[Kamailio-Devel] [SR-Dev] sip_msg and hdrs anchors

[Daniel-Constantin Mierla]

On 03/31/2009 12:38 PM, Andrei Pelinescu-Onciul wrote:
> 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  :-)
>   

ok :-) ... this time we have to advocate better.

> 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.).
>   
the part with tm cloning is almost always a problem - people forget to 
add it to tm... maybe in the future we will find something more 
automatic, however not a subject for now.

> 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).
>   
Yes, that shortcut can be get_body_len(...) or extend get_body(). I want 
single simple way to get them across code, instead of using some 
expression based on other fields.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
SIP Router Masterclass - Kamailio (OpenSER) Training
http://www.asipto.com/index.php/sip-router-masterclass/