From c3fe63a65893ebdb48a71c309f96da3e87d5965c Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Fri, 25 Jun 2021 14:44:30 +0200
Subject: [PATCH] client/pkg/fileutil: use golang.org/x/sys/windows for
 FileLockEx

Use the FileLockEx wrapper and the corresponding LOCKFILE_* and error
constants from the golang.org/x/sys/windows package rather than
implementing these in the fileutil package.
---
 client/pkg/fileutil/lock_windows.go | 44 ++++++-----------------------
 1 file changed, 8 insertions(+), 36 deletions(-)

diff --git a/client/pkg/fileutil/lock_windows.go b/client/pkg/fileutil/lock_windows.go
index 5cbf2bc3d5e..4e938b67c7e 100644
--- a/client/pkg/fileutil/lock_windows.go
+++ b/client/pkg/fileutil/lock_windows.go
@@ -22,31 +22,18 @@ import (
 	"fmt"
 	"os"
 	"syscall"
-	"unsafe"
-)
-
-var (
-	modkernel32    = syscall.NewLazyDLL("kernel32.dll")
-	procLockFileEx = modkernel32.NewProc("LockFileEx")
 
-	errLocked = errors.New("the process cannot access the file because another process has locked a portion of the file")
+	"golang.org/x/sys/windows"
 )
 
-const (
-	// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
-	LOCKFILE_EXCLUSIVE_LOCK   = 2
-	LOCKFILE_FAIL_IMMEDIATELY = 1
-
-	// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
-	errLockViolation syscall.Errno = 0x21
-)
+var errLocked = errors.New("the process cannot access the file because another process has locked a portion of the file")
 
 func TryLockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
 	f, err := open(path, flag, perm)
 	if err != nil {
 		return nil, err
 	}
-	if err := lockFile(syscall.Handle(f.Fd()), LOCKFILE_FAIL_IMMEDIATELY); err != nil {
+	if err := lockFile(windows.Handle(f.Fd()), windows.LOCKFILE_FAIL_IMMEDIATELY); err != nil {
 		f.Close()
 		return nil, err
 	}
@@ -58,7 +45,7 @@ func LockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
 	if err != nil {
 		return nil, err
 	}
-	if err := lockFile(syscall.Handle(f.Fd()), 0); err != nil {
+	if err := lockFile(windows.Handle(f.Fd()), 0); err != nil {
 		f.Close()
 		return nil, err
 	}
@@ -95,32 +82,17 @@ func open(path string, flag int, perm os.FileMode) (*os.File, error) {
 	return os.NewFile(uintptr(fd), path), nil
 }
 
-func lockFile(fd syscall.Handle, flags uint32) error {
-	var flag uint32 = LOCKFILE_EXCLUSIVE_LOCK
-	flag |= flags
-	if fd == syscall.InvalidHandle {
+func lockFile(fd windows.Handle, flags uint32) error {
+	if fd == windows.InvalidHandle {
 		return nil
 	}
-	err := lockFileEx(fd, flag, 1, 0, &syscall.Overlapped{})
+	err := windows.LockFileEx(fd, flags|windows.LOCKFILE_EXCLUSIVE_LOCK, 0, 1, 0, &windows.Overlapped{})
 	if err == nil {
 		return nil
 	} else if err.Error() == errLocked.Error() {
 		return ErrLocked
-	} else if err != errLockViolation {
+	} else if err != windows.ERROR_LOCK_VIOLATION {
 		return err
 	}
 	return nil
 }
-
-func lockFileEx(h syscall.Handle, flags, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
-	var reserved uint32 = 0
-	r1, _, e1 := syscall.Syscall6(procLockFileEx.Addr(), 6, uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
-	if r1 == 0 {
-		if e1 != 0 {
-			err = error(e1)
-		} else {
-			err = syscall.EINVAL
-		}
-	}
-	return err
-}