windows/svc/service.go - sys - Git at Google

 // Copyright 2012 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.

 //go:build windows

 // Package svc provides everything required to build Windows service.
 package svc

 import (
 	"errors"
 	"sync"
 	"unsafe"

 	"golang.org/x/sys/windows"
 )

 // State describes service execution state (Stopped, Running and so on).
 type State uint32

 const (
 	Stopped         = State(windows.SERVICE_STOPPED)
 	StartPending    = State(windows.SERVICE_START_PENDING)
 	StopPending     = State(windows.SERVICE_STOP_PENDING)
 	Running         = State(windows.SERVICE_RUNNING)
 	ContinuePending = State(windows.SERVICE_CONTINUE_PENDING)
 	PausePending    = State(windows.SERVICE_PAUSE_PENDING)
 	Paused          = State(windows.SERVICE_PAUSED)
 )

 // Cmd represents service state change request. It is sent to a service
 // by the service manager, and should be actioned upon by the service.
 type Cmd uint32

 const (
 	Stop                  = Cmd(windows.SERVICE_CONTROL_STOP)
 	Pause                 = Cmd(windows.SERVICE_CONTROL_PAUSE)
 	Continue              = Cmd(windows.SERVICE_CONTROL_CONTINUE)
 	Interrogate           = Cmd(windows.SERVICE_CONTROL_INTERROGATE)
 	Shutdown              = Cmd(windows.SERVICE_CONTROL_SHUTDOWN)
 	ParamChange           = Cmd(windows.SERVICE_CONTROL_PARAMCHANGE)
 	NetBindAdd            = Cmd(windows.SERVICE_CONTROL_NETBINDADD)
 	NetBindRemove         = Cmd(windows.SERVICE_CONTROL_NETBINDREMOVE)
 	NetBindEnable         = Cmd(windows.SERVICE_CONTROL_NETBINDENABLE)
 	NetBindDisable        = Cmd(windows.SERVICE_CONTROL_NETBINDDISABLE)
 	DeviceEvent           = Cmd(windows.SERVICE_CONTROL_DEVICEEVENT)
 	HardwareProfileChange = Cmd(windows.SERVICE_CONTROL_HARDWAREPROFILECHANGE)
 	PowerEvent            = Cmd(windows.SERVICE_CONTROL_POWEREVENT)
 	SessionChange         = Cmd(windows.SERVICE_CONTROL_SESSIONCHANGE)
 	PreShutdown           = Cmd(windows.SERVICE_CONTROL_PRESHUTDOWN)
 )

 // Accepted is used to describe commands accepted by the service.
 // Note that Interrogate is always accepted.
 type Accepted uint32

 const (
 	AcceptStop                  = Accepted(windows.SERVICE_ACCEPT_STOP)
 	AcceptShutdown              = Accepted(windows.SERVICE_ACCEPT_SHUTDOWN)
 	AcceptPauseAndContinue      = Accepted(windows.SERVICE_ACCEPT_PAUSE_CONTINUE)
 	AcceptParamChange           = Accepted(windows.SERVICE_ACCEPT_PARAMCHANGE)
 	AcceptNetBindChange         = Accepted(windows.SERVICE_ACCEPT_NETBINDCHANGE)
 	AcceptHardwareProfileChange = Accepted(windows.SERVICE_ACCEPT_HARDWAREPROFILECHANGE)
 	AcceptPowerEvent            = Accepted(windows.SERVICE_ACCEPT_POWEREVENT)
 	AcceptSessionChange         = Accepted(windows.SERVICE_ACCEPT_SESSIONCHANGE)
 	AcceptPreShutdown           = Accepted(windows.SERVICE_ACCEPT_PRESHUTDOWN)
 )

 // ActivityStatus allows for services to be selected based on active and inactive categories of service state.
 type ActivityStatus uint32

 const (
 	Active      = ActivityStatus(windows.SERVICE_ACTIVE)
 	Inactive    = ActivityStatus(windows.SERVICE_INACTIVE)
 	AnyActivity = ActivityStatus(windows.SERVICE_STATE_ALL)
 )

