--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Discovery/Src/crcmodel.c	Sat Apr 28 11:52:34 2018 +0200
@@ -0,0 +1,137 @@
+/******************************************************************************/
+/*                             Start of crcmodel.c                            */
+/******************************************************************************/
+/*                                                                            */
+/* Author : Ross Williams (ross@guest.adelaide.edu.au.).                      */
+/* Date   : 3 June 1993.                                                      */
+/* Status : Public domain.                                                    */
+/*                                                                            */
+/* Description : This is the implementation (.c) file for the reference       */
+/* implementation of the Rocksoft^tm Model CRC Algorithm. For more            */
+/* information on the Rocksoft^tm Model CRC Algorithm, see the document       */
+/* titled "A Painless Guide to CRC Error Detection Algorithms" by Ross        */
+/* Williams (ross@guest.adelaide.edu.au.). This document is likely to be in   */
+/* "ftp.adelaide.edu.au/pub/rocksoft".                                        */
+/*                                                                            */
+/* Note: Rocksoft is a trademark of Rocksoft Pty Ltd, Adelaide, Australia.    */
+/*                                                                            */
+/******************************************************************************/
+/*                                                                            */
+/* Implementation Notes                                                       */
+/* --------------------                                                       */
+/* To avoid inconsistencies, the specification of each function is not echoed */
+/* here. See the header file for a description of these functions.            */
+/* This package is light on checking because I want to keep it short and      */
+/* simple and portable (i.e. it would be too messy to distribute my entire    */
+/* C culture (e.g. assertions package) with this package.                     */
+/*                                                                            */
+/******************************************************************************/
+
+#include "crcmodel.h"
+
+/******************************************************************************/
+
+/* The following definitions make the code more readable. */
+
+#define BITMASK(X) (1L << (X))
+#define MASK32 0xFFFFFFFFL
+#define LOCAL static
+
+/******************************************************************************/
+
+LOCAL ulong reflect P_((ulong v,int b));
+LOCAL ulong reflect (ulong v,int b)
+/* Returns the value v with the bottom b [0,32] bits reflected. */
+/* Example: reflect(0x3e23L,3) == 0x3e26                        */
+{
+ int   i;
+ ulong t = v;
+ for (i=0; i<b; i++)
+   {
+    if (t & 1L)
+       v|=  BITMASK((b-1)-i);
+    else
+       v&= ~BITMASK((b-1)-i);
+    t>>=1;
+   }
+ return v;
+}
+
+/******************************************************************************/
+
+LOCAL ulong widmask P_((p_cm_t));
+LOCAL ulong widmask (p_cm_t p_cm)
+/* Returns a longword whose value is (2^p_cm->cm_width)-1.     */
+/* The trick is to do this portably (e.g. without doing <<32). */
+{
+ return (((1L<<(p_cm->cm_width-1))-1L)<<1)|1L;
+}
+
+/******************************************************************************/
+
+void cm_ini (p_cm_t p_cm)
+{
+ p_cm->cm_reg = p_cm->cm_init;
+}
+
+/******************************************************************************/
+
+void cm_nxt (p_cm_t p_cm, int ch)
+{
+ int   i;
+ ulong uch  = (ulong) ch;
+ ulong topbit = BITMASK(p_cm->cm_width-1);
+
+ if (p_cm->cm_refin) uch = reflect(uch,8);
+ p_cm->cm_reg ^= (uch << (p_cm->cm_width-8));
+ for (i=0; i<8; i++)
+   {
+    if (p_cm->cm_reg & topbit)
+       p_cm->cm_reg = (p_cm->cm_reg << 1) ^ p_cm->cm_poly;
+    else
+       p_cm->cm_reg <<= 1;
+    p_cm->cm_reg &= widmask(p_cm);
+   }
+}
+
+/******************************************************************************/
+
+void cm_blk (p_cm_t p_cm,p_ubyte_ blk_adr,ulong blk_len)
+{
+ while (blk_len--) cm_nxt(p_cm,*blk_adr++);
+}
+
+/******************************************************************************/
+
+ulong cm_crc (p_cm_t p_cm)
+{
+ if (p_cm->cm_refot)
+    return p_cm->cm_xorot ^ reflect(p_cm->cm_reg,p_cm->cm_width);
+ else
+    return p_cm->cm_xorot ^ p_cm->cm_reg;
+}
+
+/******************************************************************************/
+
+ulong cm_tab (p_cm_t p_cm, int index)
+{
+ int   i;
+ ulong r;
+ ulong topbit = BITMASK(p_cm->cm_width-1);
+ ulong inbyte = (ulong) index;
+
+ if (p_cm->cm_refin) inbyte = reflect(inbyte,8);
+ r = inbyte << (p_cm->cm_width-8);
+ for (i=0; i<8; i++)
+    if (r & topbit)
+       r = (r << 1) ^ p_cm->cm_poly;
+    else
+       r<<=1;
+ if (p_cm->cm_refin) r = reflect(r,p_cm->cm_width);
+ return r & widmask(p_cm);
+}
+
+/******************************************************************************/
+/*                             End of crcmodel.c                              */
+/******************************************************************************/
+