podman

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// Copyright (c) 2019 FOSS contributors of https://github.com/nxadm/tail
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// Copyright (c) 2015 HPE Software Inc. All rights reserved.
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// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
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package watch
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import (
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	"fmt"
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	"os"
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	"path/filepath"
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	"github.com/nxadm/tail/util"
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    "github.com/fsnotify/fsnotify"
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	"gopkg.in/tomb.v1"
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)
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// InotifyFileWatcher uses inotify to monitor file changes.
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type InotifyFileWatcher struct {
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	Filename string
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	Size     int64
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}
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func NewInotifyFileWatcher(filename string) *InotifyFileWatcher {
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	fw := &InotifyFileWatcher{filepath.Clean(filename), 0}
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	return fw
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}
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func (fw *InotifyFileWatcher) BlockUntilExists(t *tomb.Tomb) error {
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	err := WatchCreate(fw.Filename)
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	if err != nil {
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		return err
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	}
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	defer RemoveWatchCreate(fw.Filename)
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	// Do a real check now as the file might have been created before
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	// calling `WatchFlags` above.
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	if _, err = os.Stat(fw.Filename); !os.IsNotExist(err) {
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		// file exists, or stat returned an error.
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		return err
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	}
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	events := Events(fw.Filename)
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	for {
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		select {
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		case evt, ok := <-events:
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			if !ok {
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				return fmt.Errorf("inotify watcher has been closed")
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			}
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			evtName, err := filepath.Abs(evt.Name)
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			if err != nil {
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				return err
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			}
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			fwFilename, err := filepath.Abs(fw.Filename)
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			if err != nil {
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				return err
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			}
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			if evtName == fwFilename {
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				return nil
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			}
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		case <-t.Dying():
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			return tomb.ErrDying
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		}
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	}
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	panic("unreachable")
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}
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func (fw *InotifyFileWatcher) ChangeEvents(t *tomb.Tomb, pos int64) (*FileChanges, error) {
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	err := Watch(fw.Filename)
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	if err != nil {
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		return nil, err
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	}
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	changes := NewFileChanges()
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	fw.Size = pos
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	go func() {
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		events := Events(fw.Filename)
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		for {
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			prevSize := fw.Size
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			var evt fsnotify.Event
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			var ok bool
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			select {
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			case evt, ok = <-events:
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				if !ok {
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					RemoveWatch(fw.Filename)
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					return
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				}
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			case <-t.Dying():
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				RemoveWatch(fw.Filename)
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				return
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			}
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			switch {
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			case evt.Op&fsnotify.Remove == fsnotify.Remove:
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				fallthrough
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			case evt.Op&fsnotify.Rename == fsnotify.Rename:
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				RemoveWatch(fw.Filename)
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				changes.NotifyDeleted()
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				return
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			//With an open fd, unlink(fd) - inotify returns IN_ATTRIB (==fsnotify.Chmod)
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			case evt.Op&fsnotify.Chmod == fsnotify.Chmod:
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				fallthrough
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			case evt.Op&fsnotify.Write == fsnotify.Write:
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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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						RemoveWatch(fw.Filename)
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						changes.NotifyDeleted()
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						return
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					}
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					// XXX: report this error back to the user
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					util.Fatal("Failed to stat file %v: %v", fw.Filename, err)
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				}
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				fw.Size = fi.Size()
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				if prevSize > 0 && prevSize > fw.Size {
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					changes.NotifyTruncated()
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				} else {
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					changes.NotifyModified()
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				}
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				prevSize = fw.Size
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			}
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		}
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	}()
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	return changes, nil
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}
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