[sr-dev] need help understanding $null

[Daniel-Constantin Mierla]

Hello,

$var(...) cannot be deleted. Its implementation relies on startup
replacement of the name with a pointer in memory, at runtime being used
only the pointer (for speed considerations). You should use $avp() if
you want to deal with $null.

For the second, it depends on transformation, afaik, most
transformations don't return null, but empty string (at least the string
transformations). If you implement a new one and want to return $null,
the value must have the flag PV_VAL_NULL set, like: val->flags  |=
PV_VAL_NULL

Cheers,
Daniel

On 05/01/15 13:36, Luis Azedo wrote:
> HI Daniel,
>
> thanks, so in the first case instead of assigning the value to the
> $var(x) can i delete the $var(x) so that comparison works ?
>
> in the second case (returned value from transform) what value should i
> compare against to check if returned value was null ?
>
> ------------------------------------------------------------------------
> *From:* sr-dev [sr-dev-bounces at lists.sip-router.org] on behalf of
> Daniel-Constantin Mierla [miconda at gmail.com]
> *Sent:* Monday, January 05, 2015 3:51 AM
> *To:* Kamailio (SER) - Development Mailing List
> *Subject:* Re: [sr-dev] need help understanding $null
>
> Hello,
>
> $var(...) cannot be null by design, setting it to $null makes it 0.
>
> $null is more for variables that don't exist, e.g., you don't have the
> $avp(x), then it is null if you compare it.
>
> Cheers,
> Daniel
>
> On 04/01/15 12:35, Luis Azedo wrote:
>> Hi Daniel,
>>
>> can you help on this ?
>>
>> Thank you
>> ------------------------------------------------------------------------
>> *From:* sr-dev [sr-dev-bounces at lists.sip-router.org] on behalf of
>> Luis Azedo [luis at 2600hz.com]
>> *Sent:* Wednesday, December 31, 2014 4:19 AM
>> *To:* sr-dev at lists.sip-router.org
>> *Subject:* [sr-dev] need help understanding $null
>>
>> Hi,
>>
>> if we return val.flags = PV_VAL_NULL, does the == $null comparison work ?
>>
>> script example
>>
>> my_function("some param","$var(result)");
>> if( $var(result) == $null {
>>   do something
>> }
>> in code => dst_pv->setf(msg, &dst_pv->pvp, (int)EQ_T, &dst_val);
>>  should the comparison work if we set dst_val.flags = PV_VAL_NULL ?
>>
>>
>> if( $(myPvar{my.mytransform,transformParameter}) == $null) {
>>   ....
>> }
>> should this work if the transform returns val.flags = PV_VAL_NULL ?
>>
>>
>> thank you
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> sr-dev mailing list
>> sr-dev at lists.sip-router.org
>> http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-dev
>
> -- 
> Daniel-Constantin Mierla
> http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda

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

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