load-path.cc

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/*

  Copyright (C) 2006-2018 John W. Eaton
  Copyright (C) 2010 VZLU Prague

  This file is part of Octave.

  Octave 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 3 of the License, or
  (at your option) any later version.

  Octave is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with Octave; see the file COPYING.  If not, see
  <https://www.gnu.org/licenses/>.

*/

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include <algorithm>

#include "dir-ops.h"
#include "file-ops.h"
#include "file-stat.h"
#include "oct-env.h"
#include "pathsearch.h"

#include "defaults.h"
#include "defun.h"
#include "input.h"
#include "interpreter-private.h"
#include "interpreter.h"
#include "load-path.h"
#include "ov-usr-fcn.h"
#include "pager.h"
#include "parse.h"
#include "unwind-prot.h"
#include "utils.h"

static void
maybe_add_path_elts (std::string& path, const std::string& dir)
{
  std::string tpath = octave::genpath (dir);

  if (! tpath.empty ())
    {
      if (path.empty ())
        path = tpath;
      else
        path += octave::directory_path::path_sep_str () + tpath;
    }
}

static std::list<std::string>
split_path (const std::string& p)
{
  std::list<std::string> retval;

  size_t beg = 0;
  size_t end = p.find (octave::directory_path::path_sep_char ());

  size_t len = p.length ();

  while (end != std::string::npos)
    {
      std::string elt = p.substr (beg, end-beg);

      if (! elt.empty ())
        retval.push_back (elt);

      beg = end + 1;

      if (beg == len)
        break;

      end = p.find (octave::directory_path::path_sep_char (), beg);
    }

  std::string elt = p.substr (beg);

  if (! elt.empty ())
    retval.push_back (elt);

  return retval;
}

// Strip trailing directory separators.

static std::string
strip_trailing_separators (const std::string& dir_arg)
{
  std::string dir = dir_arg;

  size_t k = dir.length ();

  while (k > 1 && octave::sys::file_ops::is_dir_sep (dir[k-1]))
    k--;

  if (k < dir.length ())
    dir.resize (k);

  return dir;
}

// Should we cache all files in private directories, or is it OK to just
// look them up each time as needed?

static std::string
find_private_file (const std::string& fname)
{
  std::string retval;

  // Look in private directory corresponding to current function (if
  // any).

  octave::symbol_scope scope = octave::__get_current_scope__ ("find_private_file");

  octave_user_function *curr_fcn = scope ? scope.function () : nullptr;

  if (curr_fcn)
    {
      // Even for private functions, dir_name doesn't contain the
      // "private" directory component so we append it here in all
      // cases.

      std::string dir_name = curr_fcn->dir_name ();

      if (! dir_name.empty ())
        {
          std::string pfname = dir_name + octave::sys::file_ops::dir_sep_str ()
                               + "private" + octave::sys::file_ops::dir_sep_str () + fname;

          octave::sys::file_stat fs (pfname);

          if (fs.exists () && fs.is_reg ())
            retval = pfname;
        }
    }

  return retval;
}

static void
execute_pkg_add_or_del (const std::string& dir,
                        const std::string& script_file)
{
  if (! octave_interpreter_ready)
    return;

  octave::unwind_protect frame;

  std::string file = octave::sys::file_ops::concat (dir, script_file);

  octave::sys::file_stat fs (file);

  if (fs.exists ())
    octave::source_file (file, "base");
}

// True if a path is contained in a path list separated by path_sep_char

static bool
in_path_list (const std::string& path_list, const std::string& path)
{
  size_t ps = path.size ();
  size_t pls = path_list.size ();
  size_t pos = path_list.find (path);
  char psc = octave::directory_path::path_sep_char ();
  while (pos != std::string::npos)
    {
      if ((pos == 0 || path_list[pos-1] == psc)
          && (pos + ps == pls || path_list[pos + ps] == psc))
        return true;
      else
        pos = path_list.find (path, pos + 1);
    }

  return false;
}

static void
rehash_internal (void)
{
  octave::load_path& lp = octave::__get_load_path__ ("rehash_internal");

  lp.update ();

  // FIXME: maybe we should rename this variable since it is being
  // used for more than keeping track of the prompt time.

  // This will force updated functions to be found.
  Vlast_prompt_time.stamp ();
}

namespace octave
{
  std::string load_path::sys_path;
  load_path::abs_dir_cache_type load_path::abs_dir_cache;

  void
  load_path::initialize (bool set_initial_path)
  {
    sys_path = "";

    if (set_initial_path)
      {
        maybe_add_path_elts (sys_path, config::local_ver_oct_file_dir ());
        maybe_add_path_elts (sys_path, config::local_api_oct_file_dir ());
        maybe_add_path_elts (sys_path, config::local_oct_file_dir ());
        maybe_add_path_elts (sys_path, config::local_ver_fcn_file_dir ());
        maybe_add_path_elts (sys_path, config::local_api_fcn_file_dir ());
        maybe_add_path_elts (sys_path, config::local_fcn_file_dir ());
        maybe_add_path_elts (sys_path, config::oct_file_dir ());
        maybe_add_path_elts (sys_path, config::fcn_file_dir ());
        maybe_add_path_elts (sys_path, config::oct_data_dir ());
      }

    std::string tpath = load_path::m_command_line_path;

    if (tpath.empty ())
      tpath = sys::env::getenv ("OCTAVE_PATH");

    std::string xpath;

    if (! tpath.empty ())
      {
        xpath = tpath;

        if (! sys_path.empty ())
          xpath += directory_path::path_sep_str () + sys_path;
      }
    else
      xpath = sys_path;

    set (xpath, false, true);
  }

  void
  load_path::clear (void)
  {
    dir_info_list.clear ();

    top_level_package.clear ();

    package_map.clear ();
  }

  void
  load_path::set (const std::string& p, bool warn, bool is_init)
  {
    // Use a list when we need to preserve order.
    std::list<std::string> elts = split_path (p);

    // Use a set when we need to search and order is not important.
    std::set<std::string> elts_set (elts.begin (), elts.end ());

    if (is_init)
      init_dirs = elts_set;
    else
      {
        for (const auto& init_dir : init_dirs)
          {
            if (elts_set.find (init_dir) == elts_set.end ())
              {
                warning_with_id ("Octave:remove-init-dir",
                                 "default load path altered.  Some built-in functions may not be found.  Try restoredefaultpath() to recover it.");
                break;
              }
          }
      }

    // Temporarily disable add hook.

    unwind_protect frame;
    frame.protect_var (add_hook);

    add_hook = nullptr;

    clear ();

    for (const auto& elt : elts)
      append (elt, warn);

    // Restore add hook and execute for all newly added directories.
    frame.run_first ();

    // FIXME: Shouldn't the test for add_hook be outside the for loop?
    //        Why not use const here?  Does add_hook change dir_info_list?
    for (auto& di : dir_info_list)
      {
        if (add_hook)
          add_hook (di.dir_name);
      }

    // Always prepend current directory.
    prepend (".", warn);
  }

  void
  load_path::append (const std::string& dir, bool warn)
  {
    if (! dir.empty ())
      add (dir, true, warn);
  }

  void
  load_path::prepend (const std::string& dir, bool warn)
  {
    if (! dir.empty ())
      add (dir, false, warn);
  }

  bool
  load_path::remove (const std::string& dir_arg)
  {
    bool retval = false;

    if (! dir_arg.empty ())
      {
        if (dir_arg == ".")
          {
            warning (R"(rmpath: can't remove "." from path)");

