// Copyright 2009 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.

// Windows system calls.

package syscall

import (
	errorspkg "errors"
	"internal/bytealg"
	"internal/itoa"
	"internal/oserror"
	"internal/race"
	"runtime"
	"sync"
	"unsafe"
)

type Handle uintptr

const InvalidHandle = ^Handle(0)

// StringToUTF16 returns the UTF-16 encoding of the UTF-8 string s,
// with a terminating NUL added. If s contains a NUL byte this
// function panics instead of returning an error.
//
// Deprecated: Use UTF16FromString instead.
func StringToUTF16(s string) []uint16 {
	a, err := UTF16FromString(s)
	if err != nil {
		panic("syscall: string with NUL passed to StringToUTF16")
	}
	return a
}

// UTF16FromString returns the UTF-16 encoding of the UTF-8 string
// s, with a terminating NUL added. If s contains a NUL byte at any
// location, it returns (nil, EINVAL). Unpaired surrogates
// are encoded using WTF-8.
func UTF16FromString(s string) ([]uint16, error) {
	if bytealg.IndexByteString(s, 0) != -1 {
		return nil, EINVAL
	}
	// Valid UTF-8 characters between 1 and 3 bytes require one uint16.
	// Valid UTF-8 characters of 4 bytes require two uint16.
	// Bytes with invalid UTF-8 encoding require maximum one uint16 per byte.
	// So the number of UTF-8 code units (len(s)) is always greater or
	// equal than the number of UTF-16 code units.
	// Also account for the terminating NUL character.
	buf := make([]uint16, 0, len(s)+1)
	buf = encodeWTF16(s, buf)
	return append(buf, 0), nil
}

// UTF16ToString returns the UTF-8 encoding of the UTF-16 sequence s,
// with a terminating NUL removed. Unpaired surrogates are decoded
// using WTF-8 instead of UTF-8 encoding.
func UTF16ToString(s []uint16) string {
	maxLen := 0
	for i, v := range s {
		if v == 0 {
			s = s[0:i]
			break
		}
		switch {
		case v <= rune1Max:
			maxLen += 1
		case v <= rune2Max:
			maxLen += 2
		default:
			// r is a non-surrogate that decodes to 3 bytes,
			// or is an unpaired surrogate (also 3 bytes in WTF-8),
			// or is one half of a valid surrogate pair.
			// If it is half of a pair, we will add 3 for the second surrogate
			// (total of 6) and overestimate by 2 bytes for the pair,
			// since the resulting rune only requires 4 bytes.
			maxLen += 3
		}
	}
	buf := decodeWTF16(s, make([]byte, 0, maxLen))
	return unsafe.String(unsafe.SliceData(buf), len(buf))
}

// utf16PtrToString is like UTF16ToString, but takes *uint16
// as a parameter instead of []uint16.
func utf16PtrToString(p *uint16) string {
	if p == nil {
		return ""
	}
	end := unsafe.Pointer(p)
	n := 0
	for *(*uint16)(end) != 0 {
		end = unsafe.Pointer(uintptr(end) + unsafe.Sizeof(*p))
		n++
	}
	return UTF16ToString(unsafe.Slice(p, n))
}

// StringToUTF16Ptr returns pointer to the UTF-16 encoding of
// the UTF-8 string s, with a terminating NUL added. If s
// contains a NUL byte this function panics instead of
// returning an error.
//
// Deprecated: Use UTF16PtrFromString instead.
func StringToUTF16Ptr(s string) *uint16 { return &StringToUTF16(s)[0] }

// UTF16PtrFromString returns pointer to the UTF-16 encoding of
// the UTF-8 string s, with a terminating NUL added. If s
// contains a NUL byte at any location, it returns (nil, EINVAL).
// Unpaired surrogates are encoded using WTF-8.
func UTF16PtrFromString(s string) (*uint16, error) {
	a, err := UTF16FromString(s)
	if err != nil {
		return nil, err
	}
	return &a[0], nil
}

// Errno is the Windows error number.
//
// Errno values can be tested against error values using errors.Is.
// For example:
//
//	_, _, err := syscall.Syscall(...)
//	if errors.Is(err, fs.ErrNotExist) ...
type Errno uintptr

func langid(pri, sub uint16) uint32 { return uint32(sub)<<10 | uint32(pri) }

// FormatMessage is deprecated (msgsrc should be uintptr, not uint32, but can
// not be changed due to the Go 1 compatibility guarantee).
//
// Deprecated: Use FormatMessage from golang.org/x/sys/windows instead.
func FormatMessage(flags uint32, msgsrc uint32, msgid uint32, langid uint32, buf []uint16, args *byte) (n uint32, err error) {
	return formatMessage(flags, uintptr(msgsrc), msgid, langid, buf, args)
}

func (e Errno) Error() string {
	// deal with special go errors
	idx := int(e - APPLICATION_ERROR)
	if 0 <= idx && idx < len(errors) {
		return errors[idx]
	}
	// ask windows for the remaining errors
	var flags uint32 = FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ARGUMENT_ARRAY | FORMAT_MESSAGE_IGNORE_INSERTS
	b := make([]uint16, 300)
	n, err := formatMessage(flags, 0, uint32(e), langid(LANG_ENGLISH, SUBLANG_ENGLISH_US), b, nil)
	if err != nil {
		n, err = formatMessage(flags, 0, uint32(e), 0, b, nil)
		if err != nil {
			return "winapi error #" + itoa.Itoa(int(e))
		}
	}
	// trim terminating \r and \n
	for ; n > 0 && (b[n-1] == '\n' || b[n-1] == '\r'); n-- {
	}
	return UTF16ToString(b[:n])
}

const (
	_ERROR_NOT_ENOUGH_MEMORY    = Errno(8)
	_ERROR_NOT_SUPPORTED        = Errno(50)
	_ERROR_BAD_NETPATH          = Errno(53)
	_ERROR_CALL_NOT_IMPLEMENTED = Errno(120)
)

func (e Errno) Is(target error) bool {
	switch target {
	case oserror.ErrPermission:
		return e == ERROR_ACCESS_DENIED ||
			e == EACCES ||
			e == EPERM
	case oserror.ErrExist:
		return e == ERROR_ALREADY_EXISTS ||
			e == ERROR_DIR_NOT_EMPTY ||
			e == ERROR_FILE_EXISTS ||
			e == EEXIST ||
			e == ENOTEMPTY
	case oserror.ErrNotExist:
		return e == ERROR_FILE_NOT_FOUND ||
			e == _ERROR_BAD_NETPATH ||
			e == ERROR_PATH_NOT_FOUND ||
			e == ENOENT
	case errorspkg.ErrUnsupported:
		return e == _ERROR_NOT_SUPPORTED ||
			e == _ERROR_CALL_NOT_IMPLEMENTED ||
			e == ENOSYS ||
			e == ENOTSUP ||
			e == EOPNOTSUPP ||
			e == EWINDOWS
	}
	return false
}

func (e Errno) Temporary() bool {
	return e == EINTR || e == EMFILE || e.Timeout()
}

func (e Errno) Timeout() bool {
	return e == EAGAIN || e == EWOULDBLOCK || e == ETIMEDOUT
}

// Implemented in runtime/syscall_windows.go.
func compileCallback(fn any, cleanstack bool) uintptr

// NewCallback converts a Go function to a function pointer conforming to the stdcall calling convention.
// This is useful when interoperating with Windows code requiring callbacks.
// The argument is expected to be a function with one uintptr-sized result. The function must not have arguments with size larger than the size of uintptr.
// Only a limited number of callbacks may be created in a single Go process, and any memory allocated
// for these callbacks is never released.
// Between NewCallback and NewCallbackCDecl, at least 1024 callbacks can always be created.
func NewCallback(fn any) uintptr {
	return compileCallback(fn, true)
}

// NewCallbackCDecl converts a Go function to a function pointer conforming to the cdecl calling convention.
// This is useful when interoperating with Windows code requiring callbacks.
// The argument is expected to be a function with one uintptr-sized result. The function must not have arguments with size larger than the size of uintptr.
// Only a limited number of callbacks may be created in a single Go process, and any memory allocated
// for these callbacks is never released.
// Between NewCallback and NewCallbackCDecl, at least 1024 callbacks can always be created.
func NewCallbackCDecl(fn any) uintptr {
	return compileCallback(fn, false)
}

