switcheml

git-svn-id: svn://tug.org/texlive/trunk@1363 c570f23f-e606-0410-a88d-b1316a301751

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+%
+% 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
+%       some@one.place.com
+%   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 abc@def.ghi.jkl, 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