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db_ndbm.c

/*
 * db_ndbm.c: low level ndbm interface routines for man.
 *
 * Copyright (C) 1994, 1995 Graeme W. Wilford. (Wilf.)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Mon Aug  8 20:35:30 BST 1994  Wilf. (G.Wilford@ee.surrey.ac.uk)
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif /* HAVE_CONFIG_H */

#ifdef NDBM

#include <stdio.h>

#if HAVE_SYS_FILE_H
#  include <sys/file.h> /* for flock() */
#endif

#include <sys/types.h> /* for open() */
#include <sys/stat.h>

#if HAVE_FCNTL_H
#  include <fcntl.h>
#endif

#ifdef STDC_HEADERS
#include <stdlib.h>
#endif /* STDC_HEADERS */

#ifdef HAVE_UNISTD_H
#  include <unistd.h>
#endif /* HAVE_UNISTD_H */

#include "manconfig.h"
#include "lib/flock.h"
#include "mydbm.h"
#include "db_storage.h"

/* release the lock and close the database */
int ndbm_flclose (DBM *dbf)
{
      flock (dbm_dirfno (dbf), LOCK_UN);
      dbm_close (dbf);
      return 0;
}

/* open a ndbm type database, with file locking. */
DBM* ndbm_flopen (char *filename, int flags, int mode)
{
      DBM *dbf;
      int lock_op;
      int lock_failed;

      if (flags & ~O_RDONLY) {
            /* flags includes O_RDWR or O_WRONLY, need an exclusive lock */
            lock_op = LOCK_EX | LOCK_NB;
      } else {
            lock_op = LOCK_SH | LOCK_NB;
      }

      if (flags & O_TRUNC) {
            /* opening the db is destructive, need to lock first */
            char *dir_fname;
            int dir_fd;

            dbf = NULL;
            lock_failed = 1;
            dir_fname = xmalloc (strlen (filename) + 5);
            sprintf (dir_fname, "%s.dir", filename);
            dir_fd = open (dir_fname, flags & ~O_TRUNC, mode);
            free (dir_fname);
            if (dir_fd != -1) {
                  if (!(lock_failed = flock (dir_fd, lock_op)))
                        dbf = dbm_open (filename, flags, mode);
                  close (dir_fd);
            }
      } else {
            dbf = dbm_open (filename, flags, mode);
            if (dbf)
                  lock_failed = flock (dbm_dirfno (dbf), lock_op);
      }

      if (!dbf)
            return NULL;

      if (lock_failed) {
            gripe_lock (filename);
            dbm_close (dbf);
            return NULL;
      }

      return dbf;
}

#endif /* NDBM */

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