}
}

// Write implements io.Writer.
func (fd *FD) Write(p []byte) (int, error) {
	if err := fd.writeLock(); err != nil {
		return 0, err
	}
	defer fd.writeUnlock()
	if err := fd.pd.prepareWrite(fd.isFile); err != nil {
		return 0, err
	}
	var nn int
	for {
		max := len(p)
		if fd.IsStream && max-nn > maxRW {
			max = nn + maxRW
		}

	defer func() {
		TestHookDidSendFile(dstFD, src, written, err, handled)
	}()
	if err := dstFD.writeLock(); err != nil {
		return 0, err, false
	}
	defer dstFD.writeUnlock()

	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
		return 0, err, false
	}

	dst := dstFD.Sysfd
	for remain > 0 {
		n := maxSendfileSize
		if int64(n) > remain {
			n = int(remain)
		}

	defer func() {
		TestHookDidSendFile(dstFD, src, written, err, handled)
	}()
	if err := dstFD.writeLock(); err != nil {
		return 0, err, false
	}
	defer dstFD.writeUnlock()

	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
		return 0, err, false
	}

	dst := dstFD.Sysfd
	for remain > 0 {
		n := maxSendfileSize
		if int64(n) > remain {
			n = int(remain)
		}
		pos1 := pos

	defer func() {
		TestHookDidSendFile(dstFD, src, written, err, handled)
	}()
	if err := dstFD.writeLock(); err != nil {
		return 0, err, false
	}
	defer dstFD.writeUnlock()

	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
		return 0, err, false
	}

	dst := dstFD.Sysfd
	for remain > 0 {
		n := maxSendfileSize
		if int64(n) > remain {
			n = int(remain)
		}
		pos1 := pos

	"syscall"
)

// Writev wraps the writev system call.
func (fd *FD) Writev(v *[][]byte) (int64, error) {
	if err := fd.writeLock(); err != nil {
		return 0, err
	}
	defer fd.writeUnlock()
	if err := fd.pd.prepareWrite(fd.isFile); err != nil {
		return 0, err
	}

	var iovecs []syscall.Iovec
	if fd.iovecs != nil {
		iovecs = *fd.iovecs
	}
	// TODO: read from sysconf(_SC_IOV_MAX)? The Linux default is

	if pd.closing {
		return errClosing(isFile)
	}
	return nil
}

func (pd *pollDesc) prepareRead(isFile bool) error { return pd.prepare('r', isFile) }

func (pd *pollDesc) prepareWrite(isFile bool) error { return pd.prepare('w', isFile) }

func (pd *pollDesc) wait(mode int, isFile bool) error {
	if pd.closing {
		return errClosing(isFile)
	}

	}
	res := runtime_pollReset(pd.runtimeCtx, mode)
	return convertErr(res, isFile)
}

func (pd *pollDesc) prepareRead(isFile bool) error {
	return pd.prepare('r', isFile)
}

func (pd *pollDesc) prepareWrite(isFile bool) error {
	return pd.prepare('w', isFile)
}

func (pd *pollDesc) wait(mode int, isFile bool) error {
	if pd.runtimeCtx == 0 {
		return errors.New("waiting for unsupported file type")
	}

// step of an io.Copy in userspace.
func splicePump(sock *FD, pipefd int, inPipe int) (int, error) {
	if err := sock.writeLock(); err != nil {
		return 0, err
	}
	defer sock.writeUnlock()
	if err := sock.pd.prepareWrite(sock.isFile); err != nil {
		return 0, err
	}
	written := 0
	for inPipe > 0 {
		// In theory calling splice(2) with SPLICE_F_NONBLOCK could end up an infinite loop here,