Re: [boost] Re: [network] An RFC - updated

From: Iain Hanson (Iain.Hanson_at_[hidden])
Date: 2005-04-22 09:04:31

On Fri, 2005-04-22 at 14:23 +0300, Peter Dimov wrote:
> Iain Hanson wrote:
> > On Fri, 2005-04-22 at 12:42 +0300, Peter Dimov wrote:
> >
[ snip ]

> > This would give a significant performance hit as there will now be two
> > copies of the data. The 1st from kennel space to the library and the
> > second in the callback from the library to the user.
> 
> Sometimes, yes, but not always. You don't have to make a copy in the 
> callback, and for small packets and low bandwidth, the extra copy may not be 
> significant. Also note the "by default" in the above. I am not against 
> manual buffer management, just against the absence of automatic buffer 
> management. 
> 
I really don't see this as workable in the general case. The library has
to guess the size of the read buffer. It would also prevent reading a
complete record on a stream by reading a header up to the length field
and then making a 2nd read call for that length with the correct size
buffer.

It would also add dynamic memory allocation to the library and be a
source of runtime errors as a result a user not copying the buffer and
trying to use it after its lifetime expired.

I know we can't always protect users from themselves but we do try to
not make it easy for them to make mistakes.

/ikh