Re: Bug 687986, Incorrect code in HEAD spdiff.c |

Alex,

Please make the cast more evident (even if it compiles to the
same thing):

RCS file: /cvs/ghostscript/gs/src/spdiff.c,v
retrieving revision 1.9
diff -u -r1.9 spdiff.c
--- gs/src/spdiff.c	16 Mar 2005 14:57:42 -0000	1.9
+++ gs/src/spdiff.c	27 Mar 2005 19:07:52 -0000
@@ -482,7 +482,7 @@
  	    ss->prev[0] = s0;
  	    for (; count >= colors; count -= colors)
  		for (ci = 0; ci < colors; ++ci) {
-		    ti = *++p >> 8;
- 		    ss->prev[ci] += ti + *++p;
+		    ti = (int)(*++p) << 8;
+		    ss->prev[ci] += ti + (int)(*++p);
  		    *++q = ss->prev[ci] >> 8;
  		    *++q = ss->prev[ci] & 0xff;

If you agree that this is equivalent to the intent fo your patch,
please commit.

I recall that this code would be executed by the PDF interpreter when
it imports a PDF that has a 16 bit deep image (at least under some
subset conditions). I don't have a test file handy, but I think Dan
Coby may have created a couple with newer PhotoShop or Illustrator.

Regards,
Ray
_____________________________________________________________________


Alex Cherepanov wrote:

> Correctly read a big endian number from the unaligned buffer in
> 16 bit decoding pixel differencing filter.
> Fix bug 687986.
> 
> DETAILS :
> The same operation is done in the line 467. So the line 485
> should be the same. This code has not been tested because I
> don't know when Ghostscript executes it.
> 
> 
> ------------------------------------------------------------------------
> 
> Index: gs/src/spdiff.c
> ===================================================================
> RCS file: /cvs/ghostscript/gs/src/spdiff.c,v
> retrieving revision 1.9
> diff -u -r1.9 spdiff.c
> --- gs/src/spdiff.c	16 Mar 2005 14:57:42 -0000	1.9
> +++ gs/src/spdiff.c	27 Mar 2005 19:07:52 -0000
> @@ -482,7 +482,7 @@
>  	    ss->prev[0] = s0;
>  	    for (; count >= colors; count -= colors)
>  		for (ci = 0; ci < colors; ++ci) {
> -		    ti = *++p >> 8;
> +		    ti = (int)*++p << 8;
>  		    ss->prev[ci] += ti + *++p;
>  		    *++q = ss->prev[ci] >> 8;
>  		    *++q = ss->prev[ci] & 0xff;
> 
> 
> ------------------------------------------------------------------------
> 
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