% \iffalse meta-comment
%
%% File: GS1.dtx Copyright (C) 2012-2017 Markus Kohm
%%
%% It may be distributed and/or modified under the conditions of the
%% LaTeX Project Public License (LPPL), either version 1.3c of this
%% license or (at your option) any later version.  The latest version
%% of this license is in the file
%%
%%    http://www.latex-project.org/lppl.txt
%%
%% This file is part of the "GS1 bundle" (The Work in LPPL)
%% and all files in that bundle must be distributed together.
%%
%% The released version of this bundle is available from CTAN.
%%
%% -------------------------------------------------------------------------
%
%<*driver|package|test>
\RequirePackage{expl3}[2017/05/29]
\GetIdInfo$Id: GS1.dtx 23 2021-06-17 07:00:36Z mjk $
  {GS1 code handler and barcode generator}
%</driver|package|test>
%<*driver>
\documentclass{l3doc}
\begin{document}
  \DocInput{\jobname.dtx}
\end{document}
%</driver>
%<*test>
\documentclass{article}
\usepackage{GS1}
\ExplSyntaxOn
\msg_new:nnn { GS1/test } { function }
  {
    Something~is~wrong~with~function~#1
    \msg_line_context:~~of~\c_sys_jobname_str.tex.
  }
\ExplSyntaxOff
\begin{document}
%</test>
% \fi
%
% \title{^^A
%   The \pkg{GS1}\thanks
%     {^^A
%       GS1 is a registered trademark of GS1 AISBL.  Nevertheless, GS1 AISBL
%       neither has any rights on this package, nor is responsible for it in
%       any kind.  The package's name should indicate only, that the package
%       implements some aspects of GS1 codes.^^A
%     }
%   package\\
%   GS1 Code Handler and Barcode Generator\thanks
%     {^^A
%       This file describes v\ExplFileVersion,
%       last revised \ExplFileDate.^^A
%     }^^A
% }
%
% \author{^^A
%   Markus Kohm\thanks
%     {^^A
%       E-mail: \href{mailto:komascript@gmx.info}{komascript@gmx.info}^^A
%     }^^A
% }
%
% \date{Released \ExplFileDate}
%
% \maketitle
%
% \begin{documentation}
% \begin{abstract}
% There are several barcode packages out in the world, but they either need
% PStricks, or are restricted to EAN-13 barcodes.  And most of all, they are
% all \LaTeXe.  I've decided to write a package, that supports several GS1
% codes, and at almost the same time, I've decided to give L3 a chance.  So
% I've started an experimental GS1 package using \pkg{expl3}.  Using
% \pkg{expl3} was the main reason writing this package.
% \end{abstract}
%
% \tableofcontents
%
% \section*{Preface}
%
% Design and implementation of this package based on
% \begin{quote}\begin{description}
% \item[GS1:] ``Allgemeine GS1 Spezifikation'', Version~12.0, Januar~2012,
% Ausgabe~1.
% \end{description}\end{quote}
% This is the official GS1 specification for Germany, Austria and Switzerland.
%
% Currently only EAN-8 and EAN-13 codes and bar codes without extension have
% been implemented.  Others may follow in future.
%
%
% \section{L3 Functions and Variables for GS1 Codes}
% \label{sec:doc:functions.and.variables}
%
% First of all: Please note, that the concept of private functions and
% variables is not well defined in \TeX.  Several variables, that I'd have
% made private in C++, haven't been declared to be private in this
% implementation.  Maybe I should change this.
%
% You should also know, that several test files may be created from the
% package source, and each of those may be used as an example for using the
% code.  Nevertheless, \LaTeXe{} users will not need the following functions
% and should continue reading with \autoref{sec:doc:latex2e}.
%
% \begin{function}{\GS_set_code_digit_seq:Nn}
%   \begin{syntax}
%     "\GS_set_code_digit_seq:Nn" \meta{GS1 sequence variable} \Arg{token list}
%   \end{syntax}
%   Makes a GS1 sequence, that consist in digits only, from a \meta{token
%   list}.  To do so, only the tokens from 0 up to 9 of the \meta{token list}
%   are set to the \meta{GS1 sequence variable}.  All other tokens are
%   ignored.  So may, e.g., convert the string ``ISBN 978-3-86541-459-5'' into
%   a GS1 sequence with the digits ``9783865414595'', where each digit is one
%   item of the sequence.
% \end{function}
%
% \begin{function}{\GS_cut_EAN_control_digit:N}
%   \begin{syntax}
%     "\GS_cut_EAN_control_digit:N" \meta{GS1 sequence variable}
%   \end{syntax}
%   The \meta{GS1 sequence variable} should store either a EAN-8 or EAN-13
%   code with or without control digit.  If the code has seven or twelve
%   digits, nothing happens.  If the code has eight or 13 digits, the last one
%   will be removed.  All other cases result in an error message.
% \end{function}
%
% \begin{function}{\GS_set_EAN_control_digit:N}
%   \begin{syntax}
%     "\GS_set_EAN_control_digit:N" \meta{GS1 sequence variable}
%   \end{syntax}
%   The \meta{GS1 sequence variable} should store either a EAN-8 or EAN-13
%   code with or without control digit.  A new control digit will be
%   calculated.  If the code has seven or twelve digits the new control digit
%   will be added.  If the code has eight or 13 digits, the old control digit
%   will be replaced by the new one.  All other cases result in an error
%   message.
% \end{function}
%
% \begin{function}{\int_set_to_EAN_control_digit:NN}
%   \begin{syntax}
%     "\int_set_to_EAN_control_digit:NN" \meta{integer variable} \meta{GS1 sequence variable}
%   \end{syntax}