// windows api calls

//sys	GetLastError() (lasterr error)
//sys	LoadLibrary(libname string) (handle Handle, err error) = LoadLibraryW
//sys	FreeLibrary(handle Handle) (err error)
//sys	GetProcAddress(module Handle, procname string) (proc uintptr, err error)
//sys	GetVersion() (ver uint32, err error)
//sys	rtlGetNtVersionNumbers(majorVersion *uint32, minorVersion *uint32, buildNumber *uint32) = ntdll.RtlGetNtVersionNumbers
//sys	formatMessage(flags uint32, msgsrc uintptr, msgid uint32, langid uint32, buf []uint16, args *byte) (n uint32, err error) = FormatMessageW
//sys	ExitProcess(exitcode uint32)
//sys	CreateFile(name *uint16, access uint32, mode uint32, sa *SecurityAttributes, createmode uint32, attrs uint32, templatefile int32) (handle Handle, err error) [failretval==InvalidHandle] = CreateFileW
//sys	readFile(handle Handle, buf []byte, done *uint32, overlapped *Overlapped) (err error) = ReadFile
//sys	writeFile(handle Handle, buf []byte, done *uint32, overlapped *Overlapped) (err error) = WriteFile
//sys	SetFilePointer(handle Handle, lowoffset int32, highoffsetptr *int32, whence uint32) (newlowoffset uint32, err error) [failretval==0xffffffff]
//sys	CloseHandle(handle Handle) (err error)
//sys	GetStdHandle(stdhandle int) (handle Handle, err error) [failretval==InvalidHandle]
//sys	findFirstFile1(name *uint16, data *win32finddata1) (handle Handle, err error) [failretval==InvalidHandle] = FindFirstFileW
//sys	findNextFile1(handle Handle, data *win32finddata1) (err error) = FindNextFileW
//sys	FindClose(handle Handle) (err error)
//sys	GetFileInformationByHandle(handle Handle, data *ByHandleFileInformation) (err error)
//sys	GetCurrentDirectory(buflen uint32, buf *uint16) (n uint32, err error) = GetCurrentDirectoryW
//sys	SetCurrentDirectory(path *uint16) (err error) = SetCurrentDirectoryW
//sys	CreateDirectory(path *uint16, sa *SecurityAttributes) (err error) = CreateDirectoryW
//sys	RemoveDirectory(path *uint16) (err error) = RemoveDirectoryW
//sys	DeleteFile(path *uint16) (err error) = DeleteFileW
//sys	MoveFile(from *uint16, to *uint16) (err error) = MoveFileW
//sys	GetComputerName(buf *uint16, n *uint32) (err error) = GetComputerNameW
//sys	SetEndOfFile(handle Handle) (err error)
//sys	GetSystemTimeAsFileTime(time *Filetime)
//sys	GetTimeZoneInformation(tzi *Timezoneinformation) (rc uint32, err error) [failretval==0xffffffff]
//sys	createIoCompletionPort(filehandle Handle, cphandle Handle, key uintptr, threadcnt uint32) (handle Handle, err error) = CreateIoCompletionPort
//sys	getQueuedCompletionStatus(cphandle Handle, qty *uint32, key *uintptr, overlapped **Overlapped, timeout uint32) (err error) = GetQueuedCompletionStatus
//sys	postQueuedCompletionStatus(cphandle Handle, qty uint32, key uintptr, overlapped *Overlapped) (err error) = PostQueuedCompletionStatus
//sys	CancelIo(s Handle) (err error)
//sys	CancelIoEx(s Handle, o *Overlapped) (err error)
//sys	CreateProcess(appName *uint16, commandLine *uint16, procSecurity *SecurityAttributes, threadSecurity *SecurityAttributes, inheritHandles bool, creationFlags uint32, env *uint16, currentDir *uint16, startupInfo *StartupInfo, outProcInfo *ProcessInformation) (err error) = CreateProcessW
//sys	CreateProcessAsUser(token Token, appName *uint16, commandLine *uint16, procSecurity *SecurityAttributes, threadSecurity *SecurityAttributes, inheritHandles bool, creationFlags uint32, env *uint16, currentDir *uint16, startupInfo *StartupInfo, outProcInfo *ProcessInformation) (err error) = advapi32.CreateProcessAsUserW
//sys	OpenProcess(da uint32, inheritHandle bool, pid uint32) (handle Handle, err error)
//sys	TerminateProcess(handle Handle, exitcode uint32) (err error)
//sys	GetExitCodeProcess(handle Handle, exitcode *uint32) (err error)
//sys	GetStartupInfo(startupInfo *StartupInfo) (err error) = GetStartupInfoW
//sys	GetCurrentProcess() (pseudoHandle Handle, err error)
//sys	GetProcessTimes(handle Handle, creationTime *Filetime, exitTime *Filetime, kernelTime *Filetime, userTime *Filetime) (err error)
//sys	DuplicateHandle(hSourceProcessHandle Handle, hSourceHandle Handle, hTargetProcessHandle Handle, lpTargetHandle *Handle, dwDesiredAccess uint32, bInheritHandle bool, dwOptions uint32) (err error)
//sys	WaitForSingleObject(handle Handle, waitMilliseconds uint32) (event uint32, err error) [failretval==0xffffffff]
//sys	GetTempPath(buflen uint32, buf *uint16) (n uint32, err error) = GetTempPathW
//sys	CreatePipe(readhandle *Handle, writehandle *Handle, sa *SecurityAttributes, size uint32) (err error)
//sys	GetFileType(filehandle Handle) (n uint32, err error)
//sys	CryptAcquireContext(provhandle *Handle, container *uint16, provider *uint16, provtype uint32, flags uint32) (err error) = advapi32.CryptAcquireContextW
//sys	CryptReleaseContext(provhandle Handle, flags uint32) (err error) = advapi32.CryptReleaseContext
//sys	CryptGenRandom(provhandle Handle, buflen uint32, buf *byte) (err error) = advapi32.CryptGenRandom
//sys	GetEnvironmentStrings() (envs *uint16, err error) [failretval==nil] = kernel32.GetEnvironmentStringsW
//sys	FreeEnvironmentStrings(envs *uint16) (err error) = kernel32.FreeEnvironmentStringsW
//sys	GetEnvironmentVariable(name *uint16, buffer *uint16, size uint32) (n uint32, err error) = kernel32.GetEnvironmentVariableW
//sys	SetEnvironmentVariable(name *uint16, value *uint16) (err error) = kernel32.SetEnvironmentVariableW
//sys	SetFileTime(handle Handle, ctime *Filetime, atime *Filetime, wtime *Filetime) (err error)
//sys	GetFileAttributes(name *uint16) (attrs uint32, err error) [failretval==INVALID_FILE_ATTRIBUTES] = kernel32.GetFileAttributesW
//sys	SetFileAttributes(name *uint16, attrs uint32) (err error) = kernel32.SetFileAttributesW
//sys	GetFileAttributesEx(name *uint16, level uint32, info *byte) (err error) = kernel32.GetFileAttributesExW
//sys	GetCommandLine() (cmd *uint16) = kernel32.GetCommandLineW
//sys	CommandLineToArgv(cmd *uint16, argc *int32) (argv *[8192]*[8192]uint16, err error) [failretval==nil] = shell32.CommandLineToArgvW
//sys	LocalFree(hmem Handle) (handle Handle, err error) [failretval!=0]
//sys	SetHandleInformation(handle Handle, mask uint32, flags uint32) (err error)
//sys	FlushFileBuffers(handle Handle) (err error)
//sys	GetFullPathName(path *uint16, buflen uint32, buf *uint16, fname **uint16) (n uint32, err error) = kernel32.GetFullPathNameW
//sys	GetLongPathName(path *uint16, buf *uint16, buflen uint32) (n uint32, err error) = kernel32.GetLongPathNameW
//sys	GetShortPathName(longpath *uint16, shortpath *uint16, buflen uint32) (n uint32, err error) = kernel32.GetShortPathNameW
//sys	CreateFileMapping(fhandle Handle, sa *SecurityAttributes, prot uint32, maxSizeHigh uint32, maxSizeLow uint32, name *uint16) (handle Handle, err error) = kernel32.CreateFileMappingW
//sys	MapViewOfFile(handle Handle, access uint32, offsetHigh uint32, offsetLow uint32, length uintptr) (addr uintptr, err error)
//sys	UnmapViewOfFile(addr uintptr) (err error)
//sys	FlushViewOfFile(addr uintptr, length uintptr) (err error)
//sys	VirtualLock(addr uintptr, length uintptr) (err error)
//sys	VirtualUnlock(addr uintptr, length uintptr) (err error)
//sys	TransmitFile(s Handle, handle Handle, bytesToWrite uint32, bytsPerSend uint32, overlapped *Overlapped, transmitFileBuf *TransmitFileBuffers, flags uint32) (err error) = mswsock.TransmitFile
//sys	ReadDirectoryChanges(handle Handle, buf *byte, buflen uint32, watchSubTree bool, mask uint32, retlen *uint32, overlapped *Overlapped, completionRoutine uintptr) (err error) = kernel32.ReadDirectoryChangesW
//sys	CertOpenSystemStore(hprov Handle, name *uint16) (store Handle, err error) = crypt32.CertOpenSystemStoreW
//sys   CertOpenStore(storeProvider uintptr, msgAndCertEncodingType uint32, cryptProv uintptr, flags uint32, para uintptr) (handle Handle, err error) = crypt32.CertOpenStore
//sys	CertEnumCertificatesInStore(store Handle, prevContext *CertContext) (context *CertContext, err error) [failretval==nil] = crypt32.CertEnumCertificatesInStore
//sys   CertAddCertificateContextToStore(store Handle, certContext *CertContext, addDisposition uint32, storeContext **CertContext) (err error) = crypt32.CertAddCertificateContextToStore
//sys	CertCloseStore(store Handle, flags uint32) (err error) = crypt32.CertCloseStore
//sys   CertGetCertificateChain(engine Handle, leaf *CertContext, time *Filetime, additionalStore Handle, para *CertChainPara, flags uint32, reserved uintptr, chainCtx **CertChainContext) (err error) = crypt32.CertGetCertificateChain
//sys   CertFreeCertificateChain(ctx *CertChainContext) = crypt32.CertFreeCertificateChain
//sys   CertCreateCertificateContext(certEncodingType uint32, certEncoded *byte, encodedLen uint32) (context *CertContext, err error) [failretval==nil] = crypt32.CertCreateCertificateContext
//sys   CertFreeCertificateContext(ctx *CertContext) (err error) = crypt32.CertFreeCertificateContext
//sys   CertVerifyCertificateChainPolicy(policyOID uintptr, chain *CertChainContext, para *CertChainPolicyPara, status *CertChainPolicyStatus) (err error) = crypt32.CertVerifyCertificateChainPolicy
//sys	RegOpenKeyEx(key Handle, subkey *uint16, options uint32, desiredAccess uint32, result *Handle) (regerrno error) = advapi32.RegOpenKeyExW
//sys	RegCloseKey(key Handle) (regerrno error) = advapi32.RegCloseKey
//sys	RegQueryInfoKey(key Handle, class *uint16, classLen *uint32, reserved *uint32, subkeysLen *uint32, maxSubkeyLen *uint32, maxClassLen *uint32, valuesLen *uint32, maxValueNameLen *uint32, maxValueLen *uint32, saLen *uint32, lastWriteTime *Filetime) (regerrno error) = advapi32.RegQueryInfoKeyW
//sys	regEnumKeyEx(key Handle, index uint32, name *uint16, nameLen *uint32, reserved *uint32, class *uint16, classLen *uint32, lastWriteTime *Filetime) (regerrno error) = advapi32.RegEnumKeyExW
//sys	RegQueryValueEx(key Handle, name *uint16, reserved *uint32, valtype *uint32, buf *byte, buflen *uint32) (regerrno error) = advapi32.RegQueryValueExW
//sys	getCurrentProcessId() (pid uint32) = kernel32.GetCurrentProcessId
//sys	GetConsoleMode(console Handle, mode *uint32) (err error) = kernel32.GetConsoleMode
//sys	WriteConsole(console Handle, buf *uint16, towrite uint32, written *uint32, reserved *byte) (err error) = kernel32.WriteConsoleW
//sys	ReadConsole(console Handle, buf *uint16, toread uint32, read *uint32, inputControl *byte) (err error) = kernel32.ReadConsoleW
//sys	CreateToolhelp32Snapshot(flags uint32, processId uint32) (handle Handle, err error) [failretval==InvalidHandle] = kernel32.CreateToolhelp32Snapshot
//sys	Process32First(snapshot Handle, procEntry *ProcessEntry32) (err error) = kernel32.Process32FirstW
//sys	Process32Next(snapshot Handle, procEntry *ProcessEntry32) (err error) = kernel32.Process32NextW
//sys	DeviceIoControl(handle Handle, ioControlCode uint32, inBuffer *byte, inBufferSize uint32, outBuffer *byte, outBufferSize uint32, bytesReturned *uint32, overlapped *Overlapped) (err error)
// This function returns 1 byte BOOLEAN rather than the 4 byte BOOL.
//sys	CreateSymbolicLink(symlinkfilename *uint16, targetfilename *uint16, flags uint32) (err error) [failretval&0xff==0] = CreateSymbolicLinkW
//sys	CreateHardLink(filename *uint16, existingfilename *uint16, reserved uintptr) (err error) [failretval&0xff==0] = CreateHardLinkW
//sys	initializeProcThreadAttributeList(attrlist *_PROC_THREAD_ATTRIBUTE_LIST, attrcount uint32, flags uint32, size *uintptr) (err error) = InitializeProcThreadAttributeList
//sys	deleteProcThreadAttributeList(attrlist *_PROC_THREAD_ATTRIBUTE_LIST) = DeleteProcThreadAttributeList
//sys	updateProcThreadAttribute(attrlist *_PROC_THREAD_ATTRIBUTE_LIST, flags uint32, attr uintptr, value unsafe.Pointer, size uintptr, prevvalue unsafe.Pointer, returnedsize *uintptr) (err error) = UpdateProcThreadAttribute
//sys	getFinalPathNameByHandle(file Handle, filePath *uint16, filePathSize uint32, flags uint32) (n uint32, err error) [n == 0 || n >= filePathSize] = kernel32.GetFinalPathNameByHandleW

