harvey/sys/lib/ghostscript/gs_epsf.ps

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% $Id: gs_epsf.ps,v 1.2 2000/09/19 18:29:11 lpd Exp $
% Allow the interpreter to recognize MS-DOS EPSF file headers, and skip to
% the PostScript section of the file.

/.runnoepsf /run load def
/.epsfheader <C5D0D3C6> def
/run
 { dup type /filetype ne { (r) file } if
		% Check for MS-DOS EPSF file (see Red Book p. 729).
   true exch 0 1 3
    {		% Stack: true file index
      1 index read dup { pop dup .epsfheader 3 index get eq } if
       { pop pop }	% if matched, don't need the character
       {	% unread characters (wasn't EPSF)
	 2 index exch unread     % unread mismatch character
	 dup {   % loop unreading backwards in .epsfheader
	   1 sub dup .epsfheader exch get 2 index exch unread
	 } repeat pop
	 exch not exch exit	% change true to false
       }
      ifelse
    }
   for exch	% Stack: file true/false
    {		% This block is executed if the file is MS-DOS EPSF.
		% Build up the little-endian byte offset and length.
      2
	{ 1 0 4
	   { 2 index read not { pop exit } if % if EOF, let error happen
	     2 index mul add exch 256 mul exch
	   }
	  repeat exch pop exch
	}
      repeat
		% Stack: offset length file
		% Use flushfile to skip quickly to the start of the
		% PostScript section.
      dup 4 -1 roll 12 sub () /SubFileDecode filter flushfile
		% Now interpret the PostScript.
      exch () /SubFileDecode filter cvx .runexec
    }
    { .runnoepsf
    }
   ifelse
 } odef