126 lines
3.3 KiB
Go
126 lines
3.3 KiB
Go
// Copyright 2015 The etcd Authors
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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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// +build windows
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package fileutil
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import (
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"errors"
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"fmt"
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"os"
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"syscall"
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"unsafe"
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)
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var (
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modkernel32 = syscall.NewLazyDLL("kernel32.dll")
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procLockFileEx = modkernel32.NewProc("LockFileEx")
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errLocked = errors.New("the process cannot access the file because another process has locked a portion of the file")
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)
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const (
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// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
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LOCKFILE_EXCLUSIVE_LOCK = 2
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LOCKFILE_FAIL_IMMEDIATELY = 1
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// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
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errLockViolation syscall.Errno = 0x21
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)
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func TryLockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
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f, err := open(path, flag, perm)
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if err != nil {
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return nil, err
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}
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if err := lockFile(syscall.Handle(f.Fd()), LOCKFILE_FAIL_IMMEDIATELY); err != nil {
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f.Close()
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return nil, err
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}
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return &LockedFile{f}, nil
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}
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func LockFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
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f, err := open(path, flag, perm)
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if err != nil {
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return nil, err
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}
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if err := lockFile(syscall.Handle(f.Fd()), 0); err != nil {
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f.Close()
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return nil, err
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}
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return &LockedFile{f}, nil
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}
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func open(path string, flag int, perm os.FileMode) (*os.File, error) {
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if path == "" {
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return nil, fmt.Errorf("cannot open empty filename")
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}
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var access uint32
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switch flag {
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case syscall.O_RDONLY:
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access = syscall.GENERIC_READ
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case syscall.O_WRONLY:
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access = syscall.GENERIC_WRITE
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case syscall.O_RDWR:
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access = syscall.GENERIC_READ | syscall.GENERIC_WRITE
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case syscall.O_WRONLY | syscall.O_CREAT:
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access = syscall.GENERIC_ALL
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default:
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panic(fmt.Errorf("flag %v is not supported", flag))
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}
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fd, err := syscall.CreateFile(&(syscall.StringToUTF16(path)[0]),
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access,
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syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE,
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nil,
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syscall.OPEN_ALWAYS,
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syscall.FILE_ATTRIBUTE_NORMAL,
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0)
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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 lockFile(fd syscall.Handle, flags uint32) error {
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var flag uint32 = LOCKFILE_EXCLUSIVE_LOCK
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flag |= flags
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if fd == syscall.InvalidHandle {
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return nil
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}
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err := lockFileEx(fd, flag, 1, 0, &syscall.Overlapped{})
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if err == nil {
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return nil
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} else if err.Error() == errLocked.Error() {
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return ErrLocked
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} else if err != errLockViolation {
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return err
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}
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return nil
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}
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func lockFileEx(h syscall.Handle, flags, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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var reserved uint32 = 0
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r1, _, e1 := syscall.Syscall6(procLockFileEx.Addr(), 6, uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
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if r1 == 0 {
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if e1 != 0 {
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err = error(e1)
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} else {
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err = syscall.EINVAL
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}
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}
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return err
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}
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