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ed75533cb1
* optionally protect against multiple starts with flock Fixes #1823 * use traditional .lock extension * move config key to top level
77 lines
1.9 KiB
Go
77 lines
1.9 KiB
Go
// Copyright 2015 Tim Heckman. All rights reserved.
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// Use of this source code is governed by the BSD 3-Clause
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// license that can be found in the LICENSE file.
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// +build windows
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package flock
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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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kernel32, _ = syscall.LoadLibrary("kernel32.dll")
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procLockFileEx, _ = syscall.GetProcAddress(kernel32, "LockFileEx")
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procUnlockFileEx, _ = syscall.GetProcAddress(kernel32, "UnlockFileEx")
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)
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const (
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winLockfileFailImmediately = 0x00000001
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winLockfileExclusiveLock = 0x00000002
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winLockfileSharedLock = 0x00000000
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)
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// Use of 0x00000000 for the shared lock is a guess based on some the MS Windows
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// `LockFileEX` docs, which document the `LOCKFILE_EXCLUSIVE_LOCK` flag as:
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//
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// > The function requests an exclusive lock. Otherwise, it requests a shared
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// > lock.
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//
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// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
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func lockFileEx(handle syscall.Handle, flags uint32, reserved uint32, numberOfBytesToLockLow uint32, numberOfBytesToLockHigh uint32, offset *syscall.Overlapped) (bool, syscall.Errno) {
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r1, _, errNo := syscall.Syscall6(
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uintptr(procLockFileEx),
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6,
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uintptr(handle),
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uintptr(flags),
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uintptr(reserved),
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uintptr(numberOfBytesToLockLow),
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uintptr(numberOfBytesToLockHigh),
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uintptr(unsafe.Pointer(offset)))
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if r1 != 1 {
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if errNo == 0 {
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return false, syscall.EINVAL
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}
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return false, errNo
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}
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return true, 0
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}
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func unlockFileEx(handle syscall.Handle, reserved uint32, numberOfBytesToLockLow uint32, numberOfBytesToLockHigh uint32, offset *syscall.Overlapped) (bool, syscall.Errno) {
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r1, _, errNo := syscall.Syscall6(
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uintptr(procUnlockFileEx),
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5,
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uintptr(handle),
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uintptr(reserved),
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uintptr(numberOfBytesToLockLow),
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uintptr(numberOfBytesToLockHigh),
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uintptr(unsafe.Pointer(offset)),
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0)
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if r1 != 1 {
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if errNo == 0 {
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return false, syscall.EINVAL
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}
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return false, errNo
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}
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return true, 0
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}
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