// It returns the number of utf8 bytes read and an error, if any.
+func (fd *FD) readConsole(b []byte) (int, error) {
+	if len(b) == 0 {
+		return 0, nil
+	}
+
+	if fd.readuint16 == nil {
+		// Note: syscall.ReadConsole fails for very large buffers.
+		// The limit is somewhere around (but not exactly) 16384.
+		// Stay well below.
+		fd.readuint16 = make([]uint16, 0, 10000)
+		fd.readbyte = make([]byte, 0, 4*cap(fd.readuint16))
+	}
+
+	for fd.readbyteOffset >= len(fd.readbyte) {
+		n := cap(fd.readuint16) - len(fd.readuint16)
+		if n > len(b) {
+			n = len(b)
+		}
+		var nw uint32
+		err := ReadConsole(fd.Sysfd, &fd.readuint16[:len(fd.readuint16)+1][len(fd.readuint16)], uint32(n), &nw, nil)
+		if err != nil {
+			return 0, err
+		}
+		uint16s := fd.readuint16[:len(fd.readuint16)+int(nw)]
+		fd.readuint16 = fd.readuint16[:0]
+		buf := fd.readbyte[:0]
+		for i := 0; i < len(uint16s); i++ {
+			r := rune(uint16s[i])
+			if utf16.IsSurrogate(r) {
+				if i+1 == len(uint16s) {
+					if nw > 0 {
+						// Save half surrogate pair for next time.
+						fd.readuint16 = fd.readuint16[:1]
+						fd.readuint16[0] = uint16(r)
+						break
+					}
+					r = utf8.RuneError
+				} else {
+					r = utf16.DecodeRune(r, rune(uint16s[i+1]))
+					if r != utf8.RuneError {
+						i++
+					}
+				}
+			}
+			buf = utf8.AppendRune(buf, r)
+		}
+		fd.readbyte = buf
+		fd.readbyteOffset = 0
+		if nw == 0 {
+			break
+		}
+	}
+
+	src := fd.readbyte[fd.readbyteOffset:]
+	var i int
+	for i = 0; i < len(src) && i < len(b); i++ {
+		x := src[i]
+		if x == 0x1A { // Ctrl-Z
+			if i == 0 {
+				fd.readbyteOffset++
+			}
+			break
+		}
+		b[i] = x
+	}
+	fd.readbyteOffset += i
+	return i, nil
+}
+
+// Pread emulates the Unix pread system call.
+func (fd *FD) Pread(b []byte, off int64) (int, error) {
+	// Call incref, not readLock, because since pread specifies the
+	// offset it is independent from other reads.
+	if err := fd.incref(); err != nil {
+		return 0, err
+	}
+	defer fd.decref()
+
+	if len(b) > maxRW {
+		b = b[:maxRW]
+	}
+
+	fd.l.Lock()
+	defer fd.l.Unlock()
+	curoffset, e := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent)
+	if e != nil {
+		return 0, e
+	}
+	defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart)
+	o := syscall.Overlapped{
+		OffsetHigh: uint32(off >> 32),
+		Offset:     uint32(off),
+	}
+	var done uint32
+	e = syscall.ReadFile(fd.Sysfd, b, &done, &o)
+	if e != nil {
+		done = 0
+		if e == syscall.ERROR_HANDLE_EOF {
+			e = io.EOF
+		}
+	}
+	if len(b) != 0 {
+		e = fd.eofError(int(done), e)
+	}
+	return int(done), e
+}
+
+// ReadFrom wraps the recvfrom network call.
+func (fd *FD) ReadFrom(buf []byte) (int, syscall.Sockaddr, error) {
+	if len(buf) == 0 {
+		return 0, nil, nil
+	}
+	if len(buf) > maxRW {
+		buf = buf[:maxRW]
+	}
+	if err := fd.readLock(); err != nil {
+		return 0, nil, err
+	}
+	defer fd.readUnlock()
+	o := &fd.rop
+	o.InitBuf(buf)
+	n, err := execIO(o, func(o *operation) error {
+		if o.rsa == nil {
+			o.rsa = new(syscall.RawSockaddrAny)
+		}
+		o.rsan = int32(unsafe.Sizeof(*o.rsa))
+		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
+	})
+	err = fd.eofError(n, err)
+	if err != nil {
+		return n, nil, err
+	}
+	sa, _ := o.rsa.Sockaddr()
+	return n, sa, nil
+}
+
+// ReadFromInet4 wraps the recvfrom network call for IPv4.
