\def\fileversion{1.20}
\def\filedate{2002/06/09}
%
% \iffalse
%% File: backref.dtx Copyright (C) 1995-2002 David Carlisle, Sebastian Rahtz, Heiko Oberdiek
%
%% This file is part of the `Hyperref Bundle'.
%% -------------------------------------------
%% 
%% It may be distributed under the conditions of the LaTeX Project Public
%% License, either version 1.2 of this license or (at your option) any
%% later version.  The latest version of this license is in
%%    http://www.latex-project.org/lppl.txt
%% and version 1.2 or later is part of all distributions of LaTeX 
%% version 1999/12/01 or later.
%% 
%% The list of all files belonging to the `Hyperref Bundle' is
%% given in the file `manifest.txt'.
%<*driver>
\documentclass{ltxdoc}
\begin{document}
  \title{%
    Back referencing from bibliographical citations%
    \thanks{%
      This file has version number \fileversion,
      last revised \filedate.%
    }%
  }
  \author{David Carlisle and Sebastian Rahtz}
  \date{\filedate}
  \maketitle
  \tableofcontents
  \DocInput{backref.dtx}
\end{document}
%</driver>
% \fi
% \CheckSum{240}
% \MakeShortVerb{|}
% \section{Introduction}
%
% \section{Usage}
%
% \StopEventually{}
%
% \section{The macros}
%    Internal command names of this package start with |\BR@|,
%    commands, that store the original meaning of commands, which
%    will be redefined, are prefixed with |\BRorg@|.
%
% \subsection{Package identification}
%    \begin{macrocode}
%<*package>
\ProvidesPackage{backref}%
  [\filedate\space v\fileversion\space Bibliographical back referencing]
%    \end{macrocode}
%
% \subsection{Options}
%
% \subsubsection{Option verbose}
%    If package hyperref is loaded, then its setting is used as
%    default for the verbose switch.
%    \begin{macrocode}
\newif\ifBR@verbose
\@ifundefined{ifHy@verbose}{%
  \BR@verbosefalse
}{%
  \let\ifBR@verbose\ifHy@verbose
}
\DeclareOption{verbose}{\BR@verbosetrue}
%    \end{macrocode}
%
% \subsubsection{Options for way of working}
%
%    What is printed depends on how the 3 available items of
%    information are used (page number, section number, label).
%    \begin{macrocode}
\long\def\page@backref#1#2#3{#1}
\long\def\section@backref#1#2#3{#2}
\long\def\hyper@section@backref#1#2#3{\hyperlink{#3}{#2}}
\long\def\hyper@page@backref#1#2#3{\hyperlink{page.#1}{#1}}
%    \end{macrocode}
%    \begin{macro}{\backrefpagesname}
%    \begin{macro}{\backrefsectionsname}
%    Text strings are implemented via \cmd{\...name} commands for
%    language independence.
%    \begin{macrocode}
\def\backrefpagesname{pages}
\def\backrefsectionsname{sections}
%    \end{macrocode}
%    \end{macro}
%    \end{macro}
%    Now the options follows, that can be used without
%    package hyperref.
%    \begin{macrocode}
\DeclareOption{pageref}{%
  \def\backref{\backrefpagesname\ }%
  \let\backrefxxx\page@backref
}
\DeclareOption{ref}{%
  \def\backref{\backrefsectionsname\ }%
  \let\backrefxxx\section@backref
}
%    \end{macrocode}
%    Set up back-referencing to be hyper links, by page or section.
%    \begin{macrocode}
\DeclareOption{hyperref}{%
  \def\backref{}\let\backrefxxx\hyper@section@backref
}
\DeclareOption{hyperpageref}{%
  \def\backref{}\let\backrefxxx\hyper@page@backref
}
%    \end{macrocode}
%
% \subsubsection{Process options}
%
%    \begin{macrocode}
\ExecuteOptions{pageref}
\ProcessOptions
%    \end{macrocode}
%
% \subsection{The bibliography}
%
%    \begin{macro}{\BR@bibitem}
%    \begin{macrocode}
\def\BR@bibitem{\@ifnextchar[\BR@@lbibitem\BR@@bibitem}
%    \end{macrocode}
%    \end{macro}
%    \begin{macrocode}
\def\BR@@lbibitem[#1]#2#3\par{%
  \BRorg@bibitem[#1]{#2}#3
  \newblock
  \begingroup
    \csname @safe@activestrue\endcsname
    \backref{\csname br@#2\endcsname}%
  \endgroup
  \par
}%
\def\BR@@bibitem#1#2\par{%
  \BRorg@bibitem{#1}#2
  \newblock
  \begingroup
    \csname @safe@activestrue\endcsname
    \backref{\csname br@#1\endcsname}%
  \endgroup
  \par
}
\@ifundefined{newblock}{\def\newblock{\par}}{}
%    \end{macrocode}
%
% \subsection{Reading .brf file}
%
%    \begin{macro}{\backcite}
%    The file |\jobname.brf| collects the back cite informations
%    as calls of \cmd{\backcite} with the informations
%    in the arguments.
