github.com/coocood/badger@v1.5.1-0.20200528065104-c02ac3616d04/dir_windows.go (about)

     1  // +build windows
     2  
     3  /*
     4   * Copyright 2017 Dgraph Labs, Inc. and Contributors
     5   *
     6   * Licensed under the Apache License, Version 2.0 (the "License");
     7   * you may not use this file except in compliance with the License.
     8   * You may obtain a copy of the License at
     9   *
    10   *     http://www.apache.org/licenses/LICENSE-2.0
    11   *
    12   * Unless required by applicable law or agreed to in writing, software
    13   * distributed under the License is distributed on an "AS IS" BASIS,
    14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    15   * See the License for the specific language governing permissions and
    16   * limitations under the License.
    17   */
    18  
    19  package badger
    20  
    21  // OpenDir opens a directory in windows with write access for syncing.
    22  import (
    23  	"fmt"
    24  	"os"
    25  	"path/filepath"
    26  	"syscall"
    27  
    28  	"github.com/pingcap/errors"
    29  )
    30  
    31  func openDir(path string) (*os.File, error) {
    32  	fd, err := openDirWin(path)
    33  	if err != nil {
    34  		return nil, err
    35  	}
    36  	return os.NewFile(uintptr(fd), path), nil
    37  }
    38  
    39  func openDirWin(path string) (fd syscall.Handle, err error) {
    40  	if len(path) == 0 {
    41  		return syscall.InvalidHandle, syscall.ERROR_FILE_NOT_FOUND
    42  	}
    43  	pathp, err := syscall.UTF16PtrFromString(path)
    44  	if err != nil {
    45  		return syscall.InvalidHandle, err
    46  	}
    47  	access := uint32(syscall.GENERIC_READ | syscall.GENERIC_WRITE)
    48  	sharemode := uint32(syscall.FILE_SHARE_READ | syscall.FILE_SHARE_WRITE)
    49  	createmode := uint32(syscall.OPEN_EXISTING)
    50  	fl := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS)
    51  	return syscall.CreateFile(pathp, access, sharemode, nil, createmode, fl, 0)
    52  }
    53  
    54  // DirectoryLockGuard holds a lock on the directory.
    55  type directoryLockGuard struct {
    56  	path string
    57  }
    58  
    59  // AcquireDirectoryLock acquires exclusive access to a directory.
    60  func acquireDirectoryLock(dirPath string, pidFileName string, readOnly bool) (*directoryLockGuard, error) {
    61  	if readOnly {
    62  		return nil, ErrWindowsNotSupported
    63  	}
    64  
    65  	// Convert to absolute path so that Release still works even if we do an unbalanced
    66  	// chdir in the meantime.
    67  	absLockFilePath, err := filepath.Abs(filepath.Join(dirPath, pidFileName))
    68  	if err != nil {
    69  		return nil, errors.Wrap(err, "Cannot get absolute path for pid lock file")
    70  	}
    71  
    72  	f, err := os.OpenFile(absLockFilePath, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
    73  	if err != nil {
    74  		return nil, errors.Wrapf(err,
    75  			"Cannot create pid lock file %q.  Another process is using this Badger database",
    76  			absLockFilePath)
    77  	}
    78  	_, err = fmt.Fprintf(f, "%d\n", os.Getpid())
    79  	closeErr := f.Close()
    80  	if err != nil {
    81  		return nil, errors.Wrap(err, "Cannot write to pid lock file")
    82  	}
    83  	if closeErr != nil {
    84  		return nil, errors.Wrap(closeErr, "Cannot close pid lock file")
    85  	}
    86  	return &directoryLockGuard{path: absLockFilePath}, nil
    87  }
    88  
    89  // Release removes the directory lock.
    90  func (g *directoryLockGuard) release() error {
    91  	path := g.path
    92  	g.path = ""
    93  	return os.Remove(path)
    94  }