make watch.go its own package

for the purpose for upcoming changes to the watch functionality.

tail.go

@@ -10,6 +10,7 @@ import (
 	"log"
 	"os"
 	"time"
+	"github.com/ActiveState/tail/watch"
 )
 
 type Line struct {
@@ -34,7 +35,7 @@ type Tail struct {
 
 	file    *os.File
 	reader  *bufio.Reader
-	watcher FileWatcher
+	watcher watch.FileWatcher
 
 	tomb.Tomb // provides: Done, Kill, Dying
 }
@@ -62,9 +63,9 @@ func TailFile(filename string, config Config) (*Tail, error) {
 		Config:   config}
 
 	if t.Poll {
-		t.watcher = NewPollingFileWatcher(filename)
+		t.watcher = watch.NewPollingFileWatcher(filename)
 	} else {
-		t.watcher = NewInotifyFileWatcher(filename)
+		t.watcher = watch.NewInotifyFileWatcher(filename)
 	}
 
 	if t.MustExist {

tail_test.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"testing"
 	"time"
+	"./watch"
 )
 
 func init() {
@@ -104,7 +105,7 @@ func _TestReOpen(_t *testing.T, poll bool) {
 	if poll {
 		// Give polling a chance to read the just-written lines (more;
 		// data), before we recreate the file again below.
-		<-time.After(POLL_DURATION)
+		<-time.After(watch.POLL_DURATION)
 	}
 
 	// rename must trigger reopen
@@ -114,7 +115,7 @@ func _TestReOpen(_t *testing.T, poll bool) {
 	if poll {
 		// This time, wait a bit before creating the file to test
 		// PollingFileWatcher's BlockUntilExists.
-		<-time.After(POLL_DURATION)
+		<-time.After(watch.POLL_DURATION)
 	}
 	t.CreateFile("test.txt", "endofworld")
 
@@ -159,7 +160,7 @@ func _TestReSeek(_t *testing.T, poll bool) {
 	if poll {
 		// Give polling a chance to read the just-written lines (more;
 		// data), before we truncate the file again below.
-		<-time.After(POLL_DURATION)
+		<-time.After(watch.POLL_DURATION)
 	}
 	println("truncating..")
 	t.TruncateFile("test.txt", "h311o\nw0r1d\nendofworld\n")
@@ -167,7 +168,7 @@ func _TestReSeek(_t *testing.T, poll bool) {
 	if poll {
 		// Give polling a chance to read the just-written lines (more;
 		// data), before we recreate the file again below.
-		<-time.After(POLL_DURATION)
+		<-time.After(watch.POLL_DURATION)
 	}
 
 	// Delete after a reasonable delay, to give tail sufficient time
@@ -206,7 +207,7 @@ func NewTailTest(name string, t *testing.T) TailTest {
 	}
 
 	// Use a smaller poll duration for faster test runs.
-	POLL_DURATION = 25 * time.Millisecond
+	watch.POLL_DURATION = 25 * time.Millisecond
 
