1 files changed, 76 insertions, 0 deletions
diff --git a/src/util/open_lock.c b/src/util/open_lock.c
new file mode 100644
index 0000000..87e852d
--- /dev/null
+++ b/src/util/open_lock.c
@@ -0,0 +1,76 @@
+/*++
+/* NAME
+/*	open_lock 3
+/* SUMMARY
+/*	open or create file and lock it for exclusive access
+/* SYNOPSIS
+/*	#include <open_lock.h>
+/*
+/*	VSTREAM	*open_lock(path, flags, mode, why)
+/*	const char *path;
+/*	int	flags;
+/*	mode_t	mode;
+/*	VSTRING *why;
+/* DESCRIPTION
+/*	This module opens or creates the named file and attempts to
+/*	acquire an exclusive lock.  The lock is lost when the last
+/*	process closes the file.
+/*
+/*	Arguments:
+/* .IP "path, flags, mode"
+/*	These are passed on to safe_open().
+/* .IP why
+/*	storage for diagnostics.
+/* SEE ALSO
+/*	safe_open(3) carefully open or create file
+/*	myflock(3) get exclusive lock on file
+/* DIAGNOSTICS
+/*	In case of problems the result is a null pointer and a problem
+/*	description is returned via the global \fIerrno\fR variable.
+/* LICENSE
+/* .ad
+/* .fi
+/*	The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/*	Wietse Venema
+/*	IBM T.J. Watson Research
+/*	P.O. Box 704
+/*	Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstream.h>
+#include <vstring.h>
+#include <safe_open.h>
+#include <myflock.h>
+#include <open_lock.h>
+
+/* open_lock - open file and lock it for exclusive access */
+
+VSTREAM *open_lock(const char *path, int flags, mode_t mode, VSTRING *why)
+{
+    VSTREAM *fp;
+
+    /*
+     * Carefully create or open the file, and lock it down. Some systems
+     * don't have the O_LOCK open() flag, or the flag does not do what we
+     * want, so we roll our own lock.
+     */
+    if ((fp = safe_open(path, flags, mode, (struct stat *) 0, -1, -1, why)) == 0)
+	return (0);
+    if (myflock(vstream_fileno(fp), INTERNAL_LOCK,
+		MYFLOCK_OP_EXCLUSIVE | MYFLOCK_OP_NOWAIT) < 0) {
+	vstring_sprintf(why, "unable to set exclusive lock: %m");
+	vstream_fclose(fp);
+	return (0);
+    }
+    return (fp);
+}