// syscall interface implementation for other packages

func makeInheritSa() *SecurityAttributes {
	var sa SecurityAttributes
	sa.Length = uint32(unsafe.Sizeof(sa))
	sa.InheritHandle = 1
	return &sa
}

func Open(path string, mode int, perm uint32) (fd Handle, err error) {
	if len(path) == 0 {
		return InvalidHandle, ERROR_FILE_NOT_FOUND
	}
	pathp, err := UTF16PtrFromString(path)
	if err != nil {
		return InvalidHandle, err
	}
	var access uint32
	switch mode & (O_RDONLY | O_WRONLY | O_RDWR) {
	case O_RDONLY:
		access = GENERIC_READ
	case O_WRONLY:
		access = GENERIC_WRITE
	case O_RDWR:
		access = GENERIC_READ | GENERIC_WRITE
	}
	if mode&O_CREAT != 0 {
		access |= GENERIC_WRITE
	}
	if mode&O_APPEND != 0 {
		access &^= GENERIC_WRITE
		access |= FILE_APPEND_DATA
	}
	sharemode := uint32(FILE_SHARE_READ | FILE_SHARE_WRITE)
	var sa *SecurityAttributes
	if mode&O_CLOEXEC == 0 {
		sa = makeInheritSa()
	}
	var createmode uint32
	switch {
	case mode&(O_CREAT|O_EXCL) == (O_CREAT | O_EXCL):
		createmode = CREATE_NEW
	case mode&(O_CREAT|O_TRUNC) == (O_CREAT | O_TRUNC):
		createmode = CREATE_ALWAYS
	case mode&O_CREAT == O_CREAT:
		createmode = OPEN_ALWAYS
	case mode&O_TRUNC == O_TRUNC:
		createmode = TRUNCATE_EXISTING
	default:
		createmode = OPEN_EXISTING
	}
	var attrs uint32 = FILE_ATTRIBUTE_NORMAL
	if perm&S_IWRITE == 0 {
		attrs = FILE_ATTRIBUTE_READONLY
		if createmode == CREATE_ALWAYS {
			// We have been asked to create a read-only file.
			// If the file already exists, the semantics of
			// the Unix open system call is to preserve the
			// existing permissions. If we pass CREATE_ALWAYS
			// and FILE_ATTRIBUTE_READONLY to CreateFile,
			// and the file already exists, CreateFile will
			// change the file permissions.
			// Avoid that to preserve the Unix semantics.
			h, e := CreateFile(pathp, access, sharemode, sa, TRUNCATE_EXISTING, FILE_ATTRIBUTE_NORMAL, 0)
			switch e {
			case ERROR_FILE_NOT_FOUND, _ERROR_BAD_NETPATH, ERROR_PATH_NOT_FOUND:
				// File does not exist. These are the same
				// errors as Errno.Is checks for ErrNotExist.
				// Carry on to create the file.
			default:
				// Success or some different error.
				return h, e
			}
		}
	}
	if createmode == OPEN_EXISTING && access == GENERIC_READ {
		// Necessary for opening directory handles.
		attrs |= FILE_FLAG_BACKUP_SEMANTICS
	}
	return CreateFile(pathp, access, sharemode, sa, createmode, attrs, 0)
}

