Mercurial > public > ostc4
view Discovery/Src/crcmodel.c @ 112:fdf0272e9213 FlipDisplay
Added new nvm parameter"FlipDisplay" indicating the screen orientation
author | Ideenmodellierer |
---|---|
date | Tue, 01 Jan 2019 21:03:33 +0100 |
parents | 5f11787b4f42 |
children |
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/******************************************************************************/ /* 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 */ /******************************************************************************/