[SR-Users] Syntax of xavp

[Daniel-Constantin Mierla]

On 12/12/12 11:08 AM, Olle E. Johansson wrote:
>
> 12 dec 2012 kl. 10:44 skrev Daniel-Constantin Mierla 
> <miconda at gmail.com <mailto:miconda at gmail.com>>:
>
>> Hello,
>>
>> On 10/9/12 3:59 PM, Andreas Granig wrote:
>>> Hi,
>>>
>>> I'm playing around with xavp, but there are some things I can't wrap my
>>> head around.
>>>
>>> What basically works is this:
>>>
>>> $xavp(a=>foo) = 'foo';
>>> $xavp(a[0]=>bar) = 'bar';
>>>
>>> Getting the value like this:
>>>
>>> xlog("L_INFO", "a-foo='$xavp(a=>foo)' and a-bar='$xavp(a=>bar)'");
>>> as well as
>>> xlog("L_INFO", "a-foo='$xavp(a[0]=>foo)' and a-bar='$xavp(a[0]=>bar)'");
>>>
>>> ... works, because when omitting the index, it assumes [0]. I really
>>> like to avoid such implicit assumptions though, to make the config
>>> really clear, so I prefer the second approach.
>>>
>>> What doesn't work for me then is explicit assignment of the very first
>>> value, like this:
>>>
>>> $xavp(a[0]=>foo) = 'foo';
>>> $xavp(a[0]=>bar) = 'bar';
>>>
>>> If I do this, the "a" xavp is never created. Wouldn't it be good
>>> practice to create the xavp on first assignment? That way, I don't have
>>> to take care in the config file whether the xavp is used for the first
>>> time, where I have to omit the index.
>>
>> xavps are reusing the avps architecture in regards of working as a 
>> stack. So last added is first in the list.
>>
>> The problem of creating the structure when providing the index is 
>> also related to it. What should happen if one does:
>>
>> $xavp(a[5]=>foo) = 'foo';
>>
>> Create other 5 xavps named 'a' (indexes 0 to 4)?
>>
>> It seemed the right approach not to create new structures at invalid 
>> position, by simply not providing the position. For overwriting a 
>> value, the index has to be provided.
>>
>> The xavps system was under rfc at some point:
>> http://lists.sip-router.org/pipermail/users/2009-July/024180.html
>>
>> Of course, it can be adjusted when something can be better, for the 
>> moment I don't see a solution to this case, unless a new operator is 
>> introduced.
>>
>>> What I'm also wondering is whether it's possible to directly access
>>> nested xavps, like this:
>>>
>>> $xavp(a=>foo) = 'afoo';
>>> $xavp(b=>foo) = 'bfoo';
>>> $xavp(c=>a) = $xavp(a);
>>> $xavp(c=>b) = $xavp(b);
>>> xlog("L_INFO", "a-foo='$xavp(c=>a[0]=>foo)'");
>>> or
>>> xlog("L_INFO", "a-foo='$xavp(c=>a=>foo)'");
>>>
>>> Both ways give me "a-foo='<<xavp:0x7f0d387fe178>>'". Is this even
>>> intended? Would be really cool if that's possible!
>> Internally it is possible to have as many nested xavps (the value for 
>> an xavp can be a list of xavps). At this moment, the config file 
>> syntax has support only for two levels, your example is returning the 
>> value of c=>a, which is a pointer to another xavp list.
>
> A question I came up with yesterday evening:
>
> I have an AVP with five values (0-4) called "jultomte".
>
> Is there a way to assign the FULL avp - all five values - to an xavp 
> value?
>
> Like:
> xavp(xmas=>tree) = $avp(jultomte)[*];
The star index [*] for avps (also hdrs and xavps) returns all the values 
in a comma separated string. So all five values will be concatenated, 
with comma in between, the result will be stored as a string value in 
the xavp.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla - http://www.asipto.com
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda

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