On the use of 'decmatch' in TTCN-3

historical

Hi Pau,

On Thu, Feb 01, 2018 at 12:18:11AM +0100, Pau Espin Pedrol wrote:

> thanks for the explanation! However, it's still not clear to me how to get
> the decoded payload out of the receive statement. From
> https://www.eclipse.org/forums/index.php/t/1089269/ I saw there's this
> "@decoded" keyword you can use but I couldn't figure out how to really use
> it in a proper way, and what exactly I would be getting with it.

The ETSI TTCN-3 language spec actually has plenty of useful examples.

>From ETSI ES 201 873-1 V4.8.1, Section 22.2.2 Example 2:

MyPort.receive(MyType2:{header := ?, payload := decmatch mw_myTemplate}) -> value (v_myVar := @decoded payload);
// The encoded payload field of the received message is decoded and matched with
// mw_myTemplate; if the matching is successful the decoded payload is stored in v_myVar.

> I'm also wondering if several decmatch expressions can be stacked in a
> single statment, for instance image something like:

I have no idea, guess you'd have to try.

> RSL.receive(tr_RSL_DATA_REQ(g_chan_nr, ?, decmatch tr_RRM_RR_STATUS(foo,
> bar, decmatch tr_ANOTHER_TEMPLATE)).
> Linking it with first question, what I would be getting when using the
> @decoded keyword in this case?

I guess you should raise that in the Eclipse Titan forum ;)

> And extra question I asked myself while doing some tests today: is there a
> way to check if a template received through a function parameter matches a
> specific template? 

templates cannot match other templates.  They can only match values 

> I tried with match() but from what I understood from the
> compilation errors, it seems match() actually checks a value vs a template,

correct.

> Hm maybe just using "==" would work, I didn't check it.

You can compare if two templates are equal.  I would argue that this is not the
same as your question "a template matches a template".  So using "==" between
two identical templates should evaluate true (I don't think I ever tried).  But
for sure, a more generic template wound not be equal to a more specific template,
even though there are values that could match both templates.

> Last query: Did you find a good tutorial or well documented examples for
> beginners in some specific place?

I've so far been looking primarily at
* https://www.ttcn-3.org/files/TTCN3_P.pdf
* the above-mentioned ETSI core language spec for TTCN-3
* the Eclipse/Ericsson TITAN referenceguide.pdf "Programmers Guide"
  which is part of https://www.eclipse.org/downloads/download.php?file=/titan/TitanDocuments_6_3_0.zip

-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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