out_display.hxx

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// out_display.hxx: this file is part of the Vaucanson project.
//
// Vaucanson, a generic library for finite state machines.
//
// Copyright (C) 2005, 2006, 2007, 2011 The Vaucanson Group.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// The complete GNU General Public Licence Notice can be found as the
// `COPYING' file in the root directory.
//
// The Vaucanson Group consists of people listed in the `AUTHORS' file.
//

#ifndef VCSN_TOOLS_OUT_DISPLAY_HXX
# define VCSN_TOOLS_OUT_DISPLAY_HXX

# include <vaucanson/tools/out_display.hh>
# include <sys/types.h>
# include <sys/wait.h>
# include <unistd.h>

namespace vcsn {

  namespace tools {

    template <class S, class T>
    bool
    out_display(const AutomataBase<S>&,
                const T&,
                const Element<S, T>& a,
                const std::string& name,
                const bool bg,
                const char *const argv[],
                void (*function)(std::ostream& o,
                                 const Element<S, T>& a,
                                 const std::string& name))

    {
      int filedes[2];
      if (pipe(filedes))
        return false;

      pid_t child_pid = fork();
      if (child_pid)
        {
          close(filedes[0]);
          if (child_pid == -1)
            {
              close(filedes[1]);
              return false;
            }
          else
            {
              // FIXME: That trick is dirty!
              {
                std::cout.flush();
                int old = dup(STDOUT_FILENO);
                if (old != -1)
                  dup2(filedes[1], STDOUT_FILENO);
                close(filedes[1]);

                function(std::cout, a, name);

                if (old != -1)
                  {
                    dup2(old, STDOUT_FILENO);
                    close(old);
                  }
              }
              return bg or waitpid(child_pid, NULL, 0) == child_pid;
            }
        }
      else
        {
          close(filedes[1]);
          dup2(filedes[0], STDIN_FILENO);
          close(filedes[0]);
          // execvp will treat its second argument as if it was
          // "const char* const*".  See the following page for an
          // explanation of why it is only declared as "char* const*".
          // http://www.opengroup.org/onlinepubs/000095399/functions/exec.html
          execvp(argv[0], const_cast<char *const *>(argv));
          std::cerr << "Failed to execute `" << argv[0] << "'." << std::endl;
          exit(1);
        }
    }

  } // End of namespace tools.

} // End of namespace vcsn.

#endif // ! VCSN_TOOLS_OUT_DISPLAY_HXX