+func (fd *FD) ReadFromInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+	if len(buf) > maxRW {
+		buf = buf[:maxRW]
+	}
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
+	o := &fd.rop
+	o.InitBuf(buf)
+	n, err := execIO(o, func(o *operation) error {
+		if o.rsa == nil {
+			o.rsa = new(syscall.RawSockaddrAny)
+		}
+		o.rsan = int32(unsafe.Sizeof(*o.rsa))
+		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
+	})
+	err = fd.eofError(n, err)
+	if err != nil {
+		return n, err
+	}
+	rawToSockaddrInet4(o.rsa, sa4)
+	return n, err
+}
+
+// ReadFromInet6 wraps the recvfrom network call for IPv6.
+func (fd *FD) ReadFromInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+	if len(buf) > maxRW {
+		buf = buf[:maxRW]
+	}
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
+	o := &fd.rop
+	o.InitBuf(buf)
+	n, err := execIO(o, func(o *operation) error {
+		if o.rsa == nil {
+			o.rsa = new(syscall.RawSockaddrAny)
+		}
+		o.rsan = int32(unsafe.Sizeof(*o.rsa))
+		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
+	})
+	err = fd.eofError(n, err)
+	if err != nil {
+		return n, err
+	}
+	rawToSockaddrInet6(o.rsa, sa6)
+	return n, err
+}
+
+// Write implements io.Writer.
+func (fd *FD) Write(buf []byte) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if fd.isFile {
+		fd.l.Lock()
+		defer fd.l.Unlock()
+	}
+
+	ntotal := 0
+	for len(buf) > 0 {
+		b := buf
+		if len(b) > maxRW {
+			b = b[:maxRW]
+		}
+		var n int
+		var err error
+		if fd.isFile {
+			switch fd.kind {
+			case kindConsole:
+				n, err = fd.writeConsole(b)
+			default:
+				n, err = syscall.Write(fd.Sysfd, b)
+				if fd.kind == kindPipe && err == syscall.ERROR_OPERATION_ABORTED {
+					// Close uses CancelIoEx to interrupt concurrent I/O for pipes.
+					// If the fd is a pipe and the Write was interrupted by CancelIoEx,
+					// we assume it is interrupted by Close.
+					err = ErrFileClosing
+				}
+			}
+			if err != nil {
+				n = 0
+			}
+		} else {
+			if race.Enabled {
+				race.ReleaseMerge(unsafe.Pointer(&ioSync))
+			}
+			o := &fd.wop
+			o.InitBuf(b)
+			n, err = execIO(o, func(o *operation) error {
+				return syscall.WSASend(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, &o.o, nil)
+			})
+		}
+		ntotal += n
+		if err != nil {
+			return ntotal, err
+		}
+		buf = buf[n:]
+	}
+	return ntotal, nil
+}
+
+// writeConsole writes len(b) bytes to the console File.
+// It returns the number of bytes written and an error, if any.
+func (fd *FD) writeConsole(b []byte) (int, error) {
+	n := len(b)
+	runes := make([]rune, 0, 256)
+	if len(fd.lastbits) > 0 {
+		b = append(fd.lastbits, b...)
+		fd.lastbits = nil
+
+	}
+	for len(b) >= utf8.UTFMax || utf8.FullRune(b) {
+		r, l := utf8.DecodeRune(b)
+		runes = append(runes, r)
+		b = b[l:]
+	}
+	if len(b) > 0 {
+		fd.lastbits = make([]byte, len(b))
+		copy(fd.lastbits, b)
+	}
+	// syscall.WriteConsole seems to fail, if given large buffer.
+	// So limit the buffer to 16000 characters. This number was
+	// discovered by experimenting with syscall.WriteConsole.
+	const maxWrite = 16000
+	for len(runes) > 0 {
+		m := len(runes)
+		if m > maxWrite {
+			m = maxWrite
+		}
+		chunk := runes[:m]
+		runes = runes[m:]
+		uint16s := utf16.Encode(chunk)
+		for len(uint16s) > 0 {
+			var written uint32
+			err := syscall.WriteConsole(fd.Sysfd, &uint16s[0], uint32(len(uint16s)), &written, nil)
+			if err != nil {
+				return 0, err
+			}
+			uint16s = uint16s[written:]
+		}
+	}
+	return n, nil
+}
+
+// Pwrite emulates the Unix pwrite system call.
+func (fd *FD) Pwrite(buf []byte, off int64) (int, error) {
+	// Call incref, not writeLock, because since pwrite specifies the
+	// offset it is independent from other writes.
