Add rotating hash algorithm.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@793 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/algos/rotating_hash.h b/algos/rotating_hash.h
new file mode 100755 (executable)
index 0000000..d307c5c
--- /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