[Spice-devel] [PATCH win-vdagent] Support file transfer for existing files

[Jonathon Jongsma]

On Wed, 2017-04-26 at 17:50 -0400, Frediano Ziglio wrote:
> > 
> > Previously, if the user attempted to transfer a file that had the
> > same
> > name as a file that already exists on the guest, we would just fail
> > the
> > transfer. This patch tries to match the behavior of the linux
> > vdagent
> > where we try to append an integer onto the name of the new file to
> > make
> > it unique. For example, if you tried to transfer 'file.doc' to the
> > guest
> > and that file already existed, it would try to create 'file.doc
> > (1)'
> > instead. If that also failed, it would attempt 'file.doc (2)', etc,
> > up
> > to 63.
> > 
> 
> Not really user friendly, Windows is really extension based.
> Would be better to be 'file (1).doc' for 'file.doc'.
> Yes, not easy to implement as adding " (xx)".

True, I just tried to copy the behavior of the linux vdagent (as
suggested in the bug), but perhaps we should do it a bit differently
for windows. Or maybe we should change both the linux and vdagent to
work this way...

> 
> > Resolves: rhbz#1410181
> > ---
> >  vdagent/file_xfer.cpp | 38 ++++++++++++++++++++++++++++++++------
> >  1 file changed, 32 insertions(+), 6 deletions(-)
> > 
> > diff --git a/vdagent/file_xfer.cpp b/vdagent/file_xfer.cpp
> > index f763ed3..14e2098 100644
> > --- a/vdagent/file_xfer.cpp
> > +++ b/vdagent/file_xfer.cpp
> > @@ -61,6 +61,7 @@ void
> > FileXfer::handle_start(VDAgentFileXferStartMessage*
> > start,
> >      HANDLE handle;
> >      AsUser as_user;
> >      int wlen;
> > +    int attempt = 0;
> >  
> >      status->id = start->id;
> >      status->result = VD_AGENT_FILE_XFER_STATUS_ERROR;
> > @@ -99,15 +100,40 @@ void
> > FileXfer::handle_start(VDAgentFileXferStartMessage*
> > start,
> >  
> >      file_path[wlen++] = TEXT('\\');
> >      file_path[wlen] = TEXT('\0');
> > -    if((wlen = MultiByteToWideChar(CP_UTF8, 0, file_name, -1,
> > file_path +
> > wlen, MAX_PATH - wlen)) == 0){
> > -        vd_printf("failed converting file_name:%s to WideChar",
> > file_name);
> > -        return;
> > +
> > +    const int MAX_ATTEMPTS = 64; // matches behavior of linux
> > vdagent
> > +    const size_t POSTFIX_LEN = 6; // up to 2 digits in parentheses
> > and final
> > NULL: " (xx)"
> > +    size_t name_len = strlen(file_name);
> > +    for (attempt = 0; attempt < MAX_ATTEMPTS; attempt++) {
> > +        char *pos = &file_name[name_len];
> > +        if (attempt > 0) {
> > +            if (name_len + POSTFIX_LEN > MAX_PATH) {
> > +                vd_printf("failed creating %ls. Postfix makes name
> > too long
> > for the buffer.", file_path);
> > +                return;
> > +            }
> > +            snprintf(pos, POSTFIX_LEN, " (%d)", attempt);
> > +        }
> > +        if((MultiByteToWideChar(CP_UTF8, 0, file_name, -1,
> > file_path + wlen,
> > MAX_PATH - wlen)) == 0){
> > +            vd_printf("failed converting file_name:%s to
> > WideChar",
> > file_name);
> > +            return;
> > +        }
> > +        handle = CreateFile(file_path, GENERIC_WRITE, 0, NULL,
> > CREATE_NEW,
> > 0, NULL);
> > +        if (handle != INVALID_HANDLE_VALUE) {
> > +            break;
> > +        }
> > +
> > +        // If the file already exists, we can re-try with a new
> > filename. If
> > +        // it's a different error, there's not much we can do.
> > +        if (GetLastError() != ERROR_FILE_EXISTS) {
> 
> I would include the old line:
> 
>    vd_printf("failed creating %ls %lu", file_path, GetLastError());
> 
> > +            return;
> > +        }
> >      }
> > -    handle = CreateFile(file_path, GENERIC_WRITE, 0, NULL,
> > CREATE_NEW, 0,
> > NULL);
> > -    if (handle == INVALID_HANDLE_VALUE) {
> > -        vd_printf("failed creating %ls %lu", file_path,
> > GetLastError());
> > +
> > +    if (attempt == MAX_ATTEMPTS) {
> > +        vd_printf("Failed creating %ls. More than 63 copies
> > exist?",
> > file_path);
> >          return;
> >      }
> > +
> >      task = new FileXferTask(handle, file_size, file_path);
> >      _tasks[start->id] = task;
> >      status->result = VD_AGENT_FILE_XFER_STATUS_CAN_SEND_DATA;
> 
> Frediano