/usr/share/tth/tthxspac.sty is in tth-common 4.03+ds-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | \def\xspace#1{%
\ifx#1\bgroup#1\else%
\ifx#1\egroup#1\else%
\ifx#1\/#1\else%
\ifx#1\#1\else%
\ifx#1~#1\else%
\ifx#1.#1\else%
\ifx#1!#1\else%
\ifx#1,#1\else%
\ifx#1:#1\else%
\ifx#1;#1\else%
\ifx#1?#1\else%
\ifx#1/#1\else%
\ifx#1'#1\else%
\ifx#1)#1\else%
\ifx#1-#1\else%
\ifx#1\@xobeysp#1\else%
\ifx#1\space#1\else%
\ifx#1\@sptoken#1\else%
#1\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi\fi}
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