LaTeX: to compile 1TeX source using ordinary LaTeX

ez1tex.sty

% ez1tex.sty

%% package declaration
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{ez1tex}[2015/11/11 v1.1 ez-1TeX]
\def\bxii@pkgname{ez1tex}

%------------------- handle options

%% \bxii@srcname
\edef\bxii@srcname{\jobname.1tex}

%% options
\DeclareOption*{%
  \edef\bxii@srcname{\CurrentOption}%
}
\ProcessOptions*

%% check sequence
\def\next{%
  \let\documentclass\@twoclasseserror
  \if@compatibility\else\let\usepackage\RequirePackage\fi
  \@fileswithoptions\@clsextension}
\ifx\next\documentclass\else
  \PackageError\bxii@pkgname
    {This package must be loaded before
     \string\documentclass}
    {Package loading is aborted.\MessageBreak\@ehc}
\expandafter\endinput\fi\relax

%------------------- prepare "very-end" hook

\AtEndOfPackage{%
  \let\next\@reset@ptions
  \def\@reset@ptions{%
    \let\@reset@ptions\next
    \@reset@ptions
    \let\next\bxii@endpkg@hook
    \let\bxii@endpkg@hook\@undefined
    \next
  }%
}

%------------------- prepare clean-up procedure

%% \bxii@onlyinoneproc\CS
\def\bxii@onlyinoneproc#1{%
  \g@addto@macro\bxii@revoke@all{\bxii@revoke#1}%
}
\let\bxii@revoke@all\@empty
\def\bxii@revoke#1{\let#1=\@undefined}
%
\bxii@onlyinoneproc\bxii@srcname

%% \bxii@cleanup
\bxii@onlyinoneproc\bxii@cleanup
\def\bxii@cleanup{%
  \bxii@onlyinoneproc\bxii@onlyinoneproc
  \bxii@onlyinoneproc\bxii@revoke@all
  \bxii@onlyinoneproc\bxii@revoke % must be the last
  \bxii@revoke@all
  \let\bxii@onetex@setup\@empty
}

%------------------- setup catcodes etc.

%% \bxii@latex@active
%% \bxii@onetex@active
\bxii@onlyinoneproc\bxii@latex@active
\bxii@onlyinoneproc\bxii@onetex@active
\begingroup
 \catcode13=13 \catcode`1=13 %
 \gdef\bxii@latex@active{\let^^M=\par \let1=\@undefined}%
 \gdef\bxii@onetex@active{\let^^M=\bxii@cr \let1=\bxii@one}%
\endgroup

%% \bxii@set@catcodes{<start>}{<end>}{<value>}
\bxii@onlyinoneproc\bxii@set@catcodes
\def\bxii@set@catcodes#1#2#3{%
  \@tempcnta=#1\relax
  \loop
    \catcode\@tempcnta=#3\relax
  \ifnum \@tempcnta<#2\relax
    \advance\@tempcnta\@ne
  \repeat
}

%% \bxii@onetex@setup
\bxii@onlyinoneproc\bxii@onetex@setup
\def\bxii@onetex@setup{%
  \catcode12=10
  \catcode13=13
  \bxii@set@catcodes{33}{255}{9}%
  \catcode`1=13
  \bxii@onetex@active
  \bxii@oneproc@init
}

%% \bxii@latex@setup
\bxii@onlyinoneproc\bxii@latex@catcodes
\def\bxii@latex@setup{%
  \catcode12=13
  \catcode13=5
  \bxii@set@catcodes{33}{34}{12}%
  \bxii@set@catcodes{33}{34}{12}%
  \catcode35=6
  \catcode36=3
  \catcode37=14
  \catcode38=4
  \catcode35=6
  \catcode36=3
  \catcode37=14
  \catcode38=4
  \bxii@set@catcodes{39}{64}{12}%
  \bxii@set@catcodes{65}{90}{11}%
  \catcode91=12
  \catcode92=0
  \catcode93=12
  \catcode94=7
  \catcode95=8
  \catcode96=12
  \bxii@set@catcodes{97}{122}{11}%
  \catcode123=1
  \catcode124=12
  \catcode125=2
  \catcode126=13
  \catcode127=15
  \bxii@set@catcodes{128}{255}{12}%
  \bxii@latex@active
}

%------------------- decode procedure

%% \let\bxii@outfile
\let\bxii@outfile\@mainaux

%% \bxii@outname
% Temporary output file name.
\bxii@onlyinoneproc\bxii@set@outname
\def\bxii@outname{texput.one}
\def\bxii@set@outname{%
  \edef\bxii@outname{\jobname.one}%
}

%% \bxii@oneproc@init
\bxii@onlyinoneproc\bxii@oneproc@init
\def\bxii@oneproc@init{%
  \immediate\openout\bxii@outfile=\bxii@outname\relax
  \count@=\z@
  \let\bxii@line\@empty
}

%% \bxii@one
\bxii@onlyinoneproc\bxii@one
\def\bxii@one{%
  \advance\count@\@ne
}

%% \bxii@cr
\bxii@onlyinoneproc\bxii@cr
\def\bxii@cr{%
  \ifnum\count@=\z@
    \expandafter\bxii@oneproc@fin
  \else\ifnum\count@=10
    \immediate\write\bxii@outfile{\bxii@line}%
    \let\bxii@line\@empty
    \count@=\z@
  \else\ifnum\count@<128
    \begingroup
      \lccode`\Z=\count@
      \lowercase{\xdef\bxii@line{\bxii@line Z}}%
    \endgroup
    \count@=\z@
  \fi\fi\fi
}

%% \bxii@oneproc@fin
\bxii@onlyinoneproc\bxii@oneproc@fin
\def\bxii@oneproc@fin{%
  \ifx\bxii@line\@empty\else
    \immediate\write\bxii@outfile{\bxii@line}%
    \let\bxii@line\@empty
  \fi
  \count@=\z@
  \immediate\closeout\bxii@outfile
  \edef\next{%
    \noexpand\@@input\bxii@outname\space
  }%
  \bxii@latex@setup
  \bxii@cleanup
  \next
}

%------------------- attach hooks

%% \everyjob hook
\bxii@onlyinoneproc\bxii@endpkg@hook
\def\bxii@endpkg@hook{%
  \bxii@set@outname
  \bxii@onetex@setup
  \@@input\bxii@srcname\space
  \ifx\bxii@oneproc@fin\@undefined\else
    \expandafter\bxii@oneproc@fin
  \fi
  \endinput
}

%------------------- all done
\endinput
%% EOF