github.com/cbeuw/gotfo@v0.0.0-20180331191851-f2b091af84de/fd_go110_windows.go

// Copyright 2010 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.

// +build go1.10

package gotfo

import (
	"net"
	"sync"
	"syscall"
	"unsafe"
)

var (
	initErr error
)

// CancelIo Windows API cancels all outstanding IO for a particular
// socket on current thread. To overcome that limitation, we run
// special goroutine, locked to OS single thread, that both starts
// and cancels IO. It means, there are 2 unavoidable thread switches
// for every IO.
// Some newer versions of Windows has new CancelIoEx API, that does
// not have that limitation and can be used from any thread. This
// package uses CancelIoEx API, if present, otherwise it fallback
// to CancelIo.

var (
	skipSyncNotif bool
)

func sysInit() {
	var d syscall.WSAData
	e := syscall.WSAStartup(uint32(0x202), &d)
	if e != nil {
		initErr = e
	}

	// It's not safe to use FILE_SKIP_COMPLETION_PORT_ON_SUCCESS if non IFS providers are installed:
	// http://support.microsoft.com/kb/2568167
	skipSyncNotif = true
	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 {
		skipSyncNotif = false
	} else {
		for i := int32(0); i < n; i++ {
			if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
				skipSyncNotif = false
				break
			}
		}
	}
}

// internal/syscall/windows/syscall_windows.go
type WSAMsg struct {
	Name        *syscall.RawSockaddrAny
	Namelen     int32
	Buffers     *syscall.WSABuf
	BufferCount uint32
	Control     syscall.WSABuf
	Flags       uint32
}

// 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   *pollFD
	errc chan error
	buf  syscall.WSABuf
	// new in go1.10 https://github.com/golang/go/commit/e49bc465a3acb2dd72e9afa5d40e541205c7d460
	msg    WSAMsg
	sa     syscall.Sockaddr
	rsa    *syscall.RawSockaddrAny
	rsan   int32
	handle syscall.Handle
	flags  uint32
	bufs   []syscall.WSABuf
}

type pollFD 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.
	isConsole      bool
	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

	// new in go1.10 https://github.com/golang/go/commit/382d4928b8a758a91f06de9e6cb10b92bb882eff#diff-618b3f21201d29fa6d82d50df02dcdba
	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 normal file.
	isFile bool

	// Whether this is a directory.
	isDir bool
}

// Network file descriptor.
type netFD struct {
	pollFD

	// immutable until Close
	family      int
	sotype      int
	isConnected bool
	net         string
	laddr       net.Addr
	raddr       net.Addr
}

func newFD(sysfd syscall.Handle, family int) (*netFD, error) {
	if initErr != nil {
		return nil, initErr
	}

	ret := &netFD{
		pollFD: pollFD{
			sysfd:         sysfd,
			IsStream:      true,
			ZeroReadIsEOF: true,
		},
		family: family,
		sotype: syscall.SOCK_STREAM,
		net:    "tcp",
	}
	return ret, nil
}

func (fd *netFD) init() error {
	if initErr != nil {
		return initErr
	}

	if err := fd.pd.init(fd); err != nil {
		return err
	}

	// 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:
	// http://blogs.technet.com/b/winserverperformance/archive/2008/06/26/designing-applications-for-high-performance-part-iii.aspx
	if skipSyncNotif {
		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
	}

	fd.rop.mode = 'r'
	fd.wop.mode = 'w'
	fd.rop.fd = &fd.pollFD
	fd.wop.fd = &fd.pollFD
	fd.rop.runtimeCtx = fd.pd.runtimeCtx
	fd.wop.runtimeCtx = fd.pd.runtimeCtx

	return nil
}

func (fd *pollFD) incref() error {
	if !fd.fdmu.incref() {
		return errClosing
	}
	return nil
}

// decref removes a reference from fd.
// It also closes fd when the state of fd is set to closed and there
// is no remaining reference.
func (fd *pollFD) decref() error {
	if fd.fdmu.decref() {
		return fd.destroy()
	}
	return nil
}

func (fd *pollFD) 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
	if fd.isFile || fd.isConsole {
		err = syscall.CloseHandle(fd.sysfd)
	} else if fd.isDir {
		err = syscall.FindClose(fd.sysfd)
	} else {
		// The net package uses the CloseFunc variable for testing.
		err = syscall.Closesocket(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 *pollFD) Close() error {
	if !fd.fdmu.increfAndClose() {
		return errClosing
	}
	// 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
}

// Shutdown wraps the shutdown network call.
func (fd *pollFD) Shutdown(how int) error {
	if err := fd.incref(); err != nil {
		return err
	}
	defer fd.decref()
	return syscall.Shutdown(fd.sysfd, how)
}