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-rw-r--r--src/util/open_lock.c76
1 files changed, 76 insertions, 0 deletions
diff --git a/src/util/open_lock.c b/src/util/open_lock.c
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+/*++
+/* 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);
+}