1 files changed, 108 insertions, 0 deletions
diff --git a/liblock/mail.h b/liblock/mail.h
new file mode 100644
index 0000000..8980a0b
--- /dev/null
+++ b/liblock/mail.h
@@ -0,0 +1,108 @@
+
+#ifndef liblockmail_h
+#define liblockmail_h
+
+/*
+** Copyright 2002 Double Precision, Inc.  See COPYING for
+** distribution information.
+*/
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+	/*
+	** Functions for mbox mail locks
+	*/
+
+struct ll_mail {
+	char *file;		/* File being locked */
+
+	/* c-client type lock */
+
+	int cclientfd;
+	char *cclientfile;
+
+
+	/* dotlock */
+
+	char *dotlock;
+};
+
+struct ll_mail *ll_mail_alloc(const char *filename);
+
+/*
+** Create a c-client type lock.  NOTE: c-clients will ping you with SIGUSR2,
+** which must be ignored for this implementation.
+** Returns: 0 - ok, < 0 - error.
+**
+** An error return from ll_mail_lock carries some additional context in
+** errno:
+**
+** errno == EAGAIN: potential race condition.  The current lock holder MIGHT
+** have just terminated.  The caller should sleep for AT LEAST 5 seconds, then
+** try again.
+**
+** errno == EEXIST: another process on this server DEFINITELY has the lock.
+**
+** Implementations might choose to wait and try again on EEXIST as well.
+*/
+
+int ll_mail_lock(struct ll_mail *);
+
+/*
+** Open the mail file, read/write (creating a dot-lock).
+** Returns: >= 0 - file descriptor, < 0 - error (if EPERM, try ll_open_ro).
+**
+** errno == EEXIST: another process appears to hold a dot-lock.
+**
+** errno == EAGAIN: We just blew away a stale dotlock, should try again
+** in at least five seconds.  Should NOT get two EAGAIN's in a row.
+*/
+
+int ll_mail_open(struct ll_mail *);
+
+/*
+** Open in read-only mode.
+*/
+
+int ll_mail_open_ro(struct ll_mail *);
+
+/*
+** Release all locks, deallocate structure.  NOTE: file descriptor from
+** ll_mail_open(_ro)? is NOT closed, it's your responsibility to do that.
+*/
+
+void ll_mail_free(struct ll_mail *);
+
+/*
+** As long as we have the logic done already, here's a generic dot-locking
+** function.
+**
+** dotlock - the actual filename of a dotlock file.
+** tmpfile - the filename of a temporary file to create first.
+** timeout - optional timeout.
+**
+** Return code: 0: dotlock is created.  Just unlink(dotlock) when you're done.
+**
+** -1 error.  Check errno:
+**
+**    EEXIST - dotlock is locked
+**
+**    EAGAIN - dotlock is stale (dotlock created on this machine, and the
+**             process no longer exists, or dotlock created on another
+**             machine, and timeout argument was > 0, and the dotlock's
+**             timestamp was older than timeout seconds.
+**
+**    E????? - something's broken.
+**           
+*/
+
+int ll_dotlock(const char *dotlock, const char *tmpfile,
+	       int timeout);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif