On Wed, Nov 5, 2014 at 11:01 AM, Luca Barbato <[email protected]> wrote:
> On 05/11/14 16:29, Vittorio Giovara wrote:
>>
>> Add a comment to explain the code.
>>
>> CC: [email protected]
>> Bug-Id: CID 1194388
>> ---
>> New version, after a visit at the oracles shrine.
>> Vittorio
>>
>>   libavcodec/mjpegdec.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
>> index d9a73d8..01e11be 100644
>> --- a/libavcodec/mjpegdec.c
>> +++ b/libavcodec/mjpegdec.c
>> @@ -964,7 +964,9 @@ static int
>> mjpeg_decode_scan_progressive_ac(MJpegDecodeContext *s, int ss,
>>           init_get_bits(&mb_bitmask_gb, mb_bitmask, s->mb_width *
>> s->mb_height);
>>
>>       if (!Al) {
>> -        s->coefs_finished[c] |= (1LL << (se + 1)) - (1LL << ss);
>> +        // s->coefs_finished is a bitmask for coefficients coded
>> +        // ss and se are parameters telling start and end coefficients
>> +        s->coefs_finished[c] |= (~0ULL >> (63 - (se - ss))) << ss;
>>           last_scan = !~s->coefs_finished[c];
>>       }
>
>
> Do we check that se - ss is positive? If yes fine for me.

We check "se < ss" and return immediately if so. That should cover
that case, right?
-- 
Vittorio
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