[[email protected]: Re: Fix for 687474, Damaged pdf files won't display with Ghostscript]

On Tue, May 25, 2004 at 08:10:06PM -0400, Alex Cherepanov wrote:

> Search the whole PDF file for the last occurrence of %%EOF, because
> there are files that have large amount of garbage at the end.
> For efficiency search the last 1024 bytes first.
> Fix bug 687474 from customer 580.

It was agreed to accept this patch during the recent bug review. However,
the comment doesn't unambiguously indicate that the file is invalid.
Please change the comment so this is clear and commit.

 -r

> Index: gs/lib/pdf_main.ps
> ===================================================================
> RCS file: /cvs/ghostscript/gs/lib/pdf_main.ps,v
> retrieving revision 1.86
> diff -b -u -r1.86 pdf_main.ps
> --- a/gs/lib/pdf_main.ps	1 Apr 2004 06:14:00 -0000	1.86
> +++ b/gs/lib/pdf_main.ps	25 May 2004 23:52:42 -0000
> @@ -491,32 +491,49 @@
>     currentdict end
>   } bind def
>  
> +% Look for [\r\n]%%EO from the current position of the file.
> +% Return the position of %%EO if found or -1 .
> +/findeof {  % <file> find_eof <file> <position>
> +  -1 exch
> +  {
> +    dup bytesavailable 4 lt { exit } if
> +    dup 0 (%%EO) /SubFileDecode filter flushfile
> +    dup dup fileposition 5 sub setfileposition
> +    dup 5 string readstring not { pop exit } if
> +    dup (\r%%EO) eq exch (\n%%EO) eq or {
> +      dup fileposition 4 sub
> +      3 1 roll exch pop
> +    } if
> +  } loop
> +  exch
> +} bind def
> +
>  % Skip backward over the %%EOF at the end of the PDF file, and read
>  % the preceding startxref line.  The PDF specification unambiguously
>  % requires that the %%EOF appear on a line by itself, and that the
>  % startxref and the following position value appear on separate lines;
> -% however, some applications (including, apparently, Acrobat Distiller
> -% on the Macintosh) may add up to 2K of garbage after the %%EOF, and some
> -% other applications also truncate the %%EOF to %%EO, and/or put the
> +% however, some applications truncate the %%EOF to %%EO, and/or put the
>  % startxref and the following value on the same line.
> -% A file reported from Distiller 3.02b for AIX 4.1.1 has 2076 bytes
> -% of garbage. The tolerance is increased to 4K to cover future
> -% applications and bigger allocation units.
> +% There seems to be no limit on the amount of garbage that can be
> +% appended to the PDF file. Current record (60K) belongs to 
> +% PDF-Out (v 2.0 - 35). We start the search for %%EO from the last 1024
> +% bytes and continue from the beginning of the file.
>  /findxref {		% - findxref <xrefpos>
> -  PDFfile dup dup 0 setfileposition bytesavailable
> +  PDFfile dup dup dup 0 setfileposition bytesavailable
>    dup /PDFfilelen exch def
> -	% Find the last %%EOF string (within 4096 bytes)
> -  4096 sub PDFoffset .max
> -  2 copy setfileposition
> -  PDFfilelen exch sub string 1 index exch readstring pop {
> -    (\015%%EO) search {		% Adobe can handle truncated key string
> -      pop pop			% if found, keep searching 'post' string
> -    } {
> -      (\012%%EO) search
> -	{ pop pop } { exit } ifelse	% exit if neither string found
> -    } ifelse
> -  } loop
> -  PDFfilelen exch length sub 4 sub PDFoffset .max exch 1 index setfileposition
> +	% Find the last %%EOF string (within 1024 bytes)
> +  1024 sub PDFoffset .max
> +  setfileposition findeof                  % search the last 1024 bytes
> +  dup 0 le {
> +    pop
> +    dup PDFoffset setfileposition findeof  % search from the beginnibg
> +    dup 0 le {
> +       (   **** Error: Cannot find a %%EOF marker anywhere in the file.\n)
> +       pdfformaterror
> +       /findxref cvx /syntaxerror signalerror
> +    } if
> +  } if
> +  dup 3 1 roll setfileposition
>  	% Stack: eofpos
>  	% Check for whether this is, in fact, a valid PDF file.
>    dup PDFfilelen exch sub dup dup 7 gt exch 5 lt or {

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