harvey/sys/src/cmd/gs/lib/gs_diskf.ps

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% $Id: gs_diskf.ps,v 1.2 2000/09/19 18:29:11 lpd Exp $
% Support for converting Type 1 fonts without eexec encryption to
% Type 4 fonts that load individual character outlines on demand.

% If DISKFONTS is true, we load individual CharStrings as they are needed.
% (This is intended primarily for machines with very small memories.)
% Initially, the character definition is the file position of the definition;
% this gets replaced with the actual CharString.
% Note that if we are loading characters lazily, CharStrings is writable.

% _Cstring must be long enough to hold the longest CharString for
% a character defined using seac.  This is lenIV + 4 * 5 (for the operands
% of sbw, assuming div is not used) + 2 (for sbw) + 3 * 5 (for the operands
% of seac other than the character codes) + 2 * 2 (for the character codes)
% + 2 (for seac), i.e., lenIV + 43.

/_Cstring 60 string def

% When we initially load the font, we call
%	<index|charname> <length> <readproc> cskip_C
% to skip over each character definition and return the file position instead.
% This substitutes for the procedure
%	<index|charname> <length> string currentfile exch read[hex]string pop
%	  [encrypt]
% What we actually store in the CharString is fileposition * 1000 + length,
%   negated if the string is stored in binary form.

/cskip_C
 { exch dup 1000 ge 3 index type /nametype ne or
    { % This is a Subrs string, or the string is so long we can't represent
      % its length.  Load it now.
      exch exec
    }
    { % Record the position and length, and skip the string.
      dup currentfile fileposition 1000 mul add
      2 index 3 get /readstring cvx eq { neg } if
      3 1 roll
      dup _Cstring length idiv
       { currentfile _Cstring 3 index 3 get exec pop pop
       } repeat
      _Cstring length mod _Cstring exch 0 exch getinterval
      currentfile exch 3 -1 roll 3 get exec pop pop
    }
   ifelse
 } bind def

% Load a CharString from the file.  The font is the top entry
% on the dictionary stack.
/load_C		% <charname> <fileposandlength> load_C -
 { dup abs 1000 idiv FontFile exch setfileposition
   CharStrings 3 1 roll
   .currentglobal CharStrings .gcheck .setglobal exch
   dup 0 lt
    { neg 1000 mod string FontFile exch readstring }
    { 1000 mod string FontFile exch readhexstring }
   ifelse pop
   exch .setglobal
% If the CharStrings aren't encrypted on the file, encrypt now.
   Private /-| get 0 get
   dup type /nametype ne
    { dup length 5 sub 5 exch getinterval exec }
    { pop }
   ifelse dup 4 1 roll put
% If the character is defined with seac, load its components now.
   mark exch seac_C
   counttomark
    { StandardEncoding exch get dup CharStrings exch get
      dup type /integertype eq { load_C } { pop pop } ifelse
    } repeat
   pop		% the mark
 } bind def

/seac_C		% <charstring> seac_C <achar> <bchar> ..or nothing..
 { dup length _Cstring length le
    { 4330 exch _Cstring .type1decrypt exch pop
      dup dup length 2 sub 2 getinterval <0c06> eq	% seac
       { dup length
         Private /lenIV known { Private /lenIV get } { 4 } ifelse
	 exch 1 index sub getinterval
% Parse the string just enough to extract the seac information.
% We assume that the only possible operators are hsbw, sbw, and seac,
% and that there are no 5-byte numbers.
	 mark 0 3 -1 roll
	  { exch
	     { { dup 32 lt
	          { pop 0 }
		  { dup 247 lt
		     { 139 sub 0 }
		     { dup 251 lt
			{ 247 sub 256 mul 108 add 1 1 }
			{ 251 sub -256 mul -108 add -1 1 }
		       ifelse
		     }
		    ifelse
		  }
		 ifelse
	       }			% 0
	       { mul add 0 }		% 1
	     }
	    exch get exec
	  }
	 forall pop
	 counttomark 1 add 2 roll cleartomark	% pop all but achar bchar
       }
       { pop	% not seac
       }
      ifelse
    }
    { pop	% punt
    }
   ifelse
 } bind def

% Define replacement procedures for loading fonts.
% If DISKFONTS is true and the body of the font is not encrypted with eexec:
%    - Prevent the CharStrings from being made read-only.
%    - Substitute a different CharString-reading procedure.
% (eexec disables this because the implicit 'systemdict begin' hides
% the redefinitions that make the scheme work.)
% We assume that:
%    - The magic procedures (-|, -!, |-, and |) are defined with
%	executeonly or readonly;
%    - The contents of the reading procedures are as defined in bdftops.ps;
%    - The font includes the code
%	<font> /CharStrings <CharStrings> readonly put
/.loadfontdict 6 dict def mark
 /begin			% push this dict after systemdict
  { dup begin
    //systemdict eq { //.loadfontdict begin } if
  } bind
 /end			% match begin
  { currentdict end
    //.loadfontdict eq currentdict //systemdict eq and { end } if
  } bind
 /dict			% leave room for FontFile, BuildChar, BuildGlyph
  { 3 add dict
  } bind
 /executeonly		% for reading procedures
  { readonly
  }
 /noaccess		% for Subrs strings and Private dictionary
  { readonly
  }
 /readonly		% for procedures and CharStrings dictionary
  {	% We want to take the following non-standard actions here:
  	%   - If the operand is the CharStrings dictionary, do nothing;
	%   - If the operand is a number (a file position replacing the
	%	actual CharString), do nothing;
	%   - If the operand is either of the reading procedures (-| or -!),
	%	substitute a different one.
    dup type /dicttype eq		% CharStrings or Private
    count 2 gt and
     { 1 index /CharStrings ne { readonly } if }
     { dup type /arraytype eq		% procedure or data array
	{ dup length 5 ge 1 index xcheck and
	   { dup 0 get /string eq
	     1 index 1 get /currentfile eq and
	     1 index 2 get /exch eq and
	     1 index 3 get dup /readstring eq exch /readhexstring eq or and
	     1 index 4 get /pop eq and
	      { /cskip_C cvx 2 packedarray cvx
	      }
	      { readonly
	      }
	     ifelse
	   }
	   { readonly
	   }
	  ifelse
	}
	{ dup type /stringtype eq	% must be a Subr string
	   { readonly }
	  if
	}
       ifelse
     }
    ifelse
  } bind
 /definefont		% to insert BuildChar/Glyph and change FontType
  { dup /FontType get 1 eq
     { dup /FontType 4 put
       dup /BuildChar /build_C load put
       dup /BuildGlyph /build_C load put
     }
    if definefont
  } bind
counttomark 2 idiv { .loadfontdict 3 1 roll put } repeat pop
.loadfontdict readonly pop

% Define the BuildChar and BuildGlyph procedures for modified fonts.
% A single procedure serves for both.
/build_C		% <font> <code|name> build_C -
 { 1 index begin
   dup dup type /integertype eq { Encoding exch get } if
		% Stack: font code|name name
   dup CharStrings exch .knownget not
    { 2 copy eq { exch pop /.notdef exch } if
      QUIET not
       { (Substituting .notdef for ) print = flush }
       { pop }
      ifelse
      /.notdef CharStrings /.notdef get
    } if
		% Stack: font code|name name charstring   
   dup type /integertype eq
    { load_C end build_C }
    { end .type1execchar }
   ifelse
 } bind def