Boost logo

Boost :

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-10-18 06:21:25


Beman Dawes wrote:
> "Christopher Kohlhoff" <chris_at_[hidden]> wrote in message
> news:20051017052938.33920.qmail_at_web32604.mail.mud.yahoo.com...

>> Hmm, I'm not sure. Here are the current uses of void* and their
>> rationales:
>>
>> * buffer() and buffers() - so that arbitrary application data
>> structures can be sent without an additional buffer copy.
>
> Where did this idea come from that the only way to avoid an
> additional copy is to use a void *?
>
> Think about the iterator interfaces to Standard Library algorithms.
> They traffic nicely in pointers, yet not a buffer copy or void * to
> be seen.

But the algorithms operate on typed data, and asio/sockets operate on
untyped data. They gain nothing from an iterator interface, because they
simply can't provide type safety. When you send a type T over the wire, what
comes out at the other end is an untyped sequence of bytes that may have
been a T on the source machine, but is not necessarily a T on the target; so
even if the target could somehow deduce the type - and it cannot - it
wouldn't be very useful to cast the byte sequence to an invalid T.

It's better to not provide an illusion of type safety when there is none;
the buffer is a raw sequence of bytes and (void*, size_t), (unsigned char*,
size_t) and (unsigned char*, unsigned char*) are its natural
representations. It really is of type "raw sequence of bytes", and using
another type to describe it decreases type safety rather than increasing it.


Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk