1 files changed, 154 insertions, 0 deletions
diff --git a/src/lock.c b/src/lock.c
new file mode 100644
index 0000000..0168ff9
--- /dev/null
+++ b/src/lock.c
@@ -0,0 +1,154 @@
+/* lock.c - Implement basic file locking for GDBM. */
+
+/* This file is part of GDBM, the GNU data base manager.
+   Copyright (C) 2008, 2011, 2013 Free Software Foundation, Inc.
+
+   GDBM 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, or (at your option)
+   any later version.
+
+   GDBM 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 GDBM. If not, see <http://www.gnu.org/licenses/>.   */
+
+/* Include system configuration before all else. */
+#include "autoconf.h"
+
+#include "gdbmdefs.h"
+
+#include <errno.h>
+
+#if HAVE_FLOCK
+# ifndef LOCK_SH
+#  define LOCK_SH 1
+# endif
+
+# ifndef LOCK_EX
+#  define LOCK_EX 2
+# endif
+
+# ifndef LOCK_NB
+#  define LOCK_NB 4
+# endif
+
+# ifndef LOCK_UN
+#  define LOCK_UN 8
+# endif
+#endif
+
+#if defined(F_SETLK) && defined(F_RDLCK) && defined(F_WRLCK)
+# define HAVE_FCNTL_LOCK 1
+#else
+# define HAVE_FCNTL_LOCK 0
+#endif
+
+#if 0
+int
+gdbm_locked (GDBM_FILE dbf)
+{
+  return (dbf->lock_type != LOCKING_NONE);
+}
+#endif
+
+void
+_gdbm_unlock_file (GDBM_FILE dbf)
+{
+#if HAVE_FCNTL_LOCK
+  struct flock fl;
+#endif
+
+  switch (dbf->lock_type)
+    {
+      case LOCKING_FLOCK:
+#if HAVE_FLOCK
+	flock (dbf->desc, LOCK_UN);
+#endif
+	break;
+
+      case LOCKING_LOCKF:
+#if HAVE_LOCKF
+	lockf (dbf->desc, F_ULOCK, (off_t)0L);
+#endif
+	break;
+
+      case LOCKING_FCNTL:
+#if HAVE_FCNTL_LOCK
+	fl.l_type = F_UNLCK;
+	fl.l_whence = SEEK_SET;
+	fl.l_start = fl.l_len = (off_t)0L;
+	fcntl (dbf->desc, F_SETLK, &fl);
+#endif
+	break;
+
+      case LOCKING_NONE:
+        break;
+    }
+
+  dbf->lock_type = LOCKING_NONE;
+}
+
+/* Try each supported locking mechanism. */
+int
+_gdbm_lock_file (GDBM_FILE dbf)
+{
+#if HAVE_FCNTL_LOCK
+  struct flock fl;
+#endif
+  int lock_val = -1;
+
+#if HAVE_FLOCK
+  if (dbf->read_write == GDBM_READER)
+    lock_val = flock (dbf->desc, LOCK_SH + LOCK_NB);
+  else
+    lock_val = flock (dbf->desc, LOCK_EX + LOCK_NB);
+
+  if ((lock_val == -1) && (errno == EWOULDBLOCK))
+    {
+      dbf->lock_type = LOCKING_NONE;
+      return lock_val;
+    }
+  else if (lock_val != -1)
+    {
+      dbf->lock_type = LOCKING_FLOCK;
+      return lock_val;
+    }
+#endif
+
+#if HAVE_LOCKF
+  /* Mask doesn't matter for lockf. */
+  lock_val = lockf (dbf->desc, F_LOCK, (off_t)0L);
+  if ((lock_val == -1) && (errno == EDEADLK))
+    {
+      dbf->lock_type = LOCKING_NONE;
+      return lock_val;
+    }
+  else if (lock_val != -1)
+    {
+      dbf->lock_type = LOCKING_LOCKF;
+      return lock_val;
+    }
+#endif
+
+#if HAVE_FCNTL_LOCK
+  /* If we're still here, try fcntl. */
+  if (dbf->read_write == GDBM_READER)
+    fl.l_type = F_RDLCK;
+  else
+    fl.l_type = F_WRLCK;
+  fl.l_whence = SEEK_SET;
+  fl.l_start = fl.l_len = (off_t)0L;
+  lock_val = fcntl (dbf->desc, F_SETLK, &fl);
+
+  if (lock_val != -1)
+    dbf->lock_type = LOCKING_FCNTL;
+#endif
+
+  if (lock_val == -1)
+    dbf->lock_type = LOCKING_NONE;
+  return lock_val;
+}