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109 lines
2.2 KiB
Go
109 lines
2.2 KiB
Go
// +build windows
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package state
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import (
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"math"
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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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procCreateEventW = modkernel32.NewProc("CreateEventW")
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)
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const (
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// dwFlags defined for LockFileEx
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// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
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_LOCKFILE_FAIL_IMMEDIATELY = 1
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_LOCKFILE_EXCLUSIVE_LOCK = 2
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)
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func (s *LocalState) lock() error {
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// even though we're failing immediately, an overlapped event structure is
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// required
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ol, err := newOverlapped()
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if err != nil {
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return err
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}
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defer syscall.CloseHandle(ol.HEvent)
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return lockFileEx(
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syscall.Handle(s.stateFileOut.Fd()),
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_LOCKFILE_EXCLUSIVE_LOCK|_LOCKFILE_FAIL_IMMEDIATELY,
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0, // reserved
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0, // bytes low
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math.MaxUint32, // bytes high
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ol,
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)
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}
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func (s *LocalState) unlock() error {
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// the file is closed in Unlock
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return nil
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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(
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procLockFileEx.Addr(),
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6,
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uintptr(h),
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uintptr(flags),
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uintptr(reserved),
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uintptr(locklow),
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uintptr(lockhigh),
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uintptr(unsafe.Pointer(ol)),
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)
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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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// newOverlapped creates a structure used to track asynchronous
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// I/O requests that have been issued.
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func newOverlapped() (*syscall.Overlapped, error) {
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event, err := createEvent(nil, true, false, nil)
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if err != nil {
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return nil, err
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}
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return &syscall.Overlapped{HEvent: event}, nil
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}
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func createEvent(sa *syscall.SecurityAttributes, manualReset bool, initialState bool, name *uint16) (handle syscall.Handle, err error) {
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var _p0 uint32
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if manualReset {
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_p0 = 1
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}
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var _p1 uint32
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if initialState {
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_p1 = 1
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}
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r0, _, e1 := syscall.Syscall6(
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procCreateEventW.Addr(),
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4,
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uintptr(unsafe.Pointer(sa)),
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uintptr(_p0),
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uintptr(_p1),
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uintptr(unsafe.Pointer(name)),
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0,
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0,
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)
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handle = syscall.Handle(r0)
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if handle == syscall.InvalidHandle {
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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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