Christian Mayer wrote:
> The missing functionality is the ability to figure out if the tile has
> changed IIRC.
>
> But that'n no problem - HTTP already supports that. IIRC it send's a
> status code of 302 if the reqested data didn't change...

There seems to be some confusion about what rsync is and what it does.
Unlike FTP and HTTP, it does more than a date stamp and file size
check to determine whether or not to resend a file.  Rsync is
essentially a binary "diff" utility.  It is capable of finding
continguous unchanged sections in otherwise-modified files and sending
*only* the sections that change.  And it does it in time linear in the
size of the file and network bandwidth linear in the size of the
changes, without either side needing to see both copies to do it.

It's a very, very cool program.  There is a (amazingly readable!)
paper on how it works available at http://www.rsync.org for those
interested.

For some applications, this is critically important.  Simply
downloading new scenery underneath your airplane won't be any
different, but *updating* preexisting scenery will (probably) work
much better with rsync than with any other web protocol.  This is
likely to be the more important feature, IMHO.  In the future, you
won't need to do anything to get access to new runway lighting, large
building models, new elevation data, etc...

Now, whether rsync is really a win for terrasync depends on the
details of the data files and whether or not they'll have contiguous
unchanged sections after typical updates.  I don't know enough about
it to say.  The only point is that rsync is most definitely *not* a
new and incompatible file transfer protocol.  It solves a much harder
problem.

About the windows binary: is anyone really opposed to shipping a
rsync.exe and cygwin.dll with the rest of the binaries?  I'm not a
windows guy, but this really doesn't seem to awful to me.

Andy

-- 
Andrew J. Ross                NextBus Information Systems
Senior Software Engineer      Emeryville, CA
[EMAIL PROTECTED]              http://www.nextbus.com
"Men go crazy in conflagrations.  They only get better one by one."
 - Sting (misquoted)


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