 // Status combines State and Accepted commands to fully describe running service.
 type Status struct {
 	State                   State
 	Accepts                 Accepted
 	CheckPoint              uint32 // used to report progress during a lengthy operation
 	WaitHint                uint32 // estimated time required for a pending operation, in milliseconds
 	ProcessId               uint32 // if the service is running, the process identifier of it, and otherwise zero
 	Win32ExitCode           uint32 // set if the service has exited with a win32 exit code
 	ServiceSpecificExitCode uint32 // set if the service has exited with a service-specific exit code
 }

 // StartReason is the reason that the service was started.
 type StartReason uint32

 const (
 	StartReasonDemand           = StartReason(windows.SERVICE_START_REASON_DEMAND)
 	StartReasonAuto             = StartReason(windows.SERVICE_START_REASON_AUTO)
 	StartReasonTrigger          = StartReason(windows.SERVICE_START_REASON_TRIGGER)
 	StartReasonRestartOnFailure = StartReason(windows.SERVICE_START_REASON_RESTART_ON_FAILURE)
 	StartReasonDelayedAuto      = StartReason(windows.SERVICE_START_REASON_DELAYEDAUTO)
 )

 // ChangeRequest is sent to the service Handler to request service status change.
 type ChangeRequest struct {
 	Cmd           Cmd
 	EventType     uint32
 	EventData     uintptr
 	CurrentStatus Status
 	Context       uintptr
 }

 // Handler is the interface that must be implemented to build Windows service.
 type Handler interface {
 	// Execute will be called by the package code at the start of
 	// the service, and the service will exit once Execute completes.
 	// Inside Execute you must read service change requests from r and
 	// act accordingly. You must keep service control manager up to date
 	// about state of your service by writing into s as required.
 	// args contains service name followed by argument strings passed
 	// to the service.
 	// You can provide service exit code in exitCode return parameter,
 	// with 0 being "no error". You can also indicate if exit code,
 	// if any, is service specific or not by using svcSpecificEC
 	// parameter.
 	Execute(args []string, r <-chan ChangeRequest, s chan<- Status) (svcSpecificEC bool, exitCode uint32)
 }

 type ctlEvent struct {
 	cmd       Cmd
 	eventType uint32
 	eventData uintptr
 	context   uintptr
 	errno     uint32
 }

 // service provides access to windows service api.
 type service struct {
 	name    string
 	h       windows.Handle
 	c       chan ctlEvent
 	handler Handler
 }

 type exitCode struct {
 	isSvcSpecific bool
 	errno         uint32
 }

 func (s *service) updateStatus(status *Status, ec *exitCode) error {
 	if s.h == 0 {
 		return errors.New("updateStatus with no service status handle")
 	}
 	var t windows.SERVICE_STATUS
 	t.ServiceType = windows.SERVICE_WIN32_OWN_PROCESS
 	t.CurrentState = uint32(status.State)
 	if status.Accepts&AcceptStop != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_STOP
 	}
 	if status.Accepts&AcceptShutdown != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_SHUTDOWN
 	}
 	if status.Accepts&AcceptPauseAndContinue != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_PAUSE_CONTINUE
 	}
 	if status.Accepts&AcceptParamChange != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_PARAMCHANGE
 	}
 	if status.Accepts&AcceptNetBindChange != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_NETBINDCHANGE
 	}
 	if status.Accepts&AcceptHardwareProfileChange != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_HARDWAREPROFILECHANGE
 	}
 	if status.Accepts&AcceptPowerEvent != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_POWEREVENT
 	}
 	if status.Accepts&AcceptSessionChange != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_SESSIONCHANGE
 	}
 	if status.Accepts&AcceptPreShutdown != 0 {
 		t.ControlsAccepted |= windows.SERVICE_ACCEPT_PRESHUTDOWN
 	}
 	if ec.errno == 0 {
 		t.Win32ExitCode = windows.NO_ERROR
 		t.ServiceSpecificExitCode = windows.NO_ERROR
 	} else if ec.isSvcSpecific {
 		t.Win32ExitCode = uint32(windows.ERROR_SERVICE_SPECIFIC_ERROR)
 		t.ServiceSpecificExitCode = ec.errno
 	} else {
 		t.Win32ExitCode = ec.errno
 		t.ServiceSpecificExitCode = windows.NO_ERROR
 	}
 	t.CheckPoint = status.CheckPoint
 	t.WaitHint = status.WaitHint
 	return windows.SetServiceStatus(s.h, &t)
 }

 var (
 	initCallbacks       sync.Once
 	ctlHandlerCallback  uintptr
 	serviceMainCallback uintptr
 )

 func ctlHandler(ctl, evtype, evdata, context uintptr) uintptr {
 	s := (*service)(unsafe.Pointer(context))
 	e := ctlEvent{cmd: Cmd(ctl), eventType: uint32(evtype), eventData: evdata, context: 123456} // Set context to 123456 to test issue #25660.
 	s.c <- e
 	return 0
 }

 var theService service // This is, unfortunately, a global, which means only one service per process.

