gs_lev2.ps

GhostScript的源代码

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% 
% This file is part of Aladdin Ghostscript.
% 
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% or she says so in writing.  Refer to the Aladdin Ghostscript Free Public
% License (the "License") for full details.
% 
% Every copy of Aladdin Ghostscript must include a copy of the License,
% normally in a plain ASCII text file named PUBLIC.  The License grants you
% the right to copy, modify and redistribute Aladdin Ghostscript, but only
% under certain conditions described in the License.  Among other things, the
% License requires that the copyright notice and this notice be preserved on
% all copies.

% $Id: gs_lev2.ps $
% Initialization file for Level 2 functions.
% When this is run, systemdict is still writable,
% but (almost) everything defined here goes into level2dict.

level2dict begin

% ------ System and user parameters ------ %

% User parameters must obey save/restore, and must also be maintained
% per-context.  We implement the former, and some of the latter, here
% with PostScript code.  NOTE: our implementation assumes that user
% parameters change only as a result of setuserparams -- that there are
% no user parameters that are ever changed dynamically by the interpreter
% (although the interpreter may adjust the value presented to setuserparams)
%
% There are two types of user parameters: those which are actually
% maintained in the interpreter, and those which exist only at the
% PostScript level.  We maintain the current state of both types in
% a read-only local dictionary named userparams, defined in systemdict.
% In a multi-context system, each context has its own copy of this
% dictionary.  In addition, there is a constant dictionary named
% psuserparams whose keys are the names of user parameters that exist
% only in PostScript and whose values are (currently) arbitrary values
% of the correct datatype: setuserparams uses this for type checking.
% setuserparams updates userparams explicitly, in addition to setting
% any user parameters in the interpreter; thus we can use userparams
% to reset those parameters after a restore or a context switch.
% NOTE: the name userparams is known to the interpreter, and in fact
% the interpreter creates the userparams dictionary.

% Check parameters that are managed at the PostScript level.
% Currently we allow resetting them iff the new value is of the same type.
/.checksetparams {		% <newdict> <opname> <checkdict>
				%   .checksetparams <newdict>
  2 index {
		% Stack: newdict opname checkdict key newvalue
    3 copy pop .knownget
       { type 1 index type ne
	  { pop pop pop load /typecheck signalerror }
	 if
	 dup type /stringtype eq
	  { dup rcheck not
	     { pop pop pop load /invalidaccess signalerror }
	    if
	  }
	 if
       }
    if pop pop
  } forall pop pop
} .bind def	% not odef, shouldn't reset stacks

% currentuser/systemparams creates and returns a dictionary in the
% current VM.  The easiest way to make this work is to copy any composite
% PostScript-level parameters to global VM.  Currently, the only such
% parameters are strings.  In fact, we always copy string parameters,
% so that we can be sure the contents won't be changed.
/.copyparam {			% <value> .copyparam <value'>
  dup type /stringtype eq {
    .currentglobal true .setglobal
    1 index length string exch .setglobal
    copy readonly
  } if
} .bind def

% Some user parameters are managed entirely at the PostScript level.
% We take care of that here.
systemdict begin
/psuserparams 40 dict def
/getuserparam {			% <name> getuserparam <value>
  /userparams .systemvar 1 index get exch pop
} odef
% Fill in userparams (created by the interpreter) with current values.
mark .currentuserparams
counttomark 2 idiv {
  userparams 3 1 roll put
} repeat pop
/.definepsuserparam {		% <name> <value> .definepsuserparam -
  psuserparams 3 copy pop put
  userparams 3 1 roll put
} .bind def
end
/currentuserparams {		% - currentuserparams <dict>
  /userparams .systemvar dup length dict .copydict
} odef
/setuserparams {		% <dict> setuserparams -
	% Check that we will be able to set the PostScript-level
	% user parameters.
  /setuserparams /psuserparams .systemvar .checksetparams
	% Set the C-level user params.  If this succeeds, we know that
	% the password check succeeded.
  dup .setuserparams
	% Now set the PostScript-level params.
	% The interpreter may have adjusted the values of some of the
	% parameters, so we have to read them back.
  dup {
    /userparams .systemvar 2 index known {
      psuserparams 2 index known not {
	pop dup .getuserparam
      } if
      .copyparam
      /userparams .systemvar 3 1 roll .forceput  % userparams is read-only
    } {
      pop pop
    } ifelse
  } forall
	% A context switch might have occurred during the above loop,
	% causing the interpreter-level parameters to be reset.
	% Set them again to the new values.  From here on, we are safe,
	% since a context switch will consult userparams.
  .setuserparams
} .bind odef
% Initialize user parameters managed here.
/JobName () .definepsuserparam

