[SR-Dev] sip_msg and hdrs anchors

[Andrei Pelinescu-Onciul]

On Mar 30, 2009 at 23:21, Daniel-Constantin Mierla <miconda at gmail.com> wrote:
> Hello,
> 
> it became a trend to add anchors to each header used by some module to 
> sip_msg structure. While the average is 15 headers per SIP message (some 
> without anchors in the sip_msg), sip_msg has over 35.
> 
> Many of these are used only once, e.g., presence related headers are 
> used by router as endpoint, not as a proxy. Intended to endpoint are 
> subject, supported, unsupported, and perhaps others... Keeping them and 
> cloning in TM when proxying makes no sense. They are not used for routing.
> 
> I think would be good to replace some anchors or at least for future the 
> addition of anchors with functions like:
> 
> get_hdr_xyz(sip_msg) - that will take care of parsing and return the 
> right hdr_field structure.

I fully agree. I tried this once before, but hit some opposition  :-)

The problem with lots of anchors is that each one uses 8 bytes on a
64-bit system and they add up (clone in tm a.s.o.).
I would keep anchors only for the headers that are use a lot and that
are used more then once per message processing cycle (e.g. if Foo is
used only once by one module, it shouldn't get an anchor/shortcut).

> 
> On another hand I propose to add sortcut to body (start and length) - in 
> this case if there is a correction done by the parser, will be in effect 
> everywhere. Looking now in the code, there are functions that extract 
> body in different ways, some correcting the length by skipping \r, \n at 
> the end.

Why isn't get_body() enough?
The message end is always at msg->buf+msg->len (but we can write a
function or extend get_body() to return the len too).


Andrei