%   Calculates the control digit of the \meta{GS1 sequence variable} using the
%   EAN control digit algorithm and stores it into the \meta{integer
%   variable}.  Note, that the \meta{GS1 sequence variable} may be a sequence
%   of digits of any length not only seven digits for EAN-8 or twelve digits
%   for EAN-13.
% \end{function}
%
% \begin{function}{\GS_use_as_EAN_barcode:N}
%   \begin{syntax}
%     "\GS_use_as_EAN_barcode:N" \meta{GS1 sequence variable}
%   \end{syntax}
%   Prints an EAN-8 or EAN-13 bar code depending on
%   \cs{l_GS_code_size_int}. Note, that the \meta{GS1 sequence variable} may
%   have more than 8 resp. 13 items but not less!  Use \cs{EANBarcode} if you
%   need a more save function.
% \end{function}
%
%
% \section{\LaTeXe{} User Interface for GS1 Codes}
% \label{sec:doc:latex2e}
%
% This section describes the \LaTeXe-compatible user interface.  Note, that
% the test files \file{EANControlDigit.tex}, \file{EANBarcode.tex},
% \file{GSSetup.tex}, and the resulting PDF files may be used as examples of
% the following commands.
%
% \begin{function}{\EANControlDigit}
%   \begin{syntax}
%     "\EANControlDigit"\Arg{string}
%   \end{syntax}
%   Only the digits of the \meta{string} will be used. All other tokens
%   will be ignored.  If the \meta{string} has 7 or 8 digits, the control
%   digit of an EAN-8 code will be calculated and output.  If the
%   \meta{string} has 12 or 13 digits, the control digit of an EAN-13 code
%   will be calculated and output.  If the \meta{string} has 8 or 13 digits
%   the last digit will be ignored.  Any other number of digits will result in
%   an error message.
% \end{function}
%
% \begin{function}{\EANBarcode}
%   \begin{syntax}
%     "\EANBarcode"\oarg{options}\Arg{string}
%   \end{syntax}
%   Creates the EAN bar code corresponding with \meta{string}.  The optional
%   argument \meta{options} may be used to use different settings from the
%   defaults set by \cmd{\GSSetup}.  
%
%   Each digit of a EAN bar code is represented by seven modules.  Each module
%   is either black or white.  A black module is a black, vertical line.  A
%   white module is just a gap.  The seven modules start either with a black
%   sequence of up to four modules, followed by a white sequence of up to four
%   modules, followed by a black sequence of up to four modules, finished by a
%   white sequence of up to four modules, or they start with a white sequence
%   of up to four modules, followed by a black sequence of up to four modules,
%   followed by a white sequence of up to four modules, finished by a black
%   sequence of up to four modules.
% \end{function}
%
% \begin{function}{\GSSetup}
%   \begin{syntax}
%     "\GSSetup" \Arg{options}
%   \end{syntax}
%   \meta{options} is a list of \meta{key}=\meta{value} pairs.  They are used
%   to setup the default of several settings:
%   \begin{description}
%     \item[\texttt{ocrb=}\meta{boolean}]\hfill\\
%       If \meta{boolean} is \texttt{true} the digits at the bottom of the bar
%       code will be printed using OCR-b font ocrb/T1/m/n in 9pt.  Predefined
%       default is |ocrb=true|.
%     \item[\texttt{module\_width=}\meta{dimension expression}]\hfill\\
%       This is the width of one module.  GS1 specifies a minimum module width
%       of 0.264\,mm and a normal width of 0.33\,mm.  You should not set a
%       width below the minimum!
%     \item[\texttt{module\_height=}\meta{dimension expression}]\hfill\\
%       This is the height of a black module.  GS1 specifies a normal bar code
%       height of 21.31\,mm for EAN-8 and 25.01\,mm for EAN-13.  Both values
%       are inclusive the digits at the bottom of the bar code.  Some marker
%       modules are higher than the digit modules.
%     \item[\texttt{code=}\meta{string}]\hfill\\
%       The \meta{string} should either be \texttt{EAN-8} or \texttt{EAN-13}.
%       The predefined default is |EAN-13|.  More types will be
%       supported in future.
%     \item[\texttt{scale=}\meta{floating point}]\hfill\\
%       This is the scale factor for the bar code.  GS1 specifies scale classes
%       from 0.8 up to 2.0 with steps of 0.05.  Factors less than 0.8
%       shouldn't be used. \emph{Currently \texttt{scale} won't be used!}
%     \item[\texttt{scale\_to\_font=}\meta{boolean}]\hfill\\
%       Ignore \texttt{module_width} and instead set the module width
%       depending on the width of digit 0 of the current font.  Note, that
%       this will not scale the whole bar code but only the module width.  To
%       scale the whole bar code, you should use \texttt{scale}.
%     \item[\texttt{add\_control=}\meta{boolean}]\hfill\\
%       Add the control digit to the GS1 code.  If there's already a control
%       digit, replace it by the calculated one.  The predefined default is
%       |add_control=false|.
%    \end{description}
% \end{function}
%
%
% \section{Internal Functions and Variables}
% \label{sec:doc:internal}
%
% You should not use or manipulate these! So, maybe it's better to stop
% reading now.
%
% \begin{function}{\__GS_set_key_code:nn}
%   \begin{syntax}
%     "\__GS_set_key_code:nn" \Arg{token list} \Arg{integer expression}
%   \end{syntax}
%   Sets \cs{l_GS_code_type_tl} to \meta{token list} and
%   \cs{l_GS_code_size_int} to value of \Arg{integer expression}.
% \end{function}
%