func Read(fd Handle, p []byte) (n int, err error) {
	var done uint32
	e := ReadFile(fd, p, &done, nil)
	if e != nil {
		if e == ERROR_BROKEN_PIPE {
			// NOTE(brainman): work around ERROR_BROKEN_PIPE is returned on reading EOF from stdin
			return 0, nil
		}
		return 0, e
	}
	return int(done), nil
}

func Write(fd Handle, p []byte) (n int, err error) {
	var done uint32
	e := WriteFile(fd, p, &done, nil)
	if e != nil {
		return 0, e
	}
	return int(done), nil
}

func ReadFile(fd Handle, p []byte, done *uint32, overlapped *Overlapped) error {
	err := readFile(fd, p, done, overlapped)
	if race.Enabled {
		if *done > 0 {
			race.WriteRange(unsafe.Pointer(&p[0]), int(*done))
		}
		race.Acquire(unsafe.Pointer(&ioSync))
	}
	if msanenabled && *done > 0 {
		msanWrite(unsafe.Pointer(&p[0]), int(*done))
	}
	if asanenabled && *done > 0 {
		asanWrite(unsafe.Pointer(&p[0]), int(*done))
	}
	return err
}

func WriteFile(fd Handle, p []byte, done *uint32, overlapped *Overlapped) error {
	if race.Enabled {
		race.ReleaseMerge(unsafe.Pointer(&ioSync))
	}
	err := writeFile(fd, p, done, overlapped)
	if race.Enabled && *done > 0 {
		race.ReadRange(unsafe.Pointer(&p[0]), int(*done))
	}
	if msanenabled && *done > 0 {
		msanRead(unsafe.Pointer(&p[0]), int(*done))
	}
	if asanenabled && *done > 0 {
		asanRead(unsafe.Pointer(&p[0]), int(*done))
	}
	return err
}

var ioSync int64

var procSetFilePointerEx = modkernel32.NewProc("SetFilePointerEx")

const ptrSize = unsafe.Sizeof(uintptr(0))

// setFilePointerEx calls SetFilePointerEx.
// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365542(v=vs.85).aspx
func setFilePointerEx(handle Handle, distToMove int64, newFilePointer *int64, whence uint32) error {
	var e1 Errno
	if unsafe.Sizeof(uintptr(0)) == 8 {
		_, _, e1 = Syscall6(procSetFilePointerEx.Addr(), 4, uintptr(handle), uintptr(distToMove), uintptr(unsafe.Pointer(newFilePointer)), uintptr(whence), 0, 0)
	} else {
		// Different 32-bit systems disgaree about whether distToMove starts 8-byte aligned.
		switch runtime.GOARCH {
		default:
			panic("unsupported 32-bit architecture")
		case "386":
			// distToMove is a LARGE_INTEGER, which is 64 bits.
			_, _, e1 = Syscall6(procSetFilePointerEx.Addr(), 5, uintptr(handle), uintptr(distToMove), uintptr(distToMove>>32), uintptr(unsafe.Pointer(newFilePointer)), uintptr(whence), 0)
		case "arm":
			// distToMove must be 8-byte aligned per ARM calling convention
			// https://docs.microsoft.com/en-us/cpp/build/overview-of-arm-abi-conventions#stage-c-assignment-of-arguments-to-registers-and-stack
			_, _, e1 = Syscall6(procSetFilePointerEx.Addr(), 6, uintptr(handle), 0, uintptr(distToMove), uintptr(distToMove>>32), uintptr(unsafe.Pointer(newFilePointer)), uintptr(whence))
		}
	}
	if e1 != 0 {
		return errnoErr(e1)
	}
	return nil
}

func Seek(fd Handle, offset int64, whence int) (newoffset int64, err error) {
	var w uint32
	switch whence {
	case 0:
		w = FILE_BEGIN
	case 1:
		w = FILE_CURRENT
	case 2:
		w = FILE_END
	}
	err = setFilePointerEx(fd, offset, &newoffset, w)
	return
}

func Close(fd Handle) (err error) {
	return CloseHandle(fd)
}

var (
	Stdin  = getStdHandle(STD_INPUT_HANDLE)
	Stdout = getStdHandle(STD_OUTPUT_HANDLE)
	Stderr = getStdHandle(STD_ERROR_HANDLE)
)

func getStdHandle(h int) (fd Handle) {
	r, _ := GetStdHandle(h)
	return r
}

const ImplementsGetwd = true

func Getwd() (wd string, err error) {
	b := make([]uint16, 300)
	// The path of the current directory may not fit in the initial 300-word
	// buffer when long path support is enabled. The current directory may also
	// change between subsequent calls of GetCurrentDirectory. As a result, we
	// need to retry the call in a loop until the current directory fits, each
	// time with a bigger buffer.
	for {
		n, e := GetCurrentDirectory(uint32(len(b)), &b[0])
		if e != nil {
			return "", e
		}
		if int(n) <= len(b) {
			return UTF16ToString(b[:n]), nil
		}
		b = make([]uint16, n)
	}
}

func Chdir(path string) (err error) {
	pathp, err := UTF16PtrFromString(path)
	if err != nil {
		return err
	}
	return SetCurrentDirectory(pathp)
}

func Mkdir(path string, mode uint32) (err error) {
	pathp, err := UTF16PtrFromString(path)
	if err != nil {
		return err
	}
	return CreateDirectory(pathp, nil)
}

func Rmdir(path string) (err error) {
	pathp, err := UTF16PtrFromString(path)
	if err != nil {
		return err
	}
	return RemoveDirectory(pathp)
}

func Unlink(path string) (err error) {
	pathp, err := UTF16PtrFromString(path)
	if err != nil {
		return err
	}
	return DeleteFile(pathp)
}

func Rename(oldpath, newpath string) (err error) {
	from, err := UTF16PtrFromString(oldpath)
	if err != nil {
		return err
	}
	to, err := UTF16PtrFromString(newpath)
	if err != nil {
		return err
	}
	return MoveFile(from, to)
}

func ComputerName() (name string, err error) {
	var n uint32 = MAX_COMPUTERNAME_LENGTH + 1
	b := make([]uint16, n)
	e := GetComputerName(&b[0], &n)
	if e != nil {
		return "", e
	}
	return UTF16ToString(b[:n]), nil
}

func Ftruncate(fd Handle, length int64) (err error) {
	curoffset, e := Seek(fd, 0, 1)
	if e != nil {
		return e
	}
	defer Seek(fd, curoffset, 0)
	_, e = Seek(fd, length, 0)
	if e != nil {
		return e
	}
	e = SetEndOfFile(fd)
	if e != nil {
		return e
	}
	return nil
}

func Gettimeofday(tv *Timeval) (err error) {
	var ft Filetime
	GetSystemTimeAsFileTime(&ft)
	*tv = NsecToTimeval(ft.Nanoseconds())
	return nil
}

func Pipe(p []Handle) (err error) {
	if len(p) != 2 {
		return EINVAL
	}
	var r, w Handle
	e := CreatePipe(&r, &w, makeInheritSa(), 0)
	if e != nil {
		return e
	}
	p[0] = r
	p[1] = w
	return nil
}

func Utimes(path string, tv []Timeval) (err error) {
	if len(tv) != 2 {
		return EINVAL
	}
	pathp, e := UTF16PtrFromString(path)
	if e != nil {
		return e
	}
	h, e := CreateFile(pathp,
		FILE_WRITE_ATTRIBUTES, FILE_SHARE_WRITE, nil,
		OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0)
	if e != nil {
		return e
	}
	defer Close(h)
	a := Filetime{}
	w := Filetime{}
	if tv[0].Nanoseconds() != 0 {
		a = NsecToFiletime(tv[0].Nanoseconds())
	}
	if tv[0].Nanoseconds() != 0 {
		w = NsecToFiletime(tv[1].Nanoseconds())
	}
	return SetFileTime(h, nil, &a, &w)
}

