use UTF16PtrToString function instead of slicing

windows/security_windows.go

@@ -1230,7 +1230,7 @@ func (sd *SECURITY_DESCRIPTOR) String() string {
 		return ""
 	}
 	defer LocalFree(Handle(unsafe.Pointer(sddl)))
-	return UTF16ToString((*[(1 << 30) - 1]uint16)(unsafe.Pointer(sddl))[:strLen:strLen])
+	return UTF16PtrToString(sddl, int(strLen))
 }
 
 // ToAbsolute converts a self-relative security descriptor into an absolute one.

windows/svc/mgr/config.go

@@ -50,7 +50,7 @@ func toString(p *uint16) string {
 	if p == nil {
 		return ""
 	}
-	return syscall.UTF16ToString((*[4096]uint16)(unsafe.Pointer(p))[:])
+	return windows.UTF16PtrToString(p, 4096)
 }
 
 func toStringSlice(ps *uint16) []string {

windows/svc/mgr/mgr.go

@@ -73,7 +73,7 @@ func (m *Mgr) LockStatus() (*LockStatus, error) {
 		status := &LockStatus{
 			IsLocked: lockStatus.IsLocked != 0,
 			Age:      time.Duration(lockStatus.LockDuration) * time.Second,
-			Owner:    windows.UTF16ToString((*[(1 << 30) - 1]uint16)(unsafe.Pointer(lockStatus.LockOwner))[:]),
+			Owner:    toString(lockStatus.LockOwner),
 		}
 		return status, nil
 	}
@@ -204,7 +204,7 @@ func (m *Mgr) ListServices() ([]string, error) {
 	services := (*[1 << 20]windows.ENUM_SERVICE_STATUS_PROCESS)(unsafe.Pointer(&buf[0]))[:servicesReturned:servicesReturned]
 	var names []string
 	for _, s := range services {
-		name := syscall.UTF16ToString((*[1 << 20]uint16)(unsafe.Pointer(s.ServiceName))[:])
+		name := toString(s.ServiceName)
 		names = append(names, name)
 	}
 	return names, nil

windows/svc/service.go

@@ -224,10 +224,10 @@ const (
 func (s *service) run() {
 	s.goWaits.Wait()
 	s.h = windows.Handle(ssHandle)
-	argv := (*[100]*int16)(unsafe.Pointer(sArgv))[:sArgc:sArgc]
+	argv := (*[100]*uint16)(unsafe.Pointer(sArgv))[:sArgc:sArgc]
 	args := make([]string, len(argv))
 	for i, a := range argv {
-		args[i] = syscall.UTF16ToString((*[1 << 20]uint16)(unsafe.Pointer(a))[:])
+		args[i] = windows.UTF16PtrToString(a, 1<<20)
 	}
 
 	cmdsToHandler := make(chan ChangeRequest)

windows/syscall_windows.go

@@ -117,6 +117,25 @@ func UTF16PtrFromString(s string) (*uint16, error) {
 	return &a[0], nil
 }
 
+// UTF16PtrToString is like UTF16ToString, but takes *uint16
+// as a parameter instead of []uint16.
+// max is how many times p can be advanced looking for the null terminator.
+// If max is hit, the string is truncated at that point.
+func UTF16PtrToString(p *uint16, max int) string {
+	if p == nil {
+		return ""
+	}
+	// Find NUL terminator.
+	end := unsafe.Pointer(p)
+	n := 0
+	for *(*uint16)(end) != 0 && n < max {
+		end = unsafe.Pointer(uintptr(end) + unsafe.Sizeof(*p))
+		n++
+	}
+	s := (*[(1 << 30) - 1]uint16)(unsafe.Pointer(p))[:n:n]
+	return string(utf16.Decode(s))
+}
+
 func Getpagesize() int { return 4096 }
 
 // NewCallback converts a Go function to a function pointer conforming to the stdcall calling convention.