% Restore must restore the user parameters.
% (Since userparams is in local VM, save takes care of saving them.)
/restore {		% <save> restore -
  restore /userparams .systemvar .setuserparams
} .bind odef

% The pssystemparams dictionary holds some system parameters that
% are managed entirely at the PostScript level.
systemdict begin
currentdict /pssystemparams known not {
  /pssystemparams 40 dict readonly def
} if
/getsystemparam {		% <name> getsystemparam <value>
  //pssystemparams 1 index .knownget { exch pop } { .getsystemparam } ifelse
} odef
end
/currentsystemparams {		% - currentsystemparams <dict>
  mark .currentsystemparams //pssystemparams { } forall .dicttomark
} odef
/setsystemparams {		% <dict> setsystemparams -
	% Check that we will be able to set the PostScript-level
	% system parameters.
   /setsystemparams //pssystemparams .checksetparams
	% Set the C-level system params.  If this succeeds, we know that
	% the password check succeeded.
   dup .setsystemparams
	% Now set the PostScript-level params.  We must copy local strings
	% into global VM.
   dup
    { //pssystemparams 2 index known
       {		% Stack: key newvalue
	 .copyparam
	 //pssystemparams 3 1 roll .forceput	% pssystemparams is read-only
       }
       { pop pop
       }
      ifelse
    }
   forall pop
} .bind odef

% Initialize the passwords.
% NOTE: the names StartJobPassword and SystemParamsPassword are known to
% the interpreter, and must be bound to noaccess strings.
% The length of these strings must be max_password (iutil2.h) + 1.
/StartJobPassword 65 string noaccess def
/SystemParamsPassword 65 string noaccess def

% Redefine cache parameter setting to interact properly with userparams.
/setcachelimit {
  mark /MaxFontItem 2 index .dicttomark setuserparams pop
} .bind odef
/setcacheparams {
	% The MaxFontCache parameter is a system parameter, which we might
	% not be able to set.  Fortunately, this doesn't matter, because
	% system parameters don't have to be synchronized between this code
	% and the VM.
  counttomark 1 add copy setcacheparams
  currentcacheparams	% mark size lower upper
    3 -1 roll pop
    /MinFontCompress 3 1 roll
    /MaxFontItem exch
  .dicttomark setuserparams
  cleartomark
} .bind odef

% Add bogus user and system parameters to satisfy badly written PostScript
% programs that incorrectly assume the existence of all the parameters
% listed in Appendix C of the Red Book.  Note that some of these may become
% real parameters later: code near the end of gs_init.ps takes care of
% removing any such parameters from ps{user,system}params.

psuserparams begin
  /MaxFormItem 100000 def
  /MaxPatternItem 20000 def
  /MaxScreenItem 48000 def
  /MaxUPathItem 5000 def
end

pssystemparams begin
  /CurDisplayList 0 .forcedef
  /CurFormCache 0 .forcedef
  /CurOutlineCache 0 .forcedef
  /CurPatternCache 0 .forcedef
  /CurUPathCache 0 .forcedef
  /CurScreenStorage 0 .forcedef
  /CurSourceList 0 .forcedef
  /DoPrintErrors false .forcedef
  /MaxDisplayList 140000 .forcedef
  /MaxFormCache 100000 .forcedef
  /MaxOutlineCache 65000 .forcedef
  /MaxPatternCache 100000 .forcedef
  /MaxUPathCache 300000 .forcedef
  /MaxScreenStorage 84000 .forcedef
  /MaxSourceList 25000 .forcedef
  /RamSize 4194304 .forcedef
end