            // Avoid additional warnings.
            retval = true;
          }
        else
          {
            std::string dir = sys::file_ops::tilde_expand (dir_arg);

            dir = strip_trailing_separators (dir);

            dir_info_list_iterator i = find_dir_info (dir);

            if (i != dir_info_list.end ())
              {
                retval = true;

                if (remove_hook)
                  remove_hook (dir);

                dir_info& di = *i;

                remove (di);

                dir_info_list.erase (i);
              }
          }
      }

    return retval;
  }

  void
  load_path::update (void) const
  {
    // I don't see a better way to do this because we need to
    // preserve the correct directory ordering for new files that
    // have appeared.

    top_level_package.clear ();

    package_map.clear ();

    for (auto& di : dir_info_list)
      {
        di.update ();

        add (di, true, "", true);
      }
  }

  bool
  load_path::contains_canonical (const std::string& dir) const
  {
    bool retval = false;

    for (const auto& d : dir_info_list)
      {
        if (same_file (dir, d.dir_name))
          {
            retval = true;
            break;
          }
      }

    return retval;
  }

  std::list<std::string>
  load_path::overloads (const std::string& meth) const
  {
    std::list<std::string> retval;

    //  update ();

    top_level_package.overloads (meth, retval);

    for (const auto& nm_ldr : package_map)
      nm_ldr.second.overloads (meth, retval);

    return retval;
  }

  std::list<std::string>
  load_path::get_all_package_names (bool only_top_level) const
  {
    std::list<std::string> retval;

    for (const auto& dir_ldr : package_map)
      {
        if (! only_top_level || dir_ldr.first.find ('.') == std::string::npos)
          retval.push_back (dir_ldr.first);
      }

    return retval;
  }

  std::string
  load_path::find_file (const std::string& file) const
  {
    std::string retval;

    if (sys::env::absolute_pathname (file)
        || sys::env::rooted_relative_pathname (file))
      {
        sys::file_stat fs (file);

        return fs.exists () ? file : retval;
      }
    else
      {
        std::string tfile = find_private_file (file);

        if (! tfile.empty ())
          return tfile;
      }

    if (file.find_first_of (sys::file_ops::dir_sep_chars ())
        != std::string::npos)
      {
        // Given name has a directory separator, so append it to each
        // element of the load path in turn.
        for (const auto& di : dir_info_list)
          {
            std::string tfile = sys::file_ops::concat (di.dir_name, file);

            sys::file_stat fs (tfile);

            if (fs.exists ())
              return tfile;
          }
      }
    else
      {
        // Look in cache.
        for (const auto & di : dir_info_list)
          {
            string_vector all_files = di.all_files;

            octave_idx_type len = all_files.numel ();

            for (octave_idx_type i = 0; i < len; i++)
              {
                if (all_files[i] == file)
                  return sys::file_ops::concat (di.dir_name, file);
              }
          }
      }

    return retval;
  }

  std::string
  load_path::find_dir (const std::string& dir) const
  {
    std::string retval;

    if (dir.find_first_of (sys::file_ops::dir_sep_chars ()) != std::string::npos
        && (sys::env::absolute_pathname (dir)
            || sys::env::rooted_relative_pathname (dir)))
      {
        sys::file_stat fs (dir);

        if (fs.exists () && fs.is_dir ())
          return dir;
      }
    else
      {
        for (const auto& di : dir_info_list)
          {
            std::string dname = sys::env::make_absolute (di.dir_name);

            size_t dname_len = dname.length ();

            if (dname.substr (dname_len - 1)
                == sys::file_ops::dir_sep_str ())
              {
                dname = dname.substr (0, dname_len - 1);
                dname_len--;
              }

            size_t dir_len = dir.length ();

            if (dname_len > dir_len
                && sys::file_ops::is_dir_sep (dname[dname_len - dir_len - 1])
                && dir == dname.substr (dname_len - dir_len))
              {
                sys::file_stat fs (di.dir_name);

                if (fs.exists () && fs.is_dir ())
                  return di.dir_name;
              }
          }
      }

    return retval;
  }

  string_vector
  load_path::find_matching_dirs (const std::string& dir) const
  {
    std::list<std::string> retlist;

    if (dir.find_first_of (sys::file_ops::dir_sep_chars ()) != std::string::npos
        && (sys::env::absolute_pathname (dir)
            || sys::env::rooted_relative_pathname (dir)))
      {
        sys::file_stat fs (dir);

        if (fs.exists () && fs.is_dir ())
          retlist.push_back (dir);
      }
    else
      {
        for (const auto& di : dir_info_list)
          {
            std::string dname = sys::env::make_absolute (di.dir_name);

            size_t dname_len = dname.length ();

            if (dname.substr (dname_len - 1)
                == sys::file_ops::dir_sep_str ())
              {
                dname = dname.substr (0, dname_len - 1);
                dname_len--;
              }

            size_t dir_len = dir.length ();

            if (dname_len > dir_len
                && sys::file_ops::is_dir_sep (dname[dname_len - dir_len - 1])
                && dir == dname.substr (dname_len - dir_len))
              {
                sys::file_stat fs (di.dir_name);

                if (fs.exists () && fs.is_dir ())
                  retlist.push_back (di.dir_name);
              }
          }
      }

    return retlist;
  }

  std::string
  load_path::find_first_of (const string_vector& flist) const
  {
    std::string retval;

    std::string dir_name;
    std::string file_name;

    octave_idx_type flen = flist.numel ();
    octave_idx_type rel_flen = 0;

    string_vector rel_flist (flen);

    for (octave_idx_type i = 0; i < flen; i++)
      {
        std::string file = flist[i];

        if (file.find_first_of (sys::file_ops::dir_sep_chars ())
            != std::string::npos)
          {
            if (sys::env::absolute_pathname (file)
                || sys::env::rooted_relative_pathname (file))
              {
                sys::file_stat fs (file);

                if (fs.exists ())
                  return file;
              }
            else
              {
                for (const auto& di : dir_info_list)
                  {
                    std::string tfile;
                    tfile = sys::file_ops::concat (di.dir_name, file);

                    sys::file_stat fs (tfile);

                    if (fs.exists ())
                      return tfile;
                  }
              }
          }
        else
          rel_flist[rel_flen++] = file;
      }

    rel_flist.resize (rel_flen);

    for (const auto& di : dir_info_list)
      {
        string_vector all_files = di.all_files;

        octave_idx_type len = all_files.numel ();

        for (octave_idx_type i = 0; i < len; i++)
          {
            for (octave_idx_type j = 0; j < rel_flen; j++)
              {
                if (all_files[i] == rel_flist[j])
                  {
                    dir_name = di.dir_name;
                    file_name = rel_flist[j];

                    goto done;
                  }
              }
          }
      }

  done:

    if (! dir_name.empty ())
      retval = sys::file_ops::concat (dir_name, file_name);

    return retval;
  }

  string_vector
  load_path::find_all_first_of (const string_vector& flist) const
  {
    std::list<std::string> retlist;

    std::string dir_name;
    std::string file_name;

    octave_idx_type flen = flist.numel ();
    octave_idx_type rel_flen = 0;

    string_vector rel_flist (flen);

    for (octave_idx_type i = 0; i < flen; i++)
      {
        std::string file = flist[i];

        if (file.find_first_of (sys::file_ops::dir_sep_chars ())
            != std::string::npos)
          {
            if (sys::env::absolute_pathname (file)
                || sys::env::rooted_relative_pathname (file))
              {
                sys::file_stat fs (file);

