Re: named structure members

[Matthew Harrison <matth@3d-computers.co.uk>]

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that's very generous of you.
c is not my strong point yet so all help is appreciated.

attached is the sources in question. most of the code is
in src/inventory.c and src/read_config_var.c

thanks again for taking the time

On Thu, Sep 11, 2003 at 12:35:24PM -0300, Mariano Moreyra wrote:
> Are you still getting that segfault??
> Send me the section of the code where the strcpy is (if you want ofcourse
> hehe)
> 
> 
> -----Mensaje original-----
> De: Matthew Harrison [mailto:matth@3d-computers.co.uk]
> Enviado el: Jueves, 11 de Septiembre de 2003 12:28
> Para: Mariano Moreyra
> CC: linux-c-programming@vger.kernel.org
> Asunto: Re: named structure members
> 
> 
> On Thu, Sep 11, 2003 at 11:41:34AM -0300, Mariano Moreyra wrote:
> > Ok... I understood that what you wanted was to name your structure members
> > dynamically.
> > But if you will only have those for members, that's a good approach
> > Now, are you allocating memory for your strings before doing a strcpy??
> > Because you defined your members like char pointers, you have to
> dynamically
> > allocate some memory form them before use.
> > You could define your members like arrays instead of char pointers (i.e
> char
> > db_host[256])
> >
> 
> actually that was one of the things i tried to get rid of the segfault.
> 
> i used to have the struct below like:
> 
> typedef struct _CFG_struct
> {
> 	char db_host[32];
> 	...
> }
> 
> but then i changed it to the below option while trying to debug.
> 
> >
> > ------
> >
> > this is getting very complex.
> >
> > here is the struct that i want my config to go into:
> >
> > <snip>
> > typedef struct _CFG_struct
> > {
> >        char *db_host;
> >        char *db_name;
> >        char *db_pass;
> >        char *db_user;
> > }CFG;
> > </snip>
> >
> > and I am doing the following (pseudo code)
> >
> > <snip>
> > for(i = 0; i <= array_of_config_items; i++)
> > {
> > 	keyword = array_of_config_items[i];
> >
> > 	while (read_config_file != EOF)
> > 	{
> > 		check_return_value;
> > 		if keyword = 'item1'
> > 		{
> > 			item1 = value;
> > 		}
> > 		elsif keyword = 'item2'
> > 		{
> > 			item2 = value;
> > 		}
> > 		and_so_on();
> > 	}
> > }
> > </snip>
> >
> > i can sort it now with the multiple if's but now it segfaults on
> > a strcpy for some reason and i'm still learning how to use gdb.
> >
> > On Thu, Sep 11, 2003 at 11:03:59AM -0300, Mariano Moreyra wrote:
> > > > what i'm doing is stepping thru an array of different config options
> > > > calling the read_config_var on each one and checking the output.
> > > > if the output is good then i want to store the value in a member of
> > > > a structure. for example i want the config options to be stored like
> > > > this:
> > >
> > > > config.db_host = 'maiden.genestate.com'
> > > > config.db_user = 'root'
> > >
> > > > you get the idea. my question is how do i dynamically assign a name
> > > > to a structure member. I have good_values[i] which contains the
> > > > current config directive but if you look at line 8 of the example,
> > > > you can see the problem, how do i say config.good_values[i], when
> > > > good_values[i] is not itself a member.
> > >
> > > I think that I get the idea ...
> > > But are you sure that is that what you want??
> > > I mean, the idea is that in your config option you could have any config
> > > directives (or keys) and values??
> > > How you will handle that options later without knowing from the begining
> > > what options you could have??
> > > Anyway...I think that you could do is create your structure like this:
> > >
> > >  typedef struct {
> > > 	char key[255];
> > > 	cahr value[255];
> > >  } t_config;
> > >
> > >  t_config config[20];   // Change 20 and 255 to adapt to your needs
> > >
> > >
> > >  so your code would look like this:
> > >
> > > for(i = 0; i < n_values; ++i)
> > >         {
> > >                 strcpy(keyword, good_values[i]);
> > >
> > >                 switch (read_config_var(values_file, keyword, value))
> > >                 {
> > >                         case 0:
> > >                                 strcpy(config[i].key, keyword);
> > > 					  strcpy(config[i].value, value);
> > >                                 break;
> > >                         case -1:
> > >                                 printf("\nFile Error for [%s] \n",
> > > values_file);
> > >                                 break;
> > >                         case -2:
> > >                                 printf("\nBad User Parm for [%s] \n",
> > > keyword);
> > >                                 break;
> > >                         default:
> > >                                 printf("\nUnknown Error Occurred \n");
> > >                                 break;
> > >                 }
> > >         }
> > >
> > >
> > > I'm not sure if is that what you want...and if I really understood your
> > > problem...
> > > So, let me know if this mail sucks! :)
> > >
> > > --
> > > Mariano Moreyra <mariano_moreyra@aca.org.ar>
> >
> > --
> > Mat Harrison
> > Technical Developer
> > 3d Computer Systems Ltd.
> > matth@3d-computers.co.uk
> 
> -- 
> Mat Harrison
> Technical Developer
> 3d Computer Systems Ltd.
> matth@3d-computers.co.uk

-- 
Mat Harrison
Technical Developer
3d Computer Systems Ltd.
matth@3d-computers.co.uk

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