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Copy pathlock_windows.go
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170 lines (144 loc) · 4.48 KB
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// +build windows
/*
* Minio Cloud Storage, (C) 2016, 2017 Minio, Inc.
*
* 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 lock
import (
"fmt"
"os"
"syscall"
"unsafe"
os2 "github.com/minio/minio/pkg/x/os"
)
var (
modkernel32 = syscall.NewLazyDLL("kernel32.dll")
procLockFileEx = modkernel32.NewProc("LockFileEx")
)
const (
// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
lockFileExclusiveLock = 2
lockFileFailImmediately = 1
// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
errLockViolation syscall.Errno = 0x21
)
// lockedOpenFile is an internal function.
func lockedOpenFile(path string, flag int, perm os.FileMode, lockType uint32) (*LockedFile, error) {
f, err := open(path, flag, perm)
if err != nil {
return nil, err
}
if err = lockFile(syscall.Handle(f.Fd()), lockType); err != nil {
f.Close()
return nil, err
}
st, err := os2.Stat(path)
if err != nil {
f.Close()
return nil, err
}
if st.IsDir() {
f.Close()
return nil, &os.PathError{
Op: "open",
Path: path,
Err: syscall.EISDIR,
}
}
return &LockedFile{File: f}, nil
}
// TryLockedOpenFile - tries a new write lock, functionality
// it is similar to LockedOpenFile with with syscall.LOCK_EX
// mode but along with syscall.LOCK_NB such that the function
// doesn't wait forever but instead returns if it cannot
// acquire a write lock.
func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
return lockedOpenFile(path, flag, perm, lockFileFailImmediately)
}
// LockedOpenFile - initializes a new lock and protects
// the file from concurrent access.
func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
return lockedOpenFile(path, flag, perm, 0)
}
// perm param is ignored, on windows file perms/NT acls
// are not octet combinations. Providing access to NT
// acls is out of scope here.
func open(path string, flag int, perm os.FileMode) (*os.File, error) {
if path == "" {
return nil, syscall.ERROR_FILE_NOT_FOUND
}
pathp, err := syscall.UTF16PtrFromString(path)
if err != nil {
return nil, err
}
var access uint32
switch flag {
case syscall.O_RDONLY:
access = syscall.GENERIC_READ
case syscall.O_WRONLY:
access = syscall.GENERIC_WRITE
case syscall.O_RDWR:
fallthrough
case syscall.O_RDWR | syscall.O_CREAT:
fallthrough
case syscall.O_WRONLY | syscall.O_CREAT:
access = syscall.GENERIC_READ | syscall.GENERIC_WRITE
default:
return nil, fmt.Errorf("Unsupported flag (%d)", flag)
}
var createflag uint32
switch {
case flag&syscall.O_CREAT == syscall.O_CREAT:
createflag = syscall.OPEN_ALWAYS
default:
createflag = syscall.OPEN_EXISTING
}
shareflag := uint32(syscall.FILE_SHARE_READ | syscall.FILE_SHARE_WRITE | syscall.FILE_SHARE_DELETE)
accessAttr := uint32(syscall.FILE_ATTRIBUTE_NORMAL | 0x80000000)
fd, err := syscall.CreateFile(pathp, access, shareflag, nil, createflag, accessAttr, 0)
if err != nil {
return nil, err
}
return os.NewFile(uintptr(fd), path), nil
}
func lockFile(fd syscall.Handle, flags uint32) error {
// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
var flag uint32 = lockFileExclusiveLock // Lockfile exlusive.
flag |= flags
if fd == syscall.InvalidHandle {
return nil
}
err := lockFileEx(fd, flag, 1, 0, &syscall.Overlapped{})
if err == nil {
return nil
} else if err.Error() == "The process cannot access the file because another process has locked a portion of the file." {
return ErrAlreadyLocked
} else if err != errLockViolation {
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
}