+	if err := fd.incref(); err != nil {
+		return 0, err
+	}
+	defer fd.decref()
+
+	fd.l.Lock()
+	defer fd.l.Unlock()
+	curoffset, e := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent)
+	if e != nil {
+		return 0, e
+	}
+	defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart)
+
+	ntotal := 0
+	for len(buf) > 0 {
+		b := buf
+		if len(b) > maxRW {
+			b = b[:maxRW]
+		}
+		var n uint32
+		o := syscall.Overlapped{
+			OffsetHigh: uint32(off >> 32),
+			Offset:     uint32(off),
+		}
+		e = syscall.WriteFile(fd.Sysfd, b, &n, &o)
+		ntotal += int(n)
+		if e != nil {
+			return ntotal, e
+		}
+		buf = buf[n:]
+		off += int64(n)
+	}
+	return ntotal, nil
+}
+
+// Writev emulates the Unix writev system call.
+func (fd *FD) Writev(buf *[][]byte) (int64, error) {
+	if len(*buf) == 0 {
+		return 0, nil
+	}
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if race.Enabled {
+		race.ReleaseMerge(unsafe.Pointer(&ioSync))
+	}
+	o := &fd.wop
+	o.InitBufs(buf)
+	n, err := execIO(o, func(o *operation) error {
+		return syscall.WSASend(o.fd.Sysfd, &o.bufs[0], uint32(len(o.bufs)), &o.qty, 0, &o.o, nil)
+	})
+	o.ClearBufs()
+	TestHookDidWritev(n)
+	consume(buf, int64(n))
+	return int64(n), err
+}
+
+// WriteTo wraps the sendto network call.
+func (fd *FD) WriteTo(buf []byte, sa syscall.Sockaddr) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+
+	if len(buf) == 0 {
+		// handle zero-byte payload
+		o := &fd.wop
+		o.InitBuf(buf)
+		o.sa = sa
+		n, err := execIO(o, func(o *operation) error {
+			return syscall.WSASendto(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
+		})
+		return n, err
+	}
+
+	ntotal := 0
+	for len(buf) > 0 {
+		b := buf
+		if len(b) > maxRW {
+			b = b[:maxRW]
+		}
+		o := &fd.wop
+		o.InitBuf(b)
+		o.sa = sa
+		n, err := execIO(o, func(o *operation) error {
+			return syscall.WSASendto(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
+		})
+		ntotal += int(n)
+		if err != nil {
+			return ntotal, err
+		}
+		buf = buf[n:]
+	}
+	return ntotal, nil
+}
+
+// WriteToInet4 is WriteTo, specialized for syscall.SockaddrInet4.
+func (fd *FD) WriteToInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+
+	if len(buf) == 0 {
+		// handle zero-byte payload
+		o := &fd.wop
+		o.InitBuf(buf)
+		n, err := execIO(o, func(o *operation) error {
+			return windows.WSASendtoInet4(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa4, &o.o, nil)
+		})
+		return n, err
+	}
+
+	ntotal := 0
+	for len(buf) > 0 {
+		b := buf
+		if len(b) > maxRW {
+			b = b[:maxRW]
+		}
+		o := &fd.wop
+		o.InitBuf(b)
+		n, err := execIO(o, func(o *operation) error {
+			return windows.WSASendtoInet4(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa4, &o.o, nil)
+		})
+		ntotal += int(n)
+		if err != nil {
+			return ntotal, err
+		}
+		buf = buf[n:]
+	}
+	return ntotal, nil
+}
+
+// WriteToInet6 is WriteTo, specialized for syscall.SockaddrInet6.
+func (fd *FD) WriteToInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+
+	if len(buf) == 0 {
+		// handle zero-byte payload
+		o := &fd.wop
+		o.InitBuf(buf)
+		n, err := execIO(o, func(o *operation) error {
+			return windows.WSASendtoInet6(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa6, &o.o, nil)
+		})
+		return n, err
+	}
+
+	ntotal := 0
+	for len(buf) > 0 {
+		b := buf
+		if len(b) > maxRW {
+			b = b[:maxRW]
+		}
+		o := &fd.wop
+		o.InitBuf(b)
+		n, err := execIO(o, func(o *operation) error {
+			return windows.WSASendtoInet6(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa6, &o.o, nil)
+		})
+		ntotal += int(n)
+		if err != nil {
+			return ntotal, err
+		}
+		buf = buf[n:]
+	}
+	return ntotal, nil
+}
+
+// Call ConnectEx. This doesn't need any locking, since it is only
+// called when the descriptor is first created. This is here rather
+// than in the net package so that it can use fd.wop.
