windows: add Find*ChangeNotification APIs for file and directory monitoring

https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-findfirstchangenotificationw
https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-findnextchangenotification
https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-findclosechangenotification

Change-Id: If7abfd63cd7a60e7f95ffad9aca2b7b7b74c94f0
Reviewed-on: https://go-review.googlesource.com/c/sys/+/285713
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

windows/syscall_windows.go

@@ -264,6 +264,9 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	VirtualProtect(address uintptr, size uintptr, newprotect uint32, oldprotect *uint32) (err error) = kernel32.VirtualProtect
 //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	FindFirstChangeNotification(path string, watchSubtree bool, notifyFilter uint32) (handle Handle, err error) [failretval==InvalidHandle] = kernel32.FindFirstChangeNotificationW
+//sys	FindNextChangeNotification(handle Handle) (err error)
+//sys	FindCloseChangeNotification(handle Handle) (err error)
 //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

windows/types_windows.go

@@ -227,7 +227,7 @@ const (
 )
 
 const (
-	// filters for ReadDirectoryChangesW
+	// filters for ReadDirectoryChangesW and FindFirstChangeNotificationW
 	FILE_NOTIFY_CHANGE_FILE_NAME   = 0x001
 	FILE_NOTIFY_CHANGE_DIR_NAME    = 0x002
 	FILE_NOTIFY_CHANGE_ATTRIBUTES  = 0x004

windows/zsyscall_windows.go

@@ -183,9 +183,12 @@ var (
 	procDuplicateHandle                                      = modkernel32.NewProc("DuplicateHandle")
 	procExitProcess                                          = modkernel32.NewProc("ExitProcess")
 	procFindClose                                            = modkernel32.NewProc("FindClose")
+	procFindCloseChangeNotification                          = modkernel32.NewProc("FindCloseChangeNotification")
+	procFindFirstChangeNotificationW                         = modkernel32.NewProc("FindFirstChangeNotificationW")
 	procFindFirstFileW                                       = modkernel32.NewProc("FindFirstFileW")
 	procFindFirstVolumeMountPointW                           = modkernel32.NewProc("FindFirstVolumeMountPointW")
 	procFindFirstVolumeW                                     = modkernel32.NewProc("FindFirstVolumeW")
+	procFindNextChangeNotification                           = modkernel32.NewProc("FindNextChangeNotification")
 	procFindNextFileW                                        = modkernel32.NewProc("FindNextFileW")
 	procFindNextVolumeMountPointW                            = modkernel32.NewProc("FindNextVolumeMountPointW")
 	procFindNextVolumeW                                      = modkernel32.NewProc("FindNextVolumeW")
@@ -1525,6 +1528,36 @@ func FindClose(handle Handle) (err error) {
 	return
 }
 
+func FindCloseChangeNotification(handle Handle) (err error) {
+	r1, _, e1 := syscall.Syscall(procFindCloseChangeNotification.Addr(), 1, uintptr(handle), 0, 0)
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func FindFirstChangeNotification(path string, watchSubtree bool, notifyFilter uint32) (handle Handle, err error) {
+	var _p0 *uint16
+	_p0, err = syscall.UTF16PtrFromString(path)
+	if err != nil {
+		return
+	}
+	return _FindFirstChangeNotification(_p0, watchSubtree, notifyFilter)
+}
+
+func _FindFirstChangeNotification(path *uint16, watchSubtree bool, notifyFilter uint32) (handle Handle, err error) {
+	var _p1 uint32
+	if watchSubtree {
+		_p1 = 1
+	}
+	r0, _, e1 := syscall.Syscall(procFindFirstChangeNotificationW.Addr(), 3, uintptr(unsafe.Pointer(path)), uintptr(_p1), uintptr(notifyFilter))
+	handle = Handle(r0)
+	if handle == InvalidHandle {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func findFirstFile1(name *uint16, data *win32finddata1) (handle Handle, err error) {
 	r0, _, e1 := syscall.Syscall(procFindFirstFileW.Addr(), 2, uintptr(unsafe.Pointer(name)), uintptr(unsafe.Pointer(data)), 0)
 	handle = Handle(r0)
@@ -1552,6 +1585,14 @@ func FindFirstVolume(volumeName *uint16, bufferLength uint32) (handle Handle, er
 	return
 }
 
+func FindNextChangeNotification(handle Handle) (err error) {
+	r1, _, e1 := syscall.Syscall(procFindNextChangeNotification.Addr(), 1, uintptr(handle), 0, 0)
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func findNextFile1(handle Handle, data *win32finddata1) (err error) {
 	r1, _, e1 := syscall.Syscall(procFindNextFileW.Addr(), 2, uintptr(handle), uintptr(unsafe.Pointer(data)), 0)
 	if r1 == 0 {