 	return tt
 }

watch.go

@@ -1,215 +0,0 @@
-// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
-
-package tail
-
-import (
-	"github.com/howeyc/fsnotify"
-	"os"
-	"path/filepath"
-	"sync"
-	"time"
-)
-
-// FileWatcher monitors file-level events.
-type FileWatcher interface {
-	// BlockUntilExists blocks until the missing file comes into
-	// existence. If the file already exists, returns immediately.
-	BlockUntilExists() error
-
-	// ChangeEvents returns a channel of events corresponding to the
-	// times the file is ready to be read.
-	ChangeEvents(os.FileInfo) chan bool
-}
-
-// InotifyFileWatcher uses inotify to monitor file changes.
-type InotifyFileWatcher struct {
-	Filename string
-	Size     int64
-}
-
-func NewInotifyFileWatcher(filename string) *InotifyFileWatcher {
-	fw := &InotifyFileWatcher{filename, 0}
-	return fw
-}
-
-func (fw *InotifyFileWatcher) BlockUntilExists() error {
-	w, err := fsnotify.NewWatcher()
-	if err != nil {
-		return err
-	}
-	defer w.Close()
-
-	dirname := filepath.Dir(fw.Filename)
-
-	// Watch for new files to be created in the parent directory.
-	err = w.WatchFlags(dirname, fsnotify.FSN_CREATE)
-	if err != nil {
-		return err
-	}
-	defer w.RemoveWatch(filepath.Dir(fw.Filename))
-
-	// Do a real check now as the file might have been created before
-	// calling `WatchFlags` above.
-	if _, err = os.Stat(fw.Filename); !os.IsNotExist(err) {
-		// file exists, or stat returned an error.
-		return err
-	}
-
-	for {
-		evt := <-w.Event
-		if evt.Name == fw.Filename {
-			break
-		}
-	}
-	return nil
-}
-
-// ChangeEvents returns a channel that gets updated when the file is ready to be read.
-func (fw *InotifyFileWatcher) ChangeEvents(fi os.FileInfo) chan bool {
-	w, err := fsnotify.NewWatcher()
-	if err != nil {
-		panic(err)
-	}
-	err = w.Watch(fw.Filename)
-	if err != nil {
-		panic(err)
-	}
-
-	ch := make(chan bool)
-
-	fw.Size = fi.Size()
-
-	go func() {
-		defer w.Close()
-		defer w.RemoveWatch(fw.Filename)
-		defer close(ch)
-
-		for {
-			prevSize := fw.Size
-
-			evt := <-w.Event
-			switch {
-			case evt.IsDelete():
-				fallthrough
-
-			case evt.IsRename():
-				return
-
-			case evt.IsModify():
-				fi, err := os.Stat(fw.Filename)
-				if err != nil {
-					// XXX: no panic here
-					panic(err)
-				}
-				fw.Size = fi.Size()
-
-				if prevSize > 0 && prevSize > fw.Size {
-					return
-				}
-
-				// send only if channel is empty.
-				select {
-				case ch <- true:
-				default:
-				}
-			}
-		}
-	}()
-
-	return ch
-}
-
-// PollingFileWatcher polls the file for changes.
-type PollingFileWatcher struct {
-	Filename string
-	Size     int64
-}
-
-func NewPollingFileWatcher(filename string) *PollingFileWatcher {
-	fw := &PollingFileWatcher{filename, 0}
-	return fw
-}
-
-var POLL_DURATION time.Duration
-
-func (fw *PollingFileWatcher) BlockUntilExists() error {
-	for {
-		if _, err := os.Stat(fw.Filename); err == nil {
-			return nil
-		} else if !os.IsNotExist(err) {
-			return err
-		}
-		time.Sleep(POLL_DURATION)
-	}
-	panic("unreachable")
-}
-
-func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
-	ch := make(chan bool)
-	stop := make(chan bool)
-	var once sync.Once
-	var prevModTime time.Time
-
-	// XXX: use tomb.Tomb to cleanly manage these goroutines. replace
-	// the panic (below) with tomb's Kill.
-
-	stopAndClose := func() {
-		go func() {
-			close(ch)
-			stop <- true
-		}()
-	}
-
-	fw.Size = origFi.Size()
-
-	go func() {
-		prevSize := fw.Size
-		for {
-			select {
-			case <-stop:
-				return
-			default:
-			}
-
-			time.Sleep(POLL_DURATION)
-			fi, err := os.Stat(fw.Filename)
-			if err != nil {
-				if os.IsNotExist(err) {
-					once.Do(stopAndClose)
-					continue
-				}
-				/// XXX: do not panic here.
-				panic(err)
-			}
-
-			// File got moved/rename within POLL_DURATION?
-			if !os.SameFile(origFi, fi) {
-				once.Do(stopAndClose)
-				continue
-			}
-
-			// Was the file truncated?
-			fw.Size = fi.Size()
-			if prevSize > 0 && prevSize > fw.Size {
-				once.Do(stopAndClose)
-				continue
-			}
-
-			// If the file was changed since last check, notify.
-			modTime := fi.ModTime()
-			if modTime != prevModTime {
-				prevModTime = modTime
-				select {
-				case ch <- true:
-				default:
-				}
-			}
-		}
-	}()
-
-	return ch
-}
-
-func init() {
-	POLL_DURATION = 250 * time.Millisecond
-}

