From 8dc518b4bd7884157a6d6f1f510bac2583ffe502 Mon Sep 17 00:00:00 2001
From: batt <batt@38d2e660-2303-0410-9eaa-f027e97ec537>
Date: Thu, 7 Jun 2007 09:11:17 +0000
Subject: [PATCH] Add rotating hash algorithm.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@793 38d2e660-2303-0410-9eaa-f027e97ec537
---
 algos/rotating_hash.h | 57 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100755 algos/rotating_hash.h

diff --git a/algos/rotating_hash.h b/algos/rotating_hash.h
new file mode 100755
index 00000000..d307c5ca
--- /dev/null
+++ b/algos/rotating_hash.h
@@ -0,0 +1,57 @@
+/**
+ * \file
+ * <!--
+ * Copyright 2007 Develer S.r.l. (http://www.develer.com/)
+ * All Rights Reserved.
+ * -->
+ *
+ * \brief Rotating Hash algorithm (interface).
+ *
+ * This is a simple yet powerfull checksum algorithm.
+ * Instead of just xor-ing the data, rotating hash
+ * circular shift the checksum 4 place left before xoring.
+ * This is a bit more stronger than simply sum the data.
+ *
+ * \version $Id$
+ *
+ * \author Francesco Sacchi <batt@develer.com>
+ */
+
+/*#*
+ *#* $Log$
+ *#* Revision 1.1  2007/06/07 09:11:17  batt
+ *#* Add rotating hash algorithm.
+ *#*
+ *#* Revision 1.1  2007/01/12 20:30:49  batt
+ *#* Add right Rotating hash file.
+ *#*
+ *#*/
+
+#ifndef ALGOS_ROTATING_H
+#define ALGOS_ROTATING_H
+
+#include <cfg/compiler.h>
+
+typedef uint16_t rotating_t;
+
+/**
+ * Update checksum pointed by \c rot with \c c data.
+ */
+INLINE void rotating_update1(uint8_t c, rotating_t *rot)
+{
+	*rot = (*rot << 4) ^ (*rot >> 12) ^ c;
+}
+
+/**
+ * Update checksum pointed by \c rot with data supplied in \c buf.
+ */
+INLINE void rotating_update(const void *_buf, size_t len, rotating_t *rot)
+{
+	const uint8_t *buf = (const uint8_t *)_buf;
+
+	while (len--)
+		rotating_update1(*buf++, rot);
+}
+
+
+#endif // ALGOS_ROTATING_H
-- 
2.25.1