% \begin{function}{\__GS_new_seq_c:cn}
%   \begin{syntax}
%     "\__GS_new_seq_c:cn" \Arg{sequence name} \Arg{token list}
%   \end{syntax}
%   Creates a sequence constant \cs{c__GS_\meta{sequence name}_seq}.  The
%   value of the constant will be build by the tokens of the \meta{token
%   list}.  These tokens should be either characters ``A'' or ``B'' for
%   selection constants or digits 1--4 for module constants.
% \end{function}
%
% \begin{function}{\__GS_modules:Nn, \__GS_modules:cn, \__GS_modules:NnN}
%   \begin{syntax}
%     "\__GS_modules:Nn" \meta{sequence variable} \Arg{dimension expression}
%     "\__GS_modules:cn" \Arg{sequence variable name} \Arg{dimension expression}
%     "\__GS_modules:NnN" \meta{sequence variable} \Arg{dimension expression} \meta{boolean variable}
%   \end{syntax}
%   Draws the modules given by the \meta{sequence variable} with height
%   \Arg{dimension expression}. The arguments are:
%   \begin{arguments}
%   \item \meta{sequence variable} or \meta{sequence variable name}, each item
%     of the sequence stays for a number of modules with the same color.
%     \cs{l__GS_black_bool} signals, whether the (first) modules are black or
%     white and will be reversed after every item.  Each module has the width
%     \cs{l_GS_module_wd_dim}.
%   \item \meta{dimension expression}, the height of the black modules. The
%     modules will be raised by \cs{l_GS_module_ht_dim}.
%   \item \meta{boolean variable}, \texttt{true} indicates, that the first
%     module should be black. With \texttt{false}, the first module will be
%     white.
%   \end{arguments}
% \end{function}
%
% \begin{function}{\__GS_modules_start_black:Nn}
%   \begin{syntax}
%     "\__GS_modules_start_black:Nn" \meta{sequence variable} \Arg{dimension expression}
%   \end{syntax}
%   Same like \cs{__GS_modules:NnN} \meta{sequence variable} \Arg{dimension
%   expression} \cs{c_true_bool}.
% \end{function}
%
% \begin{function}{\__GS_modules_start_white:Nn}
%   \begin{syntax}
%     "\__GS_modules_start_white:Nn" \meta{sequence variable} \Arg{dimension expression}
%   \end{syntax}
%   Same like \cs{__GS_modules:NnN} \meta{sequence variable} \Arg{dimension
%   expression} \cs{c_false_bool}.
% \end{function}
%
% \end{documentation}
%
% \begin{implementation}
%
% \section{\pkg{GS1} implementation}
% \label{sec:implementation}
%
%    \begin{macrocode}
%<@@=GS>
%    \end{macrocode}
%
% The implementation has been done in two parts.  The first part is the L3
% code with all the functions and variables.  The second part is the
% \LaTeXe{} lookalike user interface.
%
% But before this, we just declare, what this is:
%    \begin{macrocode}
%<*package>
\ProvidesExplPackage
  {\ExplFileName}{\ExplFileDate}{\ExplFileVersion}{\ExplFileDescription}
%    \end{macrocode}
% and what it requires:
%    \begin{macrocode}
\RequirePackage{rule-D}
%</package>
%    \end{macrocode}
%
% \subsection{Implementation of Functions and Variables}
% \label{sec:impl:functions.and.variables}
%
% \subsubsection{Constants}
% \label{sec:impl:constants}
%
% \begin{macro}{\__GS_new_seq_c:cn}
%   While this is an internal function, that should allow only some tokens at
%   the arguments, it is declared \texttt{nopar}.
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \@@_new_seq_c:cn #1#2
  {
    \seq_new:c {c@@_ #1 _seq}
    \seq_set_split:Nnn \l_tmpa_seq {} {#2}
    \seq_gset_eq:cN {c@@_ #1 _seq} \l_tmpa_seq
  }
%</package>
%    \end{macrocode}
% \end{macro}
%
% \begin{variable}{\c__GS_AB0_seq, \c__GS_AB1_seq, \c__GS_AB2_seq,
%   \c__GS_AB3_seq, \c__GS_AB4_seq, \c__GS_AB5_seq, \c__GS_AB6_seq,
%   \c__GS_AB7_seq, \c__GS_AB8_seq, \c__GS_AB9_seq}
%   These constants represent the generation rules of the left side of an EAN-13
%   barcode. See figure~5.2.1.3.1-1 of the GS1 specification.
%    \begin{macrocode}
%<*package>
\@@_new_seq_c:cn {AB0} {AAAAAA}
\@@_new_seq_c:cn {AB1} {AABABB}
\@@_new_seq_c:cn {AB2} {AABBAB}
\@@_new_seq_c:cn {AB3} {AABBBA}
\@@_new_seq_c:cn {AB4} {ABAABB}
\@@_new_seq_c:cn {AB5} {ABBAAB}
\@@_new_seq_c:cn {AB6} {ABBBAA}
\@@_new_seq_c:cn {AB7} {ABABAB}
\@@_new_seq_c:cn {AB8} {ABABBA}
\@@_new_seq_c:cn {AB9} {ABBABA}
%</package>
%    \end{macrocode}
% \end{variable}
%
% \begin{variable}{\c__GS_A0_seq, \c__GS_A1_seq, \c__GS_A2_seq, \c__GS_A3_seq,
%   \c__GS_A4_seq, \c__GS_A5_seq, \c__GS_A6_seq, \c__GS_A7_seq, \c__GS_A8_seq,
%   \c__GS_A9_seq, \c__GS_B0_seq, \c__GS_B1_seq, \c__GS_B2_seq, \c__GS_B3_seq,
%   \c__GS_B4_seq, \c__GS_B5_seq, \c__GS_B6_seq, \c__GS_B7_seq, \c__GS_B8_seq,
%   \c__GS_B9_seq, \c__GS_margin_seq, \c__GS_separator_seq, \c__GS_special_seq,
%   \c__GS_extra_margin_seq, \c__GS_extra_separator_seq}
%   These constants represent the module sequences of digits and markers. See
%   figure~5.2.1.2.1-1 and 5.2.1.2.2-1 of the GS1 specification. Note, that
%   the module sequences of type C are same like type A but start with a black
%   module instead of a white one.
%    \begin{macrocode}
%<*package>
\@@_new_seq_c:cn {A0} {3211} % start white (C0 same but start with black)
\@@_new_seq_c:cn {A1} {2221}
\@@_new_seq_c:cn {A2} {2122}
\@@_new_seq_c:cn {A3} {1411}
\@@_new_seq_c:cn {A4} {1132}
\@@_new_seq_c:cn {A5} {1231}
\@@_new_seq_c:cn {A6} {1114}
\@@_new_seq_c:cn {A7} {1312}
\@@_new_seq_c:cn {A8} {1213}
\@@_new_seq_c:cn {A9} {3112}
