Re: [sr-dev] [ser-dev] re.h - subst_str ussage - sr-dev

29 Mar 2015

Hi, I am trying to use Kamailio specific function 'subst_str' for replacing
some media attributes in SDP in my module.

Finally I have resolved how to create 'subst_expr' structure so I can pass
it to 'subst_str' function. I am doing something like this:

      struct subst_expr *seMedia;

      char *pattern;      asprintf(&pattern, "/m=audio
([0-9]{0,5})/m=audio %s/", _host_port.s);

      str *subst;
      subst = (str *) pkg_malloc(sizeof(str));
      subst->s = pattern;
      subst->len = strlen(pattern);

      seMedia = subst_parser(subst);

      int count = 0;
      str *tmpBody;
      char const *oldBody = (char const *) msg->body;
      tmpBody = subst_str(oldBody, msg, seMedia, &count);

      if (count > 0) {

// do other stuff

I am trying to replace all "m=audio {port number}" attributes with port
5060. I think that the regular expression is correct. But unfortunately in
Kamailio log I am getting something like this:

 0(25049) DEBUG: <core> [re.c:329]: subst_parser(): subst_parser: ok, se is
0xb72941d8
 0(25049) DEBUG: <core> [re.c:454]: subst_run(): subst_run: running. r=1
 0(25049) DEBUG: <core> [re.c:523]: subst_str(): subst_str: no match

It seems like regex was not matched but after this I am printing out whole
message and I can see that in SDP 'm=audio' is present. I also noticed
another thing when I am printing out 'seMedia->replacement.s' in log I am
getting my replacement "m=audio 5060" but also at the end of the string I
can see some weird character:

[image: Inline image 1]

If someone came across this issue in the past and resolved it, it would be
great if he/she can share his/her knowledge with me because seriously this
issue is driving me crazy.

On Thu, Mar 12, 2015 at 9:17 PM, Cockhootec Yahrabee &lt;cockootec(a)gmail.com&gt;
wrote:

...
  Thanks a lot. I am sorry I didn't code with
pointers quite a long time so
 I need to refresh my knowledge a bit :)
 But unfortunately it was not the main problem.

 In Kamailio log I am getting something like this:

  0(17809) ERROR: <core> [re.c:181]: parse_repl(): subst_parser: bad
 specifier in replace part /$1 5060/gm

 I think, that problem is on this line
 https://gist.github.com/ivanbarlog/1b552b57e89bf4670872#file-test-c-L5
 where I am trying to use $1 as a placeholder for first matched group.

 I also tried it without it - just replace `m=audio` (not m=*) but it also
 didn't worked.

 I am also not sure if I am correctly re-transmitting updated SIP message.
 I looked at other modules which perform the same action and I tried to
 inspire with their code but unfortunately it's not working.

 Could you please review this code sample
 https://gist.github.com/ivanbarlog/4040ae5b735386a88ea0 ?

 Or maybe if you can point me to some resource where I can read more about
 it. Also it would be great if there was some tutorial for developing
 modules.

 Thanks for help

 On Wed, Mar 11, 2015 at 7:20 PM, Daniel-Constantin Mierla <
 miconda(a)gmail.com&gt; wrote:

   Hello,

 at least one problem is the next line in your code:

 subst->len = sizeof(pattern);

 should be:

 subst->len = strlen(pattern);

 Because patter is declared as 'char*', sizeof returns 4 or 8 (if 32b or
 64b architecture).

 Try with that change and see how far it goes.

 Cheers,
 Daniel

 On 11/03/15 00:43, Cockhootec Yahrabee wrote:

 Hi guys,
 I am trying to 'search&replace' some patterns in message body but
 unfortunately with no result (but bunch of errors).

  First of all I am trying to perform regex substitution as one that can
 be seen at https://regex101.com/r/vF1kZ7/1

  Since I have regular expression I am trying to convert it so it will
 work with `sub_str` function from re.h

  Here is my attempt:
 https://gist.github.com/ivanbarlog/1b552b57e89bf4670872#file-test-c-L12

  I had quite lot of errors but last error I am getting is that
 `subst_parser` cannot find separator
 https://github.com/kamailio/kamailio/blob/master/re.c#L240

  Since the `struct subst_expr` is not parsed right the next error is
 segfault in `subst_str` function.

  If someone can explain me how exactly I should use `subst_str` function
 with my regex I'll be really grateful. Little example code would be also
 great.

  Thanks in advance

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 Daniel-Constantin Mierlahttp://twitter.com/#!/miconda -
http://www.linkedin.com/in/miconda
 Kamailio World Conference, May 27-29, 2015
 Berlin, Germany - http://www.kamailioworld.com