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[EDIT] FILE: gs_dscp.ps

% Copyright (C) 2001-2019 Artifex Software, Inc.
% All Rights Reserved.
%
% This software is provided AS-IS with no warranty, either express or
% implied.
%
% This software is distributed under license and may not be copied,
% modified or distributed except as expressly authorized under the terms
% of the license contained in the file LICENSE in this distribution.
%
% Refer to licensing information at http://www.artifex.com or contact
% Artifex Software, Inc.,  1305 Grant Avenue - Suite 200, Novato,
% CA 94945, U.S.A., +1(415)492-9861, for further information.
%

%  Postscript interface routines to DSC parser

/send_orientation {			% <orientation> send_orientation -
        % .parse_dsc_comments returns -1 for an Orientation key with an
        % unrecognized value.
  dup 0 ge {
    << /Orientation 2 index >> setpagedevice
  } if pop
} bind def

% This dictionary contains local handlers for DSC comments.
% See header in zdscpars.c for more information.
% <dsc_dict> handler <dsc_dict>
/DSCparseprocs mark
   /Orientation { dup /Orientation get send_orientation } bind
   /PageOrientation { dup /PageOrientation .knownget { send_orientation }
                      { dup /Orientation .knownget { send_orientation } if }
                      ifelse } bind
   /Page { dup /Orientation .knownget { send_orientation } if } bind
   /NOP { } bind
.dicttomark readonly def

% This procedure is called whenever a DSC comment is found by the interpreter
/do_parse_dsc //false def
/parse_dsc {				% <file> <DSC string> [<prev proc>]
                                        %   parse_dsc -
        % Run any previously installed parser.
  0 get dup //null eq { pop } { 3 copy exec pop } ifelse

do_parse_dsc {			% Check if this parser is enabled
    currentglobal //true setglobal	% Go to global VM, save old state
    3 1 roll				% Put old VM state under <file> <string>
    dsc_dict exch			% <VM state> <file> <dict> <string>
    .parse_dsc_comments			% <VM state> <file> <dict> <DSC name>
    4 -1 roll				% Get old VM state from under <file> <dict> <DSC name>
    setglobal				% restore previous VM state
    //DSCparseprocs exch .knownget {	% Check DSC name against local handler list
      exec				% execute any local handler
    } if
  } if
  pop pop				% remove file, dict
} bind def

% Check whether the currently installed parser is the one defined in this file.
/.using_parse_dsc {			% - .using_parse_dsc <proc> <using?>
  currentuserparams /ProcessDSCComment get
  dup //null eq { pop {{//null} //parse_dsc exec} } if
  dup length 3 eq {
    dup dup length 1 sub get /parse_dsc load eq
  } {
    //false
  } ifelse
} bind def

% Establish a binding for dsc_dict.
userdict /dsc_dict //null put

% - dsc_init -
/dsc_init {				% Initialize DSC parser
  currentglobal //true setglobal
  /dsc_dict 50 dict store		% Size must be large enough for all DSC values
  dsc_dict .initialize_dsc_parser
  .using_parse_dsc {
        % Already using this parser.
    pop
  } {
        % Encapsulate the previous parser.  We know it is in global VM:
        % allocate the new one in global VM as well.
    1 array astore
    /parse_dsc load /exec load 3 array astore cvx readonly
    << /ProcessDSCComment 3 -1 roll >>
    setuserparams
  } ifelse
  setglobal
  /do_parse_dsc //true def
} bind def

% Enable the DSC parser defined in this file.
% - enable_dsc -
/enable_dsc {
  dsc_init
} bind def

% Disable the DSC parser defined in this file.
% - disable_dsc -
/disable_dsc {
        % There might be another parser installed: if so, restore it.
        % (If it has encapsulated our parser, we can't.)
  .using_parse_dsc {
        % Restore the parser we encapsulated.
    0 get 0 get
    currentglobal //true setglobal exch
    << /ProcessDSCComment 3 -1 roll >>
    exch setglobal setuserparams
  } {
    pop
  } ifelse
        % If we couldn't restore the old parser, at least disable ours.
  /do_parse_dsc //false def
} bind def

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