 // serviceMain is the entry point called by the service manager, registered earlier by
 // the call to StartServiceCtrlDispatcher.
 func serviceMain(argc uint32, argv **uint16) uintptr {
 	handle, err := windows.RegisterServiceCtrlHandlerEx(windows.StringToUTF16Ptr(theService.name), ctlHandlerCallback, uintptr(unsafe.Pointer(&theService)))
 	if sysErr, ok := err.(windows.Errno); ok {
 		return uintptr(sysErr)
 	} else if err != nil {
 		return uintptr(windows.ERROR_UNKNOWN_EXCEPTION)
 	}
 	theService.h = handle
 	defer func() {
 		theService.h = 0
 	}()
 	args16 := unsafe.Slice(argv, int(argc))

 	args := make([]string, len(args16))
 	for i, a := range args16 {
 		args[i] = windows.UTF16PtrToString(a)
 	}

 	cmdsToHandler := make(chan ChangeRequest)
 	changesFromHandler := make(chan Status)
 	exitFromHandler := make(chan exitCode)

 	go func() {
 		ss, errno := theService.handler.Execute(args, cmdsToHandler, changesFromHandler)
 		exitFromHandler <- exitCode{ss, errno}
 	}()

 	ec := exitCode{isSvcSpecific: true, errno: 0}
 	outcr := ChangeRequest{
 		CurrentStatus: Status{State: Stopped},
 	}
 	var outch chan ChangeRequest
 	inch := theService.c
 loop:
 	for {
 		select {
 		case r := <-inch:
 			if r.errno != 0 {
 				ec.errno = r.errno
 				break loop
 			}
 			inch = nil
 			outch = cmdsToHandler
 			outcr.Cmd = r.cmd
 			outcr.EventType = r.eventType
 			outcr.EventData = r.eventData
 			outcr.Context = r.context
 		case outch <- outcr:
 			inch = theService.c
 			outch = nil
 		case c := <-changesFromHandler:
 			err := theService.updateStatus(&c, &ec)
 			if err != nil {
 				ec.errno = uint32(windows.ERROR_EXCEPTION_IN_SERVICE)
 				if err2, ok := err.(windows.Errno); ok {
 					ec.errno = uint32(err2)
 				}
 				break loop
 			}
 			outcr.CurrentStatus = c
 		case ec = <-exitFromHandler:
 			break loop
 		}
 	}

 	theService.updateStatus(&Status{State: Stopped}, &ec)

 	return windows.NO_ERROR
 }

 // Run executes service name by calling appropriate handler function.
 func Run(name string, handler Handler) error {
 	initCallbacks.Do(func() {
 		ctlHandlerCallback = windows.NewCallback(ctlHandler)
 		serviceMainCallback = windows.NewCallback(serviceMain)
 	})
 	theService.name = name
 	theService.handler = handler
 	theService.c = make(chan ctlEvent)
 	t := []windows.SERVICE_TABLE_ENTRY{
 		{ServiceName: windows.StringToUTF16Ptr(theService.name), ServiceProc: serviceMainCallback},
 		{ServiceName: nil, ServiceProc: 0},
 	}
 	return windows.StartServiceCtrlDispatcher(&t[0])
 }

 // StatusHandle returns service status handle. It is safe to call this function
 // from inside the Handler.Execute because then it is guaranteed to be set.
 func StatusHandle() windows.Handle {
 	return theService.h
 }

 // DynamicStartReason returns the reason why the service was started. It is safe
 // to call this function from inside the Handler.Execute because then it is
 // guaranteed to be set.
 func DynamicStartReason() (StartReason, error) {
 	var allocReason *uint32
 	err := windows.QueryServiceDynamicInformation(theService.h, windows.SERVICE_DYNAMIC_INFORMATION_LEVEL_START_REASON, unsafe.Pointer(&allocReason))
 	if err != nil {
 		return 0, err
 	}
 	reason := StartReason(*allocReason)
 	windows.LocalFree(windows.Handle(unsafe.Pointer(allocReason)))
 	return reason, nil
 }
	// Copyright 2012 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.

