[FFmpeg-devel] FFmpeg source code is no longer C99 because of GNUism called case ranges

[Benoit Fouet]

Roman Shaposhnik wrote:
> On Thu, 2007-07-05 at 08:02 +0100, M?ns Rullg?rd wrote:
>   
>>>  static int mpeg4video_probe(AVProbeData *probe_packet)
>>>  {
>>>      uint32_t temp_buffer= -1;
>>> +    uint8_t b;
>>>      int VO=0, VOL=0, VOP = 0, VISO = 0, res=0;
>>>      int i;
>>>  
>>>      for(i=0; i<probe_packet->buf_size; i++){
>>>          temp_buffer = (temp_buffer<<8) + probe_packet->buf[i];
>>> -        if ((temp_buffer & 0xffffff00) == 0x100) {
>>> -            switch(temp_buffer){
>>> -            case VOP_START_CODE:             VOP++; break;
>>> -            case VISUAL_OBJECT_START_CODE:  VISO++; break;
>>> -            case 0x100 ... 0x11F:             VO++; break;
>>> -            case 0x120 ... 0x12F:            VOL++; break;
>>> -            case 0x130 ... 0x1AF:
>>> -            case 0x1B7 ... 0x1B9:
>>> -            case 0x1C4 ... 0x1FF:            res++; break;
>>> -            }
>>> -        }
>>> +        if ((temp_buffer & 0xffffff00) != 0x100)
>>> +            continue;
>>> +
>>> +        b = probe_packet->buf[i];
>>> +        if (b == VOP_START_CODE)
>>> +            VOP++;
>>> +        else if (b == VISUAL_OBJECT_START_CODE)
>>> +            VISO++;
>>> +        else if (b < 0x20)
>>> +            VO++;
>>> +        else if (b < 0x30)
>>> +            VOL++;
>>> +        else
>>> +            res += !((b > 0xAF && b < 0xB7) || (b > 0xB9 && b < 0xC4));
>>>      }
>>>  
>>>      if ( VOP >= VISO && VOP >= VOL && VO >= VOL && VOL > 0 && res==0)
>>>       
>> Why the new variable?  The logic looks correct though.
>>     
>
>   As a precaution and cosmetics. Precaution against stupid compilers,
> cosmetics because:
>         if (b == ....)
> looks nicer (IMHO) than:
>         if ((temp_buffer & 0xffffff00) == ...)
>
>   

i don't see why you would have to do the bitmask anyway...
when you reach the b variable, (temp_buffer & 0xffffff00) == temp_buffer
also, not introducing this new b variable would leave start code
constant definitions as is, which is their "real" values :)

-- 
Ben
Purple Labs S.A.
www.purplelabs.com