// This matches the value in os/file_windows.go.
const _UTIME_OMIT = -1

func UtimesNano(path string, ts []Timespec) (err error) {
	if len(ts) != 2 {
		return EINVAL
	}
	pathp, e := UTF16PtrFromString(path)
	if e != nil {
		return e
	}
	h, e := CreateFile(pathp,
		FILE_WRITE_ATTRIBUTES, FILE_SHARE_WRITE, nil,
		OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, 0)
	if e != nil {
		return e
	}
	defer Close(h)
	a := Filetime{}
	w := Filetime{}
	if ts[0].Nsec != _UTIME_OMIT {
		a = NsecToFiletime(TimespecToNsec(ts[0]))
	}
	if ts[1].Nsec != _UTIME_OMIT {
		w = NsecToFiletime(TimespecToNsec(ts[1]))
	}
	return SetFileTime(h, nil, &a, &w)
}

func Fsync(fd Handle) (err error) {
	return FlushFileBuffers(fd)
}

func Chmod(path string, mode uint32) (err error) {
	p, e := UTF16PtrFromString(path)
	if e != nil {
		return e
	}
	attrs, e := GetFileAttributes(p)
	if e != nil {
		return e
	}
	if mode&S_IWRITE != 0 {
		attrs &^= FILE_ATTRIBUTE_READONLY
	} else {
		attrs |= FILE_ATTRIBUTE_READONLY
	}
	return SetFileAttributes(p, attrs)
}

func LoadCancelIoEx() error {
	return procCancelIoEx.Find()
}

func LoadSetFileCompletionNotificationModes() error {
	return procSetFileCompletionNotificationModes.Find()
}

// net api calls

const socket_error = uintptr(^uint32(0))

//sys	WSAStartup(verreq uint32, data *WSAData) (sockerr error) = ws2_32.WSAStartup
//sys	WSACleanup() (err error) [failretval==socket_error] = ws2_32.WSACleanup
//sys	WSAIoctl(s Handle, iocc uint32, inbuf *byte, cbif uint32, outbuf *byte, cbob uint32, cbbr *uint32, overlapped *Overlapped, completionRoutine uintptr) (err error) [failretval==socket_error] = ws2_32.WSAIoctl
//sys	socket(af int32, typ int32, protocol int32) (handle Handle, err error) [failretval==InvalidHandle] = ws2_32.socket
//sys	Setsockopt(s Handle, level int32, optname int32, optval *byte, optlen int32) (err error) [failretval==socket_error] = ws2_32.setsockopt
//sys	Getsockopt(s Handle, level int32, optname int32, optval *byte, optlen *int32) (err error) [failretval==socket_error] = ws2_32.getsockopt
//sys	bind(s Handle, name unsafe.Pointer, namelen int32) (err error) [failretval==socket_error] = ws2_32.bind
//sys	connect(s Handle, name unsafe.Pointer, namelen int32) (err error) [failretval==socket_error] = ws2_32.connect
//sys	getsockname(s Handle, rsa *RawSockaddrAny, addrlen *int32) (err error) [failretval==socket_error] = ws2_32.getsockname
//sys	getpeername(s Handle, rsa *RawSockaddrAny, addrlen *int32) (err error) [failretval==socket_error] = ws2_32.getpeername
//sys	listen(s Handle, backlog int32) (err error) [failretval==socket_error] = ws2_32.listen
//sys	shutdown(s Handle, how int32) (err error) [failretval==socket_error] = ws2_32.shutdown
//sys	Closesocket(s Handle) (err error) [failretval==socket_error] = ws2_32.closesocket
//sys	AcceptEx(ls Handle, as Handle, buf *byte, rxdatalen uint32, laddrlen uint32, raddrlen uint32, recvd *uint32, overlapped *Overlapped) (err error) = mswsock.AcceptEx
//sys	GetAcceptExSockaddrs(buf *byte, rxdatalen uint32, laddrlen uint32, raddrlen uint32, lrsa **RawSockaddrAny, lrsalen *int32, rrsa **RawSockaddrAny, rrsalen *int32) = mswsock.GetAcceptExSockaddrs
//sys	WSARecv(s Handle, bufs *WSABuf, bufcnt uint32, recvd *uint32, flags *uint32, overlapped *Overlapped, croutine *byte) (err error) [failretval==socket_error] = ws2_32.WSARecv
//sys	WSASend(s Handle, bufs *WSABuf, bufcnt uint32, sent *uint32, flags uint32, overlapped *Overlapped, croutine *byte) (err error) [failretval==socket_error] = ws2_32.WSASend
//sys	WSARecvFrom(s Handle, bufs *WSABuf, bufcnt uint32, recvd *uint32, flags *uint32,  from *RawSockaddrAny, fromlen *int32, overlapped *Overlapped, croutine *byte) (err error) [failretval==socket_error] = ws2_32.WSARecvFrom
//sys	WSASendTo(s Handle, bufs *WSABuf, bufcnt uint32, sent *uint32, flags uint32, to *RawSockaddrAny, tolen int32,  overlapped *Overlapped, croutine *byte) (err error) [failretval==socket_error] = ws2_32.WSASendTo
//sys	GetHostByName(name string) (h *Hostent, err error) [failretval==nil] = ws2_32.gethostbyname
//sys	GetServByName(name string, proto string) (s *Servent, err error) [failretval==nil] = ws2_32.getservbyname
//sys	Ntohs(netshort uint16) (u uint16) = ws2_32.ntohs
//sys	GetProtoByName(name string) (p *Protoent, err error) [failretval==nil] = ws2_32.getprotobyname
//sys	DnsQuery(name string, qtype uint16, options uint32, extra *byte, qrs **DNSRecord, pr *byte) (status error) = dnsapi.DnsQuery_W
//sys	DnsRecordListFree(rl *DNSRecord, freetype uint32) = dnsapi.DnsRecordListFree
//sys	DnsNameCompare(name1 *uint16, name2 *uint16) (same bool) = dnsapi.DnsNameCompare_W
//sys	GetAddrInfoW(nodename *uint16, servicename *uint16, hints *AddrinfoW, result **AddrinfoW) (sockerr error) = ws2_32.GetAddrInfoW
//sys	FreeAddrInfoW(addrinfo *AddrinfoW) = ws2_32.FreeAddrInfoW
//sys	GetIfEntry(pIfRow *MibIfRow) (errcode error) = iphlpapi.GetIfEntry
//sys	GetAdaptersInfo(ai *IpAdapterInfo, ol *uint32) (errcode error) = iphlpapi.GetAdaptersInfo
//sys	SetFileCompletionNotificationModes(handle Handle, flags uint8) (err error) = kernel32.SetFileCompletionNotificationModes
//sys	WSAEnumProtocols(protocols *int32, protocolBuffer *WSAProtocolInfo, bufferLength *uint32) (n int32, err error) [failretval==-1] = ws2_32.WSAEnumProtocolsW