                if (fs.exists ())
                  retlist.push_back (file);
              }
            else
              {
                for (const auto& di : dir_info_list)
                  {
                    std::string tfile;
                    tfile = sys::file_ops::concat (di.dir_name, file);

                    sys::file_stat fs (tfile);

                    if (fs.exists ())
                      retlist.push_back (tfile);
                  }
              }
          }
        else
          rel_flist[rel_flen++] = file;
      }

    rel_flist.resize (rel_flen);

    for (const auto& di : dir_info_list)
      {
        string_vector all_files = di.all_files;

        octave_idx_type len = all_files.numel ();

        for (octave_idx_type i = 0; i < len; i++)
          {
            for (octave_idx_type j = 0; j < rel_flen; j++)
              {
                if (all_files[i] == rel_flist[j])
                  retlist.push_back (sys::file_ops::concat (di.dir_name,
                                                            rel_flist[j]));
              }
          }
      }

    return retlist;
  }

  string_vector
  load_path::dirs (void) const
  {
    size_t len = dir_info_list.size ();

    string_vector retval (len);

    octave_idx_type k = 0;

    for (const auto& di : dir_info_list)
      retval[k++] = di.dir_name;

    return retval;
  }

  std::list<std::string>
  load_path::dir_list (void) const
  {
    std::list<std::string> retval;

    for (const auto& di : dir_info_list)
      retval.push_back (di.dir_name);

    return retval;
  }

  string_vector
  load_path::files (const std::string& dir, bool omit_exts) const
  {
    string_vector retval;

    const_dir_info_list_iterator p = find_dir_info (dir);

    if (p != dir_info_list.end ())
      retval = p->fcn_files;

    if (omit_exts)
      {
        octave_idx_type len = retval.numel ();

        for (octave_idx_type i = 0; i < len; i++)
          {
            std::string fname = retval[i];

            size_t pos = fname.rfind ('.');

            if (pos != std::string::npos)
              retval[i] = fname.substr (0, pos);
          }
      }

    return retval;
  }

  string_vector
  load_path::fcn_names (void) const
  {
    return top_level_package.fcn_names ();
  }

  std::string
  load_path::path (void) const
  {
    std::string xpath;

    string_vector xdirs = load_path::dirs ();

    octave_idx_type len = xdirs.numel ();

    if (len > 0)
      xpath = xdirs[0];

    for (octave_idx_type i = 1; i < len; i++)
      xpath += directory_path::path_sep_str () + xdirs[i];

    return xpath;
  }

  void
  load_path::display (std::ostream& os) const
  {
    for (const auto& di : dir_info_list)
      {
        string_vector fcn_files = di.fcn_files;

        if (! fcn_files.empty ())
          {
            os << "\n*** function files in " << di.dir_name << ":\n\n";

            fcn_files.list_in_columns (os);
          }

        const dir_info::method_file_map_type& method_file_map
          = di.method_file_map;

        if (! method_file_map.empty ())
          {
            for (const auto& cls_ci : method_file_map)
              {
                os << "\n*** methods in " << di.dir_name
                   << "/@" << cls_ci.first << ":\n\n";

                const dir_info::class_info& ci = cls_ci.second;

                string_vector method_files = get_file_list (ci.method_file_map);

                method_files.list_in_columns (os);
              }
          }
      }

    top_level_package.display (os);

    for (const auto& nm_ldr : package_map)
      nm_ldr.second.display (os);
  }

  void
  load_path::execute_pkg_add (const std::string& dir)
  {
    execute_pkg_add_or_del (dir, "PKG_ADD");
  }

  void
  load_path::execute_pkg_del (const std::string& dir)
  {
    execute_pkg_add_or_del (dir, "PKG_DEL");
  }

  // FIXME: maybe we should also maintain a map to speed up this method of access.

  load_path::const_dir_info_list_iterator
  load_path::find_dir_info (const std::string& dir_arg) const
  {
    std::string dir = sys::file_ops::tilde_expand (dir_arg);

    const_dir_info_list_iterator retval = dir_info_list.begin ();

    while (retval != dir_info_list.end ())
      {
        if (retval->dir_name == dir)
          break;

        retval++;
      }

    return retval;
  }

  load_path::dir_info_list_iterator
  load_path::find_dir_info (const std::string& dir_arg)
  {
    std::string dir = sys::file_ops::tilde_expand (dir_arg);

    dir_info_list_iterator retval = dir_info_list.begin ();

    while (retval != dir_info_list.end ())
      {
        if (retval->dir_name == dir)
          break;

        retval++;
      }

    return retval;
  }

  bool
  load_path::contains (const std::string& dir) const
  {
    return find_dir_info (dir) != dir_info_list.end ();
  }

  void
  load_path::move (dir_info_list_iterator i, bool at_end)
  {
    if (dir_info_list.size () > 1)
      {
        dir_info di = *i;

        dir_info_list.erase (i);

        if (at_end)
          dir_info_list.push_back (di);
        else
          dir_info_list.push_front (di);

        move (di, at_end);
      }
  }

  void
  load_path::move (const dir_info& di, bool at_end, const std::string& pname)
  {
    package_info& l = get_package (pname);

    l.move (di, at_end);

    dir_info::package_dir_map_type package_dir_map = di.package_dir_map;

    for (const auto& pkg_di : package_dir_map)
      {
        std::string full_name = pkg_di.first;

        if (! pname.empty ())
          full_name = pname + '.' + full_name;

        move (pkg_di.second, at_end, full_name);
      }
  }

  void
  load_path::add (const std::string& dir_arg, bool at_end, bool warn)
  {
    size_t len = dir_arg.length ();

    if (len > 1 && dir_arg.substr (len-2) == "//")
      warning_with_id ("Octave:recursive-path-search",
                       "trailing '//' is no longer special in search path elements");

    std::string dir = sys::file_ops::tilde_expand (dir_arg);

    dir = strip_trailing_separators (dir);

    dir_info_list_iterator i = find_dir_info (dir);

    if (i != dir_info_list.end ())
      move (i, at_end);
    else
      {
        sys::file_stat fs (dir);

        if (fs)
          {
            if (fs.is_dir ())
              {
                dir_info di (dir);

                if (at_end)
                  dir_info_list.push_back (di);
                else
                  dir_info_list.push_front (di);

                add (di, at_end);

                if (add_hook)
                  add_hook (dir);
              }
            else if (warn)
              warning ("addpath: %s: not a directory", dir_arg.c_str ());
          }
        else if (warn)
          {
            std::string msg = fs.error ();
            warning ("addpath: %s: %s", dir_arg.c_str (), msg.c_str ());
          }
      }

    // FIXME: is there a better way to do this?

