105 lines
1.8 KiB
Go
105 lines
1.8 KiB
Go
// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
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package watch
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import (
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"os"
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"sync"
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"time"
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)
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// PollingFileWatcher polls the file for changes.
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type PollingFileWatcher struct {
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Filename string
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Size int64
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}
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func NewPollingFileWatcher(filename string) *PollingFileWatcher {
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fw := &PollingFileWatcher{filename, 0}
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return fw
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}
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var POLL_DURATION time.Duration
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func (fw *PollingFileWatcher) BlockUntilExists() error {
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for {
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if _, err := os.Stat(fw.Filename); err == nil {
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return nil
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} else if !os.IsNotExist(err) {
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return err
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}
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time.Sleep(POLL_DURATION)
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}
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panic("unreachable")
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}
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func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
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ch := make(chan bool)
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stop := make(chan bool)
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var once sync.Once
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var prevModTime time.Time
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// XXX: use tomb.Tomb to cleanly manage these goroutines. replace
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// the panic (below) with tomb's Kill.
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stopAndClose := func() {
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go func() {
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close(ch)
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stop <- true
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}()
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}
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fw.Size = origFi.Size()
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go func() {
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prevSize := fw.Size
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for {
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select {
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case <-stop:
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return
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default:
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}
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time.Sleep(POLL_DURATION)
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fi, err := os.Stat(fw.Filename)
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if err != nil {
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if os.IsNotExist(err) {
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once.Do(stopAndClose)
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continue
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}
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/// XXX: do not panic here.
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panic(err)
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}
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// File got moved/rename within POLL_DURATION?
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if !os.SameFile(origFi, fi) {
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once.Do(stopAndClose)
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continue
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}
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// Was the file truncated?
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fw.Size = fi.Size()
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if prevSize > 0 && prevSize > fw.Size {
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once.Do(stopAndClose)
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continue
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}
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// If the file was changed since last check, notify.
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modTime := fi.ModTime()
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if modTime != prevModTime {
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prevModTime = modTime
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select {
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case ch <- true:
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default:
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}
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}
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}
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}()
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return ch
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}
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func init() {
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POLL_DURATION = 250 * time.Millisecond
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}
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