// For testing: clients can set this flag to force
// creation of IPv6 sockets to return EAFNOSUPPORT.
var SocketDisableIPv6 bool

type RawSockaddrInet4 struct {
	Family uint16
	Port   uint16
	Addr   [4]byte /* in_addr */
	Zero   [8]uint8
}

type RawSockaddrInet6 struct {
	Family   uint16
	Port     uint16
	Flowinfo uint32
	Addr     [16]byte /* in6_addr */
	Scope_id uint32
}

type RawSockaddr struct {
	Family uint16
	Data   [14]int8
}

type RawSockaddrAny struct {
	Addr RawSockaddr
	Pad  [100]int8
}

type Sockaddr interface {
	sockaddr() (ptr unsafe.Pointer, len int32, err error) // lowercase; only we can define Sockaddrs
}

type SockaddrInet4 struct {
	Port int
	Addr [4]byte
	raw  RawSockaddrInet4
}

func (sa *SockaddrInet4) sockaddr() (unsafe.Pointer, int32, error) {
	if sa.Port < 0 || sa.Port > 0xFFFF {
		return nil, 0, EINVAL
	}
	sa.raw.Family = AF_INET
	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
	p[0] = byte(sa.Port >> 8)
	p[1] = byte(sa.Port)
	sa.raw.Addr = sa.Addr
	return unsafe.Pointer(&sa.raw), int32(unsafe.Sizeof(sa.raw)), nil
}

type SockaddrInet6 struct {
	Port   int
	ZoneId uint32
	Addr   [16]byte
	raw    RawSockaddrInet6
}

func (sa *SockaddrInet6) sockaddr() (unsafe.Pointer, int32, error) {
	if sa.Port < 0 || sa.Port > 0xFFFF {
		return nil, 0, EINVAL
	}
	sa.raw.Family = AF_INET6
	p := (*[2]byte)(unsafe.Pointer(&sa.raw.Port))
	p[0] = byte(sa.Port >> 8)
	p[1] = byte(sa.Port)
	sa.raw.Scope_id = sa.ZoneId
	sa.raw.Addr = sa.Addr
	return unsafe.Pointer(&sa.raw), int32(unsafe.Sizeof(sa.raw)), nil
}

type RawSockaddrUnix struct {
	Family uint16
	Path   [UNIX_PATH_MAX]int8
}

type SockaddrUnix struct {
	Name string
	raw  RawSockaddrUnix
}

func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, int32, error) {
	name := sa.Name
	n := len(name)
	if n > len(sa.raw.Path) {
		return nil, 0, EINVAL
	}
	if n == len(sa.raw.Path) && name[0] != '@' {
		return nil, 0, EINVAL
	}
	sa.raw.Family = AF_UNIX
	for i := 0; i < n; i++ {
		sa.raw.Path[i] = int8(name[i])
	}
	// length is family (uint16), name, NUL.
	sl := int32(2)
	if n > 0 {
		sl += int32(n) + 1
	}
	if sa.raw.Path[0] == '@' {
		sa.raw.Path[0] = 0
		// Don't count trailing NUL for abstract address.
		sl--
	}

	return unsafe.Pointer(&sa.raw), sl, nil
}

func (rsa *RawSockaddrAny) Sockaddr() (Sockaddr, error) {
	switch rsa.Addr.Family {
	case AF_UNIX:
		pp := (*RawSockaddrUnix)(unsafe.Pointer(rsa))
		sa := new(SockaddrUnix)
		if pp.Path[0] == 0 {
			// "Abstract" Unix domain socket.
			// Rewrite leading NUL as @ for textual display.
			// (This is the standard convention.)
			// Not friendly to overwrite in place,
			// but the callers below don't care.
			pp.Path[0] = '@'
		}

		// Assume path ends at NUL.
		// This is not technically the Linux semantics for
		// abstract Unix domain sockets--they are supposed
		// to be uninterpreted fixed-size binary blobs--but
		// everyone uses this convention.
		n := 0
		for n < len(pp.Path) && pp.Path[n] != 0 {
			n++
		}
		sa.Name = string(unsafe.Slice((*byte)(unsafe.Pointer(&pp.Path[0])), n))
		return sa, nil

	case AF_INET:
		pp := (*RawSockaddrInet4)(unsafe.Pointer(rsa))
		sa := new(SockaddrInet4)
		p := (*[2]byte)(unsafe.Pointer(&pp.Port))
		sa.Port = int(p[0])<<8 + int(p[1])
		sa.Addr = pp.Addr
		return sa, nil

	case AF_INET6:
		pp := (*RawSockaddrInet6)(unsafe.Pointer(rsa))
		sa := new(SockaddrInet6)
		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
		return sa, nil
	}
	return nil, EAFNOSUPPORT
}

func Socket(domain, typ, proto int) (fd Handle, err error) {
	if domain == AF_INET6 && SocketDisableIPv6 {
		return InvalidHandle, EAFNOSUPPORT
	}
	return socket(int32(domain), int32(typ), int32(proto))
}

func SetsockoptInt(fd Handle, level, opt int, value int) (err error) {
	v := int32(value)
	return Setsockopt(fd, int32(level), int32(opt), (*byte)(unsafe.Pointer(&v)), int32(unsafe.Sizeof(v)))
}

func Bind(fd Handle, sa Sockaddr) (err error) {
	ptr, n, err := sa.sockaddr()
	if err != nil {
		return err
	}
	return bind(fd, ptr, n)
}

func Connect(fd Handle, sa Sockaddr) (err error) {
	ptr, n, err := sa.sockaddr()
	if err != nil {
		return err
	}
	return connect(fd, ptr, n)
}

func Getsockname(fd Handle) (sa Sockaddr, err error) {
	var rsa RawSockaddrAny
	l := int32(unsafe.Sizeof(rsa))
	if err = getsockname(fd, &rsa, &l); err != nil {
		return
	}
	return rsa.Sockaddr()
}

func Getpeername(fd Handle) (sa Sockaddr, err error) {
	var rsa RawSockaddrAny
	l := int32(unsafe.Sizeof(rsa))
	if err = getpeername(fd, &rsa, &l); err != nil {
		return
	}
	return rsa.Sockaddr()
}

func Listen(s Handle, n int) (err error) {
	return listen(s, int32(n))
}

func Shutdown(fd Handle, how int) (err error) {
	return shutdown(fd, int32(how))
}

func WSASendto(s Handle, bufs *WSABuf, bufcnt uint32, sent *uint32, flags uint32, to Sockaddr, overlapped *Overlapped, croutine *byte) (err error) {
	var rsa unsafe.Pointer
	var len int32
	if to != nil {
		rsa, len, err = to.sockaddr()
		if err != nil {
			return err
		}
	}
	r1, _, e1 := Syscall9(procWSASendTo.Addr(), 9, uintptr(s), uintptr(unsafe.Pointer(bufs)), uintptr(bufcnt), uintptr(unsafe.Pointer(sent)), uintptr(flags), uintptr(unsafe.Pointer(rsa)), uintptr(len), uintptr(unsafe.Pointer(overlapped)), uintptr(unsafe.Pointer(croutine)))
	if r1 == socket_error {
		if e1 != 0 {
			err = errnoErr(e1)
		} else {
			err = EINVAL
		}
	}
	return err
}

func wsaSendtoInet4(s Handle, bufs *WSABuf, bufcnt uint32, sent *uint32, flags uint32, to *SockaddrInet4, overlapped *Overlapped, croutine *byte) (err error) {
	rsa, len, err := to.sockaddr()
	if err != nil {
		return err
	}
	r1, _, e1 := Syscall9(procWSASendTo.Addr(), 9, uintptr(s), uintptr(unsafe.Pointer(bufs)), uintptr(bufcnt), uintptr(unsafe.Pointer(sent)), uintptr(flags), uintptr(unsafe.Pointer(rsa)), uintptr(len), uintptr(unsafe.Pointer(overlapped)), uintptr(unsafe.Pointer(croutine)))
	if r1 == socket_error {
		if e1 != 0 {
			err = errnoErr(e1)
		} else {
			err = EINVAL
		}
	}
	return err
}