\@@_new_seq_c:cn {B0} {1123} % start white
\@@_new_seq_c:cn {B1} {1222}
\@@_new_seq_c:cn {B2} {2212}
\@@_new_seq_c:cn {B3} {1141}
\@@_new_seq_c:cn {B4} {2311}
\@@_new_seq_c:cn {B5} {1321}
\@@_new_seq_c:cn {B6} {4111}
\@@_new_seq_c:cn {B7} {2131}
\@@_new_seq_c:cn {B8} {3121}
\@@_new_seq_c:cn {B9} {2113}
\@@_new_seq_c:cn {margin}         {111} % start black
\@@_new_seq_c:cn {separator}    {11111} % start white
\@@_new_seq_c:cn {special}     {111111} % start white
\@@_new_seq_c:cn {extra_margin}   {112} % start black
\@@_new_seq_c:cn {extra_separator} {11} % start white
%</package>
%    \end{macrocode}
% \end{variable}
%
% There are some basic dimensions for the modules at the specification:
% \begin{variable}{\c__GS_module_min_width_dim, \c__GS_module_norm_width_dim}
%    \begin{macrocode}
%<*package>
\dim_const:Nn \c_@@_module_min_width_dim {0.264mm}
\dim_const:Nn \c_@@_module_norm_width_dim {0.33mm}
%</package>
%    \end{macrocode}
% \end{variable}
%
% \subsubsection{Settings and Variables}
% \label{seq:impl.settings}
%
% These settings will influence the work of several of the user functions.
% They are defined as keys of family \texttt{GS1}.
%
% \begin{variable}{ \l_GS_use_ocrb_bool, \l_GS_module_wd_dim,
%   \l_GS_module_ht_dim, \l_GS_scale_fp, \l_GS_scale_to_font_bool,
%   \l_GS_add_control_bool, \l_GS_code_type_tl, \l_GS_code_size_int }
% \begin{macro}{\__GS_set_key_code:nn}
%   Needed to set both \cmd{\l_GS_code_type_tl} and \cmd{\l_GS_code_size_int}
%   with one key.  Together they are the type of code, to be handled.
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \@@_set_key_code:nn #1#2
  {
    \tl_if_exist:NF \l_GS_code_type_tl { \tl_new:N \l_GS_code_type_tl }
    \tl_set:Nn \l_GS_code_type_tl { #1 }
    \int_if_exist:NF \l_GS_code_size_int { \int_new:N \l_GS_code_size_int }
    \int_set:Nn \l_GS_code_size_int { #2 }
  }
%    \end{macrocode}
% \end{macro}
%    \begin{macrocode}
\keys_define:nn { GS1 }
  {
    ocrb          .bool_set:N = \l_GS_use_ocrb_bool,
    ocrb          .initial:n  = true,
    module_width  .dim_set:N  = \l_GS_module_wd_dim,
    module_width  .initial:V  = \c_@@_module_norm_width_dim,
    module_height .dim_set:N  = \l_GS_module_ht_dim,
    module_height .initial:V  = \c_zero_dim,
    code          .choice:,
    code / EAN-8  .code:n = { \@@_set_key_code:nn { EAN } {  8 } },
    code / EAN8   .code:n = { \@@_set_key_code:nn { EAN } {  8 } },
    code / EAN-13 .code:n = { \@@_set_key_code:nn { EAN } { 13 } },
    code / EAN13  .code:n = { \@@_set_key_code:nn { EAN } { 13 } },
    code          .initial:n = EAN-13,
    scale         .fp_set:N   = \l_GS_scale_fp,
    scale         .initial:n  = 1.0,
    scale_to_font .bool_set:N = \l_GS_scale_to_font_bool,
    scale_to_font .initial:n  = false,
    add_control   .bool_set:N = \l_GS_add_control_bool,
    add_control   .initial:n  = false,
  }
%</package>
%    \end{macrocode}
% \end{variable}
%
% Note: Later I'll define a \LaTeXe{} command to change the defaults of those
% keys.  Additionally local changes of those keys may be done using the
% optional argument of the \LaTeXe{} user commands. See
% \autoref{sec:impl:user.interface} for more information.
%
% \begin{variable}{\l__GS_code_seq}
%   This will be used later for several local GS1 sequences.  It is private
%   and also shouldn't be used in global context.
%    \begin{macrocode}
%<*package>
\seq_new:N \l_@@_code_seq
%</package>
%    \end{macrocode}
% \end{variable}
%
% \subsubsection{Messages}
% \label{seq:impl.messages}
%
% We need a message for not supported lengths of EAN codes, because currently
% only EAN-8 and EAN-13 are supported, both with or without control
% digit. This message will be used as an error message.
%    \begin{macrocode}
%<*package>
\msg_new:nnnn { GS1 } { EAN-code-size }
  {
    #1~isn't~a~valid~EAN~code~\msg_line_context:.
  }
  {
    The~given~code~is~neither~a~EAN-8~with~or~without~control~digit,\\
    nor~a~EAN-13~with~or~without~control~digit.\\\\
    The~GS1~module~currently~only~supports~EAN-8~and~EAN~13.
  }
%</package>
%    \end{macrocode}
%
% Another message is only a warning message. It will be used whenever the used
% module width would be less than the minimum module width given by the GS1
% specification.
%    \begin{macrocode}
%<*package>
\msg_new:nnn { GS1 } { module/minwidth }
  {
    Resulting~module~width~is~less~than~allowed~minimum~\msg_line_context:.\\\\
    GS1~specification~declares~a~minimum~module~width~of~#2.\\
    Currently~the~module~with~would~be~#1.\\
    To~avoid~problems,~I'll~increase~module~width~to~#2.
  }
%</package>
%    \end{macrocode}
%
% \subsubsection{Functions}
% \label{seq:impl.functions}
%
% \begin{macro}{\GS_set_code_digit_seq:Nn}
%   Convert a string into a code sequence ignoring all but digits.
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \GS_set_code_digit_seq:Nn #1#2 
  {
    \seq_set_eq:NN #1 \c_empty_seq
    \tl_map_inline:nn 
      { #2 }
      {
        \tl_if_in:nnT
          {0123456789}
          {##1}
          {
            \seq_put_right:Nn #1 { ##1 }
          }
      }
  }
%</package>
%    \end{macrocode}
%
% \TestFiles{GS_set_code_digit.tex}\UnitTested
%    \begin{macrocode}
%<*test&GS.set.code.digit.seq>
\ExplSyntaxOn
\seq_new:N \l_testa_seq
\seq_new:N \l_testb_seq

