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Define a new Features() method for Fs

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Optional interfaces are becoming more important in rclone,
--track-renames and --backup-dir both rely on them.

Up to this point rclone has used interface upgrades to define optional
behaviour on Fs objects.  However when one Fs object wraps another it
is very difficult for this scheme to work accurately.  rclone has
relied on specific error messages being returned when the interface
isn't supported - this is unsatisfactory because it means you have to
call the interface to see whether it is supported.

This change enables accurate detection of optional interfaces by use
of a Features struct as returned by an obligatory Fs.Features()
method.  The Features struct contains flags and function pointers
which can be tested against nil to see whether they can be used.

As a result crypt and hubic can accurately reflect the capabilities of
the underlying Fs they are wrapping.
This commit is contained in:
Nick Craig-Wood 2017-01-13 17:21:47 +00:00
parent 3745c526f1
commit 1fa258c2b4
19 changed files with 386 additions and 129 deletions
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28
fs/operations.go
View file

@ -252,9 +252,9 @@ func Copy(f Fs, dst Object, remote string, src Object) (err error) {
// Try server side copy first - if has optional interface and
// is same underlying remote
actionTaken = "Copied (server side copy)"
if fCopy, ok := f.(Copier); ok && SameConfig(src.Fs(), f) {
if doCopy := f.Features().Copy; doCopy != nil && SameConfig(src.Fs(), f) {
var newDst Object
newDst, err = fCopy.Copy(src, remote)
newDst, err = doCopy(src, remote)
if err == nil {
dst = newDst
}
@ -353,7 +353,7 @@ func Move(fdst Fs, dst Object, remote string, src Object) (err error) {
return nil
}
// See if we have Move available
if do, ok := fdst.(Mover); ok && SameConfig(src.Fs(), fdst) {
if doMove := fdst.Features().Move; doMove != nil && SameConfig(src.Fs(), fdst) {
// Delete destination if it exists
if dst != nil {
err = DeleteFile(dst)
@ -362,7 +362,7 @@ func Move(fdst Fs, dst Object, remote string, src Object) (err error) {
}
}
// Move dst <- src
_, err := do.Move(src, remote)
_, err := doMove(src, remote)
switch err {
case nil:
Debug(src, "Moved (server side)")
@ -391,8 +391,8 @@ func Move(fdst Fs, dst Object, remote string, src Object) (err error) {
// Some remotes simulate rename by server-side copy and delete, so include
// remotes that implements either Mover or Copier.
func CanServerSideMove(fdst Fs) bool {
_, canMove := fdst.(Mover)
_, canCopy := fdst.(Copier)
canMove := fdst.Features().Move != nil
canCopy := fdst.Features().Copy != nil
return canMove || canCopy
}
@ -880,12 +880,12 @@ func Rmdir(f Fs, dir string) error {
func Purge(f Fs) error {
doFallbackPurge := true
var err error
if purger, ok := f.(Purger); ok {
if doPurge := f.Features().Purge; doPurge != nil {
doFallbackPurge = false
if Config.DryRun {
Log(f, "Not purging as --dry-run set")
} else {
err = purger.Purge()
err = doPurge()
if err == ErrorCantPurge {
doFallbackPurge = true
}
@ -929,8 +929,8 @@ func Delete(f Fs) error {
// dedupeRename renames the objs slice to different names
func dedupeRename(remote string, objs []Object) {
f := objs[0].Fs()
mover, ok := f.(Mover)
if !ok {
doMove := f.Features().Move
if doMove == nil {
log.Fatalf("Fs %v doesn't support Move", f)
}
ext := path.Ext(remote)
@ -938,7 +938,7 @@ func dedupeRename(remote string, objs []Object) {
for i, o := range objs {
newName := fmt.Sprintf("%s-%d%s", base, i+1, ext)
if !Config.DryRun {
newObj, err := mover.Move(o, newName)
newObj, err := doMove(o, newName)
if err != nil {
Stats.Error()
ErrorLog(o, "Failed to rename: %v", err)
@ -1159,15 +1159,15 @@ func listToChan(list *Lister) ObjectsChan {
// CleanUp removes the trash for the Fs
func CleanUp(f Fs) error {
fc, ok := f.(CleanUpper)
if !ok {
doCleanUp := f.Features().CleanUp
if doCleanUp == nil {
return errors.Errorf("%v doesn't support cleanup", f)
}
if Config.DryRun {
Log(f, "Not running cleanup as --dry-run set")
return nil
}
return fc.CleanUp()
return doCleanUp()
}
// Cat any files to the io.Writer