mirror of https://github.com/k3s-io/k3s
103 lines
2.6 KiB
Go
103 lines
2.6 KiB
Go
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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package filemutex
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import (
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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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procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
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)
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const (
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lockfileExclusiveLock = 2
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)
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func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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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
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}
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func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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r1, _, e1 := syscall.Syscall6(procUnlockFileEx.Addr(), 5, uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0)
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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
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}
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// FileMutex is similar to sync.RWMutex, but also synchronizes across processes.
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// This implementation is based on flock syscall.
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type FileMutex struct {
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fd syscall.Handle
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}
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func New(filename string) (*FileMutex, error) {
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fd, err := syscall.CreateFile(&(syscall.StringToUTF16(filename)[0]), syscall.GENERIC_READ|syscall.GENERIC_WRITE,
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syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE, nil, syscall.OPEN_ALWAYS, syscall.FILE_ATTRIBUTE_NORMAL, 0)
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if err != nil {
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return nil, err
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}
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return &FileMutex{fd: fd}, nil
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}
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func (m *FileMutex) Lock() error {
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var ol syscall.Overlapped
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if err := lockFileEx(m.fd, lockfileExclusiveLock, 0, 1, 0, &ol); err != nil {
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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 (m *FileMutex) Unlock() error {
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var ol syscall.Overlapped
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if err := unlockFileEx(m.fd, 0, 1, 0, &ol); err != nil {
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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 (m *FileMutex) RLock() error {
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var ol syscall.Overlapped
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if err := lockFileEx(m.fd, 0, 0, 1, 0, &ol); err != nil {
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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 (m *FileMutex) RUnlock() error {
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var ol syscall.Overlapped
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if err := unlockFileEx(m.fd, 0, 1, 0, &ol); err != nil {
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return err
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}
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return nil
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}
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// Close does an Unlock() combined with closing and unlinking the associated
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// lock file. You should create a New() FileMutex for every Lock() attempt if
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// using Close().
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func (m *FileMutex) Close() error {
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var ol syscall.Overlapped
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if err := unlockFileEx(m.fd, 0, 1, 0, &ol); err != nil {
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return err
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}
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return syscall.Close(m.fd)
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}
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