breaklines.tex

\documentclass{article}
\usepackage[margin=2cm]{geometry}
\usepackage{calc}
\makeatletter

\def\test#1{%
  \begingroup
  \edef\@tempa{#1}%
  \edef\@tempa{\detokenize\expandafter{\@tempa}}%
  \expandafter\scan\@tempa\scanstop
  \printwrappedtext{\wrappedtext}
  \endgroup
}

\newcount\charcount
\newcount\wordcount

\def\scanstop{}

\def\scan{%
  \futurelet\let@token\process
}

{\def\1{}
\global\futurelet\blankspace\1 }

\def\currtext{}
\def\currline{}
\def\currword{}

\protected\def\NL{}

\charcount=-1

\newcount\maxlinecount

\def\process{%
  \ifx\let@token\scanstop\relax
    \ifnum\numexpr\charcount+\wordcount+1\relax<\maxlinecount
      \protected@edef\wrappedtext{\currtext\currline\space\currword}%
    \else
      \protected@edef\wrappedtext{\currtext\currline\NL\currword}%
    \fi
    \let\next\relax
  \else\ifx\let@token\blankspace
    \ifnum\numexpr\charcount+\wordcount\relax<\maxlinecount
      \advance\charcount by \wordcount
      \advance\charcount by 1% account for the space character      
      \protected@edef\currline{\currline\space\currword}%
      %\showtokens{\the\charcount: \currword}
    \else
      \charcount=\numexpr\wordcount\relax
      \protected@edef\currtext{\currtext\currline\NL}%
      \let\currline\currword
    \fi
    \wordcount=1 
    \let\currword\@empty
    \let\next\dochar
  \else
    \advance\wordcount by 1
    \let\next\dochar
  \fi\fi
  \next}

\def\dochar#1{\edef\currword{\currword#1}\scan}

\begin{document}

\def\printwrappedtext#1{%
  \def\NL{\\}
  \setlength\@tempdima{\widthof{\ttfamily 0}}%
  \@tempdima=\dimexpr \the\maxlinecount\@tempdima\relax
  \noindent Hard-wrapped text:\\
  \fbox{\parbox{\@tempdima}{%
    \ttfamily
    \frenchspacing % important!
    #1}}
}

\noindent
\fbox{\ttfamily 12345678901234567890123456789012345678901234567890123456789012345678901234567890}\par

\maxlinecount=40

\test{%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  Ut purus elit, vestibu 
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Curabitur auctor semper
ut, placerat ac, \string\adipiscing\space vitae, felis. Curabitur dictum gravida mauris. Nam arcu
libero, nonummy eget, consectetuer id, vulputate a, magna. Donec
vehicula augue eu neque. Pellentesque habitant morbi tristique
senectus et netus et malesuada fames ac turpis egestas. Mauris ut
leo. Cras viverra metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices.  Phasellus eu tellus sit amet tortor gravida
  placerat. Integer sapien est, iaculis in, pretium quis, viverra ac,
  nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus.
  Morbi nulla. Donec varius orci eget risus. Duis
  nibh mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis
  eget orci sit amet orci dignissim rutrum.}
  


\maxlinecount=60

\test{%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  Ut purus elit, vestibu 
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Curabitur auctor semper
ut, placerat ac, \string\adipiscing\space vitae, felis. Curabitur dictum gravida mauris. Nam arcu
libero, nonummy eget, consectetuer id, vulputate a, magna. Donec
vehicula augue eu neque. Pellentesque habitant morbi tristique
senectus et netus et malesuada fames ac turpis egestas. Mauris ut
leo. Cras viverra metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices.  Phasellus eu tellus sit amet tortor gravida
  placerat. Integer sapien est, iaculis in, pretium quis, viverra ac,
  nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus.
  Morbi nulla. Donec varius orci eget risus. Duis
  nibh mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis
  eget orci sit amet orci dignissim rutrum.}
  

\maxlinecount=79

\test{%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  Ut purus elit, vestibu 
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Curabitur auctor semper
ut, placerat ac, \string\adipiscing\space vitae, felis. Curabitur dictum gravida mauris. Nam arcu
libero, nonummy eget, consectetuer id, vulputate a, magna. Donec
vehicula augue eu neque. Pellentesque habitant morbi tristique
senectus et netus et malesuada fames ac turpis egestas. Mauris ut
leo. Cras viverra metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices.  Phasellus eu tellus sit amet tortor gravida
  placerat. Integer sapien est, iaculis in, pretium quis, viverra ac,
  nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus.
  Morbi nulla. Donec varius orci eget risus. Duis
  nibh mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis
  eget orci sit amet orci dignissim rutrum.}

\maxlinecount=50

\def\printwrappedtext#1{%
  \def\NL{\MessageBreak}
  \PackageWarning{breaklines}{#1}
}

\test{%
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  Ut purus elit, vestibu 
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Curabitur auctor semper
ut, placerat ac, \string\adipiscing\space vitae, felis. Curabitur dictum gravida mauris. Nam arcu
libero, nonummy eget, consectetuer id, vulputate a, magna. Donec
vehicula augue eu neque. Pellentesque habitant morbi tristique
senectus et netus et malesuada fames ac turpis egestas. Mauris ut
leo. Cras viverra metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices.  Phasellus eu tellus sit amet tortor gravida
  placerat. Integer sapien est, iaculis in, pretium quis, viverra ac,
  nunc. Praesent eget sem vel leo ultrices bibendum. Aenean faucibus.
  Morbi nulla. Donec varius orci eget risus. Duis
  nibh mi, congue eu, accumsan eleifend, sagittis quis, diam. Duis
  eget orci sit amet orci dignissim rutrum.}

\end{document}