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

[Stefano Sabatini <stefasab@gmail.com>]

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

[...]

Looks good otherwise, thanks. 

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