	//go:build windows

	// Package svc provides everything required to build Windows service.
	package svc

	import (
	"errors"
	"sync"
	"unsafe"

	"golang.org/x/sys/windows"
	)

	// State describes service execution state (Stopped, Running and so on).
	type State uint32

	const (
	Stopped = State(windows.SERVICE_STOPPED)
	StartPending = State(windows.SERVICE_START_PENDING)
	StopPending = State(windows.SERVICE_STOP_PENDING)
	Running = State(windows.SERVICE_RUNNING)
	ContinuePending = State(windows.SERVICE_CONTINUE_PENDING)
	PausePending = State(windows.SERVICE_PAUSE_PENDING)
	Paused = State(windows.SERVICE_PAUSED)
	)

	// Cmd represents service state change request. It is sent to a service
	// by the service manager, and should be actioned upon by the service.
	type Cmd uint32

	const (
	Stop = Cmd(windows.SERVICE_CONTROL_STOP)
	Pause = Cmd(windows.SERVICE_CONTROL_PAUSE)
	Continue = Cmd(windows.SERVICE_CONTROL_CONTINUE)
	Interrogate = Cmd(windows.SERVICE_CONTROL_INTERROGATE)
	Shutdown = Cmd(windows.SERVICE_CONTROL_SHUTDOWN)
	ParamChange = Cmd(windows.SERVICE_CONTROL_PARAMCHANGE)
	NetBindAdd = Cmd(windows.SERVICE_CONTROL_NETBINDADD)
	NetBindRemove = Cmd(windows.SERVICE_CONTROL_NETBINDREMOVE)
	NetBindEnable = Cmd(windows.SERVICE_CONTROL_NETBINDENABLE)
	NetBindDisable = Cmd(windows.SERVICE_CONTROL_NETBINDDISABLE)
	DeviceEvent = Cmd(windows.SERVICE_CONTROL_DEVICEEVENT)
	HardwareProfileChange = Cmd(windows.SERVICE_CONTROL_HARDWAREPROFILECHANGE)
	PowerEvent = Cmd(windows.SERVICE_CONTROL_POWEREVENT)
	SessionChange = Cmd(windows.SERVICE_CONTROL_SESSIONCHANGE)
	PreShutdown = Cmd(windows.SERVICE_CONTROL_PRESHUTDOWN)
	)

	// Accepted is used to describe commands accepted by the service.
	// Note that Interrogate is always accepted.
	type Accepted uint32

	const (
	AcceptStop = Accepted(windows.SERVICE_ACCEPT_STOP)
	AcceptShutdown = Accepted(windows.SERVICE_ACCEPT_SHUTDOWN)
	AcceptPauseAndContinue = Accepted(windows.SERVICE_ACCEPT_PAUSE_CONTINUE)
	AcceptParamChange = Accepted(windows.SERVICE_ACCEPT_PARAMCHANGE)
	AcceptNetBindChange = Accepted(windows.SERVICE_ACCEPT_NETBINDCHANGE)
	AcceptHardwareProfileChange = Accepted(windows.SERVICE_ACCEPT_HARDWAREPROFILECHANGE)
	AcceptPowerEvent = Accepted(windows.SERVICE_ACCEPT_POWEREVENT)
	AcceptSessionChange = Accepted(windows.SERVICE_ACCEPT_SESSIONCHANGE)
	AcceptPreShutdown = Accepted(windows.SERVICE_ACCEPT_PRESHUTDOWN)
	)

	// ActivityStatus allows for services to be selected based on active and inactive categories of service state.
	type ActivityStatus uint32

	const (
	Active = ActivityStatus(windows.SERVICE_ACTIVE)
	Inactive = ActivityStatus(windows.SERVICE_INACTIVE)
	AnyActivity = ActivityStatus(windows.SERVICE_STATE_ALL)
	)

