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flock_winapi.go
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flock_winapi.go
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// Copyright 2015 Tim Heckman. All rights reserved.
// Use of this source code is governed by the BSD 3-Clause
// license that can be found in the LICENSE file.
// +build windows
package flock
import (
"syscall"
"unsafe"
)
var (
kernel32, _ = syscall.LoadLibrary("kernel32.dll")
procLockFileEx, _ = syscall.GetProcAddress(kernel32, "LockFileEx")
procUnlockFileEx, _ = syscall.GetProcAddress(kernel32, "UnlockFileEx")
)
const (
LOCKFILE_FAIL_IMMEDIATELY = 0x00000001
LOCKFILE_EXCLUSIVE_LOCK = 0x00000002
)
// Do the interface allocations only once for common
// Errno values.
const (
errnoERROR_IO_PENDING = 997
)
var (
errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
)
// errnoErr returns common boxed Errno values, to prevent
// allocations at runtime.
func errnoErr(e syscall.Errno) error {
switch e {
case 0:
return nil
case errnoERROR_IO_PENDING:
return errERROR_IO_PENDING
}
// TODO: add more here, after collecting data on the common
// error values see on Windows. (perhaps when running
// all.bat?)
return e
}
func lockFileEx(handle syscall.Handle, flags uint32, reserved uint32, numberOfBytesToLockLow uint32, numberOfBytesToLockHigh uint32, offset *syscall.Overlapped) (success bool, err error) {
r1, _, e1 := syscall.Syscall6(
uintptr(procLockFileEx),
6,
uintptr(handle),
uintptr(flags),
uintptr(reserved),
uintptr(numberOfBytesToLockLow),
uintptr(numberOfBytesToLockHigh),
uintptr(unsafe.Pointer(offset)))
success = r1 == 1
if !success {
if e1 != 0 {
err = errnoErr(e1)
} else {
err = syscall.EINVAL
}
}
return
}
func unlockFileEx(handle syscall.Handle, reserved uint32, numberOfBytesToLockLow uint32, numberOfBytesToLockHigh uint32, offset *syscall.Overlapped) (success bool, err error) {
r1, _, e1 := syscall.Syscall6(
uintptr(procUnlockFileEx),
5,
uintptr(handle),
uintptr(reserved),
uintptr(numberOfBytesToLockLow),
uintptr(numberOfBytesToLockHigh),
uintptr(unsafe.Pointer(offset)),
0)
success = r1 == 1
if !success {
if e1 != 0 {
err = errnoErr(e1)
} else {
err = syscall.EINVAL
}
}
return
}