    i = find_dir_info (".");

    if (i != dir_info_list.end ())
      move (i, false);
  }

  void
  load_path::remove (const dir_info& di, const std::string& pname)
  {
    package_info& l = get_package (pname);

    l.remove (di);

    dir_info::package_dir_map_type package_dir_map = di.package_dir_map;

    for (const auto& pkg_di : package_dir_map)
      {
        std::string full_name = pkg_di.first;

        if (! pname.empty ())
          full_name = pname + '.' + full_name;

        remove (pkg_di.second, full_name);
      }
  }

  bool
  load_path::is_package (const std::string& name) const
  {
    for (const auto& di : dir_info_list)
      {
        if (di.is_package (name))
          return true;
      }

    return false;
  }

  void
  load_path::add (const dir_info& di, bool at_end,
                  const std::string& pname, bool updating) const
  {
    package_info& l = get_package (pname);

    l.add (di, at_end, updating);

    dir_info::package_dir_map_type package_dir_map = di.package_dir_map;

    for (const auto& pkg_di : package_dir_map)
      {
        std::string full_name = pkg_di.first;

        if (! pname.empty ())
          full_name = pname + '.' + full_name;

        add (pkg_di.second, at_end, full_name);
      }
  }

  string_vector
  load_path::get_file_list (const load_path::dir_info::fcn_file_map_type& lst) const
  {
    octave_idx_type n = lst.size ();

    string_vector retval (n);

    octave_idx_type count = 0;

    for (const auto& nm_typ : lst)
      {
        std::string nm = nm_typ.first;

        int types = nm_typ.second;

        if (types & load_path::OCT_FILE)
          nm += ".oct";
        else if (types & load_path::MEX_FILE)
          nm += ".mex";
        else
          nm += ".m";

        retval[count++] = nm;
      }

    return retval;
  }

  load_path::dir_info::fcn_file_map_type
  get_fcn_files (const std::string& d)
  {
    load_path::dir_info::fcn_file_map_type retval;

    sys::dir_entry dir (d);

    if (dir)
      {
        string_vector flist = dir.read ();

        octave_idx_type len = flist.numel ();

        for (octave_idx_type i = 0; i < len; i++)
          {
            std::string fname = flist[i];

            size_t pos = fname.rfind ('.');

            if (pos != std::string::npos)
              {
                std::string base = fname.substr (0, pos);
                std::string ext = fname.substr (pos);

                if (valid_identifier (base))
                  {
                    int t = 0;

                    if (ext == ".m")
                      t = load_path::M_FILE;
                    else if (ext == ".oct")
                      t = load_path::OCT_FILE;
                    else if (ext == ".mex")
                      t = load_path::MEX_FILE;

                    if (t)
                      {
                        load_path::dir_info::fcn_file_map_iterator p
                          = retval.find (base);

                        if (p == retval.end ())
                          retval[base] = t;
                        else
                          p->second |= t;
                      }
                  }
              }
          }
      }
    else
      {
        std::string msg = dir.error ();
        warning ("load_path: %s: %s", d.c_str (), msg.c_str ());
      }

    return retval;
  }

  void
  load_path::dir_info::update (void)
  {
    sys::file_stat fs (dir_name);

    sys::file_stat pfs (sys::file_ops::concat (dir_name, "private"));
    bool has_private_dir = pfs && pfs.is_dir ();

    if (! fs)
      {
        std::string msg = fs.error ();
        warning ("load_path: %s: %s", dir_name.c_str (), msg.c_str ());
      }
    else
      {
        if (is_relative)
          {
            try
              {
                std::string abs_name = sys::env::make_absolute (dir_name);

                const_abs_dir_cache_iterator p = abs_dir_cache.find (abs_name);

                if (p != abs_dir_cache.end ())
                  {
                    // The directory is in the cache of all directories we have
                    // visited (indexed by absolute name).  If it is out of date,
                    // initialize it.  Otherwise, copy the info from the cache.
                    // By doing that, we avoid unnecessary calls to stat that can
                    // slow things down tremendously for large directories.
                    const dir_info& di = p->second;

                    if ((fs.mtime () + fs.time_resolution ()
                         > di.dir_time_last_checked)
                        || (has_private_dir
                            && (pfs.mtime () + pfs.time_resolution ()
                                > dir_time_last_checked)))
                      initialize ();
                    else
                      {
                        // Copy over info from cache, but leave dir_name and
                        // is_relative unmodified.
                        this->abs_dir_name = di.abs_dir_name;
                        this->dir_mtime = di.dir_mtime;
                        this->dir_time_last_checked = di.dir_time_last_checked;
                        this->all_files = di.all_files;
                        this->fcn_files = di.fcn_files;
                        this->private_file_map = di.private_file_map;
                        this->method_file_map = di.method_file_map;
                        this->package_dir_map = di.package_dir_map;
                      }
                  }
                else
                  {
                    // We haven't seen this directory before.
                    initialize ();
                  }
              }
            catch (const execution_exception&)
              {
                // Skip updating if we don't know where we are,
                // but don't treat it as an error.
                interpreter::recover_from_exception ();
              }
          }
        // Absolute path, check timestamp to see whether it requires re-caching
        else if (fs.mtime () + fs.time_resolution () > dir_time_last_checked
                 || (has_private_dir
                     && (pfs.mtime () + pfs.time_resolution ()
                         > dir_time_last_checked)))
          initialize ();
      }
  }

  bool
  load_path::dir_info::is_package (const std::string& name) const
  {
    size_t pos = name.find ('.');

    if (pos == std::string::npos)
      return package_dir_map.find (name) != package_dir_map.end ();
    else
      {
        std::string name_head = name.substr (0, pos);
        std::string name_tail = name.substr (pos + 1);

        const_package_dir_map_iterator it = package_dir_map.find (name_head);

        if (it != package_dir_map.end ())
          return it->second.is_package (name_tail);
        else
          return false;
      }
  }

  void
  load_path::dir_info::initialize (void)
  {
    is_relative = ! sys::env::absolute_pathname (dir_name);

    dir_time_last_checked = sys::time (static_cast<time_t> (0));

    sys::file_stat fs (dir_name);

    if (fs)
      {
        method_file_map.clear ();
        package_dir_map.clear ();

        dir_mtime = fs.mtime ();
        dir_time_last_checked = sys::time ();

        get_file_list (dir_name);

        try
          {
            std::string abs_name = sys::env::make_absolute (dir_name);

            // FIXME: nothing is ever removed from this cache of
            // directory information, so there could be some resource
            // problems.  Perhaps it should be pruned from time to time.

            abs_dir_cache[abs_name] = *this;
          }
        catch (const execution_exception&)
          {
            // Skip updating if we don't know where we are but don't treat
            // it as an error.

            interpreter::recover_from_exception ();
          }
      }
    else
      {
        std::string msg = fs.error ();
        warning ("load_path: %s: %s", dir_name.c_str (), msg.c_str ());
      }
  }

  void
  load_path::dir_info::get_file_list (const std::string& d)
  {
    sys::dir_entry dir (d);

    if (dir)
      {
        string_vector flist = dir.read ();

        octave_idx_type len = flist.numel ();

        all_files.resize (len);
        fcn_files.resize (len);

        octave_idx_type all_files_count = 0;
        octave_idx_type fcn_files_count = 0;

        for (octave_idx_type i = 0; i < len; i++)
          {
            std::string fname = flist[i];

            std::string full_name = sys::file_ops::concat (d, fname);

            sys::file_stat fs (full_name);

            if (fs)
              {
                if (fs.is_dir ())
                  {
                    if (fname == "private")
                      get_private_file_map (full_name);
                    else if (fname[0] == '@')
                      get_method_file_map (full_name, fname.substr (1));
                    else if (fname[0] == '+')
                      get_package_dir (full_name, fname.substr (1));
                  }
                else
                  {
                    all_files[all_files_count++] = fname;

                    size_t pos = fname.rfind ('.');

                    if (pos != std::string::npos)
                      {
                        std::string ext = fname.substr (pos);

                        if (ext == ".m" || ext == ".oct" || ext == ".mex")
                          {
                            std::string base = fname.substr (0, pos);

