From 35261f5208e90ac9a2f8474068b0419bde5ca6c8 Mon Sep 17 00:00:00 2001
From: adamdunkels <adamdunkels>
Date: Mon, 7 Jul 2008 23:24:36 +0000
Subject: [PATCH] Added a function for computing the CRC16 over a portion of
 data

---
 core/lib/crc16.c | 63 +++++++++++++++++++++++++++++-------------------
 core/lib/crc16.h | 19 ++++++++++++++-
 2 files changed, 56 insertions(+), 26 deletions(-)

diff --git a/core/lib/crc16.c b/core/lib/crc16.c
index cdb5a9f05..9be8317f9 100644
--- a/core/lib/crc16.c
+++ b/core/lib/crc16.c
@@ -1,34 +1,34 @@
 /*
  * Copyright (c) 2005, Swedish Institute of Computer Science
- * All rights reserved. 
+ * All rights reserved.
  *
- * Redistribution and use in source and binary forms, with or without 
- * modification, are permitted provided that the following conditions 
- * are met: 
- * 1. Redistributions of source code must retain the above copyright 
- *    notice, this list of conditions and the following disclaimer. 
- * 2. Redistributions in binary form must reproduce the above copyright 
- *    notice, this list of conditions and the following disclaimer in the 
- *    documentation and/or other materials provided with the distribution. 
- * 3. Neither the name of the Institute nor the names of its contributors 
- *    may be used to endorse or promote products derived from this software 
- *    without specific prior written permission. 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
  *
- * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
- * SUCH DAMAGE. 
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
  *
  * This file is part of the Contiki operating system.
  *
- * @(#)$Id: crc16.c,v 1.1 2006/06/17 22:41:17 adamdunkels Exp $
+ * @(#)$Id: crc16.c,v 1.2 2008/07/07 23:24:36 adamdunkels Exp $
  */
 
 /** \addtogroup crc16
@@ -39,7 +39,7 @@
  *         Implementation of the CRC16 calculcation
  * \author
  *         Adam Dunkels <adam@sics.se>
- * 
+ *
  */
 
 /* CITT CRC16 polynomial ^16 + ^12 + ^5 + 1 */
@@ -63,5 +63,18 @@ crc16_add(unsigned char b, unsigned short acc)
   return acc;
 }
 /*---------------------------------------------------------------------------*/
+unsigned short
+crc16_data(unsigned char *data, int len, unsigned short acc)
+{
+  int i;
+  unsigned short crc = 0;
+  
+  for(i = 0; i < len; ++i) {
+    crc = crc16_add(*data, crc);
+    ++data;
+  }
+  return crc;
+}
+/*---------------------------------------------------------------------------*/
 
 /** @} */
diff --git a/core/lib/crc16.h b/core/lib/crc16.h
index e7264bde4..827bf6d8c 100644
--- a/core/lib/crc16.h
+++ b/core/lib/crc16.h
@@ -50,7 +50,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * @(#)$Id: crc16.h,v 1.1 2006/06/17 22:41:17 adamdunkels Exp $
+ * @(#)$Id: crc16.h,v 1.2 2008/07/07 23:24:36 adamdunkels Exp $
  */
 #ifndef __CRC16_H__
 #define __CRC16_H__
@@ -73,6 +73,23 @@
  */
 unsigned short crc16_add(unsigned char b, unsigned short crc);
 
+/**
+ * \brief      Calculate the CRC16 over a data area
+ * \param data Pointer to the data
+ * \param datalen The length of the data
+ * \param crc  The accumulated CRC that is to be updated (or zero).
+ * \return     The CRC16 checksum.
+ *
+ *             This function calculates the CRC16 checksum of a data area.
+ *
+ *             \note The algorithm used in this implementation is
+ *             tailored for a running checksum and does not perform as
+ *             well as a table-driven algorithm when checksumming an
+ *             entire data block.
+ */
+unsigned short crc16_data(unsigned char *data, int datalen,
+			  unsigned short acc);
+
 #endif /* __CRC16_H__ */
 
 /** @} */