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

[Stefano Sabatini <stefasab@gmail.com>]

On date Monday 2023-05-01 13:44:54 +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.
> ---
>  doc/APIchanges         |  4 ++++
>  libavutil/dict.c       | 27 +++++++++++++++++++++++++++
>  libavutil/dict.h       | 20 ++++++++++++++++++++
>  libavutil/tests/dict.c | 34 ++++++++++++++++++++++++++++++++++
>  libavutil/version.h    |  2 +-
>  tests/ref/fate/dict    | 12 ++++++++++++
>  6 files changed, 98 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 0b609e3d3b..5b807873b7 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:
>  
> +2023-04-29 - xxxxxxxxxx - lavu 58.7.100 - dict.c
> +  Add av_dict_pop() to remove an entry from a dict
> +  and get ownership of the removed key/value.
> +
>  2023-04-10 - xxxxxxxxxx - lavu 58.6.100 - frame.h
>    av_frame_get_plane_buffer() now accepts const AVFrame*.
>  
> 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);
> +    }

I'm not sure this is the right behavior. Should we clear the
dictionary when it is empty? What if you need to refill it later?

> +    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..b2ab55a026 100644
> --- a/libavutil/dict.h
> +++ b/libavutil/dict.h
> @@ -172,6 +172,26 @@ 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 `key` and remove it, if found. Optionally

Not sure the `foo` syntax is supported by doxygen (and probably we
should eschew it for consistency with the other doxys).

> + * the found key and/or value can be returned using the `out_key`/`out_value`
> + * arguments.

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