                            if (valid_identifier (base))
                              fcn_files[fcn_files_count++] = fname;
                          }
                      }
                  }
              }
          }

        all_files.resize (all_files_count);
        fcn_files.resize (fcn_files_count);
      }
    else
      {
        std::string msg = dir.error ();
        warning ("load_path: %s: %s", d.c_str (), msg.c_str ());
      }
  }

  void
  load_path::dir_info::get_private_file_map (const std::string& d)
  {
    private_file_map = get_fcn_files (d);
  }

  void
  load_path::dir_info::get_method_file_map (const std::string& d,
                                            const std::string& class_name)
  {
    method_file_map[class_name].method_file_map = get_fcn_files (d);

    std::string pd = sys::file_ops::concat (d, "private");

    sys::file_stat fs (pd);

    if (fs && fs.is_dir ())
      method_file_map[class_name].private_file_map = get_fcn_files (pd);
  }

  void
  load_path::dir_info::get_package_dir (const std::string& d,
                                        const std::string& package_name)
  {
    package_dir_map[package_name] = dir_info (d);
  }

  void
  load_path::package_info::move (const dir_info& di, bool at_end)
  {
    std::string dir_name = di.dir_name;

    std::list<std::string>::iterator s =
      std::find (dir_list.begin (), dir_list.end (), dir_name);

    if (s != dir_list.end ())
      {
        dir_list.erase (s);

        if (at_end)
          dir_list.push_back (dir_name);
        else
          dir_list.push_front (dir_name);
      }

    move_fcn_map (dir_name, di.fcn_files, at_end);

    // No need to move elements of private function map.

    move_method_map (dir_name, at_end);
  }

  void
  load_path::package_info::remove (const dir_info& di)
  {
    std::string dir = di.dir_name;

    string_vector fcn_files = di.fcn_files;

    dir_list.remove (dir);

    remove_fcn_map (dir, fcn_files);

    remove_private_fcn_map (dir);

    remove_method_map (dir);
  }

  void
  load_path::package_info::display (std::ostream& os) const
  {
    os << "*** package_info: "
       << (m_package_name.empty () ? "<top-level>" : m_package_name)
       << "\n\n";

    for (const auto& dir : dir_list)
      os << dir << "\n";
    os << "\n";

    for (const auto& dir_fnlst : private_fcn_map)
      {
        os << "\n*** private functions in "
           << sys::file_ops::concat (dir_fnlst.first, "private")
           << ":\n\n";

        print_fcn_list (os, dir_fnlst.second);
      }

#if defined (DEBUG_LOAD_PATH)

    for (const auto& nm_filst : fcn_map)
      {
        os << nm_filst.first << ":\n";

        const file_info_list_type& file_info_list = nm_filst.second;

        for (const auto& finfo : file_info_list)
          {
            os << "  " << finfo.dir_name << " (";

            print_types (os, finfo.types);

            os << ")\n";
          }
      }

    for (const auto& cls_fnmap : method_map)
      {
        os << "CLASS " << cls_fnmap.first << ":\n";

        const fcn_map_type& fm = cls_fnmap.second;

        for (const auto& nm_fnlst : fcn_map)
          {
            os << "  " << nm_fnlst.first << ":\n";

            const file_info_list_type& file_info_list = nm_fnlst.second;

            for (const auto& finfo : file_info_list)
              {
                os << "  " << finfo.dir_name << " (";

                print_types (os, finfo.types);

                os << ")\n";
              }
          }
      }

    os << "\n";

#endif
  }

  std::string
  load_path::package_info::find_fcn (const std::string& fcn,
                                     std::string& dir_name,
                                     int type) const
  {
    std::string retval;

    //  update ();

    if (fcn.length () > 0 && fcn[0] == '@')
      {
        size_t pos = fcn.find ('/');

        if (pos != std::string::npos)
          {
            std::string class_name = fcn.substr (1, pos-1);
            std::string meth = fcn.substr (pos+1);

            retval = find_method (class_name, meth, dir_name);
          }
        else
          retval = "";
      }
    else
      {
        dir_name = "";

        const_fcn_map_iterator p = fcn_map.find (fcn);

        if (p != fcn_map.end ())
          {
            const file_info_list_type& file_info_list = p->second;

            for (const auto& fi : file_info_list)
              {
                retval = sys::file_ops::concat (fi.dir_name, fcn);

                if (check_file_type (retval, type, fi.types,
                                     fcn, "load_path::find_fcn"))
                  {
                    dir_name = fi.dir_name;
                    break;
                  }
                else
                  retval = "";
              }
          }
      }

    return retval;
  }

  std::string
  load_path::package_info::find_private_fcn (const std::string& dir,
                                             const std::string& fcn,
                                             int type) const
  {
    std::string retval;

    //  update ();

    const_private_fcn_map_iterator q = private_fcn_map.find (dir);

    if (q != private_fcn_map.end ())
      {
        const dir_info::fcn_file_map_type& m = q->second;

        dir_info::const_fcn_file_map_iterator p = m.find (fcn);

        if (p != m.end ())
          {
            std::string fname
              = sys::file_ops::concat (sys::file_ops::concat (dir, "private"), fcn);

            if (check_file_type (fname, type, p->second, fcn,
                                 "load_path::find_private_fcn"))
              retval = fname;
          }
      }

    return retval;
  }

  std::string
  load_path::package_info::find_method (const std::string& class_name,
                                        const std::string& meth,
                                        std::string& dir_name,
                                        int type) const
  {
    std::string retval;

    //  update ();

    dir_name = "";

    const_method_map_iterator q = method_map.find (class_name);

    if (q != method_map.end ())
      {
        const fcn_map_type& m = q->second;

        const_fcn_map_iterator p = m.find (meth);

        if (p != m.end ())
          {
            const file_info_list_type& file_info_list = p->second;

            for (const auto& fi : file_info_list)
              {
                retval = sys::file_ops::concat (fi.dir_name, meth);

                bool found = check_file_type (retval, type, fi.types,
                                              meth, "load_path::find_method");

                if (found)
                  {
                    dir_name = fi.dir_name;
                    break;
                  }
                else
                  retval = "";
              }
          }
      }

    return retval;
  }

  std::list<std::string>
  load_path::package_info::methods (const std::string& class_name) const
  {
    std::list<std::string> retval;

    //  update ();

    const_method_map_iterator mtd_map_it = method_map.find (class_name);

    if (mtd_map_it != method_map.end ())
      {
        for (const auto& nm_filst : mtd_map_it->second)
          retval.push_back (nm_filst.first);
      }

    if (! retval.empty ())
      retval.sort ();

    return retval;
  }

  void
  load_path::package_info::overloads (const std::string& meth,
                                      std::list<std::string>& l) const
  {
    for (const auto& cls_fnmap : method_map)
      {
        const fcn_map_type& m = cls_fnmap.second;

        if (m.find (meth) != m.end ())
          {
            std::string class_name = cls_fnmap.first;

            if (! m_package_name.empty ())
              class_name = m_package_name + '.' + class_name;

            l.push_back (class_name);
          }
      }
  }

  string_vector
  load_path::package_info::fcn_names (void) const
  {
    size_t len = fcn_map.size ();

    string_vector retval (len);

    octave_idx_type count = 0;

    for (const auto& nm_filst : fcn_map)
      retval[count++] = nm_filst.first;

    return retval;
  }

  void
  load_path::package_info::add_to_fcn_map (const dir_info& di,
                                           bool at_end, bool updating)
  {
    std::string dir_name = di.dir_name;

    string_vector fcn_files = di.fcn_files;

    octave_idx_type len = fcn_files.numel ();

    for (octave_idx_type i = 0; i < len; i++)
      {
        std::string fname = fcn_files[i];

        std::string ext;
        std::string base = fname;

        size_t pos = fname.rfind ('.');

        if (pos != std::string::npos)
          {
            base = fname.substr (0, pos);
            ext = fname.substr (pos);
          }

        file_info_list_type& file_info_list = fcn_map[base];

        file_info_list_iterator p = file_info_list.begin ();

        while (p != file_info_list.end ())
          {
            if (p->dir_name == dir_name)
              break;

            p++;
          }

        int t = 0;
        if (ext == ".m")
          t = load_path::M_FILE;
        else if (ext == ".oct")
          t = load_path::OCT_FILE;
        else if (ext == ".mex")
          t = load_path::MEX_FILE;

        if (p == file_info_list.end ())
          {
            // Warn if a built-in or library function is being shadowed,
            // but not if we are just updating (rehashing) the list.

