Re: Ordered list of strings in registry

On 2024-11-21 05:55, Jean Truc wrote:
> Hi,
> 
> I'm looking for the best way to read and save an ordered list of
> strings from and to the registry.
> 
> Something like:
> 
> [MY_LIST]
> 
> key1=data1
> 
> key2=data2
> 
> key3=data3
> 
> ...
> 
> and reading writing the key/data entries in the order they appear in
> the registry file.
> 
> I've tried using an FXStringDict dictionary but it's not ordered. It
> seems that the keys are read in a random order.
> 
> Any ideas?

FXRegistry (FXSettings) is a two-level hash table, i.e. a hash-table of
FXStringDict, or string hash-tables.  By definition, its not sorted.

The order is a function of the distribution of the hash-keys of the
strings.  We're using the "FNV1a" hash algorithm to compute the
keys, but older FOX versions used a different algorithm.  For
access speed the exact hash algorithm doesn't matter, but fewer
collisions is preferable as it maximizes the chance of items with
the same key representing the same strings.

You can walk the hash tables, skipping over the empty slots, then
place the keys in an array, and sort it.

   // Array with room for N keys...
   const FXchar** array=...

   for(i=j=0; i<stringdict.no(); ++i){
     if(stringdict.empty(i)) continue;
     array[j++]=stringdict.key(i).text();
   }

   // Sort N keys
   qsort(array,N,sizeof(const FXchar*),strcmp);

Then, mutatis mutandum, you'll have a sorted array.
of the keys. Note the key strings themselves are
not copied, only the pointers are..

Hope this helps,

    -- JVZ