watch/inotify.go

@@ -0,0 +1,107 @@
+// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
+
+package watch
+
+import (
+	"github.com/howeyc/fsnotify"
+	"os"
+	"path/filepath"
+)
+
+// InotifyFileWatcher uses inotify to monitor file changes.
+type InotifyFileWatcher struct {
+	Filename string
+	Size     int64
+}
+
+func NewInotifyFileWatcher(filename string) *InotifyFileWatcher {
+	fw := &InotifyFileWatcher{filename, 0}
+	return fw
+}
+
+func (fw *InotifyFileWatcher) BlockUntilExists() error {
+	w, err := fsnotify.NewWatcher()
+	if err != nil {
+		return err
+	}
+	defer w.Close()
+
+	dirname := filepath.Dir(fw.Filename)
+
+	// Watch for new files to be created in the parent directory.
+	err = w.WatchFlags(dirname, fsnotify.FSN_CREATE)
+	if err != nil {
+		return err
+	}
+	defer w.RemoveWatch(filepath.Dir(fw.Filename))
+
+	// Do a real check now as the file might have been created before
+	// calling `WatchFlags` above.
+	if _, err = os.Stat(fw.Filename); !os.IsNotExist(err) {
+		// file exists, or stat returned an error.
+		return err
+	}
+
+	for {
+		evt := <-w.Event
+		if evt.Name == fw.Filename {
+			break
+		}
+	}
+	return nil
+}
+
+// ChangeEvents returns a channel that gets updated when the file is ready to be read.
+func (fw *InotifyFileWatcher) ChangeEvents(fi os.FileInfo) chan bool {
+	w, err := fsnotify.NewWatcher()
+	if err != nil {
+		panic(err)
+	}
+	err = w.Watch(fw.Filename)
+	if err != nil {
+		panic(err)
+	}
+
+	ch := make(chan bool)
+
+	fw.Size = fi.Size()
+
+	go func() {
+		defer w.Close()
+		defer w.RemoveWatch(fw.Filename)
+		defer close(ch)
+
+		for {
+			prevSize := fw.Size
+
+			evt := <-w.Event
+			switch {
+			case evt.IsDelete():
+				fallthrough
+
+			case evt.IsRename():
+				return
+
+			case evt.IsModify():
+				fi, err := os.Stat(fw.Filename)
+				if err != nil {
+					// XXX: no panic here
+					panic(err)
+				}
+				fw.Size = fi.Size()
+
+				if prevSize > 0 && prevSize > fw.Size {
+					return
+				}
+
+				// send only if channel is empty.
+				select {
+				case ch <- true:
+				default:
+				}
+			}
+		}
+	}()
+
+	return ch
+}

watch/polling.go

@@ -0,0 +1,104 @@
+// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
+
+package watch
+
+import (
+	"os"
+	"sync"
+	"time"
+)
+
+// PollingFileWatcher polls the file for changes.
+type PollingFileWatcher struct {
+	Filename string
+	Size     int64
+}
+
+func NewPollingFileWatcher(filename string) *PollingFileWatcher {
+	fw := &PollingFileWatcher{filename, 0}
+	return fw
+}
+
+var POLL_DURATION time.Duration
+
+func (fw *PollingFileWatcher) BlockUntilExists() error {
+	for {
+		if _, err := os.Stat(fw.Filename); err == nil {
+			return nil
+		} else if !os.IsNotExist(err) {
+			return err
+		}
+		time.Sleep(POLL_DURATION)
+	}
+	panic("unreachable")
+}
+
+func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
+	ch := make(chan bool)
+	stop := make(chan bool)
+	var once sync.Once
+	var prevModTime time.Time
+
+	// XXX: use tomb.Tomb to cleanly manage these goroutines. replace
+	// the panic (below) with tomb's Kill.
+
+	stopAndClose := func() {
+		go func() {
+			close(ch)
+			stop <- true
+		}()
+	}
+
+	fw.Size = origFi.Size()
+
+	go func() {
+		prevSize := fw.Size
+		for {
+			select {
+			case <-stop:
+				return
+			default:
+			}
+
+			time.Sleep(POLL_DURATION)
+			fi, err := os.Stat(fw.Filename)
+			if err != nil {
+				if os.IsNotExist(err) {
+					once.Do(stopAndClose)
+					continue
+				}
+				/// XXX: do not panic here.
+				panic(err)
+			}
+
+			// File got moved/rename within POLL_DURATION?
+			if !os.SameFile(origFi, fi) {
+				once.Do(stopAndClose)
+				continue
+			}
+
+			// Was the file truncated?
+			fw.Size = fi.Size()
+			if prevSize > 0 && prevSize > fw.Size {
+				once.Do(stopAndClose)
+				continue
+			}
+
+			// If the file was changed since last check, notify.
+			modTime := fi.ModTime()
+			if modTime != prevModTime {
+				prevModTime = modTime
+				select {
+				case ch <- true:
+				default:
+				}
+			}
+		}
+	}()
+
+	return ch
+}
+
+func init() {
+	POLL_DURATION = 250 * time.Millisecond
+}

watch/watch.go

@@ -0,0 +1,19 @@
+// Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
+
+package watch
+
+import (
+	"os"
+)
+
+// FileWatcher monitors file-level events.
+type FileWatcher interface {
+	// BlockUntilExists blocks until the missing file comes into
+	// existence. If the file already exists, returns immediately.
+	BlockUntilExists() error
+
+	// ChangeEvents returns a channel of events corresponding to the
+	// times the file is ready to be read.
+	ChangeEvents(os.FileInfo) chan bool
+}
+