+// $Id: util-lockfile.c,v 1.1 2004/07/02 23:34:52 ensc Exp $ --*- c -*--
+
+// Copyright (C) 2004 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
+//
+// 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; version 2 of the License.
+//
+// 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, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "util-lockfile.h"
+#include "errinfo.h"
+
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/file.h>
+#include <errno.h>
+
+static volatile sig_atomic_t alarm_flag = 0;
+
+static void
+alarmFunc(int UNUSED sig)
+{
+ alarm_flag = 1;
+ signal(SIGALRM, alarmFunc);
+}
+
+bool
+lockfile(int *fd, char const *filename, int op, long timeout,
+ struct ErrorInformation *err)
+{
+ char const *errstr = 0;
+ void (*old_sighandler)(int) = 0;
+
+ errstr = "open()";
+ *fd = open(filename, O_CREAT|O_RDONLY|O_NOFOLLOW|O_NONBLOCK, 0644);
+ if (*fd==-1) goto err;
+
+ if (timeout!=-1) {
+ errstr = "siginterrupt()";
+ if (siginterrupt(SIGALRM, 1)==-1) goto err;
+
+ errstr = "signal()";
+ old_sighandler = signal(SIGALRM, alarmFunc);
+ if (old_sighandler==SIG_ERR) goto err;
+
+ alarm(timeout);
+ }
+
+ errstr = "flock()";
+ while (flock(*fd, op)==-1) {
+ if ((errno!=EINTR && errno!=EINTR) || alarm_flag) goto err;
+ }
+
+ if (timeout!=-1 && old_sighandler!=0)
+ signal(SIGALRM, old_sighandler);
+
+ errstr = "fcntl()";
+ if (fcntl(*fd, F_SETFD, FD_CLOEXEC)==-1) goto err;
+
+ return true;
+
+ err:
+ if (err) {
+ err->pos = errstr;
+ err->id = errno;
+ }
+ if (timeout!=-1 && old_sighandler!=0)
+ signal(SIGALRM, old_sighandler);
+ if (*fd!=-1) close(*fd);
+ return false;
+}