            if (! updating)
              {
                if (file_info_list.empty ())
                  {
                    symbol_table& symtab
                      = __get_symbol_table__ ("load_path::package_info::add_to_fcn_map");

                    if (symtab.is_built_in_function_name (base))
                      {
                        std::string fcn_path = sys::file_ops::concat (dir_name, fname);

                        warning_with_id ("Octave:shadowed-function",
                                         "function %s shadows a built-in function",
                                         fcn_path.c_str ());
                      }
                  }
                else if (! at_end)
                  {
                    file_info& old = file_info_list.front ();

                    // FIXME: do we need to be more careful about the
                    // way we look for old.dir_name in sys_path to avoid
                    // partial matches?

                    // Don't warn about Contents.m files since we expect
                    // more than one to exist in the load path.

                    if (fname != "Contents.m"
                        && sys_path.find (old.dir_name) != std::string::npos
                        && in_path_list (sys_path, old.dir_name))
                      {
                        std::string fcn_path = sys::file_ops::concat (dir_name, fname);

                        warning_with_id ("Octave:shadowed-function",
                                         "function %s shadows a core library function",
                                         fcn_path.c_str ());
                      }
                  }
              }

            file_info fi (dir_name, t);

            if (at_end)
              file_info_list.push_back (fi);
            else
              file_info_list.push_front (fi);
          }
        else
          {
            file_info& fi = *p;

            fi.types |= t;
          }
      }
  }

  void
  load_path::package_info::add_to_private_fcn_map (const dir_info& di)
  {
    dir_info::fcn_file_map_type private_file_map = di.private_file_map;

    if (! private_file_map.empty ())
      private_fcn_map[di.dir_name] = private_file_map;
  }

  void
  load_path::package_info::add_to_method_map (const dir_info& di, bool at_end)
  {
    std::string dir_name = di.dir_name;

    // <CLASS_NAME, CLASS_INFO>
    dir_info::method_file_map_type method_file_map = di.method_file_map;

    for (const auto& cls_ci : method_file_map)
      {
        std::string class_name = cls_ci.first;

        fcn_map_type& fm = method_map[class_name];

        std::string full_dir_name
          = sys::file_ops::concat (dir_name, '@' + class_name);

        const dir_info::class_info& ci = cls_ci.second;

        // <FCN_NAME, TYPES>
        const dir_info::fcn_file_map_type& m = ci.method_file_map;

        for (const auto& nm_typ : m)
          {
            std::string base = nm_typ.first;
            int types = nm_typ.second;

            file_info_list_type& file_info_list = fm[base];

            file_info_list_iterator p2 = file_info_list.begin ();
            while (p2 != file_info_list.end ())
              {
                if (p2->dir_name == full_dir_name)
                  break;

                p2++;
              }

            if (p2 == file_info_list.end ())
              {
                file_info fi (full_dir_name, types);

                if (at_end)
                  file_info_list.push_back (fi);
                else
                  file_info_list.push_front (fi);
              }
            else
              {
                // FIXME: is this possible?
                file_info& fi = *p2;

                fi.types = types;
              }
          }

        // <FCN_NAME, TYPES>
        dir_info::fcn_file_map_type private_file_map = ci.private_file_map;

        if (! private_file_map.empty ())
          private_fcn_map[full_dir_name] = private_file_map;
      }
  }

  void
  load_path::package_info::move_fcn_map (const std::string& dir_name,
                                         const string_vector& fcn_files, bool at_end)
  {
    octave_idx_type len = fcn_files.numel ();

    for (octave_idx_type k = 0; k < len; k++)
      {
        std::string fname = fcn_files[k];

        std::string ext;
        std::string base = fname;

        size_t pos = fname.rfind ('.');

        if (pos != std::string::npos)
          {
            base = fname.substr (0, pos);
            ext = fname.substr (pos);
          }

        file_info_list_type& file_info_list = fcn_map[base];

        if (file_info_list.size () == 1)
          continue;
        else
          {
            for (auto fi_it = file_info_list.begin ();
                 fi_it != file_info_list.end ();
                 fi_it++)
              {
                if (fi_it->dir_name == dir_name)
                  {
                    file_info fi_tmp = *fi_it;

                    file_info_list.erase (fi_it);

                    if (at_end)
                      file_info_list.push_back (fi_tmp);
                    else
                      file_info_list.push_front (fi_tmp);

                    break;
                  }
              }
          }
      }
  }

  void
  load_path::package_info::move_method_map (const std::string& dir_name,
                                            bool at_end)
  {
    for (auto& cls_fnmap : method_map)
      {
        std::string class_name = cls_fnmap.first;

        fcn_map_type& fn_map = cls_fnmap.second;

        std::string full_dir_name
          = sys::file_ops::concat (dir_name, '@' + class_name);

        for (auto& nm_filst : fn_map)
          {
            file_info_list_type& file_info_list = nm_filst.second;

            if (file_info_list.size () == 1)
              continue;
            else
              {
                for (auto fi_it = file_info_list.begin ();
                     fi_it != file_info_list.end (); fi_it++)
                  {
                    if (fi_it->dir_name == full_dir_name)
                      {
                        file_info fi_tmp = *fi_it;

                        file_info_list.erase (fi_it);

                        if (at_end)
                          file_info_list.push_back (fi_tmp);
                        else
                          file_info_list.push_front (fi_tmp);

                        break;
                      }
                  }
              }
          }
      }
  }

  void
  load_path::package_info::remove_fcn_map (const std::string& dir,
                                           const string_vector& fcn_files)
  {
    octave_idx_type len = fcn_files.numel ();

    for (octave_idx_type k = 0; k < len; k++)
      {
        std::string fname = fcn_files[k];

        std::string ext;
        std::string base = fname;

        size_t pos = fname.rfind ('.');

        if (pos != std::string::npos)
          {
            base = fname.substr (0, pos);
            ext = fname.substr (pos);
          }

        file_info_list_type& file_info_list = fcn_map[base];

        for (auto fi_it = file_info_list.begin ();
             fi_it != file_info_list.end ();
             fi_it++)
          {
            if (fi_it->dir_name == dir)
              {
                file_info_list.erase (fi_it);

                if (file_info_list.empty ())
                  fcn_map.erase (fname);

                break;
              }
          }
      }
  }

  void
  load_path::package_info::remove_private_fcn_map (const std::string& dir)
  {
    private_fcn_map_iterator p = private_fcn_map.find (dir);

    if (p != private_fcn_map.end ())
      private_fcn_map.erase (p);
  }

  void
  load_path::package_info::remove_method_map (const std::string& dir)
  {
    for (auto& cls_fnmap : method_map)
      {
        std::string class_name = cls_fnmap.first;

        fcn_map_type& fn_map = cls_fnmap.second;

        std::string full_dir_name
          = sys::file_ops::concat (dir, '@' + class_name);

        for (auto& nm_filst : fn_map)
          {
            file_info_list_type& file_info_list = nm_filst.second;

            if (file_info_list.size () == 1)
              continue;
            else
              {
                for (auto fi_it = file_info_list.begin ();
                     fi_it != file_info_list.end (); fi_it++)
                  {
                    if (fi_it->dir_name == full_dir_name)
                      {
                        file_info_list.erase (fi_it);
                        // FIXME: if there are no other elements, we
                        // should remove this element of fn_map but calling
                        // erase here would invalidate the iterator fi_it.