func wsaSendtoInet6(s Handle, bufs *WSABuf, bufcnt uint32, sent *uint32, flags uint32, to *SockaddrInet6, overlapped *Overlapped, croutine *byte) (err error) {
	rsa, len, err := to.sockaddr()
	if err != nil {
		return err
	}
	r1, _, e1 := Syscall9(procWSASendTo.Addr(), 9, uintptr(s), uintptr(unsafe.Pointer(bufs)), uintptr(bufcnt), uintptr(unsafe.Pointer(sent)), uintptr(flags), uintptr(unsafe.Pointer(rsa)), uintptr(len), uintptr(unsafe.Pointer(overlapped)), uintptr(unsafe.Pointer(croutine)))
	if r1 == socket_error {
		if e1 != 0 {
			err = errnoErr(e1)
		} else {
			err = EINVAL
		}
	}
	return err
}

func LoadGetAddrInfo() error {
	return procGetAddrInfoW.Find()
}

var connectExFunc struct {
	once sync.Once
	addr uintptr
	err  error
}

func LoadConnectEx() error {
	connectExFunc.once.Do(func() {
		var s Handle
		s, connectExFunc.err = Socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)
		if connectExFunc.err != nil {
			return
		}
		defer CloseHandle(s)
		var n uint32
		connectExFunc.err = WSAIoctl(s,
			SIO_GET_EXTENSION_FUNCTION_POINTER,
			(*byte)(unsafe.Pointer(&WSAID_CONNECTEX)),
			uint32(unsafe.Sizeof(WSAID_CONNECTEX)),
			(*byte)(unsafe.Pointer(&connectExFunc.addr)),
			uint32(unsafe.Sizeof(connectExFunc.addr)),
			&n, nil, 0)
	})
	return connectExFunc.err
}

func connectEx(s Handle, name unsafe.Pointer, namelen int32, sendBuf *byte, sendDataLen uint32, bytesSent *uint32, overlapped *Overlapped) (err error) {
	r1, _, e1 := Syscall9(connectExFunc.addr, 7, uintptr(s), uintptr(name), uintptr(namelen), uintptr(unsafe.Pointer(sendBuf)), uintptr(sendDataLen), uintptr(unsafe.Pointer(bytesSent)), uintptr(unsafe.Pointer(overlapped)), 0, 0)
	if r1 == 0 {
		if e1 != 0 {
			err = error(e1)
		} else {
			err = EINVAL
		}
	}
	return
}

func ConnectEx(fd Handle, sa Sockaddr, sendBuf *byte, sendDataLen uint32, bytesSent *uint32, overlapped *Overlapped) error {
	err := LoadConnectEx()
	if err != nil {
		return errorspkg.New("failed to find ConnectEx: " + err.Error())
	}
	ptr, n, err := sa.sockaddr()
	if err != nil {
		return err
	}
	return connectEx(fd, ptr, n, sendBuf, sendDataLen, bytesSent, overlapped)
}

// Invented structures to support what package os expects.
type Rusage struct {
	CreationTime Filetime
	ExitTime     Filetime
	KernelTime   Filetime
	UserTime     Filetime
}

type WaitStatus struct {
	ExitCode uint32
}

func (w WaitStatus) Exited() bool { return true }

func (w WaitStatus) ExitStatus() int { return int(w.ExitCode) }

func (w WaitStatus) Signal() Signal { return -1 }

func (w WaitStatus) CoreDump() bool { return false }

func (w WaitStatus) Stopped() bool { return false }

func (w WaitStatus) Continued() bool { return false }

func (w WaitStatus) StopSignal() Signal { return -1 }

func (w WaitStatus) Signaled() bool { return false }

func (w WaitStatus) TrapCause() int { return -1 }

// Timespec is an invented structure on Windows, but here for
// consistency with the syscall package for other operating systems.
type Timespec struct {
	Sec  int64
	Nsec int64
}

func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }

func NsecToTimespec(nsec int64) (ts Timespec) {
	ts.Sec = nsec / 1e9
	ts.Nsec = nsec % 1e9
	return
}

// TODO(brainman): fix all needed for net

func Accept(fd Handle) (nfd Handle, sa Sockaddr, err error) { return 0, nil, EWINDOWS }
func Recvfrom(fd Handle, p []byte, flags int) (n int, from Sockaddr, err error) {
	return 0, nil, EWINDOWS
}
func Sendto(fd Handle, p []byte, flags int, to Sockaddr) (err error)       { return EWINDOWS }
func SetsockoptTimeval(fd Handle, level, opt int, tv *Timeval) (err error) { return EWINDOWS }

// The Linger struct is wrong but we only noticed after Go 1.
// sysLinger is the real system call structure.

// BUG(brainman): The definition of Linger is not appropriate for direct use
// with Setsockopt and Getsockopt.
// Use SetsockoptLinger instead.

type Linger struct {
	Onoff  int32
	Linger int32
}

type sysLinger struct {
	Onoff  uint16
	Linger uint16
}

type IPMreq struct {
	Multiaddr [4]byte /* in_addr */
	Interface [4]byte /* in_addr */
}

type IPv6Mreq struct {
	Multiaddr [16]byte /* in6_addr */
	Interface uint32
}

func GetsockoptInt(fd Handle, level, opt int) (int, error) { return -1, EWINDOWS }

func SetsockoptLinger(fd Handle, level, opt int, l *Linger) (err error) {
	sys := sysLinger{Onoff: uint16(l.Onoff), Linger: uint16(l.Linger)}
	return Setsockopt(fd, int32(level), int32(opt), (*byte)(unsafe.Pointer(&sys)), int32(unsafe.Sizeof(sys)))
}

func SetsockoptInet4Addr(fd Handle, level, opt int, value [4]byte) (err error) {
	return Setsockopt(fd, int32(level), int32(opt), (*byte)(unsafe.Pointer(&value[0])), 4)
}
func SetsockoptIPMreq(fd Handle, level, opt int, mreq *IPMreq) (err error) {
	return Setsockopt(fd, int32(level), int32(opt), (*byte)(unsafe.Pointer(mreq)), int32(unsafe.Sizeof(*mreq)))
}
func SetsockoptIPv6Mreq(fd Handle, level, opt int, mreq *IPv6Mreq) (err error) { return EWINDOWS }

func Getpid() (pid int) { return int(getCurrentProcessId()) }

func FindFirstFile(name *uint16, data *Win32finddata) (handle Handle, err error) {
	// NOTE(rsc): The Win32finddata struct is wrong for the system call:
	// the two paths are each one uint16 short. Use the correct struct,
	// a win32finddata1, and then copy the results out.
	// There is no loss of expressivity here, because the final
	// uint16, if it is used, is supposed to be a NUL, and Go doesn't need that.
	// For Go 1.1, we might avoid the allocation of win32finddata1 here
	// by adding a final Bug [2]uint16 field to the struct and then
	// adjusting the fields in the result directly.
	var data1 win32finddata1
	handle, err = findFirstFile1(name, &data1)
	if err == nil {
		copyFindData(data, &data1)
	}
	return
}

func FindNextFile(handle Handle, data *Win32finddata) (err error) {
	var data1 win32finddata1
	err = findNextFile1(handle, &data1)
	if err == nil {
		copyFindData(data, &data1)
	}
	return
}

func getProcessEntry(pid int) (*ProcessEntry32, error) {
	snapshot, err := CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)
	if err != nil {
		return nil, err
	}
	defer CloseHandle(snapshot)
	var procEntry ProcessEntry32
	procEntry.Size = uint32(unsafe.Sizeof(procEntry))
	if err = Process32First(snapshot, &procEntry); err != nil {
		return nil, err
	}
	for {
		if procEntry.ProcessID == uint32(pid) {
			return &procEntry, nil
		}
		err = Process32Next(snapshot, &procEntry)
		if err != nil {
			return nil, err
		}
	}
}

func Getppid() (ppid int) {
	pe, err := getProcessEntry(Getpid())
	if err != nil {
		return -1
	}
	return int(pe.ParentProcessID)
}

func fdpath(fd Handle, buf []uint16) ([]uint16, error) {
	const (
		FILE_NAME_NORMALIZED = 0
		VOLUME_NAME_DOS      = 0
	)
	for {
		n, err := getFinalPathNameByHandle(fd, &buf[0], uint32(len(buf)), FILE_NAME_NORMALIZED|VOLUME_NAME_DOS)
		if err == nil {
			buf = buf[:n]
			break
		}
		if err != _ERROR_NOT_ENOUGH_MEMORY {
			return nil, err
		}
		buf = append(buf, make([]uint16, n-uint32(len(buf)))...)
	}
	return buf, nil
}

func Fchdir(fd Handle) (err error) {
	var buf [MAX_PATH + 1]uint16
	path, err := fdpath(fd, buf[:])
	if err != nil {
		return err
	}
	// When using VOLUME_NAME_DOS, the path is always pefixed by "\\?\".
	// That prefix tells the Windows APIs to disable all string parsing and to send
	// the string that follows it straight to the file system.
	// Although SetCurrentDirectory and GetCurrentDirectory do support the "\\?\" prefix,
	// some other Windows APIs don't. If the prefix is not removed here, it will leak
	// to Getwd, and we don't want such a general-purpose function to always return a
	// path with the "\\?\" prefix after Fchdir is called.
	// The downside is that APIs that do support it will parse the path and try to normalize it,
	// when it's already normalized.
	if len(path) >= 4 && path[0] == '\\' && path[1] == '\\' && path[2] == '?' && path[3] == '\\' {
		path = path[4:]
	}
	return SetCurrentDirectory(&path[0])
}

