[FFmpeg-devel] ADPCM task (was Re: files in incoming)

[Stefan Gehrer]

Michael Niedermayer wrote:
> On Thu, Jan 29, 2009 at 08:40:53PM +0100, Stefan Gehrer wrote:

>> The reason is that the + operator does not constitute a sequence point,
>> thus the side-effects of the bytestream_get_x calls, i.e. incrementing
>> src, can actually take place before reading src as the left operand.
>> In case that explanation is correct, you have to thank Mans for
>> teaching me this particular insight into C programming.
>>
>> Independent of my patch, I think the pointer srcC should get some
>> sanity checking at that point?
>>
>> Stefan
> 
> 
> 
>> Index: libavcodec/adpcm.c
>> ===================================================================
>> --- libavcodec/adpcm.c	(revision 16828)
>> +++ libavcodec/adpcm.c	(working copy)
>> @@ -1300,9 +1300,10 @@
>>          }
>>  
>>          for (channel=0; channel<avctx->channels; channel++) {
>> -            srcC = src + (big_endian ? bytestream_get_be32(&src)
>> -                                     : bytestream_get_le32(&src))
>> -                       + (avctx->channels-channel-1) * 4;
>> +            uint32_t offset = (big_endian ? bytestream_get_be32(&src)
>> +                                          : bytestream_get_le32(&src));
>> +                                     
>> +            srcC = src + offset + (avctx->channels-channel-1) * 4;
> 
> the offset variable seems unneeded besides this looks ok

applied without extra variable, the pointer sanity check is still tbd.

Stefan