/* Detect cycles in file tree walks.

   Copyright (C) 2003-2006, 2009-2017 Free Software Foundation, Inc.

   Written by Jim Meyering.

   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 3 of the License, or

   (at your option) any later version.

   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "cycle-check.h"

#include "hash.h"

/* Use each of these to map a device/inode pair to an FTSENT.  */

struct Active_dir

{

  dev_t dev;

  ino_t ino;

  FTSENT *fts_ent;

};

static bool

AD_compare (void const *x, void const *y)

{

  struct Active_dir const *ax = x;

  struct Active_dir const *ay = y;

  return ax->ino == ay->ino

      && ax->dev == ay->dev;

}

static size_t

AD_hash (void const *x, size_t table_size)

{

  struct Active_dir const *ax = x;

  return (uintmax_t) ax->ino % table_size;

}

/* Set up the cycle-detection machinery.  */

static bool

setup_dir (FTS *fts)

{

  if (fts->fts_options & (FTS_TIGHT_CYCLE_CHECK | FTS_LOGICAL))

    {

      enum { HT_INITIAL_SIZE = 31 };

      fts->fts_cycle.ht = hash_initialize (HT_INITIAL_SIZE, NULL, AD_hash,

                                           AD_compare, free);

      if (! fts->fts_cycle.ht)

        return false;

    }

  else

    {

      fts->fts_cycle.state = malloc (sizeof *fts->fts_cycle.state);

      if (! fts->fts_cycle.state)

        return false;

      cycle_check_init (fts->fts_cycle.state);

    }

  return true;

}

/* Enter a directory during a file tree walk.  */

static bool

enter_dir (FTS *fts, FTSENT *ent)

{

  if (fts->fts_options & (FTS_TIGHT_CYCLE_CHECK | FTS_LOGICAL))

    {

      struct stat const *st = ent->fts_statp;

      struct Active_dir *ad = malloc (sizeof *ad);

      struct Active_dir *ad_from_table;

      if (!ad)

        return false;

      ad->dev = st->st_dev;

      ad->ino = st->st_ino;

      ad->fts_ent = ent;

      /* See if we've already encountered this directory.

         This can happen when following symlinks as well as

         with a corrupted directory hierarchy. */

      ad_from_table = hash_insert (fts->fts_cycle.ht, ad);

      if (ad_from_table != ad)

        {

          free (ad);

          if (!ad_from_table)

            return false;

          /* There was an entry with matching dev/inode already in the table.

             Record the fact that we've found a cycle.  */

          ent->fts_cycle = ad_from_table->fts_ent;

          ent->fts_info = FTS_DC;

        }

    }

  else

    {

      if (cycle_check (fts->fts_cycle.state, ent->fts_statp))

        {

          /* FIXME: setting fts_cycle like this isn't proper.

             To do what the documentation requires, we'd have to

             go around the cycle again and find the right entry.

             But no callers in coreutils use the fts_cycle member. */

          ent->fts_cycle = ent;

          ent->fts_info = FTS_DC;

        }

    }

  return true;

}

/* Leave a directory during a file tree walk.  */

static void

leave_dir (FTS *fts, FTSENT *ent)

{

  struct stat const *st = ent->fts_statp;

  if (fts->fts_options & (FTS_TIGHT_CYCLE_CHECK | FTS_LOGICAL))

    {

      struct Active_dir obj;

      void *found;

      obj.dev = st->st_dev;

      obj.ino = st->st_ino;

      found = hash_delete (fts->fts_cycle.ht, &obj);

      if (!found)

        abort ();

      free (found);

    }

  else

    {

      FTSENT *parent = ent->fts_parent;

      if (parent != NULL && 0 <= parent->fts_level)

        CYCLE_CHECK_REFLECT_CHDIR_UP (fts->fts_cycle.state,

                                      *(parent->fts_statp), *st);

    }

}

/* Free any memory used for cycle detection.  */

static void

free_dir (FTS *sp)

{

  if (sp->fts_options & (FTS_TIGHT_CYCLE_CHECK | FTS_LOGICAL))

    {

      if (sp->fts_cycle.ht)

        hash_free (sp->fts_cycle.ht);

    }

  else

    free (sp->fts_cycle.state);

}