%
% switcheml.sty
%
% Charles Duan (2004/02/10)
%
% Obfuscates an e-mail address so that it is unreadable by automated document
% crawlers but appears correct when displayed.
%
% Commands provided by this package are:
%
% \switchemail{EMAIL}
%   Obfuscates EMAIL by reversing on the @ and . symbols, so
%       [email protected]
%   will be written to the document as:
%       com place. one. some@
%   but it will appear properly on the document page.
%
% \switch{DELIM}{TEXT}
%   Obfuscates TEXT by reversing values around DELIM, so
%       \switch{,}{abc,def,ghi,jkl}
%   will be written to the document as:
%       jkl ghi, def, abc
%   but it will appear on the document page as:
%       abc,def,ghi,jkl
%
% \kernhack{A}{B}
%   Produces a kern equivalent to the kern that would normally appear between A
%   and B.
%
\ProvidesPackage{switcheml}[2004/02/10 Obfuscate e-mail addresses]
% Produce a kern equivalent to the kern between #1 and #2
\def\kernhack#1#2{%
   \begingroup
       \setbox\z@\hbox{#1#2}%
       \dimen@\wd\z@
       \setbox\z@\hbox{#1{}#2}\advance\dimen@-\wd\z@
       \ifdim\dimen@=\z@\else\kern\dimen@\fi
   \endgroup
}
% Given a character to find (e.g., period) and a string of text, obfuscate the
% text so that the last part of the text is placed first, etc., so everything
% comes up in reverse order when you try to copy/paste but it looks fine on
% screen. For instance,
%
% some.domain.com
%
% is rewritten as:
%
% box{com} box{domain.} box{some.}
%
% with each of the boxes placed such that they print out properly.
%
\def\switch#1#2{%
   \begingroup
       \def\@switch##1#1##2\@nil#1##3\@stop{%
           \def\reserved@a{##3}%
           \ifx\reserved@a\@empty#2\else
               \setbox\z@\hbox{##1#1}%
               \setbox\tw@\hbox{\kernhack{#1}{##2}\switch{#1}{##2}}%
               \dimen@\wd\tw@\advance\dimen@\wd\z@%
               \wd\z@\dimen@%
               \rlap{\hb@xt@\dimen@{\hfil\unhbox\tw@}}%
               \box\z@
           \fi
       }%
       \@switch#2\@nil#1\@nil#1\@stop
   \endgroup
}
% Given an e-mail address of the form [email protected], reverses it to be jkl
% ghi. def. abc@
\def\switchemail#1{%
   \expandafter\@switchemail#1\@stop
}
% Helper function for \switchemail. Note the \copy, because \kernhack will
% destroy the box otherwise. Need to do some funky stuff because of catcodes.
\begingroup
   \makeatother
   \def\tmp#1#2#3{%
       \gdef#1##1@##2#2{%
           \begingroup
               \setbox#3\hbox{\switch{.}{##2}}%
               \switch{@}{##1@\copy#3}%
           \endgroup
       }%
   }
   \makeatletter
   \tmp\@switchemail\@stop\@tempboxa
\endgroup

\endinput

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