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-rw-r--r--libraries/liblutil/lockf.c118
1 files changed, 118 insertions, 0 deletions
diff --git a/libraries/liblutil/lockf.c b/libraries/liblutil/lockf.c
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+++ b/libraries/liblutil/lockf.c
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+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 1998-2021 The OpenLDAP Foundation.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/*
+ * File Locking Routines
+ *
+ * Implementations (in order of preference)
+ * - lockf
+ * - fcntl
+ * - flock
+ *
+ * Other implementations will be added as needed.
+ *
+ * NOTE: lutil_lockf() MUST block until an exclusive lock is acquired.
+ */
+
+#include "portable.h"
+
+#include <stdio.h>
+#include <ac/unistd.h>
+
+#undef LOCK_API
+
+#if defined(HAVE_LOCKF) && defined(F_LOCK)
+# define USE_LOCKF 1
+# define LOCK_API "lockf"
+#endif
+
+#if !defined(LOCK_API) && defined(HAVE_FCNTL)
+# ifdef HAVE_FCNTL_H
+# include <fcntl.h>
+# endif
+# ifdef F_WRLCK
+# define USE_FCNTL 1
+# define LOCK_API "fcntl"
+# endif
+#endif
+
+#if !defined(LOCK_API) && defined(HAVE_FLOCK)
+# ifdef HAVE_SYS_FILE_H
+# include <sys/file.h>
+# endif
+# define USE_FLOCK 1
+# define LOCK_API "flock"
+#endif
+
+#if !defined(USE_LOCKF) && !defined(USE_FCNTL) && !defined(USE_FLOCK)
+int lutil_lockf ( int fd ) {
+ fd = fd;
+ return 0;
+}
+
+int lutil_unlockf ( int fd ) {
+ fd = fd;
+ return 0;
+}
+#endif
+
+#ifdef USE_LOCKF
+int lutil_lockf ( int fd ) {
+ /* use F_LOCK instead of F_TLOCK, ie: block */
+ return lockf( fd, F_LOCK, 0 );
+}
+
+int lutil_unlockf ( int fd ) {
+ return lockf( fd, F_ULOCK, 0 );
+}
+#endif
+
+#ifdef USE_FCNTL
+int lutil_lockf ( int fd ) {
+ struct flock file_lock;
+
+ memset( &file_lock, '\0', sizeof( file_lock ) );
+ file_lock.l_type = F_WRLCK;
+ file_lock.l_whence = SEEK_SET;
+ file_lock.l_start = 0;
+ file_lock.l_len = 0;
+
+ /* use F_SETLKW instead of F_SETLK, ie: block */
+ return( fcntl( fd, F_SETLKW, &file_lock ) );
+}
+
+int lutil_unlockf ( int fd ) {
+ struct flock file_lock;
+
+ memset( &file_lock, '\0', sizeof( file_lock ) );
+ file_lock.l_type = F_UNLCK;
+ file_lock.l_whence = SEEK_SET;
+ file_lock.l_start = 0;
+ file_lock.l_len = 0;
+
+ return( fcntl ( fd, F_SETLKW, &file_lock ) );
+}
+#endif
+
+#ifdef USE_FLOCK
+int lutil_lockf ( int fd ) {
+ /* use LOCK_EX instead of LOCK_EX|LOCK_NB, ie: block */
+ return flock( fd, LOCK_EX );
+}
+
+int lutil_unlockf ( int fd ) {
+ return flock( fd, LOCK_UN );
+}
+#endif