% ------ Miscellaneous ------ %

(<<) cvn			% - << -mark-
  /mark load def
(>>) cvn			% -mark- <key1> <value1> ... >> <dict>
  /.dicttomark load def
/languagelevel 2 def
% When running in Level 2 mode, this interpreter is supposed to be
% compatible with Adobe version 2017.
/version (2017) readonly def

% If binary tokens are supported by this interpreter,
% set an appropriate default binary object format.
/setobjectformat where
 { pop
   /RealFormat getsystemparam (IEEE) eq { 1 } { 3 } ifelse
   /ByteOrder getsystemparam { 1 add } if
   setobjectformat
 } if

% ------ Virtual memory ------ %

/currentglobal			% - currentglobal <bool>
  /currentshared load def
/gcheck				% <obj> gcheck <bool>
  /scheck load def
/setglobal			% <bool> setglobal -
  /setshared load def
% We can make the global dictionaries very small, because they auto-expand.
/globaldict currentdict /shareddict .knownget not { 4 dict } if def
/GlobalFontDirectory SharedFontDirectory def

% VMReclaim and VMThreshold are user parameters.
/setvmthreshold {		% <int> setvmthreshold -
  mark /VMThreshold 2 index .dicttomark setuserparams pop
} odef
/vmreclaim {			% <int> vmreclaim -
  dup 0 gt {
    .vmreclaim
  } {
    mark /VMReclaim 2 index .dicttomark setuserparams pop
  } ifelse
} odef
-1 setvmthreshold

% ------ IODevices ------ %

/.getdevparams where {
  pop /currentdevparams {	% <iodevice> currentdevparams <dict>
    .getdevparams .dicttomark
  } odef
} if
/.putdevparams where {
  pop /setdevparams {		% <iodevice> <dict> setdevparams -
    mark 1 index { } forall counttomark 2 add index
    .putdevparams pop pop
  } odef
} if

% ------ Job control ------ %

serverdict begin

% We could protect the job information better, but we aren't attempting
% (currently) to protect ourselves against maliciousness.

/.jobsave null def		% top-level save object
/.jobsavelevel 0 def		% save depth of job (0 if .jobsave is null,
				% 1 otherwise)
/.adminjob true def		% status of current unencapsulated job

end		% serverdict

% Because there may be objects on the e-stack created since the job save,
% we have to clear the e-stack before doing the end-of-job restore.
% We do this by executing a 2 .stop, which is caught by the 2 .stopped
% in .runexec; we leave on the o-stack a procedure to execute aftewards.
%
%**************** The definition of startjob is not complete yet, since
% it doesn't reset stdin/stdout.
/.startnewjob {			% <exit_bool> <password_level>
				%   .startnewjob -
    serverdict /.jobsave get dup null eq { pop } { restore } ifelse
    exch {
			% Unencapsulated job
      serverdict /.jobsave null put
      serverdict /.jobsavelevel 0 put
      serverdict /.adminjob 3 -1 roll 1 gt put
		% The Adobe documentation doesn't say what happens to the
		% graphics state stack in this case, but an experiment
		% produced results suggesting that a grestoreall occurs.
      grestoreall
    } {
			% Encapsulated job
      pop
      serverdict /.jobsave save put
      serverdict /.jobsavelevel 1 put
      .userdict /quit /stop load put
    } ifelse
		% Reset the interpreter state.
  clear cleardictstack
  initgraphics
  false setglobal
} bind def
/.startjob {			% <exit_bool> <password> <finish_proc>
				%   .startjob <ok_bool>
  vmstatus pop pop serverdict /.jobsavelevel get eq
  2 index .checkpassword 0 gt and {
    exch .checkpassword exch count 3 roll count 3 sub { pop } repeat
    cleardictstack
		% Reset the e-stack back to the 2 .stopped in .runexec,
		% passing the finish_proc to be executed afterwards.
    2 .stop
  } {		% Password check failed
    pop pop pop false
  } ifelse
} odef
/startjob {			% <exit_bool> <password> startjob <ok_bool>
  { .startnewjob true } .startjob
} odef

systemdict begin
/quit {				% - quit -
  //systemdict begin serverdict /.jobsave get null eq
   { end //quit }
   { /quit load /invalidaccess /signalerror load end exec }