110 lines
3.8 KiB
Go
110 lines
3.8 KiB
Go
// +build windows
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/*
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* Copyright 2017 Dgraph Labs, Inc. and Contributors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package badger
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// OpenDir opens a directory in windows with write access for syncing.
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import (
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"os"
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"path/filepath"
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"syscall"
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"github.com/pkg/errors"
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)
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// FILE_ATTRIBUTE_TEMPORARY - A file that is being used for temporary storage.
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// FILE_FLAG_DELETE_ON_CLOSE - The file is to be deleted immediately after all of its handles are
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// closed, which includes the specified handle and any other open or duplicated handles.
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// See: https://docs.microsoft.com/en-us/windows/desktop/FileIO/file-attribute-constants
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// NOTE: Added here to avoid importing golang.org/x/sys/windows
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const (
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FILE_ATTRIBUTE_TEMPORARY = 0x00000100
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FILE_FLAG_DELETE_ON_CLOSE = 0x04000000
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)
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func openDir(path string) (*os.File, error) {
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fd, err := openDirWin(path)
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if err != nil {
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return nil, err
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}
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return os.NewFile(uintptr(fd), path), nil
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}
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func openDirWin(path string) (fd syscall.Handle, err error) {
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if len(path) == 0 {
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return syscall.InvalidHandle, syscall.ERROR_FILE_NOT_FOUND
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}
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pathp, err := syscall.UTF16PtrFromString(path)
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if err != nil {
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return syscall.InvalidHandle, err
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}
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access := uint32(syscall.GENERIC_READ | syscall.GENERIC_WRITE)
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sharemode := uint32(syscall.FILE_SHARE_READ | syscall.FILE_SHARE_WRITE)
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createmode := uint32(syscall.OPEN_EXISTING)
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fl := uint32(syscall.FILE_FLAG_BACKUP_SEMANTICS)
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return syscall.CreateFile(pathp, access, sharemode, nil, createmode, fl, 0)
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}
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// DirectoryLockGuard holds a lock on the directory.
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type directoryLockGuard struct {
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h syscall.Handle
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path string
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}
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// AcquireDirectoryLock acquires exclusive access to a directory.
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func acquireDirectoryLock(dirPath string, pidFileName string, readOnly bool) (*directoryLockGuard, error) {
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if readOnly {
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return nil, ErrWindowsNotSupported
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}
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// Convert to absolute path so that Release still works even if we do an unbalanced
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// chdir in the meantime.
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absLockFilePath, err := filepath.Abs(filepath.Join(dirPath, pidFileName))
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if err != nil {
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return nil, errors.Wrap(err, "Cannot get absolute path for pid lock file")
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}
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// This call creates a file handler in memory that only one process can use at a time. When
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// that process ends, the file is deleted by the system.
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// FILE_ATTRIBUTE_TEMPORARY is used to tell Windows to try to create the handle in memory.
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// FILE_FLAG_DELETE_ON_CLOSE is not specified in syscall_windows.go but tells Windows to delete
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// the file when all processes holding the handler are closed.
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// XXX: this works but it's a bit klunky. i'd prefer to use LockFileEx but it needs unsafe pkg.
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h, err := syscall.CreateFile(
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syscall.StringToUTF16Ptr(absLockFilePath), 0, 0, nil,
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syscall.OPEN_ALWAYS,
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uint32(FILE_ATTRIBUTE_TEMPORARY|FILE_FLAG_DELETE_ON_CLOSE),
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0)
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if err != nil {
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return nil, errors.Wrapf(err,
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"Cannot create lock file %q. Another process is using this Badger database",
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absLockFilePath)
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}
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return &directoryLockGuard{h: h, path: absLockFilePath}, nil
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}
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// Release removes the directory lock.
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func (g *directoryLockGuard) release() error {
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g.path = ""
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return syscall.CloseHandle(g.h)
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}
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// Windows doesn't support syncing directories to the file system. See
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// https://github.com/dgraph-io/badger/issues/699#issuecomment-504133587 for more details.
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func syncDir(dir string) error { return nil }
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