\GS_set_code_digit_seq:Nn \l_testa_seq {ISBN 978-3-86541-459-5}
Sequence~for~ISBN~978-3-86541-459-5~is:~
\seq_use:Nnnn \l_testa_seq { ,~ } { ,~} { ,~ }

\GS_set_code_digit_seq:Nn \l_testb_seq {9783865414595}
\seq_map_inline:Nn \l_testa_seq
  {
    \seq_pop_left:NN \l_testb_seq \l_tmpa_tl
    \tl_set:Nn \l_tmpb_tl { #1 }
    \tl_if_eq:NNF \l_tmpa_tl \l_tmpb_tl
      { 
        \tl_show:N l_testa_seq
        \tl_show:N l_testb_seq
        \msg_fatal:nnn { GS1/test } { function } { \GS_set_code_digit_seq:Nn } 
      }
  }

\GS_set_code_digit_seq:Nn \l_testa_seq {ISBN 978-3-86541-459-5}
\seq_set_split:Nnn \l_testb_seq {,} {9,7,8,3,8,6,5,4,1,4,5,9,5}
\seq_map_inline:Nn \l_testa_seq
  {
    \seq_pop_left:NN \l_testb_seq \l_tmpa_tl
    \tl_set:Nn \l_tmpb_tl { #1 }
    \tl_if_eq:NNF \l_tmpa_tl \l_tmpb_tl
      { 
        \tl_show:N \l_testa_seq
        \tl_show:N \l_testb_seq
        \msg_fatal:nnn { GS1/test } { function } { \GS_set_code_digit_seq:Nn } 
      }
  }

