[Asterisk-Dev] Misbehaviour in ast_variable_browse

[Luis Vazquez]

Hello all,
despite I have made many minor changes to asterisk code and some bugs 
reports and fixes this is my first mail to the dev list (I was only a 
"voyeur" here until now) so first of all I want to congratulate every 
one at the list for the great list it's and to thank a lot for the many 
things I have learned reading the mails here.

I want to comment of what I consider is a inconsistency in the behavior 
of the method ast_variable_browse respect to the (suposedly analog, even 
said in the inline doc) ast_category_browse method in config.c.

The point is that with ast_category_browse(config, prev) you can really 
iterate over the config sections with a code snippet like this:

/************ works now****************/
  cat = ast_category_browse(cfg, NULL);
  while(cat) {
    .....
    cat = ast_category_browse(cfg, cat);
  }
/************************************/

So it would be logic to be able to do the same with ast_variable_browse, 
like this:

/***** not posible now **************/
var = ast_variable_browse(cfg, cat, NULL);
while( var ) {
  .........
  var = ast_variable_browse(cfg, cat, var);
}
/*************************************/

But this is not posible now because the actual prototype of 
ast_variable_browse() is:

 > struct ast_variable *ast_variable_browse(struct ast_config *config, 
char *category)

and allways returns the root ast_variable in the given category, even 
when the doc text in the header file config.h suggests it should work as 
ast_category_browse.
...................................
//! Goes through variables
/*!
 * Somewhat similar in intent as the ast_category_browse.....
*/
..........................................

The best solution I think would be to replace the prototype for 
something like this:

 > struct ast_variable *ast_variable_browse(struct ast_config *config, 
char *category, struct ast_variable *prev[=NULL])

but because gcc (at least with the compile options used in asterisk) do 
not allow default param values it would require to change all places 
where ast_variable_browse() is used with the prior prototipe (and 
meaning) with an extra NULL parameter like this:
- var = ast_variable_browse(config, cat);
+ var = ast_variable_browse(config, cat, NULL);


So to avoid this odd changes what I have done is to add a new function:

struct ast_variable *ast_variable_next(struct ast_config *config, char 
*category,struct ast_variable *prev);

that returns the next ast_variable in a config category if prev is not 
null, and the root var (as the current ast_variable_browse) if prev==NULL.

This approach allows to write code like this:
/***************************************/
  var = ast_variable_browse(cfg, cat);
  while( var ) {
    ............
  var = ast_variable_next(cfg, cat, var);
  }
/***************************************/
without changing the places where ast_variable_browse() was used previously.

This is needed when you want to retrieve all the vars in a section and 
don't know the variable names in advance.
I need this because I'm using a custom asterisk application to load the 
configuration parameters used in the many pbx facility applications 
(mostly perl or c++ agi scripts) into the asterisk db; and I want to be 
able to add a new parameter without needing to recompilate the loader 
application (what I should do to use ast_variable_retrieve() because I 
need to know the variable names in advance)

Attached is the code with the proposed new ast_variable_next() function.

Best regards and I would like to receive any feedback and opinions about 
this suggestion.
Luis





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