+func (fd *FD) ConnectEx(ra syscall.Sockaddr) error {
+	o := &fd.wop
+	o.sa = ra
+	_, err := execIO(o, func(o *operation) error {
+		return ConnectExFunc(o.fd.Sysfd, o.sa, nil, 0, nil, &o.o)
+	})
+	return err
+}
+
+func (fd *FD) acceptOne(s syscall.Handle, rawsa []syscall.RawSockaddrAny, o *operation) (string, error) {
+	// Submit accept request.
+	o.handle = s
+	o.rsan = int32(unsafe.Sizeof(rawsa[0]))
+	_, err := execIO(o, func(o *operation) error {
+		return AcceptFunc(o.fd.Sysfd, o.handle, (*byte)(unsafe.Pointer(&rawsa[0])), 0, uint32(o.rsan), uint32(o.rsan), &o.qty, &o.o)
+	})
+	if err != nil {
+		CloseFunc(s)
+		return "acceptex", err
+	}
+
+	// Inherit properties of the listening socket.
+	err = syscall.Setsockopt(s, syscall.SOL_SOCKET, syscall.SO_UPDATE_ACCEPT_CONTEXT, (*byte)(unsafe.Pointer(&fd.Sysfd)), int32(unsafe.Sizeof(fd.Sysfd)))
+	if err != nil {
+		CloseFunc(s)
+		return "setsockopt", err
+	}
+
+	return "", nil
+}
+
+// Accept handles accepting a socket. The sysSocket parameter is used
+// to allocate the net socket.
+func (fd *FD) Accept(sysSocket func() (syscall.Handle, error)) (syscall.Handle, []syscall.RawSockaddrAny, uint32, string, error) {
+	if err := fd.readLock(); err != nil {
+		return syscall.InvalidHandle, nil, 0, "", err
+	}
+	defer fd.readUnlock()
+
+	o := &fd.rop
+	var rawsa [2]syscall.RawSockaddrAny
+	for {
+		s, err := sysSocket()
+		if err != nil {
+			return syscall.InvalidHandle, nil, 0, "", err
+		}
+
+		errcall, err := fd.acceptOne(s, rawsa[:], o)
+		if err == nil {
+			return s, rawsa[:], uint32(o.rsan), "", nil
+		}
+
+		// Sometimes we see WSAECONNRESET and ERROR_NETNAME_DELETED is
+		// returned here. These happen if connection reset is received
+		// before AcceptEx could complete. These errors relate to new
+		// connection, not to AcceptEx, so ignore broken connection and
+		// try AcceptEx again for more connections.
+		errno, ok := err.(syscall.Errno)
+		if !ok {
+			return syscall.InvalidHandle, nil, 0, errcall, err
+		}
+		switch errno {
+		case syscall.ERROR_NETNAME_DELETED, syscall.WSAECONNRESET:
+			// ignore these and try again
+		default:
+			return syscall.InvalidHandle, nil, 0, errcall, err
+		}
+	}
+}
+
+// Seek wraps syscall.Seek.
+func (fd *FD) Seek(offset int64, whence int) (int64, error) {
+	if err := fd.incref(); err != nil {
+		return 0, err
+	}
+	defer fd.decref()
+
+	fd.l.Lock()
+	defer fd.l.Unlock()
+
+	return syscall.Seek(fd.Sysfd, offset, whence)
+}
+
+// Fchmod updates syscall.ByHandleFileInformation.Fileattributes when needed.
+func (fd *FD) Fchmod(mode uint32) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	var d syscall.ByHandleFileInformation
+	if err := syscall.GetFileInformationByHandle(fd.Sysfd, &d); err != nil {
+		return err
+	}
+	attrs := d.FileAttributes
+	if mode&syscall.S_IWRITE != 0 {
+		attrs &^= syscall.FILE_ATTRIBUTE_READONLY
+	} else {
+		attrs |= syscall.FILE_ATTRIBUTE_READONLY
+	}
+	if attrs == d.FileAttributes {
+		return nil
+	}
+
+	var du windows.FILE_BASIC_INFO
+	du.FileAttributes = attrs
+	l := uint32(unsafe.Sizeof(d))
+	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, uintptr(unsafe.Pointer(&du)), l)
+}
+
+// Fchdir wraps syscall.Fchdir.
