1 files changed, 68 insertions, 0 deletions
diff --git a/lib/util/idtree_random.c b/lib/util/idtree_random.c
new file mode 100644
index 0000000..d22245a
--- /dev/null
+++ b/lib/util/idtree_random.c
@@ -0,0 +1,68 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   very efficient functions to manage mapping a id (such as a fnum) to
+   a pointer. This is used for fnum and search id allocation.
+
+   Copyright (C) Andrew Tridgell 2004
+
+   This code is derived from lib/idr.c in the 2.6 Linux kernel, which was
+   written by Jim Houston jim.houston@ccur.com, and is
+   Copyright (C) 2002 by Concurrent Computer Corporation
+
+   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; either version 2 of the License, or
+   (at your option) any later version.
+
+   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, see <http://www.gnu.org/licenses/>.
+*/
+
+/*
+  see the section marked "public interface" below for documentation
+*/
+
+/**
+ * @file
+ */
+
+#include "replace.h"
+#include "samba_util.h" /* generate_random() */
+#include "idtree.h"
+#include "idtree_random.h"
+
+/**
+  allocate a new id randomly in the given range
+*/
+_PUBLIC_ int idr_get_new_random(struct idr_context *idp,
+				void *ptr,
+				int starting_id,
+				int limit)
+{
+	int id;
+
+	/* first try a random starting point in the whole range, and if that fails,
+	   then start randomly in the bottom half of the range. This can only
+	   fail if the range is over half full, and finally fallback to any
+	   free id */
+	id = idr_get_new_above(
+		idp, ptr, starting_id+(generate_random() % limit), limit);
+	if (id == -1) {
+		id = idr_get_new_above(
+			idp,
+			ptr,
+			starting_id+(generate_random()%(limit/2)),
+			limit);
+	}
+	if (id == -1) {
+		id = idr_get_new_above(idp, ptr, starting_id, limit);
+	}
+
+	return id;
+}