Re: [FFmpeg-devel] [PATCH v2 1/3] avutil/dict: add av_dict_pop

[Marvin Scholz <epirat07@gmail.com>]

On 2 Jul 2023, at 10:43, Stefano Sabatini wrote:

> On date Sunday 2023-06-25 12:49:05 +0200, Marvin Scholz wrote:
>> This new API allows to remove an entry and obtain ownership of the
>> key/value that was associated with the removed entry.
>> ---
>>
>> Changes since v1:
>> - Clarify documentation about av_free having to be used.
>> - Fix fate test to not rely on specific error code value
>>
>>  doc/APIchanges         |  4 ++++
>>  libavutil/dict.c       | 27 +++++++++++++++++++++++++++
>>  libavutil/dict.h       | 26 ++++++++++++++++++++++++++
>>  libavutil/tests/dict.c | 38 ++++++++++++++++++++++++++++++++++++++
>>  libavutil/version.h    |  4 ++--
>>  tests/ref/fate/dict    | 12 ++++++++++++
>>  6 files changed, 109 insertions(+), 2 deletions(-)
>>
>> diff --git a/doc/APIchanges b/doc/APIchanges
>> index f040211f7d..d55821f682 100644
>> --- a/doc/APIchanges
>> +++ b/doc/APIchanges
>> @@ -2,6 +2,10 @@ The last version increases of all libraries were on 2023-02-09
>>
>>  API changes, most recent first:
>>
>> +2023-06-02 - xxxxxxxxxx - lavu 58.14.100 - dict.h
>> +  Add av_dict_pop() to remove an entry from a dict
>> +  and get ownership of the removed key/value.
>> +
>>  2023-05-29 - xxxxxxxxxx - lavc 60.16.100 - avcodec.h codec_id.h
>>    Add AV_CODEC_ID_EVC, FF_PROFILE_EVC_BASELINE, and FF_PROFILE_EVC_MAIN.
>>
>> diff --git a/libavutil/dict.c b/libavutil/dict.c
>> index f673977a98..ac41771994 100644
>> --- a/libavutil/dict.c
>> +++ b/libavutil/dict.c
>> @@ -173,6 +173,33 @@ int av_dict_set_int(AVDictionary **pm, const char *key, int64_t value,
>>      return av_dict_set(pm, key, valuestr, flags);
>>  }
>>
>> +int av_dict_pop(AVDictionary **pm, const char *key,
>> +                char **out_key, char **out_value, int flags)
>> +{
>> +    AVDictionary *m = *pm;
>> +    AVDictionaryEntry *entry = NULL;
>> +    entry = (AVDictionaryEntry *)av_dict_get(m, key, NULL, flags);
>> +    if (!entry)
>> +        return AVERROR(ENOENT);
>> +
>> +    if (out_key)
>> +        *out_key = entry->key;
>> +    else
>> +        av_free(entry->key);
>> +
>> +    if (out_value)
>> +        *out_value = entry->value;
>> +    else
>> +        av_free(entry->value);
>> +
>> +    *entry = m->elems[--m->count];
>> +    if (m && !m->count) {
>> +        av_freep(&m->elems);
>> +        av_freep(pm);
>> +    }
>> +    return 0;
>> +}
>> +
>>  static int parse_key_value_pair(AVDictionary **pm, const char **buf,
>>                                  const char *key_val_sep, const char *pairs_sep,
>>                                  int flags)
>> diff --git a/libavutil/dict.h b/libavutil/dict.h
>> index 713c9e361a..31d38dabec 100644
>> --- a/libavutil/dict.h
>> +++ b/libavutil/dict.h
>> @@ -172,6 +172,32 @@ int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags
>>   */
>>  int av_dict_set_int(AVDictionary **pm, const char *key, int64_t value, int flags);
>>
>> +/**
>> + * Remove the entry with the given key from the dictionary.
>> + *
>> + * Search for an entry matching @p key and remove it, if found. Optionally
>> + * the found key and/or value can be returned using the @p out_key and
>> + * @p out_value arguments.
>
> Note: I checked the code and we see that in some cases we use `param`
> (e.g. in mem.h) but I prefer this format (although apparently not used
> in other places) since it looks more consistent with the doxygen
> syntax.
>
>> + *
>> + * If more than one entry matches, only one entry is removed and returned
>> + * on each call. Which entry is returned first in that case is undefined.
>> + *
>> + * @param pm        Pointer to a pointer to a dictionary struct.
>> + * @param key       Entry key to match.
>> + * @param out_key   Pointer whose pointee will be set to the matched
>> + *                  entry key. Must be freed using av_dict_free() by
>> + *                  the caller. May be NULL.
>> + * @param out_value Pointer whose pointee will be set to the matched
>> + *                  entry value. Must be freed using av_dict_free() by
>> + *                  the caller. May be NULL.
>
> missing docs for flags, something like:
> @param flags flags passed to av_dict_get to look for the entry
>
> should be fine
>

Can whoever ends up merging this maybe add that?
If not, I can send a new revision with this change next weekend or so.

> [...]
>
> Looks good otherwise, thanks.
>
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