--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tool/sii_crc.cpp	Tue Jul 22 14:17:20 2008 +0000
@@ -0,0 +1,50 @@
+/*****************************************************************************
+ *
+ * $Id$
+ *
+ ****************************************************************************/
+
+#include "sii_crc.h"
+
+/*****************************************************************************/
+
+/** Calculates the SII checksum field.
+ *
+ * The checksum is generated with the polynom x^8+x^2+x+1 (0x07) and an
+ * initial value of 0xff (see IEC 61158-6-12 ch. 5.4).
+ *
+ * The below code was originally generated with PYCRC
+ * http://www.tty1.net/pycrc
+ *
+ * ./pycrc.py --width=8 --poly=0x07 --reflect-in=0 --xor-in=0xff
+ *   --reflect-out=0 --xor-out=0 --generate c --algorithm=bit-by-bit
+ *
+ * \return CRC8
+ */
+uint8_t calcSiiCrc(
+        const uint8_t *data, /**< pointer to data */
+        size_t length /**< number of bytes in \a data */
+        )
+{
+    unsigned int i;
+    uint8_t bit, byte, crc = 0x48;
+
+    while (length--) {
+        byte = *data++;
+        for (i = 0; i < 8; i++) {
+            bit = crc & 0x80;
+            crc = (crc << 1) | ((byte >> (7 - i)) & 0x01);
+            if (bit) crc ^= 0x07;
+        }
+    }
+
+    for (i = 0; i < 8; i++) {
+        bit = crc & 0x80;
+        crc <<= 1;
+        if (bit) crc ^= 0x07;
+    }
+
+    return crc;
+}
+
+/*****************************************************************************/