lib/scanner: Use fs.Filesystem for all operations

One more step on the path of the great refactoring. Touches rwfolder a
little bit since it uses the Lstat from fs as well, but mostly this is
just on the scanner as rwfolder is scheduled for a later refactor.

There are a couple of usages of fs.DefaultFilesystem that will in the
end become a filesystem injected from the top, but that comes later.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4070
LGTM: AudriusButkevicius, imsodin

lib/fs/basicfs.go

@@ -32,7 +32,7 @@ func (f *BasicFilesystem) Mkdir(name string, perm FileMode) error {
 }
 
 func (f *BasicFilesystem) Lstat(name string) (FileInfo, error) {
-	fi, err := os.Lstat(name)
+	fi, err := underlyingLstat(name)
 	if err != nil {
 		return nil, err
 	}
@@ -71,11 +71,32 @@ func (f *BasicFilesystem) DirNames(name string) ([]string, error) {
 }
 
 func (f *BasicFilesystem) Open(name string) (File, error) {
-	return os.Open(name)
+	fd, err := os.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	return fsFile{fd}, err
 }
 
 func (f *BasicFilesystem) Create(name string) (File, error) {
-	return os.Create(name)
+	fd, err := os.Create(name)
+	if err != nil {
+		return nil, err
+	}
+	return fsFile{fd}, err
+}
+
+// fsFile implements the fs.File interface on top of an os.File
+type fsFile struct {
+	*os.File
+}
+
+func (f fsFile) Stat() (FileInfo, error) {
+	info, err := f.File.Stat()
+	if err != nil {
+		return nil, err
+	}
+	return fsFileInfo{info}, nil
 }
 
 // fsFileInfo implements the fs.FileInfo interface on top of an os.FileInfo.

lib/fs/filesystem.go

@@ -7,8 +7,9 @@
 package fs
 
 import (
-	"errors"
 	"io"
+	"os"
+	"path/filepath"
 	"time"
 )
 
@@ -37,6 +38,7 @@ type File interface {
 	io.WriterAt
 	io.Closer
 	Truncate(size int64) error
+	Stat() (FileInfo, error)
 }
 
 // The FileInfo interface is almost the same as os.FileInfo, but with the
@@ -57,12 +59,20 @@ type FileInfo interface {
 // FileMode is similar to os.FileMode
 type FileMode uint32
 
+// ModePerm is the equivalent of os.ModePerm
+const ModePerm = FileMode(os.ModePerm)
+
 // DefaultFilesystem is the fallback to use when nothing explicitly has
 // been passed.
-var DefaultFilesystem Filesystem = new(BasicFilesystem)
+var DefaultFilesystem Filesystem = NewBasicFilesystem()
 
 // SkipDir is used as a return value from WalkFuncs to indicate that
 // the directory named in the call is to be skipped. It is not returned
 // as an error by any function.
-var errSkipDir = errors.New("skip this directory")
-var SkipDir = errSkipDir // silences the lint warning...
+var SkipDir = filepath.SkipDir
+
+// IsExist is the equivalent of os.IsExist
+var IsExist = os.IsExist
+
+// IsNotExist is the equivalent of os.IsNotExist
+var IsNotExist = os.IsNotExist

lib/fs/lstat_broken.go

@@ -0,0 +1,29 @@
+// Copyright (C) 2015 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// +build linux android
+
+package fs
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Lstat is like os.Lstat, except lobotomized for Android. See
+// https://forum.syncthing.net/t/2395
+func underlyingLstat(name string) (fi os.FileInfo, err error) {
+	for i := 0; i < 10; i++ { // We have to draw the line somewhere
+		fi, err = os.Lstat(name)
+		if err, ok := err.(*os.PathError); ok && err.Err == syscall.EINTR {
+			time.Sleep(time.Duration(i+1) * time.Millisecond)
+			continue
+		}
+		return
+	}
+	return
+}

lib/fs/lstat_regular.go

@@ -0,0 +1,15 @@
+// Copyright (C) 2015 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// +build !linux,!android
+
+package fs
+
+import "os"
+
+func underlyingLstat(name string) (fi os.FileInfo, err error) {
+	return os.Lstat(name)
+}

lib/fs/mtimefs.go

@@ -27,12 +27,14 @@ var osChtimes = os.Chtimes
 // of what shenanigans the underlying filesystem gets up to. A nil MtimeFS
 // just does the underlying operations with no additions.
 type MtimeFS struct {
+	Filesystem
 	db database
 }
 
-func NewMtimeFS(db database) *MtimeFS {
+func NewMtimeFS(underlying Filesystem, db database) *MtimeFS {
 	return &MtimeFS{
-		db: db,
+		Filesystem: underlying,
+		db:         db,
 	}
 }
 
@@ -56,12 +58,8 @@ func (f *MtimeFS) Chtimes(name string, atime, mtime time.Time) error {
 	return nil
 }
 
-func (f *MtimeFS) Lstat(name string) (os.FileInfo, error) {
-	if f == nil {
-		return osutil.Lstat(name)
-	}
-
-	info, err := osutil.Lstat(name)
+func (f *MtimeFS) Lstat(name string) (FileInfo, error) {
+	info, err := f.Filesystem.Lstat(name)
 	if err != nil {
 		return nil, err
 	}
@@ -113,7 +111,7 @@ func (f *MtimeFS) load(name string) (real, virtual time.Time) {
 // The mtimeFileInfo is an os.FileInfo that lies about the ModTime().
 
 type mtimeFileInfo struct {
-	os.FileInfo
+	FileInfo
 	mtime time.Time
 }
 

lib/fs/mtimefs_test.go

@@ -25,7 +25,7 @@ func TestMtimeFS(t *testing.T) {
 	// a random time with nanosecond precision
 	testTime := time.Unix(1234567890, 123456789)
 
-	mtimefs := NewMtimeFS(make(mapStore))
+	mtimefs := NewMtimeFS(DefaultFilesystem, make(mapStore))
 
 	// Do one Chtimes call that will go through to the normal filesystem
 	osChtimes = os.Chtimes