	// Status combines State and Accepted commands to fully describe running service.
	type Status struct {
	State State
	Accepts Accepted
	CheckPoint uint32 // used to report progress during a lengthy operation
	WaitHint uint32 // estimated time required for a pending operation, in milliseconds
	ProcessId uint32 // if the service is running, the process identifier of it, and otherwise zero
	Win32ExitCode uint32 // set if the service has exited with a win32 exit code
	ServiceSpecificExitCode uint32 // set if the service has exited with a service-specific exit code
	}

	// StartReason is the reason that the service was started.
	type StartReason uint32

	const (
	StartReasonDemand = StartReason(windows.SERVICE_START_REASON_DEMAND)
	StartReasonAuto = StartReason(windows.SERVICE_START_REASON_AUTO)
	StartReasonTrigger = StartReason(windows.SERVICE_START_REASON_TRIGGER)
	StartReasonRestartOnFailure = StartReason(windows.SERVICE_START_REASON_RESTART_ON_FAILURE)
	StartReasonDelayedAuto = StartReason(windows.SERVICE_START_REASON_DELAYEDAUTO)
	)

	// ChangeRequest is sent to the service Handler to request service status change.
	type ChangeRequest struct {
	Cmd Cmd
	EventType uint32
	EventData uintptr
	CurrentStatus Status
	Context uintptr
	}

	// Handler is the interface that must be implemented to build Windows service.
	type Handler interface {
	// Execute will be called by the package code at the start of
	// the service, and the service will exit once Execute completes.
	// Inside Execute you must read service change requests from r and
	// act accordingly. You must keep service control manager up to date
	// about state of your service by writing into s as required.
	// args contains service name followed by argument strings passed
	// to the service.
	// You can provide service exit code in exitCode return parameter,
	// with 0 being "no error". You can also indicate if exit code,
	// if any, is service specific or not by using svcSpecificEC
	// parameter.
	Execute(args []string, r <-chan ChangeRequest, s chan<- Status) (svcSpecificEC bool, exitCode uint32)
	}

	type ctlEvent struct {
	cmd Cmd
	eventType uint32
	eventData uintptr
	context uintptr
	errno uint32
	}

	// service provides access to windows service api.
	type service struct {
	name string
	h windows.Handle
	c chan ctlEvent
	handler Handler
	}

	type exitCode struct {
	isSvcSpecific bool
	errno uint32
	}

	func (s service) updateStatus(status Status, ec *exitCode) error {
	if s.h == 0 {
	return errors.New("updateStatus with no service status handle")
	}
	var t windows.SERVICE_STATUS
	t.ServiceType = windows.SERVICE_WIN32_OWN_PROCESS
	t.CurrentState = uint32(status.State)
	if status.Accepts&AcceptStop != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_STOP
	}
	if status.Accepts&AcceptShutdown != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_SHUTDOWN
	}
	if status.Accepts&AcceptPauseAndContinue != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_PAUSE_CONTINUE
	}
	if status.Accepts&AcceptParamChange != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_PARAMCHANGE
	}
	if status.Accepts&AcceptNetBindChange != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_NETBINDCHANGE
	}
	if status.Accepts&AcceptHardwareProfileChange != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_HARDWAREPROFILECHANGE
	}
	if status.Accepts&AcceptPowerEvent != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_POWEREVENT
	}
	if status.Accepts&AcceptSessionChange != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_SESSIONCHANGE
	}
	if status.Accepts&AcceptPreShutdown != 0 {
	t.ControlsAccepted \|= windows.SERVICE_ACCEPT_PRESHUTDOWN
	}
	if ec.errno == 0 {
	t.Win32ExitCode = windows.NO_ERROR
	t.ServiceSpecificExitCode = windows.NO_ERROR
	} else if ec.isSvcSpecific {
	t.Win32ExitCode = uint32(windows.ERROR_SERVICE_SPECIFIC_ERROR)
	t.ServiceSpecificExitCode = ec.errno
	} else {
	t.Win32ExitCode = ec.errno
	t.ServiceSpecificExitCode = windows.NO_ERROR
	}
	t.CheckPoint = status.CheckPoint
	t.WaitHint = status.WaitHint
	return windows.SetServiceStatus(s.h, &t)
	}

	var (
	initCallbacks sync.Once
	ctlHandlerCallback uintptr
	serviceMainCallback uintptr
	)

	func ctlHandler(ctl, evtype, evdata, context uintptr) uintptr {
	s := (*service)(unsafe.Pointer(context))
	e := ctlEvent{cmd: Cmd(ctl), eventType: uint32(evtype), eventData: evdata, context: 123456} // Set context to 123456 to test issue #25660.
	s.c <- e
	return 0
	}

	var theService service // This is, unfortunately, a global, which means only one service per process.