                        break;
                      }
                  }
              }
          }
      }
  }

  bool
  load_path::package_info::check_file_type (std::string& fname, int type,
                                            int possible_types,
                                            const std::string& fcn,
                                            const char *who) const
  {
    bool retval = false;

    if (type == load_path::OCT_FILE)
      {
        if ((type & possible_types) == load_path::OCT_FILE)
          {
            fname += ".oct";
            retval = true;
          }
      }
    else if (type == load_path::M_FILE)
      {
        if ((type & possible_types) == load_path::M_FILE)
          {
            fname += ".m";
            retval = true;
          }
      }
    else if (type == load_path::MEX_FILE)
      {
        if ((type & possible_types) == load_path::MEX_FILE)
          {
            fname += ".mex";
            retval = true;
          }
      }
    else if (type == (load_path::M_FILE | load_path::OCT_FILE))
      {
        if (possible_types & load_path::OCT_FILE)
          {
            fname += ".oct";
            retval = true;
          }
        else if (possible_types & load_path::M_FILE)
          {
            fname += ".m";
            retval = true;
          }
      }
    else if (type == (load_path::M_FILE | load_path::MEX_FILE))
      {
        if (possible_types & load_path::MEX_FILE)
          {
            fname += ".mex";
            retval = true;
          }
        else if (possible_types & load_path::M_FILE)
          {
            fname += ".m";
            retval = true;
          }
      }
    else if (type == (load_path::OCT_FILE | load_path::MEX_FILE))
      {
        if (possible_types & load_path::OCT_FILE)
          {
            fname += ".oct";
            retval = true;
          }
        else if (possible_types & load_path::MEX_FILE)
          {
            fname += ".mex";
            retval = true;
          }
      }
    else if (type == (load_path::M_FILE | load_path::OCT_FILE
                      | load_path::MEX_FILE))
      {
        if (possible_types & load_path::OCT_FILE)
          {
            fname += ".oct";
            retval = true;
          }
        else if (possible_types & load_path::MEX_FILE)
          {
            fname += ".mex";
            retval = true;
          }
        else if (possible_types & load_path::M_FILE)
          {
            fname += ".m";
            retval = true;
          }
      }
    else
      error ("%s: %s: invalid type code = %d", who, fcn.c_str (), type);

    return retval;
  }

  void
  load_path::package_info::print_types (std::ostream& os, int types) const
  {
    bool printed_type = false;

    if (types & load_path::OCT_FILE)
      {
        os << "oct";
        printed_type = true;
      }

    if (types & load_path::MEX_FILE)
      {
        if (printed_type)
          os << '|';
        os << "mex";
        printed_type = true;
      }

    if (types & load_path::M_FILE)
      {
        if (printed_type)
          os << '|';
        os << 'm';
        printed_type = true;
      }
  }

  void
  load_path::package_info::print_fcn_list (std::ostream& os,
                                           const load_path::dir_info::fcn_file_map_type& lst) const
  {
    for (const auto& nm_typ : lst)
      {
        os << "  " << nm_typ.first << " (";

        print_types (os, nm_typ.second);

        os << ")\n";
      }
  }

  std::string
  genpath (const std::string& dirname, const string_vector& skip)
  {
    std::string retval;

    sys::dir_entry dir (dirname);

    if (dir)
      {
        retval = dirname;

        string_vector dirlist = dir.read ().sort (false);

        octave_idx_type len = dirlist.numel ();

        for (octave_idx_type i = 0; i < len; i++)
          {
            std::string elt = dirlist[i];

            bool skip_p = (elt == "." || elt == ".." || elt[0] == '@'
                           || elt[0] == '+');

            if (! skip_p)
              {
                for (octave_idx_type j = 0; j < skip.numel (); j++)
                  {
                    skip_p = (elt == skip[j]);
                    if (skip_p)
                      break;
                  }

                if (! skip_p)
                  {
                    std::string nm = sys::file_ops::concat (dirname, elt);

                    sys::file_stat fs (nm);

                    if (fs && fs.is_dir ())
                      retval += directory_path::path_sep_str () + genpath (nm, skip);
                  }
              }
          }
      }

    return retval;
  }
}

DEFUN (genpath, args, ,
       doc: /* -*- texinfo -*-
@deftypefn  {} {} genpath (@var{dir})
@deftypefnx {} {} genpath (@var{dir}, @var{skip}, @dots{})
Return a path constructed from @var{dir} and all its subdirectories.

The path does not include package directories (beginning with @samp{+}),
old-style class directories (beginning with @samp{@@}), @file{private}
directories, or any subdirectories of these types.

If additional string parameters are given, the resulting path will exclude
directories with those names.
@seealso{path, addpath}
@end deftypefn */)
{
  int nargin = args.length ();

  if (nargin == 0)
    print_usage ();

  octave_value retval;

  if (nargin == 1)
    {
      std::string dirname = args(0).xstring_value ("genpath: DIR must be a string");

      retval = octave::genpath (dirname);
    }
  else
    {
      std::string dirname = args(0).xstring_value ("genpath: all arguments must be strings");

      string_vector skip (nargin - 1);

      for (octave_idx_type i = 1; i < nargin; i++)
        skip[i-1] = args(i).xstring_value ("genpath: all arguments must be strings");

      retval = octave::genpath (dirname, skip);
    }

  return retval;
}

DEFUN (rehash, , ,
       doc: /* -*- texinfo -*-
@deftypefn {} {} rehash ()
Reinitialize Octave's load path directory cache.
@end deftypefn */)
{
  rehash_internal ();

  return ovl ();
}

DEFMETHOD (command_line_path, interp, args, ,
           doc: /* -*- texinfo -*-
@deftypefn {} {} command_line_path ()
Return the command line path variable.

@seealso{path, addpath, rmpath, genpath, pathdef, savepath, pathsep}
@end deftypefn */)
{
  if (! args.empty ())
    print_usage ();

  octave::load_path& lp = interp.get_load_path ();

  return ovl (lp.get_command_line_path ());
}

DEFMETHOD (restoredefaultpath, interp, args, ,
           doc: /* -*- texinfo -*-
@deftypefn {} {} restoredefaultpath ()
Restore Octave's path to its initial state at startup.

