127 lines
2.8 KiB
Go
127 lines
2.8 KiB
Go
// Package atexit provides handling for functions you want called when
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// the program exits unexpectedly due to a signal.
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//
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// You should also make sure you call Run in the normal exit path.
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package atexit
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import (
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"os"
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"os/signal"
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"sync"
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"sync/atomic"
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"github.com/rclone/rclone/fs"
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)
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var (
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fns = make(map[FnHandle]bool)
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fnsMutex sync.Mutex
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exitChan chan os.Signal
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exitOnce sync.Once
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registerOnce sync.Once
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signalled int32
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runCalled int32
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)
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// FnHandle is the type of the handle returned by function `Register`
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// that can be used to unregister an at-exit function
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type FnHandle *func()
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// Register a function to be called on exit.
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// Returns a handle which can be used to unregister the function with `Unregister`.
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func Register(fn func()) FnHandle {
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if running() {
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return nil
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}
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fnsMutex.Lock()
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fns[&fn] = true
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fnsMutex.Unlock()
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// Run AtExit handlers on exitSignals so everything gets tidied up properly
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registerOnce.Do(func() {
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exitChan = make(chan os.Signal, 1)
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signal.Notify(exitChan, exitSignals...)
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go func() {
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sig := <-exitChan
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if sig == nil {
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return
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}
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signal.Stop(exitChan)
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atomic.StoreInt32(&signalled, 1)
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fs.Infof(nil, "Signal received: %s", sig)
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Run()
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fs.Infof(nil, "Exiting...")
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os.Exit(0)
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}()
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})
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return &fn
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}
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// Signalled returns true if an exit signal has been received
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func Signalled() bool {
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return atomic.LoadInt32(&signalled) != 0
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}
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// running returns true if run has been called
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func running() bool {
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return atomic.LoadInt32(&runCalled) != 0
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}
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// Unregister a function using the handle returned by `Register`
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func Unregister(handle FnHandle) {
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if running() {
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return
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}
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fnsMutex.Lock()
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defer fnsMutex.Unlock()
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delete(fns, handle)
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}
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// IgnoreSignals disables the signal handler and prevents Run from being executed automatically
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func IgnoreSignals() {
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if running() {
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return
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}
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registerOnce.Do(func() {})
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if exitChan != nil {
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signal.Stop(exitChan)
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close(exitChan)
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exitChan = nil
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}
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}
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// Run all the at exit functions if they haven't been run already
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func Run() {
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atomic.StoreInt32(&runCalled, 1)
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// Take the lock here (not inside the exitOnce) so we wait
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// until the exit handlers have run before any calls to Run()
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// return.
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fnsMutex.Lock()
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defer fnsMutex.Unlock()
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exitOnce.Do(func() {
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for fnHandle := range fns {
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(*fnHandle)()
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}
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})
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}
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// OnError registers fn with atexit and returns a function which
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// runs fn() if *perr != nil and deregisters fn
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//
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// It should be used in a defer statement normally so
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//
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// defer OnError(&err, cancelFunc)()
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//
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// So cancelFunc will be run if the function exits with an error or
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// at exit.
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func OnError(perr *error, fn func()) func() {
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handle := Register(fn)
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return func() {
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defer Unregister(handle)
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if *perr != nil {
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fn()
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}
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}
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}
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