\ExplSyntaxOff
%</test&GS.set.code.digit.seq>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}[updated = 2017-07-15]{\GS_cut_EAN_control_digit:N}
%   \changes{v18}{2017/07/15}{replaced removed \cs{int_case:nnn} by
%     \cs{int_case:nnF}}^^A
%   EAN code sequences with control digit are either 8 or 13 digits.  To
%   remove the control digit we just have to remove the right most digit from
%   a 8 or 13 digits sequence.  7 or 12 digit sequences are already without
%   control digit.  All other sequences are not supported.
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \GS_cut_EAN_control_digit:N #1 
  {
    \int_case:nnF 
      { \seq_count:N #1 }
      {
        {  7 } {  }
        {  8 } { \seq_pop_right:NN #1 \l_tempa_tl }
        { 12 } {  }
        { 13 } { \seq_pop_right:NN #1 \l_tempa_tl }
      }
      {
        \msg_error:nnn { GS1 } { EAN-code-size } { #1 } 
      }
  }
%</package>
%    \end{macrocode}
%
% \TestFiles{GS_cut_EAN_control_digit.tex}\UnitTested
%    \begin{macrocode}
%<*test&GS.cut.EAN.control.digit>
\raggedright
\ExplSyntaxOn
\seq_new:N \l_testa_seq
\GS_set_code_digit_seq:Nn \l_testa_seq {ISBN 978-3-86541-459-5}
With~control:~\seq_use:Nnnn \l_testa_seq { ,~ } { ,~} { ,~ }\\
\GS_set_code_digit_seq:Nn \l_testb_seq {ISBN 978-3-86541-459}
\GS_cut_EAN_control_digit:N \l_testa_seq
\seq_map_inline:Nn \l_testa_seq
  {
    \seq_pop_left:NN \l_testb_seq \l_tmpa_tl
    \tl_set:Nn \l_tmpb_tl { #1 }
    \tl_if_eq:NNF \l_tmpa_tl \l_tmpb_tl
      { 
        \tl_show:N \l_testa_seq
        \tl_show:N \l_testb_seq
        \msg_fatal:nnn { GS1/test } { function } 
          { \GS_cut_EAN_control_digit:N } 
      }
  }
Without~control:~\seq_use:Nnnn \l_testa_seq { ,~ } { ,~} { ,~ }\\
\ExplSyntaxOff
%</test&GS.cut.EAN.control.digit>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\int_set_to_EAN_control_digit:NN}
% Sets an integer to the control digit calculated with the EAN control digit
% algorithm for a given code sequence.  Note, that the complete code
% sequence will be used to calculate the control digit.  So, if you have a
% EAN-8 or EAN-13 code sequence, you should cut of the control digit first.
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \int_set_to_EAN_control_digit:NN #1#2
  {
    \int_zero:N #1
    \seq_set_eq:NN \l_tmpa_seq #2
    \bool_until_do:nn 
      { \seq_if_empty_p:N \l_tmpa_seq }
      {
        \seq_pop_left:NN \l_tmpa_seq \l_tmpb_tl
        \int_if_even:nTF 
          { \seq_count:N \l_tmpa_seq }
          { 
            \int_add:Nn #1 { 3 * \l_tmpb_tl }
          }
          { 
            \int_add:Nn #1 { \l_tmpb_tl } 
          }
      }
    \int_set:Nn #1 { \int_mod:nn { 10 - \int_mod:nn { #1 } { 10 } } { 10 } }
  }
%</package>
%    \end{macrocode}
%
% \TestFiles{int_set_to_EAN_control_digit.tex}\UnitTested
%    \begin{macrocode}
%<*test&int.set.to.EAN.control.digit>
\ExplSyntaxOn
\seq_new:N \l_testa_seq
\tl_new:N \l_control_tl
\GS_set_code_digit_seq:Nn \l_testa_seq {ISBN 978-3-86541-459-5}
\seq_pop_right:NN \l_testa_seq \l_control_tl
\int_new:N \l_control_int
\int_set_to_EAN_control_digit:NN \l_control_int \l_testa_seq
Control~digit~should~be~\tl_use:N \l_control_tl{} ~
\int_compare:nNnTF { \l_control_tl } { = } { \l_control_int }
  {
    ~and~is~\int_use:N \l_control_int .
  }
  {
    ~but~it~\int_use:N \l_control_int .
    \msg_error:nnn { GS1/test } { function } 
      { \int_set_to_EAN_control_digit:NN }
  }
\ExplSyntaxOff
%</test&int.set.to.EAN.control.digit>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\GS_set_EAN_control_digit:N}
%   Add a new control digit to a EAN sequence
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \GS_set_EAN_control_digit:N #1
  {
    \GS_cut_EAN_control_digit:N #1
    \int_set_to_EAN_control_digit:NN \l_tmpa_int #1
    \seq_put_right:NV #1 \l_tmpa_int
  }
%</package>
%    \end{macrocode}
%
% \TestFiles{GS_set_EAN_control_digit.tex}\UnitTested
%    \begin{macrocode}
%<*test&GS.set.EAN.control.digit>
\ExplSyntaxOn
\seq_new:N \l_testa_seq
\GS_set_code_digit_seq:Nn \l_testa_seq {ISBN 978-3-86541-459-5}
\seq_new:N \l_testb_tl
\seq_pop_right:NN \l_testa_seq \l_testb_tl
\GS_set_EAN_control_digit:N \l_testa_seq
\tl_new:N \l_testa_tl
\seq_get_right:NN \l_testa_seq \l_testa_tl
Control~digit~should~be~ \tl_use:N \l_testb_tl {} ~
\int_compare:nNnTF { \l_testa_tl } { = } { \l_testb_tl }
  {
    ~and~is~\tl_use:N \l_testa_tl .
  }
  {
    ~but~it~\tl_use:N \t_testa_tl .
    \msg_error:nnn { GS1/test } { function } { \GS_set_EAN_control_digit:N }
  }
\ExplSyntaxOff
%</test&GS.set.EAN.control.digit>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\__GS_modules:Nn, \__GS_modules:NnN, \__GS_modules:cn,
%   \__GS_modules_start_black:Nn, \__GS_modules_start_white:Nn} 
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \@@_modules:Nn #1#2
  {
    \seq_map_inline:Nn #1
      {
        \bool_if:NTF \l_@@_black_bool
          {
            \bool_set_false:N \l_@@_black_bool
            \hbox_set:Nn \l_tmpa_box { 0 }
            \rule:nnn
              { 
                \dim_eval:n 
                  { 
                    \box_ht:N \l_tmpa_box + \l_GS_module_wd_dim / 2
                    - \dim_eval:n { #2 } + \l_GS_module_ht_dim 
                  } 
              } 
              { \dim_eval:n { \l_GS_module_wd_dim * ##1 } }
              { \dim_eval:n { #2 } }
          }
          {
            \bool_set_true:N \l_@@_black_bool
            \hbox_to_wd:nn { \l_GS_module_wd_dim * ##1 } { }
          }
      }
  }