+func (fd *FD) Fchdir() error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return syscall.Fchdir(fd.Sysfd)
+}
+
+// GetFileType wraps syscall.GetFileType.
+func (fd *FD) GetFileType() (uint32, error) {
+	if err := fd.incref(); err != nil {
+		return 0, err
+	}
+	defer fd.decref()
+	return syscall.GetFileType(fd.Sysfd)
+}
+
+// GetFileInformationByHandle wraps GetFileInformationByHandle.
+func (fd *FD) GetFileInformationByHandle(data *syscall.ByHandleFileInformation) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return syscall.GetFileInformationByHandle(fd.Sysfd, data)
+}
+
+// RawRead invokes the user-defined function f for a read operation.
+func (fd *FD) RawRead(f func(uintptr) bool) error {
+	if err := fd.readLock(); err != nil {
+		return err
+	}
+	defer fd.readUnlock()
+	for {
+		if f(uintptr(fd.Sysfd)) {
+			return nil
+		}
+
+		// Use a zero-byte read as a way to get notified when this
+		// socket is readable. h/t https://stackoverflow.com/a/42019668/332798
+		o := &fd.rop
+		o.InitBuf(nil)
+		if !fd.IsStream {
+			o.flags |= windows.MSG_PEEK
+		}
+		_, err := execIO(o, func(o *operation) error {
+			return syscall.WSARecv(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
+		})
+		if err == windows.WSAEMSGSIZE {
+			// expected with a 0-byte peek, ignore.
+		} else if err != nil {
+			return err
+		}
+	}
+}
+
+// RawWrite invokes the user-defined function f for a write operation.
+func (fd *FD) RawWrite(f func(uintptr) bool) error {
+	if err := fd.writeLock(); err != nil {
+		return err
+	}
+	defer fd.writeUnlock()
+
+	if f(uintptr(fd.Sysfd)) {
+		return nil
+	}
+
+	// TODO(tmm1): find a way to detect socket writability
+	return syscall.EWINDOWS
+}
+
+func sockaddrInet4ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) int32 {
+	*rsa = syscall.RawSockaddrAny{}
+	raw := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
+	raw.Family = syscall.AF_INET
+	p := (*[2]byte)(unsafe.Pointer(&raw.Port))
+	p[0] = byte(sa.Port >> 8)
+	p[1] = byte(sa.Port)
+	raw.Addr = sa.Addr
+	return int32(unsafe.Sizeof(*raw))
+}
+
+func sockaddrInet6ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) int32 {
+	*rsa = syscall.RawSockaddrAny{}
+	raw := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
+	raw.Family = syscall.AF_INET6
+	p := (*[2]byte)(unsafe.Pointer(&raw.Port))
+	p[0] = byte(sa.Port >> 8)
+	p[1] = byte(sa.Port)
+	raw.Scope_id = sa.ZoneId
+	raw.Addr = sa.Addr
+	return int32(unsafe.Sizeof(*raw))
+}
+
+func rawToSockaddrInet4(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) {
+	pp := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
+	p := (*[2]byte)(unsafe.Pointer(&pp.Port))
+	sa.Port = int(p[0])<<8 + int(p[1])
+	sa.Addr = pp.Addr
+}
+
+func rawToSockaddrInet6(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) {
+	pp := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
+	p := (*[2]byte)(unsafe.Pointer(&pp.Port))
+	sa.Port = int(p[0])<<8 + int(p[1])
+	sa.ZoneId = pp.Scope_id
+	sa.Addr = pp.Addr
+}
+
+func sockaddrToRaw(rsa *syscall.RawSockaddrAny, sa syscall.Sockaddr) (int32, error) {
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		sz := sockaddrInet4ToRaw(rsa, sa)
+		return sz, nil
+	case *syscall.SockaddrInet6:
+		sz := sockaddrInet6ToRaw(rsa, sa)
+		return sz, nil
+	default:
+		return 0, syscall.EWINDOWS
+	}
+}
+
+// ReadMsg wraps the WSARecvMsg network call.
