platex/#84 に対する修正実験

platex84.tex

\documentclass{minimal}
\makeatletter
\ifdefined\kanjiskip
\unless\ifdefined\ucs % (e-)pTeX only
%%%% EUC-JP が内部漢字コードであることを想定

\begingroup
\catcode`\"=12
\catcode`\<=12
\catcode`\.=12
\catcode`\,=12
\catcode`\;=12
\catcode`\!=12
\catcode`\~=13
\gdef\UTFviii@splitcsname#1:#2\relax{%
  % 
    \pltx@UTFviii@tobyte#2\relax\space
    (\expandafter\UTFviii@hexcodepoint\expandafter{%
    \the\numexpr\decode@UTFviii#2\relax})%
}
\endgroup


\begingroup
\count@="80
\lccode`\U=`\U
\lccode`\T=`\T
\lccode`\F=`\F
\loop\ifnum\count@<"100
  \lccode`\:=\count@
  \lowercase{\expandafter\gdef\csname pltx@UTFviii@\the\count@\endcsname
    {:}}%
  \advance\count@ 1
\repeat
\endgroup

\def\pltx@UTFviii@tobyte#1{%
  \ifx#1\relax\else
    \ifnum`#1<"100 #1\else
      \expandafter\expandafter\expandafter\strip@prefix
      \expandafter\meaning
        \csname pltx@UTFviii@\the\numexpr (`#1-"7F)/"100\relax\endcsname
      \expandafter\expandafter\expandafter\strip@prefix
      \expandafter\meaning
        \csname pltx@UTFviii@\the\numexpr
          `#1-(`#1/256)*256+256 \relax\endcsname
      \fi
  \expandafter\pltx@UTFviii@tobyte\fi
}
\def\UTFviii@checkseq#1:#2#3{%
 \ifnum`#2<"80 %
   \ifx\relax#3\else1\fi
 \else
   \ifnum`#2<"C0 %
     1 %
   \else
     \expandafter\expandafter\expandafter\UTFviii@check@continue
     \expandafter\expandafter\expandafter#3%
   \fi
  \fi}
\def\UTFviii@check@continue#1{%
  \ifx\relax#1%
  \else
  \ifnum`#1<"80 1\else\ifnum`#1>"BF
    \ifnum`#1<"807F 1\else\ifnum`#1>"BFBF 1\fi\fi
  \fi\fi
  \expandafter\UTFviii@check@continue
  \fi
}
\def\dec@de@UTFviii#1{%
\ifx\relax#1%
\else
  \ifnum`#1>"EFFF
    ((((`#1/256-"F0-1)*64
     +`#1-(`#1/256)*256+256-"80
  \else\ifnum`#1>"DFFF
    (((`#1/256-"E0-1)*64
     +`#1-(`#1/256)*256+256-"80
  \else\ifnum`#1>"BFFF
    ((`#1/256-"C0-1)*64
     +`#1-(`#1/256)*256+256-"80
  \else\ifnum`#1>"7FFF % third and fourth bytes
    )*4096+(`#1/256-"80-1)*64
     +`#1-(`#1/256)*256+256-"80
  \else\ifnum`#1>"EF
    ((((`#1-"F0)%
  \else
    \ifnum`#1>"DF
      (((`#1-"E0)%
    \else
      \ifnum`#1>"BF
        ((`#1-"C0)%
      \else
        \ifnum`#1>"7F
        )*64+(`#1-"80)%
        \else
        +`#1 %
        \fi
      \fi
    \fi
  \fi
  \fi\fi\fi\fi
  \expandafter\dec@de@UTFviii
\fi}
\fi\fi

\begin{document}

Ƀ  % U+0243  ^^c9^^83
ſ  % U+017F  ^^c5^^bf
껟 % U+AEDF  ^^ea^^bb^^9f
𢄀 % U+22100 ^^f0^^a2^^84^^80
𠢣 % U+208A3 ^^f0^^a0^^a2^^a3



\end{document}