%
%    To avoid same entries, it is checked before, whether the entry
%    already exists. Only the information needed by \cmd{\backrefxxx}
%    is compared.
%    \begin{macrocode}
\def\backcite#1#2{%
  \@for\x:=#1\do{%
    \edef\x{\expandafter\@firstofone\x\@empty}%
    \expandafter\ifx\csname br@\x\endcsname\relax
      \expandafter\protected@xdef\csname br@\x\endcsname{%
        \protect\backrefxxx#2%
      }%
    \else
      \begingroup
        \expandafter\def\expandafter\reserved@a\expandafter{%
          \backrefxxx#2%
        }%
        \let\BRorg@backrefxxx\backrefxxx
        \global\let\BR@found=N%
        \long\def\backrefxxx##1##2##3{%
          \expandafter\def\expandafter\reserved@b\expandafter{%
            \BRorg@backrefxxx{##1}{##2}{##3}%
          }%
          \ifx\reserved@a\reserved@b
            \global\let\BR@found=Y%
          \fi
        }%
        \setbox\@tempboxa\hbox{\csname br@\x\endcsname}%
      \endgroup
      \if N\BR@found
        \expandafter\protected@xdef\csname br@\x\endcsname{%
          \csname br@\x\endcsname, %
          \protect\backrefxxx#2%
        }%
      \fi
    \fi
  }%
}
%    \end{macrocode}
%    \end{macro}
%
% \subsection{Initialization}
%
%    \begin{macrocode}
\def\@currentHref{}
\AtBeginDocument{%
  \let\BRorg@bibitem\bibitem
  \let\bibitem\BR@bibitem
  \let\BRorg@thebibliography\thebibliography
  \def\thebibliography{%
    \@starttoc{brf}{}%
    \BRorg@thebibliography
  }%
  \@ifundefined{NAT@parse}{%
    \global\let\BRorg@citex\@citex
    \global\let\@citex\BR@citex
  }{%
    \PackageInfo{backref}{** backref set up for natbib **}%
  }%
}
%    \end{macrocode}
%
% \subsection{Collecting back cite informations}
%
%    \begin{macro}{\BR@citex}
%    \begin{macrocode}
\def\BR@citex[#1]#2{%
  \BRorg@citex[#1]{#2}%
  \ifBR@verbose
    \PackageInfo{backref}{back cite \string`#2\string'}%
  \fi
  \Hy@backout{#2}%
}
%    \end{macrocode}
%    \end{macro}
%
% Grr. for chicago.sty
%    \begin{macrocode}
\@ifpackageloaded{chicago}{%
  \let\BRorg@citedatax\@citedatax
  \def\@citedatax[#1]#2{%
    \BRorg@citedatax[#1]{#2}%
    \Hy@backout{#2}%
  }%
}{}
%    \end{macrocode}
%    \begin{macro}{\Hy@backout}
%    \begin{macrocode}
\def\Hy@backout#1{%
  \@bsphack
  \ifx\@empty\@currentlabel
    \protected@write\@auxout{}{%
      \string\@writefile{brf}{%
        \string\backcite{#1}{{\thepage}{(document)}{Doc-Start}}%
      }%
    }%
  \else
   \protected@write\@auxout{}{%
     \string\@writefile{brf}{%
       \string\backcite{#1}{{\thepage}{\@currentlabel}{\@currentHref}}%
     }%
   }%
  \fi
  \@esphack
}
%    \end{macrocode}
%    \end{macro}
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \Finale
%
\endinput