[FFmpeg-devel] [PATCH 1/2] lavu/dict: Add new flag to allow multiple equal keys.

[Thilo Borgmann]

Am 22.03.16 um 11:45 schrieb wm4:
> On Sun, 13 Mar 2016 21:00:23 +0100
> Thilo Borgmann <thilo.borgmann at mail.de> wrote:
> 
>> Am 13.03.16 um 15:08 schrieb wm4:
>>> On Sat, 12 Mar 2016 15:13:21 +0100
>>> Thilo Borgmann <thilo.borgmann at mail.de> wrote:
>>>   
>>>> From a1d9ce388c69eabb256e6b351c2acd36d7f4076e Mon Sep 17 00:00:00 2001
>>>> From: Thilo Borgmann <thilo.borgmann at mail.de>
>>>> Date: Sat, 12 Mar 2016 14:52:17 +0100
>>>> Subject: [PATCH 1/2] lavu/dict: Add new flag to allow multiple equal keys.
>>>>
>>>> ---
>>>>  libavutil/dict.c | 5 ++++-
>>>>  libavutil/dict.h | 5 +++--
>>>>  2 files changed, 7 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/libavutil/dict.c b/libavutil/dict.c
>>>> index 8bb65a1..70c0184 100644
>>>> --- a/libavutil/dict.c
>>>> +++ b/libavutil/dict.c
>>>> @@ -70,9 +70,12 @@ int av_dict_set(AVDictionary **pm, const char *key, const char *value,
>>>>                  int flags)
>>>>  {
>>>>      AVDictionary *m = *pm;
>>>> -    AVDictionaryEntry *tag = av_dict_get(m, key, NULL, flags);
>>>> +    AVDictionaryEntry *tag = NULL;
>>>>      char *oldval = NULL, *copy_key = NULL, *copy_value = NULL;
>>>>  
>>>> +    if (!(flags & AV_DICT_MULTIKEY)) {
>>>> +        tag = av_dict_get(m, key, NULL, flags);
>>>> +    }
>>>>      if (flags & AV_DICT_DONT_STRDUP_KEY)
>>>>          copy_key = (void *)key;
>>>>      else
>>>> diff --git a/libavutil/dict.h b/libavutil/dict.h
>>>> index b0aa784..c589bcd 100644
>>>> --- a/libavutil/dict.h
>>>> +++ b/libavutil/dict.h
>>>> @@ -76,6 +76,7 @@
>>>>  #define AV_DICT_DONT_OVERWRITE 16   ///< Don't overwrite existing entries.
>>>>  #define AV_DICT_APPEND         32   /**< If the entry already exists, append to it.  Note that no
>>>>                                        delimiter is added, the strings are simply concatenated. */
>>>> +#define AV_DICT_MULTIKEY       64   /**< Allow to store several equal keys in the dictionary */
>>>>  
>>>>  typedef struct AVDictionaryEntry {
>>>>      char *key;
>>>> @@ -118,8 +119,8 @@ int av_dict_count(const AVDictionary *m);
>>>>   *
>>>>   * @param pm pointer to a pointer to a dictionary struct. If *pm is NULL
>>>>   * a dictionary struct is allocated and put in *pm.
>>>> - * @param key entry key to add to *pm (will be av_strduped depending on flags)
>>>> - * @param value entry value to add to *pm (will be av_strduped depending on flags).
>>>> + * @param key entry key to add to *pm (will either be av_strduped or added as a new key depending on flags)
>>>> + * @param value entry value to add to *pm (will be av_strduped or added as a new key depending on flags).
>>>>   *        Passing a NULL value will cause an existing entry to be deleted.
>>>>   * @return >= 0 on success otherwise an error code <0
>>>>   */  
>>>
>>> Changing the semantics of AVDictionary just like this seems rather
>>> questionable...  
>>
>> It changes nothing for existing code, just adds a new feature. I don't
>> think it hurts anyone or anything...
> 
> It only breaks basic assumptions about a basic data type...

Although I don't share your thought about breaking a basic data type with that,
what would you suggest instead?

Add an almost redundant AVMultiDictionary data type or rename AVDictionary to that?
Or an error-prone implementation within the filter?
These seem to be worse alternatives in my eyes.

-Thilo