[boost] Re: Re: Serialization and async messaging

From: Robert Ramey (ramey_at_[hidden])
Date: 2004-12-29 01:16:51

Jody Hagins wrote:

>> I believe you could easily achive what you want to accomplish by
>> serializaiton to a memory buffer (e.g string_stream) and transmitting
>> this. On the other end the inverse of this process would occur.
>
> If I understand Scott correctly, the problem still exists, if you want
> to use the lib in that way.
>
> Assume an object whose serialization is something like 4K.  If reading
> from a file, or even a TCP stream with the socket in blocking mode,
> then
> you just keep reading until you get all the data.  However, for a
> socket
> in non-blocking mode, you will typically use select or poll or some
> other notification mechanism to be told when data is available.  You
> will then go read as much as is currently available, and then return
> to
> other tasks until more data is ready.  Let's say that data is slow,
> and
> to ready the entire 4K of data, it takes 10 different "notifications"
> and 10 different "read" operations.
>
> I think Scott is saying that operator>> is insufficient because it can
> not do a partial read of what is there... it wants to snarf all 4K.
>
>
>
> I could be missing the boat, but this is the usual problem with
> serialization methods, when using them with sockets.  For this to
> work,
> the operator>>() has to know that there is no more data (i.e.,
> correctly interpret return code of read when the fd is in
> non-blocking mode), and
> keep its current state so that the next call to operator>>() will
> continue where the last call left off.
>
>
> I do not see this as a protocol issue but as supporting non blocking
> reads where you can get the data in many small chunks.
>
>
> Then again, it is possible that the serialization library already does
> support this in some way...

Not as far as I can see.  I would say that one should serialize the data in
the chunk size you want and not attempt to break up the chunks.

Robert Ramey