[Freeipa-devel] [PATCH 0077] Refactor settings subsystem

[Petr Spacek]

Hello,

this patch refactors setting subsystem. After some experimenting I chosen 
simple implementation with static arrays, no RBT trees involved. Speed can be 
improved by reordering items in arrays.

Commit message:

    Refactor settings subsystem.

     Settings are stored in tree of settings_set_t structures.
     All settings should be accessed only through setting* functions.
     Mutual exclusion during write is done by switching to single
     thread mode.

     Setting_get() function doesn't copy strings, so changing the
     original string can lead to obscure bugs.
     This way is okay as long as strings are not changed dynamically
     at run-time.

     Unknown setting in configuration file leads to failure rather than
     silent ignoring it.

     https://fedorahosted.org/bind-dyndb-ldap/ticket/53
     https://fedorahosted.org/bind-dyndb-ldap/ticket/81


Adam, I'm still looking for way how to handle strings in settings. We have to 
prevent string change/deallocation as long as somebody has a pointer to the 
string (I mean pointer obtained through setting_get("name_of_setting") call).

The only way which I can see is returning setting_string structure like

setting_string struct {
	isc_refcount_t counter;
	isc_mem_t *mctx;	
	char *str;
};

Caller has to call setting_string_free() when string can be freed. 
Setting_string_free() will decrement counter by one and free whole structure 
if and only if counter reaches 0.

Is it meaningful? Should I separate setting_get_* for each datatype? Or just 
for setting_get_string() and let setting_get() universal for integers and 
booleans?

-- 
Petr^2 Spacek
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