	// serviceMain is the entry point called by the service manager, registered earlier by
	// the call to StartServiceCtrlDispatcher.
	func serviceMain(argc uint32, argv **uint16) uintptr {
	handle, err := windows.RegisterServiceCtrlHandlerEx(windows.StringToUTF16Ptr(theService.name), ctlHandlerCallback, uintptr(unsafe.Pointer(&theService)))
	if sysErr, ok := err.(windows.Errno); ok {
	return uintptr(sysErr)
	} else if err != nil {
	return uintptr(windows.ERROR_UNKNOWN_EXCEPTION)
	}
	theService.h = handle
	defer func() {
	theService.h = 0
	}()
	args16 := unsafe.Slice(argv, int(argc))

	args := make([]string, len(args16))
	for i, a := range args16 {
	args[i] = windows.UTF16PtrToString(a)
	}

	cmdsToHandler := make(chan ChangeRequest)
	changesFromHandler := make(chan Status)
	exitFromHandler := make(chan exitCode)

	go func() {
	ss, errno := theService.handler.Execute(args, cmdsToHandler, changesFromHandler)
	exitFromHandler <- exitCode{ss, errno}
	}()

	ec := exitCode{isSvcSpecific: true, errno: 0}
	outcr := ChangeRequest{
	CurrentStatus: Status{State: Stopped},
	}
	var outch chan ChangeRequest
	inch := theService.c
	loop:
	for {
	select {
	case r := <-inch:
	if r.errno != 0 {
	ec.errno = r.errno
	break loop
	}
	inch = nil
	outch = cmdsToHandler
	outcr.Cmd = r.cmd
	outcr.EventType = r.eventType
	outcr.EventData = r.eventData
	outcr.Context = r.context
	case outch <- outcr:
	inch = theService.c
	outch = nil
	case c := <-changesFromHandler:
	err := theService.updateStatus(&c, &ec)
	if err != nil {
	ec.errno = uint32(windows.ERROR_EXCEPTION_IN_SERVICE)
	if err2, ok := err.(windows.Errno); ok {
	ec.errno = uint32(err2)
	}
	break loop
	}
	outcr.CurrentStatus = c
	case ec = <-exitFromHandler:
	break loop
	}
	}

	theService.updateStatus(&Status{State: Stopped}, &ec)

	return windows.NO_ERROR
	}

	// Run executes service name by calling appropriate handler function.
	func Run(name string, handler Handler) error {
	initCallbacks.Do(func() {
	ctlHandlerCallback = windows.NewCallback(ctlHandler)
	serviceMainCallback = windows.NewCallback(serviceMain)
	})
	theService.name = name
	theService.handler = handler
	theService.c = make(chan ctlEvent)
	t := []windows.SERVICE_TABLE_ENTRY{
	{ServiceName: windows.StringToUTF16Ptr(theService.name), ServiceProc: serviceMainCallback},
	{ServiceName: nil, ServiceProc: 0},
	}
	return windows.StartServiceCtrlDispatcher(&t[0])
	}

	// StatusHandle returns service status handle. It is safe to call this function
	// from inside the Handler.Execute because then it is guaranteed to be set.
	func StatusHandle() windows.Handle {
	return theService.h
	}

	// DynamicStartReason returns the reason why the service was started. It is safe
	// to call this function from inside the Handler.Execute because then it is
	// guaranteed to be set.
	func DynamicStartReason() (StartReason, error) {
	var allocReason *uint32
	err := windows.QueryServiceDynamicInformation(theService.h, windows.SERVICE_DYNAMIC_INFORMATION_LEVEL_START_REASON, unsafe.Pointer(&allocReason))
	if err != nil {
	return 0, err
	}
	reason := StartReason(*allocReason)
	windows.LocalFree(windows.Handle(unsafe.Pointer(allocReason)))
	return reason, nil
	}