[FFmpeg-devel] [PATCH] avcodec/bsf: switch to av_get_token to parse bsf list string

[Gyan Doshi]

On 2021-07-03 19:47, James Almer wrote:
> On 7/3/2021 8:42 AM, Gyan Doshi wrote:
>> The recently added setts bsf makes use of the eval API whose
>> expressions can contain commas. The existing parsing in
>> av_bsf_list_parse_str() uses av_strtok to naively split
>> the string at commas, thus preventing the use of setts filter
>> with expressions containing commas.
>> ---
>>   libavcodec/bsf.c | 13 +++++++------
>>   1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/libavcodec/bsf.c b/libavcodec/bsf.c
>> index 9d67ea5395..726911785d 100644
>> --- a/libavcodec/bsf.c
>> +++ b/libavcodec/bsf.c
>> @@ -520,7 +520,8 @@ static int bsf_parse_single(char *str, AVBSFList 
>> *bsf_lst)
>>   int av_bsf_list_parse_str(const char *str, AVBSFContext **bsf_lst)
>>   {
>>       AVBSFList *lst;
>> -    char *bsf_str, *buf, *dup, *saveptr;
>> +    char *bsf_str, *dup;
>> +    const char *buf;
>>       int ret;
>>         if (!str)
>> @@ -530,18 +531,18 @@ int av_bsf_list_parse_str(const char *str, 
>> AVBSFContext **bsf_lst)
>>       if (!lst)
>>           return AVERROR(ENOMEM);
>>   -    if (!(dup = buf = av_strdup(str))) {
>> +    if (!(buf = dup = av_strdup(str))) {
>
> Is this av_strdup() even necessary? You could let av_get_token() 
> update str just fine and remove both buf and dup. Or maybe just use a 
> copy of the pointer in buf.
>
>>           ret = AVERROR(ENOMEM);
>>           goto end;
>>       }
>>   -    while (bsf_str = av_strtok(buf, ",", &saveptr)) {
>> +    do {
>> +        bsf_str = av_get_token(&buf, ",");
>
> You can reduce the scope of bsf_str now, so declare it here.
>
>>           ret = bsf_parse_single(bsf_str, lst);
>> +        av_free(bsf_str);
>>           if (ret < 0)
>>               goto end;
>> -
>> -        buf = NULL;
>> -    }
>> +    } while (*buf == ',' && buf++);
>
> You can simplify this into while (*++buf) or (*++str) if you remove 
> the av_strdup().

Won't this go out of bounds at the end?


> It will also preserve the existing behavior of discarding the last 
> comma in the string if it's the last character, instead of aborting 
> with EINVAL.
>
>>         ret = av_bsf_list_finalize(&lst, bsf_lst);
>>   end:
>>
>
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