RHCRC.cpp

/* Copyright (c) 2002, 2003, 2004  Marek Michalkiewicz
   Copyright (c) 2005, 2007 Joerg Wunsch
   All rights reserved.

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   modification, are permitted provided that the following conditions are met:

   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

   * 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.

   * Neither the name of the copyright holders nor the names of
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER OR CONTRIBUTORS BE
  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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//	Port to Energia / MPS430 by Yannick DEVOS XV4Y - (c) 2013
//	http://xv4y.radioclub.asia/
//	

// Adapted to RadioHead use by Mike McCauley 2014
// This is to prevent name collisions with other similar library functions
// and to provide a consistent API amonng all processors
//

/* $Id: RHCRC.cpp,v 1.1 2014/06/24 02:40:12 mikem Exp $ */

#include <RHCRC.h>

#define lo8(x) ((x)&0xff) 
#define hi8(x) ((x)>>8)

uint16_t RHcrc16_update(uint16_t crc, uint8_t a)
{
    int i;

    crc ^= a;
    for (i = 0; i < 8; ++i)
    {
	if (crc & 1)
	    crc = (crc >> 1) ^ 0xA001;
	else
	    crc = (crc >> 1);
    }
    return crc;
}

uint16_t RHcrc_xmodem_update (uint16_t crc, uint8_t data)
{
    int i;
    
    crc = crc ^ ((uint16_t)data << 8);
    for (i=0; i<8; i++)
    {
	if (crc & 0x8000)
	    crc = (crc << 1) ^ 0x1021;
	else
	    crc <<= 1;
    }
    
    return crc;
}

uint16_t RHcrc_ccitt_update (uint16_t crc, uint8_t data)
{
    data ^= lo8 (crc);
    data ^= data << 4;
    
    return ((((uint16_t)data << 8) | hi8 (crc)) ^ (uint8_t)(data >> 4) 
	    ^ ((uint16_t)data << 3));
}

uint8_t RHcrc_ibutton_update(uint8_t crc, uint8_t data)
{
    uint8_t i;
    
    crc = crc ^ data;
    for (i = 0; i < 8; i++)
    {
	if (crc & 0x01)
	    crc = (crc >> 1) ^ 0x8C;
	else
	    crc >>= 1;
    }
    
    return crc;
}