lockutil_windows.go

// SPDX-FileCopyrightText: Copyright The Lima Authors
// SPDX-License-Identifier: Apache-2.0

// From https://github.com/containerd/nerdctl/blob/v0.13.0/pkg/lockutil/lockutil_windows.go
/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package lockutil

import (
	"fmt"
	"os"
	"syscall"
	"unsafe"

	"github.com/sirupsen/logrus"
)

// LockFile modified from https://github.com/boltdb/bolt/blob/v1.3.1/bolt_windows.go using MIT.
var (
	modkernel32      = syscall.NewLazyDLL("kernel32.dll")
	procLockFileEx   = modkernel32.NewProc("LockFileEx")
	procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
)

// LOCKFILE_EXCLUSIVE_LOCK from https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
const flagLockfileExclusiveLock = 0x00000002

func WithDirLock(dir string, fn func() error) error {
	dirFile, err := os.OpenFile(dir+".lock", os.O_CREATE, 0o644)
	if err != nil {
		return err
	}
	defer dirFile.Close()
	if err := lockFileEx(
		syscall.Handle(dirFile.Fd()), // hFile
		flagLockfileExclusiveLock,    // dwFlags
		0,                            // dwReserved
		1,                            // nNumberOfBytesToLockLow
		0,                            // nNumberOfBytesToLockHigh
		&syscall.Overlapped{},        // lpOverlapped
	); err != nil {
		return fmt.Errorf("failed to lock %q: %w", dir, err)
	}

	defer func() {
		if err := unlockFileEx(
			syscall.Handle(dirFile.Fd()), // hFile
			0,                            // dwReserved
			1,                            // nNumberOfBytesToLockLow
			0,                            // nNumberOfBytesToLockHigh
			&syscall.Overlapped{},        // lpOverlapped
		); err != nil {
			logrus.WithError(err).Errorf("failed to unlock %q", dir)
		}
	}()
	return fn()
}

func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
	r, _, err := procLockFileEx.Call(uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
	if r == 0 {
		return err
	}
	return nil
}

func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
	r, _, err := procUnlockFileEx.Call(uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0)
	if r == 0 {
		return err
	}
	return nil
}