// TODO(brainman): fix all needed for os
func Link(oldpath, newpath string) (err error) { return EWINDOWS }
func Symlink(path, link string) (err error)    { return EWINDOWS }

func Fchmod(fd Handle, mode uint32) (err error)        { return EWINDOWS }
func Chown(path string, uid int, gid int) (err error)  { return EWINDOWS }
func Lchown(path string, uid int, gid int) (err error) { return EWINDOWS }
func Fchown(fd Handle, uid int, gid int) (err error)   { return EWINDOWS }

func Getuid() (uid int)                  { return -1 }
func Geteuid() (euid int)                { return -1 }
func Getgid() (gid int)                  { return -1 }
func Getegid() (egid int)                { return -1 }
func Getgroups() (gids []int, err error) { return nil, EWINDOWS }

type Signal int

func (s Signal) Signal() {}

func (s Signal) String() string {
	if 0 <= s && int(s) < len(signals) {
		str := signals[s]
		if str != "" {
			return str
		}
	}
	return "signal " + itoa.Itoa(int(s))
}

func LoadCreateSymbolicLink() error {
	return procCreateSymbolicLinkW.Find()
}

// Readlink returns the destination of the named symbolic link.
func Readlink(path string, buf []byte) (n int, err error) {
	fd, err := CreateFile(StringToUTF16Ptr(path), GENERIC_READ, 0, nil, OPEN_EXISTING,
		FILE_FLAG_OPEN_REPARSE_POINT|FILE_FLAG_BACKUP_SEMANTICS, 0)
	if err != nil {
		return -1, err
	}
	defer CloseHandle(fd)

	rdbbuf := make([]byte, MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
	var bytesReturned uint32
	err = DeviceIoControl(fd, FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
	if err != nil {
		return -1, err
	}

	rdb := (*reparseDataBuffer)(unsafe.Pointer(&rdbbuf[0]))
	var s string
	switch rdb.ReparseTag {
	case IO_REPARSE_TAG_SYMLINK:
		data := (*symbolicLinkReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
		p := (*[0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))
		s = UTF16ToString(p[data.SubstituteNameOffset/2 : (data.SubstituteNameOffset+data.SubstituteNameLength)/2])
		if data.Flags&_SYMLINK_FLAG_RELATIVE == 0 {
			if len(s) >= 4 && s[:4] == `\??\` {
				s = s[4:]
				switch {
				case len(s) >= 2 && s[1] == ':': // \??\C:\foo\bar
					// do nothing
				case len(s) >= 4 && s[:4] == `UNC\`: // \??\UNC\foo\bar
					s = `\\` + s[4:]
				default:
					// unexpected; do nothing
				}
			} else {
				// unexpected; do nothing
			}
		}
	case _IO_REPARSE_TAG_MOUNT_POINT:
		data := (*mountPointReparseBuffer)(unsafe.Pointer(&rdb.reparseBuffer))
		p := (*[0xffff]uint16)(unsafe.Pointer(&data.PathBuffer[0]))
		s = UTF16ToString(p[data.SubstituteNameOffset/2 : (data.SubstituteNameOffset+data.SubstituteNameLength)/2])
		if len(s) >= 4 && s[:4] == `\??\` { // \??\C:\foo\bar
			s = s[4:]
		} else {
			// unexpected; do nothing
		}
	default:
		// the path is not a symlink or junction but another type of reparse
		// point
		return -1, ENOENT
	}
	n = copy(buf, []byte(s))

	return n, nil
}

// Deprecated: CreateIoCompletionPort has the wrong function signature. Use x/sys/windows.CreateIoCompletionPort.
func CreateIoCompletionPort(filehandle Handle, cphandle Handle, key uint32, threadcnt uint32) (Handle, error) {
	return createIoCompletionPort(filehandle, cphandle, uintptr(key), threadcnt)
}

// Deprecated: GetQueuedCompletionStatus has the wrong function signature. Use x/sys/windows.GetQueuedCompletionStatus.
func GetQueuedCompletionStatus(cphandle Handle, qty *uint32, key *uint32, overlapped **Overlapped, timeout uint32) error {
	var ukey uintptr
	var pukey *uintptr
	if key != nil {
		ukey = uintptr(*key)
		pukey = &ukey
	}
	err := getQueuedCompletionStatus(cphandle, qty, pukey, overlapped, timeout)
	if key != nil {
		*key = uint32(ukey)
		if uintptr(*key) != ukey && err == nil {
			err = errorspkg.New("GetQueuedCompletionStatus returned key overflow")
		}
	}
	return err
}

// Deprecated: PostQueuedCompletionStatus has the wrong function signature. Use x/sys/windows.PostQueuedCompletionStatus.
func PostQueuedCompletionStatus(cphandle Handle, qty uint32, key uint32, overlapped *Overlapped) error {
	return postQueuedCompletionStatus(cphandle, qty, uintptr(key), overlapped)
}

// newProcThreadAttributeList allocates new PROC_THREAD_ATTRIBUTE_LIST, with
// the requested maximum number of attributes, which must be cleaned up by
// deleteProcThreadAttributeList.
func newProcThreadAttributeList(maxAttrCount uint32) (*_PROC_THREAD_ATTRIBUTE_LIST, error) {
	var size uintptr
	err := initializeProcThreadAttributeList(nil, maxAttrCount, 0, &size)
	if err != ERROR_INSUFFICIENT_BUFFER {
		if err == nil {
			return nil, errorspkg.New("unable to query buffer size from InitializeProcThreadAttributeList")
		}
		return nil, err
	}
	// size is guaranteed to be ≥1 by initializeProcThreadAttributeList.
	al := (*_PROC_THREAD_ATTRIBUTE_LIST)(unsafe.Pointer(&make([]byte, size)[0]))
	err = initializeProcThreadAttributeList(al, maxAttrCount, 0, &size)
	if err != nil {
		return nil, err
	}
	return al, nil
}

// RegEnumKeyEx enumerates the subkeys of an open registry key.
// Each call retrieves information about one subkey. name is
// a buffer that should be large enough to hold the name of the
// subkey plus a null terminating character. nameLen is its
// length. On return, nameLen will contain the actual length of the
// subkey.
//
// Should name not be large enough to hold the subkey, this function
// will return ERROR_MORE_DATA, and must be called again with an
// appropriately sized buffer.
//
// reserved must be nil. class and classLen behave like name and nameLen
// but for the class of the subkey, except that they are optional.
// lastWriteTime, if not nil, will be populated with the time the subkey
// was last written.
//
// The caller must enumerate all subkeys in order. That is
// RegEnumKeyEx must be called with index starting at 0, incrementing
// the index until the function returns ERROR_NO_MORE_ITEMS, or with
// the index of the last subkey (obtainable from RegQueryInfoKey),
// decrementing until index 0 is enumerated.
//
// Successive calls to this API must happen on the same OS thread,
// so call runtime.LockOSThread before calling this function.
func RegEnumKeyEx(key Handle, index uint32, name *uint16, nameLen *uint32, reserved *uint32, class *uint16, classLen *uint32, lastWriteTime *Filetime) (regerrno error) {
	return regEnumKeyEx(key, index, name, nameLen, reserved, class, classLen, lastWriteTime)
}
