Wireshark · Ethereal-dev: Re: [Ethereal-dev] GHashTable

[Alejandro Vaquero <alejandrovaquero@xxxxxxxxx>]

Hi Favio,
   You can check the GTK/GLIB doc located in 
file:///C:/ethereal-win32-libs/glib/share/gtk-doc/html/glib/glib-Hash-Tables.html 
(this is in Windows)


     g_hash_table_new ()

GHashTable <cid:part1.02060405.08080807@yahoo.com>* g_hash_table_new                (GHashFunc <cid:part2.05020609.04070507@yahoo.com> hash_func,
                                            GEqualFunc <cid:part3.04070006.09050301@yahoo.com> key_equal_func);

Creates a new GHashTable <cid:part1.02060405.08080807@yahoo.com>.

/hash_func/ : 	a function to create a hash value from a key. Hash values 
are used to determine where keys are stored within the GHashTable 
<cid:part1.02060405.08080807@yahoo.com> data structure. The 
g_direct_hash() <cid:part6.09000306.08030302@yahoo.com>, g_int_hash() 
<cid:part7.00090902.01020504@yahoo.com> and g_str_hash() 
<cid:part8.00030701.04010902@yahoo.com> functions are provided for some 
common types of keys. If hash_func is NULL, g_direct_hash() 
<cid:part6.09000306.08030302@yahoo.com> is used.
/key_equal_func/ : 	a function to check two keys for equality. This is 
used when looking up keys in the GHashTable 
<cid:part1.02060405.08080807@yahoo.com>. The g_direct_equal() 
<cid:part11.00040508.01060405@yahoo.com>, g_int_equal() 
<cid:part12.09000708.08000403@yahoo.com> and g_str_equal() 
<cid:part13.08030408.05010207@yahoo.com> functions are provided for the 
most common types of keys. If /key_equal_func/ is NULL, keys are 
compared directly in a similar fashion to g_direct_equal() 
<cid:part11.00040508.01060405@yahoo.com>, but without the overhead of a 
function call.
/Returns/ : 	a new GHashTable <cid:part1.02060405.08080807@yahoo.com>.



Alejandro

fabio matturro wrote:
> Hello,
> I would like to attach different data structures  to the same 
> conversation.
> This subject is not fully explained in the developer guide (par. 
> 2.2.9) so I'd like you to
> give me some tips ;)
>
> Let's take the example on the guide (taken from packet_afs.c)
>
>
> Here a structure request_key  is being initialized and is used to look 
> up into a hash table
>
> Now, how should I initialized this GHashTable structure?
> Taking packet_afs.c as an example I notice this line:
>
> afs_request_hash = g_hash_table_new(afs_hash, afs_equal);
>
> This is supposed to initialize the hash table
>
> Now, what are afs_hash & afs_equal for?
> I suppose that afs_equal contains the criterium to discern whether a 
> key is contained
> in the table
> [...]
> static gint
> afs_equal(gconstpointer v, gconstpointer w)
> {
>  const struct afs_request_key *v1 = (const struct afs_request_key *)v;
>  const struct afs_request_key *v2 = (const struct afs_request_key *)w;
>
>  if (v1 -> conversation == v2 -> conversation &&
>      v1 -> service == v2 -> service &&
>      v1 -> callnumber == v2 -> callnumber ) {
>
>    return 1;
>  }
>
>  return 0;
> }
>
> [...]
>
> and afs_hash calculates a numeric key starting from the data structure 
> pointer it is passed
>
> [...]
> static guint
> afs_hash (gconstpointer v)
> {
>     const struct afs_request_key *key = (const struct afs_request_key 
> *)v;
>     guint val;
>
>     val = key -> conversation + key -> service + key -> callnumber;
>
>     return val;
> }
> [...]
>
> Can you confirm it?
>
> : - D Thanx
>
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