/******************************************************************************//*                             Start of crcmodel.h                            *//******************************************************************************//*                                                                            *//* Author : Ross Williams (ross@guest.adelaide.edu.au.).                      *//* Date   : 3 June 1993.                                                      *//* Status : Public domain.                                                    *//*                                                                            *//* Description : This is the header (.h) 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.    *//*                                                                            *//******************************************************************************//*                                                                            *//* How to Use This Package                                                    *//* -----------------------                                                    *//* Step 1: Declare a variable of type cm_t. Declare another variable          *//*         (p_cm say) of type p_cm_t and initialize it to point to the first  *//*         variable (e.g. p_cm_t p_cm = &cm_t).                               *//*                                                                            *//* Step 2: Assign values to the parameter fields of the structure.            *//*         If you don't know what to assign, see the document cited earlier.  *//*         For example:                                                       *//*            p_cm->cm_width = 16;                                            *//*            p_cm->cm_poly  = 0x8005L;                                       *//*            p_cm->cm_init  = 0L;                                            *//*            p_cm->cm_refin = TRUE;                                          *//*            p_cm->cm_refot = TRUE;                                          *//*            p_cm->cm_xorot = 0L;                                            *//*         Note: Poly is specified without its top bit (18005 becomes 8005).  *//*         Note: Width is one bit less than the raw poly width.               *//*                                                                            *//* Step 3: Initialize the instance with a call cm_ini(p_cm);                  *//*                                                                            *//* Step 4: Process zero or more message bytes by placing zero or more         *//*         successive calls to cm_nxt. Example: cm_nxt(p_cm,ch);              *//*                                                                            *//* Step 5: Extract the CRC value at any time by calling crc = cm_crc(p_cm);   *//*         If the CRC is a 16-bit value, it will be in the bottom 16 bits.    *//*                                                                            *//******************************************************************************//*                                                                            *//* Design Notes                                                               *//* ------------                                                               *//* PORTABILITY: This package has been coded very conservatively so that       *//* it will run on as many machines as possible. For example, all external     *//* identifiers have been restricted to 6 characters and all internal ones to  *//* 8 characters. The prefix cm (for Crc Model) is used as an attempt to avoid *//* namespace collisions. This package is endian independent.                  *//*                                                                            *//* EFFICIENCY: This package (and its interface) is not designed for           *//* speed. The purpose of this package is to act as a well-defined reference   *//* model for the specification of CRC algorithms. If you want speed, cook up  *//* a specific table-driven implementation as described in the document cited  *//* above. This package is designed for validation only; if you have found or  *//* implemented a CRC algorithm and wish to describe it as a set of parameters *//* to the Rocksoft^tm Model CRC Algorithm, your CRC algorithm implementation  *//* should behave identically to this package under those parameters.          *//*                                                                            *//******************************************************************************//* The following #ifndef encloses this entire *//* header file, rendering it indempotent.     */#ifndef CM_DONE#define CM_DONE/******************************************************************************//* The following definitions are extracted from my style header file which    *//* would be cumbersome to distribute with this package. The DONE_STYLE is the *//* idempotence symbol used in my style header file.                           */#ifndef DONE_STYLEtypedef unsigned long   ulong;typedef unsigned        bool;typedef unsigned char * p_ubyte_;#ifndef TRUE#define FALSE 0#define TRUE  1#endif/* Change to the second definition if you don't have prototypes. */#define P_(A) A/* #define P_(A) () *//* Uncomment this definition if you don't have void. *//* typedef int void; */#endif/******************************************************************************//* CRC Model Abstract Type *//* ----------------------- *//* The following type stores the context of an executing instance of the  *//* model algorithm. Most of the fields are model parameters which must be *//* set before the first initializing call to cm_ini.                      */typedef struct  {   int   cm_width;   /* Parameter: Width in bits [8,32].       */   ulong cm_poly;    /* Parameter: The algorithm's polynomial. */   ulong cm_init;    /* Parameter: Initial register value.     */   bool  cm_refin;   /* Parameter: Reflect input bytes?        */   bool  cm_refot;   /* Parameter: Reflect output CRC?         */   ulong cm_xorot;   /* Parameter: XOR this to output CRC.     */   ulong cm_reg;     /* Context: Context during execution.     */  } cm_t;typedef cm_t *p_cm_t;/******************************************************************************//* Functions That Implement The Model *//* ---------------------------------- *//* The following functions animate the cm_t abstraction. */void cm_ini P_((p_cm_t p_cm));/* Initializes the argument CRC model instance.          *//* All parameter fields must be set before calling this. */void cm_nxt P_((p_cm_t p_cm,int ch));/* Processes a single message byte [0,255]. */void cm_blk P_((p_cm_t p_cm,p_ubyte_ blk_adr,ulong blk_len));/* Processes a block of message bytes. */ulong cm_crc P_((p_cm_t p_cm));/* Returns the CRC value for the message bytes processed so far. *//******************************************************************************//* Functions For Table Calculation *//* ------------------------------- *//* The following function can be used to calculate a CRC lookup table.        *//* It can also be used at run-time to create or check static tables.          */ulong cm_tab P_((p_cm_t p_cm,int index));/* Returns the i'th entry for the lookup table for the specified algorithm.   *//* The function examines the fields cm_width, cm_poly, cm_refin, and the      *//* argument table index in the range [0,255] and returns the table entry in   *//* the bottom cm_width bytes of the return value.                             *//******************************************************************************//* End of the header file idempotence #ifndef */#endif/******************************************************************************//*                             End of crcmodel.h                              *//******************************************************************************/