+func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.Sockaddr, error) {
+	if err := fd.readLock(); err != nil {
+		return 0, 0, 0, nil, err
+	}
+	defer fd.readUnlock()
+
+	if len(p) > maxRW {
+		p = p[:maxRW]
+	}
+
+	o := &fd.rop
+	o.InitMsg(p, oob)
+	if o.rsa == nil {
+		o.rsa = new(syscall.RawSockaddrAny)
+	}
+	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
+	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
+	o.msg.Flags = uint32(flags)
+	n, err := execIO(o, func(o *operation) error {
+		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
+	})
+	err = fd.eofError(n, err)
+	var sa syscall.Sockaddr
+	if err == nil {
+		sa, err = o.rsa.Sockaddr()
+	}
+	return n, int(o.msg.Control.Len), int(o.msg.Flags), sa, err
+}
+
+// ReadMsgInet4 is ReadMsg, but specialized to return a syscall.SockaddrInet4.
+func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.SockaddrInet4) (int, int, int, error) {
+	if err := fd.readLock(); err != nil {
+		return 0, 0, 0, err
+	}
+	defer fd.readUnlock()
+
+	if len(p) > maxRW {
+		p = p[:maxRW]
+	}
+
+	o := &fd.rop
+	o.InitMsg(p, oob)
+	if o.rsa == nil {
+		o.rsa = new(syscall.RawSockaddrAny)
+	}
+	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
+	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
+	o.msg.Flags = uint32(flags)
+	n, err := execIO(o, func(o *operation) error {
+		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
+	})
+	err = fd.eofError(n, err)
+	if err == nil {
+		rawToSockaddrInet4(o.rsa, sa4)
+	}
+	return n, int(o.msg.Control.Len), int(o.msg.Flags), err
+}
+
+// ReadMsgInet6 is ReadMsg, but specialized to return a syscall.SockaddrInet6.
+func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.SockaddrInet6) (int, int, int, error) {
+	if err := fd.readLock(); err != nil {
+		return 0, 0, 0, err
+	}
+	defer fd.readUnlock()
+
+	if len(p) > maxRW {
+		p = p[:maxRW]
+	}
+
+	o := &fd.rop
+	o.InitMsg(p, oob)
+	if o.rsa == nil {
+		o.rsa = new(syscall.RawSockaddrAny)
+	}
+	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
+	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
+	o.msg.Flags = uint32(flags)
+	n, err := execIO(o, func(o *operation) error {
+		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
+	})
+	err = fd.eofError(n, err)
+	if err == nil {
+		rawToSockaddrInet6(o.rsa, sa6)
+	}
+	return n, int(o.msg.Control.Len), int(o.msg.Flags), err
+}
+
+// WriteMsg wraps the WSASendMsg network call.
+func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, error) {
+	if len(p) > maxRW {
+		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
+	}
+
+	if err := fd.writeLock(); err != nil {
+		return 0, 0, err
+	}
+	defer fd.writeUnlock()
+
+	o := &fd.wop
+	o.InitMsg(p, oob)
+	if sa != nil {
+		if o.rsa == nil {
+			o.rsa = new(syscall.RawSockaddrAny)
+		}
+		len, err := sockaddrToRaw(o.rsa, sa)
+		if err != nil {
+			return 0, 0, err
+		}
+		o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
+		o.msg.Namelen = len
+	}
+	n, err := execIO(o, func(o *operation) error {
+		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
+	})
+	return n, int(o.msg.Control.Len), err
+}
+
+// WriteMsgInet4 is WriteMsg specialized for syscall.SockaddrInet4.
+func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (int, int, error) {
+	if len(p) > maxRW {
+		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
+	}
+
+	if err := fd.writeLock(); err != nil {
+		return 0, 0, err
+	}
+	defer fd.writeUnlock()
+
+	o := &fd.wop
+	o.InitMsg(p, oob)
+	if o.rsa == nil {
+		o.rsa = new(syscall.RawSockaddrAny)
+	}
+	len := sockaddrInet4ToRaw(o.rsa, sa)
+	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
+	o.msg.Namelen = len
+	n, err := execIO(o, func(o *operation) error {
+		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
+	})
+	return n, int(o.msg.Control.Len), err
+}
+
+// WriteMsgInet6 is WriteMsg specialized for syscall.SockaddrInet6.
+func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (int, int, error) {
+	if len(p) > maxRW {
+		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
+	}
+
+	if err := fd.writeLock(); err != nil {
+		return 0, 0, err
+	}
+	defer fd.writeUnlock()
+
+	o := &fd.wop
+	o.InitMsg(p, oob)
+	if o.rsa == nil {
+		o.rsa = new(syscall.RawSockaddrAny)
+	}
+	len := sockaddrInet6ToRaw(o.rsa, sa)
+	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
+	o.msg.Namelen = len
+	n, err := execIO(o, func(o *operation) error {
+		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
+	})
+	return n, int(o.msg.Control.Len), err
+}