[FFmpeg-devel] GSoC VQA v3 vptr decode function implementation

[Kostya Shishkov]

On Mon, Apr 13, 2009 at 8:53 AM, The Deep Explorer
<thedeepexplorer at gmail.com> wrote:
> Hi ,
> ? ?I am explaining my logic behind code 5 implementation :
>
> ? ?case 5:
> ? ? ? ?/*101 - Write block (Val & 0x1fff) Count times. Count is the next
> ? ? ? ? ? ? ? ? byte from the VPTR chunk.*/
> ? ? ? ? ? a) first am computing block
> ? ? ? ? ? ?block_no = code_buf & 0x1ff;
> ? ? ? ? ? b) I am reading the next byte from the vptr chunk ....
> ? ? ? ? ? ?Kostya , you mentioned that memcpy is wrong , why ??
> please elaborate...

because you copy byte into some part of variable instead of proper
assign. It will cause undefined because only part of variable is set
(and it's different part on big and little-endian systems)

> ? ? ? ? ? ? memcpy(&count,&src[src_index+2],1);
> ? ? ? ? ? ? src_index++; // Am increasing by 1 byte and later outside
> the switch in the loop incremeneting by ?2 bytes ...
>
> ? // Writing the block "count times "
> ? ? ? ? ? ? for(index=0;index<count;index++)
> ? ? ? ? ? ? ? ? dest[dest_index+index] = block_no;
> // Then updating the destination index for good...
> ? ? ? ? ?dest_index += index;
> ? ? ? ? ? ? av_log(NULL,AV_LOG_ERROR,"Code is 101 %d\n",code);
> ? ? ? ? ? ? break;
>
>
> Please tell me where am I going wrong ? WHat needs to be fixed for
> this snippet of code ?
>
> Thanks,
> -tde