\cs_new_nopar:Npn \@@_modules:NnN #1#2#3
  {
    \bool_if_exist:NF \l_@@_black_bool { \bool_new:N \l_@@_black_bool }
    \bool_set_eq:NN \l_@@_black_bool #3
    \@@_modules:Nn #1 { #2 }
  }

\cs_new_nopar:Npn \@@_modules_start_black:Nn #1#2
  {
    \@@_modules:NnN #1 { #2 } \c_true_bool
  }

\cs_new_nopar:Npn \@@_modules_start_white:Nn #1#2
  {
    \@@_modules:NnN #1 { #2 } \c_false_bool
  }

\cs_generate_variant:Nn \@@_modules:Nn { c }
%</package>  
%    \end{macrocode}
% \TestFiles{EANBarcode.tex}\UnitTested
% \end{macro}
%
% \begin{macro}{\GS_use_as_EAN_barcode:N}
%   Puts the digits, rules, and gaps for an EAN barcode into the input
%   stream.
%    \begin{macrocode}
%<*package>
\cs_new_nopar:Npn \GS_use_as_EAN_barcode:N #1
  {
    \seq_set_eq:NN \l_@@_code_seq #1

    \int_compare:nNnTF { \l_GS_code_size_int } { = } { 8 } 
      { 
        \hbox_to_wd:nn { \l_GS_module_wd_dim * 7 } { }
        \seq_set_eq:Nc \l_GS_system_seq { c_@@_AB0_seq }
      }
      {
        \hbox_to_wd:nn { \l_GS_module_wd_dim * 11 } { }
        \seq_pop_left:NN \l_@@_code_seq \l_tmpa_tl
        \seq_set_eq:Nc \l_GS_system_seq { c_@@_AB \l_tmpa_tl _seq }
        \hbox_overlap_left:n { \l_tmpa_tl }
      }

    \@@_modules_start_black:Nn \c_@@_margin_seq 
      { \l_GS_module_ht_dim + \l_GS_module_wd_dim * 5 }

    \int_step_inline:nnnn { 1 } { 1 }
      { \int_div_truncate:nn { \l_GS_code_size_int } { 2 } }
      {
        \seq_pop_left:NN \l_@@_code_seq \l_tmpa_tl
        \hbox_overlap_right:n { \l_tmpa_tl }
        \seq_pop_left:NN \l_GS_system_seq \l_tmpb_tl
        \@@_modules:cn { c_@@_ \l_tmpb_tl \l_tmpa_tl _seq } 
          { \l_GS_module_ht_dim }
      }
    
    \@@_modules_start_white:Nn \c_@@_separator_seq 
      { \l_GS_module_ht_dim + \l_GS_module_wd_dim * 5 }

    \int_step_inline:nnnn { 1 } { 1 }
      { \int_div_truncate:nn { \l_GS_code_size_int } { 2 } }
      {
        \seq_pop_left:NN \l_@@_code_seq \l_tmpa_tl
        \hbox_overlap_right:n { \l_tmpa_tl }
        \@@_modules:cn { c_@@_A \l_tmpa_tl _seq } 
          { \l_GS_module_ht_dim }
      }

    \@@_modules_start_black:Nn \c__GS_margin_seq 
      { \l_GS_module_ht_dim + \l_GS_module_wd_dim * 5 }

