/* ---------------------------------------------------------------------------
 * Crc.c - v0.1                                (c) 2008 Micro-key bv
 * ---------------------------------------------------------------------------
 * Micro-key bv
 * Industrieweg 28, 9804 TG Noordhorn
 * Postbus 92, 9800 AB Zuidhorn
 * The Netherlands
 * Tel: +31 594 503020
 * Fax: +31 594 505825
 * Email: support@microkey.nl  
 * Web: www.microkey.nl
 * ---------------------------------------------------------------------------
 * Description: 
 * ---------------------------------------------------------------------------
 * Version(s):  0.1, Jan 31, 2008, FSc
 *                   Creation.
 * ---------------------------------------------------------------------------
 */

/* ---------------------------------------------------------------------------
 * System include files
 * ---------------------------------------------------------------------------
 */

/* ---------------------------------------------------------------------------
 * Application include files
 * ---------------------------------------------------------------------------
 */
#include "crc.h"

/* ---------------------------------------------------------------------------
 * Local constant and macro definitions
 * ---------------------------------------------------------------------------
 */
const UINT16 CRC_table[256] =
{
       0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
       0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
       0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
       0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
       0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
       0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
       0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
       0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
       0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
       0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
       0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
       0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
       0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
       0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
       0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
       0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
       0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
       0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
       0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
       0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
       0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
       0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
       0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
       0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
       0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
       0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
       0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
       0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
       0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
       0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
       0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
       0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};

/* ---------------------------------------------------------------------------
 * Global variable definitions
 * ---------------------------------------------------------------------------
 */

/* ---------------------------------------------------------------------------
 * Local variable definitions
 * ---------------------------------------------------------------------------
 */

/* ---------------------------------------------------------------------------
 * Local function definitions
 * ---------------------------------------------------------------------------
 */

/*!
* \brief Calculate 16 bit CRC
*
*	a function to calculate an serial 16 bit CRC 
*	according to the CCITT V.024 standard 
*	To short down the calculation time of the serial CRC
*	a hash table is used.
*	This CRC is a fast (with hash table) and good CRC for
*	data transfer and integrity test of data storage. It can effectively
*	can detect errors by data transfer. 16 Bit is good for data blocks from 
*	0 - 4 KByte with a residual risk for non detection of 10E-8 per transfer.
*	(Multiply this with the error factor of the transmit line)
*
*   The polynoom of CRC-16-CCIT = x^16 + x^12 + x^5 + 1
*
* \param data 	Build the crc from this data block
* \param length  Length of the data block
* \param feed    Initial CRC value (take 0 by default)
*/
UINT16 crcCalc(UINT8 * data, UINT32 length, UINT16 feed)
{
	unsigned short  crc = feed;
    unsigned char   index;
	unsigned int    count;
	
	for(count=0; count<length; count++) 
	{
		index = (unsigned char)(crc >> 8);
		crc = crc & 0x00FF;
		crc = (crc << 8);
		crc &= 0xFF00;
		crc = crc ^ CRC_table[index] ^ (*data & 0x00FF);
		data++;
   	}

	return crc;
}