Hi Nicolas
On Wed, Apr 23, 2025 at 10:46:17PM +0200, Michael Niedermayer wrote:
> Hi Nicolas
>
> On Mon, Apr 21, 2025 at 05:01:19PM +0200, Nicolas George wrote:
> > Michael Niedermayer (HE12025-04-20):
[...]
> > > + *
> > > + *
> > > + * ----------- Retrieving an entry --------------
> > > + *
> > > + * AVMapEntry *e = av_map_get(map, "cat", AV_MAP_CMP_KEY); //Find an
> > > entry with the key = "cat"
> > > + *
> > > + * AVMapEntry *e = av_map_get(map, "cat",
> > > AV_MAP_CMP_KEY+AV_MAP_CMP_CASE_INSENSITIVE); //Find an entry with the key
> > > = "cat", "Cat", "cAt", ...
> >
> > > + * // this will only work if one of the set compare functions is case
> > > insensitive
> >
> > This is crucial: how? (This is redundant with my next remark.)
> >
> > > + *
> > > + *
> > > + * ----------- Iterating over all elements ------
> > > + *
> > > + * const AVMapEntry *t = NULL;
> > > + * while ((t = av_map_iterate(s, t)))
> > > + * printf("%s=%s %zu,%zu ", t->key, t->value, t->keylen,
> > > t->valuelen);
> > > + *
> > > + *
> > > + * ----------- copying all elements of a mep into another map
> > > + *
> > > + * av_map_copy(dst, src);
> > > + *
> > > + *
> > > + * ----------- freeing a map ---------------------
> > > + *
> > > + * av_map_free(&map);
> > > + *
> > > + *
> > > + * ----------- multiple compare function in a single map -----------
> > > + *
> >
> > > + * Each map has a primary compare function, which is used for ordering
> > > elements.
> > > + * Additional (compatible) compare functions can be added with
> > > av_map_add_cmp_func()
> > > + *
> > > + * What "compaibility" means here is that every added function returns
> > > the same value
> > > + * as the primary function or 0.
> > > + *
> > > + * An example, Imagine we have "cat", "dog", "Dog", "fox"
> > > + * a function that treats "dog" and "Dog" as equal is compatible to this
> > > ordering
> > > + * OTOH
> > > + * if we have have strcmp() as primary function we would order like this:
> > > + * "Dog", "cat", "dog", "fox"
> > > + * and here we could not treat "dog" and "Dog" as equal, and thus case
> > > insensitive
> > > + * compare would not be possible
> >
> > Code examples needed. For example: a map where key = name, value = phone
> > number, with AV_MAP_CMP_KEYVALUE. How do we set it up to allow
> > case-insensitive lookups and name only lookups, and name only
> > case-insensitive lookups?
>
> The phone numbers i have seen are not affected by case sensitivity.
> So case sensitivity only matters for the name (which is in key)
>
> This should work:
>
> AVMap *map = av_map_alloc(av_map_supercmp_keyvalue, AV_MAP_CMP_KEYVALUE +
> AV_MAP_CMP_CASE_SENSITIVE, NULL, NULL);
> av_map_add_cmp_func(map, av_map_supercmp_key, AV_MAP_CMP_KEY +
> AV_MAP_CMP_CASE_SENSITIVE);
> av_map_add_cmp_func(map, av_strcasecmp, AV_MAP_CMP_KEY +
> AV_MAP_CMP_CASE_INSENSITIVE);
>
> But the point you seem to try to raise, is correct,
> not every combination is possibleTo elaborate on this If we consider key_value and key searches and case sensitivity then we have 6 possible things a user might want to search for only the key there are case sensitive and case insensitive for key_value there are 4 because both key and value have their own case sensitivity If we use the syntax or I and S for the key only, and II,SS,IS,SI for the key_value ones, then we can have for example the following in the same map I ,S ,SI,SS I ,II,IS,SS I ,II,SI,SS If these combination of 4 out of 6 isnt good enough, the user can use 2 maps or we can implement the remaining by iteration over the closest subset we can efficiently search for. Currently we iterate over all entries with AVDictionary, if for a key value both case insensitive match we have to iterate over all values from a insensitive matching key. Its still alot less asymptotically thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
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