[Telepathy] File transfer spec: need for advice

Marco Barisione marco at barisione.org
Wed Aug 22 06:47:36 PDT 2007

Hi all,
I'm working on file transfer in telepathy-salut[1] and empathy[2], the
current proposed spec for file transfer channels has some problems and I
need some suggestions. The spec darcs repository is at [3], a generated
HTML is at [4].

I need to add a method and a signal to know how many bytes were
transferred, so I can show a progress bar in empathy-file-transfer. The
method should return the number of bytes (a 64-bit unsigned integer) and
not the percentage, as the total file size may be unknown.
Suggestions for the names? GetTransferredSize() and

In the current proposed spec IDs become invalid when the file transfer
is closed. Some components (such as a logger or the UI showing them)
could be run by mc only when the file transfer is already finished, so
ListFileTransfers() would return an empty list, this means that the UI
can't show the file transfer, thus the user would think that the file
wasn't sent.

I propose to keep file transfers in the list until they are explicitly
removed with AcknowledgeFileTransfer(), like we are already doing for
text messages. I'm going to add a new CLOSED state to the existing ones
(LOCAL_PENDING, REMOTE_PENDING and OPEN), but then FileTransferClosed
signal would become a duplicate of FileTransferStateChanged so I'm going
to remove it.
The problem is that FieTransferClosed has a reason argument specifying
why the file transfer was closed (local/remote error, local/remote
stopped and success). What do you suggest to do? I want to remove
FileTransferClosed but I need the reason argument. My ideas are:
- Add a reason argument to FileTransferStateChanged and pass a
NOT_CLOSED value when the new state is not CLOSED.
- Add a reason argument to FileTransferStateChanged and pass something
like ACCEPTED when the state changes from LOCAL/REMOTE_PENDING to OPEN
(other transitions are not possible at the moment). The enumeration
could be renamed from File_Transfer_Close_Reason to something like
- Do not add a reason argument but add a GetCloseReason() method, this
is what I would do in a normal API but here we have a DBUS call and I
don't like adding a roundtrip only to get the reason.

Do we need a signal to inform that a file transfer has been acknowledged
so the ID is becoming invalid?

[1] http://techn.ocracy.org/darcs/telepathy-salut/
[2] http://techn.ocracy.org/empathy/
[3] http://techn.ocracy.org/darcs/telepathy-spec.filetransfer/

Marco Barisione

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