Question

Is there any mechanism in the Apache httpd framework that would allow me to pass custom parameters from the Apache configuration file to a custom Apache module (written using the C API)? I really only need key/value pairs.

Something like in conf file:

ConfigParameter foo bar

And then in the code:

string foo = GetApacheConfigParameter("foo"); // = "bar"

Answer 1

No; not directly. A dirty hack would be

SetEnv foo bar

in the config file – and a

char * bar = getenv("foo"); 

in your module. Anything beyond that requires the use of a proper structure on a per directory, server, etc. Normally that structure would contain a lot of specific things. In your case it would just be a single table.

So somewhat clean way would be to simply use a table – and leave it at that:

 static const command_rec xxx_cmds[] = {
    AP_INIT_TAKE2("ConfigParameter", add_configparam, NULL, RSRC_CONF,
              "Arbitrary key value pair"),
   {NULL}
};

 static void * create_dir_config(apr_pool_t *p, char *dirspec ) {
    return ap_table_palloc(p);
 }

 static const char *add_configparam(cmd_parms *cmd, void *mconfig,   
                               char *key, char *val) 
 {
    ap_table_t *pairs = (ap_table_rec *) mconfig;
    ap_table_set(pairs, key, val);
    return NULL;
 }

 AP_DECLARE_MODULE(xxxx_module) =
 {
   STANDARD20_MODULE_STUFF,
   xxx_create_dir_config,    /* per-directory config creator */
   ...
   xxx_cmds,                 /* command table */

and then, everywhere where you want to use this do:

apr_table_t * pairs =  (apr_table_p *) ap_get_module_config(r->request_config, &xxxx_module);

or

 apr_table_t * pairs =  ap_get_module_config(s->module_config, &xxxx_module);

depending on where it us used – and then use:

char * bar = apr_table_get(pairs,"foo");

or similar. See mod_example_hooks and the various our_* calls to get a pointer. Above example leaves out configs on server level and merging of configs. Add those if you need them – there is a corresponding merge call for tables. mod_alias.c et.al. have good examples.