Refactor BeRTOS to be in his own directory.

[bertos.git] / bertos / algo / rotating_hash.h

diff --git a/bertos/algo/rotating_hash.h b/bertos/algo/rotating_hash.h
new file mode 100644 (file)
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+++ b/bertos/algo/rotating_hash.h
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+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * 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>
+ */
+
+
+#ifndef ALGO_ROTATING_H
+#define ALGO_ROTATING_H
+
+#include <cfg/compiler.h>
+
+typedef uint16_t rotating_t;
+
+
+/**
+ * Init rotating checksum.
+ */
+INLINE void rotating_init(rotating_t *rot)
+{
+       *rot = 0;
+}
+
+/**
+ * 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 // ALGO_ROTATING_H