    \hbox_to_wd:nn { \l_GS_module_wd_dim * 7 } { }
  }
%</package>
%    \end{macrocode}
% \TestFiles{EANBarcode.tex}\UnitTested
% \end{macro}
%
%
% \subsection{Implementation of the User Interface}
% \label{sec:impl:user.interface}
%
% For this, additional packages are needed:
%    \begin{macrocode}
%<*package>
\RequirePackage{xparse}
%    \end{macrocode}
%
% \begin{macro}{\EANControlDigit}
%    \begin{macrocode}
\NewDocumentCommand \EANControlDigit
  { m }
  {
    \group_begin:
      \GS_set_code_digit_seq:Nn \l_@@_code_seq { #1 }
      \GS_cut_EAN_control_digit:N \l_@@_code_seq
      \int_set_to_EAN_control_digit:NN \l_tmpa_int \l_@@_code_seq
      \int_to_arabic:n { \l_tmpa_int }
    \group_end:
  }
%</package>
%    \end{macrocode}
% \TestFiles{EANControlDigit.tex}\UnitTested
%
%    \begin{macrocode}
%<*test&EANControlDigit>
\begin{tabular}{ll}
  \hline
  Calculated & Known \\
  \hline
  501234567890-\EANControlDigit{501234567890} & 501234567890-0 \\
  ISBN 978-3-86541-459-\EANControlDigit{ISBN 978-3-86541-459} & ISBN
  978-3-86541-459-5 \\
  EAN-8: 2012345\EANControlDigit{2012345} & EAN-8: 20123451 \\
  \hline
\end{tabular}
%</test&EANControlDigit>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\EANBarcode}
%    \begin{macrocode}
%<*package>
\NewDocumentCommand \EANBarcode
  { o m }
  {
    \group_begin:
      \IfNoValueF{#1}{ \keys_set:nn { GS1 } { #1 } }
      \dim_compare:nNnT { \l_GS_module_ht_dim } { = } { \c_zero_dim }
        {
          \int_compare:nNnTF { \l_GS_code_size_int } { = } { 8 }
            { \dim_set:Nn \l_GS_module_ht_dim { 21.31 mm } }
            { \dim_set:Nn \l_GS_module_ht_dim { 25.01 mm } }
        }
      \bool_if:nT \l_GS_use_ocrb_bool
        {
%    \end{macrocode}
% \textsc{ToDo:} Use \pkg{fontspec} if available.
%    \begin{macrocode}
          \usefont{OT1}{ocrb}{m}{n}\fontsize{9}{9}\selectfont
        }

      \GS_set_code_digit_seq:Nn \l_@@_code_seq { #2 }

      \bool_if:NT \l_GS_add_control_bool
        {
          \GS_set_EAN_control_digit:N \l_@@_code_seq
        }

      \int_compare:nNnT
        { \seq_count:N \l__GS_code_seq } 
        { > } 
        { \l_GS_code_size_int }
        {
          \msg_error:nnn { GS1 } { EAN-code-size } { #2 }
        }
      \int_while_do:nNnn 
        { \seq_count:N \l_@@_code_seq }
        { < }
        { \l_GS_code_size_int }
        {
          \seq_put_left:Nn \l_@@_code_seq { 0 }
        }

      \bool_if:NT \l_GS_scale_to_font_bool {
        \hbox_set:Nn \l_tmpa_box { 0 }
        \dim_set:Nn \l_GS_module_wd_dim { \box_wd:N \l_tmpa_box / 7 }
      }

     \dim_set:Nn \l_tmpa_dim
       { \fp_to_decimal:N \l_GS_scale_fp \l_GS_module_wd_dim }

     \dim_compare:nNnT 
        { \l_tmpa_dim }
        { < } 
        { \c_@@_module_min_width_dim }
        {
          \msg_warning:nnxx { GS1 } { module/minwidth } 
            { \dim_use:N \l_GS_module_wd_dim }
            { \dim_use:N \c_@@_module_min_width_dim }
          \dim_set:Nn \l_GS_module_wd_dim 
          {
            \c_@@_module_min_width_dim * 
            100 / \fp_to_int:n { 100 * \l_GS_scale_fp }
          }
        }

      \hbox_set:Nn \l_tmpa_box { \GS_use_as_EAN_barcode:N \l_@@_code_seq }
      \box_scale:Nnn \l_tmpa_box
        { \fp_to_int:n { 100 * \l_GS_scale_fp } / 100 }
        { \fp_to_int:n { 100 * \l_GS_scale_fp } / 100 }
      \box_use:N \l_tmpa_box
    \group_end:
  }
%</package>
%    \end{macrocode}
% \TestFiles{EANBarcode.tex}\UnitTested
%
%    \begin{macrocode}
%<*test&EANBarcode|GSSetup>
\raggedright
\verb|\EANBarcode{ISBN 978-3-86541-459-5}|: 
      \EANBarcode{ISBN 978-3-86541-459-5}

\verb|\EANBarcode[add_control]{ISBN 978-3-86541-459-}|:
      \EANBarcode[add_control]{ISBN 978-3-86541-459-}

\verb|\EANBarcode[ocrb=false]{ISBN 978-3-86541-459-5}|:
\EANBarcode[ocrb=false]{ISBN 978-3-86541-459-5}

\verb|\EANBarcode[code=EAN-8]{20123451}|:
      \EANBarcode[code=EAN-8]{20123451}

\verb|\EANBarcode[code=EAN-8,ocrb=false,add_control]{2012345}|:
      \EANBarcode[code=EAN-8,ocrb=false,add_control]{2012345}

%</test&EANBarcode|GSSetup>
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\GSSetup}
%    \begin{macrocode}
%<*package>
\NewDocumentCommand \GSSetup
  { m }
  { \keys_set:nn { GS1 } { #1 } }
%</package>
%    \end{macrocode}
%
% \TestFiles{GSSetup.tex}\UnitTested
%    \begin{macrocode}
%<*test&GSSetup>
After \verb|\GSSetup{ocrb=false,add_control}|:
            \GSSetup{ocrb=false,add_control}

\verb|\EANBarcode[code=EAN-8]{2012345}|:
      \EANBarcode[code=EAN-8]{2012345}

\verb|\EANBarcode[code=EAN-8,ocrb,add_control=false]{20123451}|:
      \EANBarcode[code=EAN-8,ocrb,add_control=false]{20123451}

%</test&GSSetup>
%    \end{macrocode}
% \end{macro}
%
% \iffalse
%<*test>
\end{document}
%</test>
% \fi
% \end{implementation}
%
% \PrintIndex
%
\endinput
%
% end of file

% \endinput
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