mirror of
https://github.com/Threnklyn/jira.git
synced 2026-06-01 18:58:26 +02:00
Cory Bennett
101 lines
2.6 KiB
Go
101 lines
2.6 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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package flock
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import (
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"syscall"
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)
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// Lock is a blocking call to try and take the file lock. It will wait until it
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// is able to obtain the exclusive file lock. It's recommended that TryLock() be
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// used over this function. This function may block the ability to query the
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// current Locked() status due to a RW-mutex lock.
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//
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// If we are already locked, this function short-circuits and returns immediately
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// assuming it can take the mutex lock.
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func (f *Flock) Lock() error {
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f.m.Lock()
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defer f.m.Unlock()
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if f.l {
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return nil
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}
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if f.fh == nil {
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if err := f.setFh(); err != nil {
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return err
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}
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}
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if _, err := lockFileEx(syscall.Handle(f.fh.Fd()), LOCKFILE_EXCLUSIVE_LOCK, 0, 1, 0, &syscall.Overlapped{}); err != nil {
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return err
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}
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f.l = true
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return nil
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}
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// Unlock is a function to unlock the file. This file takes a RW-mutex lock, so
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// while it is running the Locked() function will be blocked.
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//
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// This function short-circuits if we are unlocked already. If not, it calls
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// syscall.LOCK_UN on the file and closes the file descriptor It does not remove
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// the file from disk. It's up to your application to do.
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func (f *Flock) Unlock() error {
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f.m.Lock()
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defer f.m.Unlock()
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// if we aren't locked or if the lockfile instance is nil
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// just return a nil error because we are unlocked
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if !f.l || f.fh == nil {
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return nil
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}
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// mark the file as unlocked
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if _, err := unlockFileEx(syscall.Handle(f.fh.Fd()), 0, 1, 0, &syscall.Overlapped{}); err != nil {
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return err
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}
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f.fh.Close()
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f.l = false
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f.fh = nil
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return nil
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}
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// TryLock is the preferred function for taking a file lock. This function does
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// take a RW-mutex lock before it tries to lock the file, so there is the
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// possibility that this function may block for a short time if another goroutine
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// is trying to take any action.
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//
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// The actual file lock is non-blocking. If we are unable to get the exclusive
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// file lock, the function will return false instead of waiting for the lock.
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// If we get the lock, we also set the *Flock instance as being locked.
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func (f *Flock) TryLock() (bool, error) {
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f.m.Lock()
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defer f.m.Unlock()
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if f.l {
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return true, nil
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}
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if f.fh == nil {
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if err := f.setFh(); err != nil {
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return false, err
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}
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}
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_, err := lockFileEx(syscall.Handle(f.fh.Fd()), LOCKFILE_EXCLUSIVE_LOCK|LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &syscall.Overlapped{})
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switch err {
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case nil:
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f.l = true
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return true, nil
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}
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return false, err
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}
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