@seealso{path, addpath, rmpath, genpath, pathdef, savepath, pathsep}
@end deftypefn */)
{
  if (! args.empty ())
    print_usage ();

  octave::load_path& lp = interp.get_load_path ();

  lp.initialize (true);

  return ovl (lp.system_path ());
}

// Return Octave's original default list of directories in which to
// search for function files.  This corresponds to the path that
// exists prior to running the system's octaverc file or the user's
// ~/.octaverc file

DEFMETHOD (__pathorig__, interp, , ,
           doc: /* -*- texinfo -*-
@deftypefn {} {@var{val} =} __pathorig__ ()
Undocumented internal function.
@end deftypefn */)
{
  octave::load_path& lp = interp.get_load_path ();

  return ovl (lp.system_path ());
}

DEFMETHOD (path, interp, args, nargout,
           doc: /* -*- texinfo -*-
@deftypefn  {} {} path ()
@deftypefnx {} {@var{str} =} path ()
@deftypefnx {} {@var{str} =} path (@var{path1}, @dots{})
Modify or display Octave's load path.

If @var{nargin} and @var{nargout} are zero, display the elements of
Octave's load path in an easy to read format.

If @var{nargin} is zero and nargout is greater than zero, return the
current load path.

If @var{nargin} is greater than zero, concatenate the arguments,
separating them with @code{pathsep}.  Set the internal search path
to the result and return it.

No checks are made for duplicate elements.
@seealso{addpath, rmpath, genpath, pathdef, savepath, pathsep}
@end deftypefn */)
{
  int nargin = args.length ();

  string_vector argv = args.make_argv ("path");

  octave::load_path& lp = interp.get_load_path ();

  if (nargin > 0)
    {
      std::string path = argv[1];

      for (int i = 2; i <= nargin; i++)
        path += octave::directory_path::path_sep_str () + argv[i];

      lp.set (path, true);

      rehash_internal ();
    }

  if (nargout > 0)
    return ovl (lp.path ());
  else if (nargin == 0 && nargout == 0)
    {
      octave_stdout <<
        "\nOctave's search path contains the following directories:\n\n";

      string_vector dirs = lp.dirs ();

      dirs.list_in_columns (octave_stdout);

      octave_stdout << "\n";
    }

  return ovl ();
}

DEFMETHOD (addpath, interp, args, nargout,
           doc: /* -*- texinfo -*-
@deftypefn  {} {} addpath (@var{dir1}, @dots{})
@deftypefnx {} {} addpath (@var{dir1}, @dots{}, @var{option})
Add named directories to the function search path.

If @var{option} is @qcode{"-begin"} or 0 (the default), prepend the
directory name to the current path.  If @var{option} is @qcode{"-end"}
or 1, append the directory name to the current path.
Directories added to the path must exist.

In addition to accepting individual directory arguments, lists of
directory names separated by @code{pathsep} are also accepted.  For example:

@example
addpath ("dir1:/dir2:~/dir3")
@end example

For each directory that is added, and that was not already in the path,
@code{addpath} checks for the existence of a file named @file{PKG_ADD}
(note lack of .m extension) and runs it if it exists.

@seealso{path, rmpath, genpath, pathdef, savepath, pathsep}
@end deftypefn */)
{
  // Originally written by Bill Denney and Etienne Grossman.
  // Heavily modified and translated to C++ by jwe.

  int nargin = args.length ();

  if (nargin == 0)
    print_usage ();

  octave::load_path& lp = interp.get_load_path ();

  octave_value retval;

  if (nargout > 0)
    retval = lp.path ();

  bool append = false;

  octave_value option_arg = args(nargin-1);

  if (option_arg.is_string ())
    {
      std::string option = option_arg.string_value ();

      if (option == "-end")
        {
          append = true;
          nargin--;
        }
      else if (option == "-begin")
        nargin--;
    }
  else if (option_arg.isnumeric ())
    {
      int val = option_arg.xint_value ("addpath: OPTION must be '-begin'/0 or '-end'/1");

      if (val == 0)
        nargin--;
      else if (val == 1)
        {
          append = true;
          nargin--;
        }
      else
        error ("addpath: OPTION must be '-begin'/0 or '-end'/1");
    }

  bool need_to_update = false;

  octave_value_list arglist (args.slice (0, nargin));
  if (! append)
    arglist.reverse ();

  for (int i = 0; i < arglist.length (); i++)
    {
      std::string arg = arglist(i).xstring_value ("addpath: all arguments must be strings");

      std::list<std::string> dir_elts = split_path (arg);

      if (! append)
        std::reverse (dir_elts.begin (), dir_elts.end ());

      for (auto dir : dir_elts)
        {
          // Remove duplicate directory separators
          std::string::iterator it_start = dir.begin ();
#if defined (OCTAVE_HAVE_WINDOWS_FILESYSTEM)
          // In Windows, start check at second character (for UNC paths).
          it_start++;
#endif
          dir.erase (std::unique (it_start, dir.end (),
                                  [](char l, char r)
                                  {
                                    return l == r &&
                                           octave::sys::file_ops::is_dir_sep (l);
                                  }),
                     dir.end ());

          auto pos = dir.find_last_of (octave::sys::file_ops::dir_sep_chars ());
          if (pos == std::string::npos)
            {
              if (! dir.empty () && dir[0] == '+')
                warning_with_id ("Octave:addpath-pkg",
                                 "addpath: package directories should not be added to path: %s\n", dir.c_str ());
            }
          else
            {
              if (pos + 1 < dir.length () && dir[pos+1] == '+')
                warning_with_id ("Octave:addpath-pkg",
                                 "addpath: package directories should not be added to path: %s\n", dir.c_str ());
            }

          if (append)
            lp.append (dir, true);
          else
            lp.prepend (dir, true);

          need_to_update = true;
        }
    }

  if (need_to_update)
    rehash_internal ();

  return retval;
}

DEFMETHOD (rmpath, interp, args, nargout,
           doc: /* -*- texinfo -*-
@deftypefn {} {} rmpath (@var{dir1}, @dots{})
Remove @var{dir1}, @dots{} from the current function search path.

In addition to accepting individual directory arguments, lists of
directory names separated by @code{pathsep} are also accepted.  For example:

@example
rmpath ("dir1:/dir2:~/dir3")
@end example

For each directory that is removed, @code{rmpath} checks for the
existence of a file named @file{PKG_DEL} (note lack of .m extension)
and runs it if it exists.

@seealso{path, addpath, genpath, pathdef, savepath, pathsep}
@end deftypefn */)
{
  // Originally written by Etienne Grossmann.  Heavily modified and translated
  // to C++ by jwe.

  int nargin = args.length ();

  if (nargin == 0)
    print_usage ();

  octave_value retval;

  octave::load_path& lp = interp.get_load_path ();

  if (nargout > 0)
    retval = lp.path ();

  bool need_to_update = false;

  for (int i = 0; i < nargin; i++)
    {
      std::string arg = args(i).xstring_value ("rmpath: all arguments must be strings");
      std::list<std::string> dir_elts = split_path (arg);

      for (const auto& dir : dir_elts)
        {
          //dir = regexprep (dir_elts{j}, '//+', "/");
          //dir = regexprep (dir, '/$', "");

          if (! lp.remove (dir))
            warning ("rmpath: %s: not found", dir.c_str ());
          else
            need_to_update = true;
        }
    }

  if (need_to_update)
    rehash_internal ();

  return retval;
}

DEFMETHOD (__dump_load_path__, interp, , ,
           doc: /* -*- texinfo -*-
@deftypefn {} {} __dump_load_path__ ()
Undocumented internal function.
@end deftypefn */)
{
  octave::load_path& lp = interp.get_load_path ();

  lp.display (octave_stdout);

  return ovl ();
}