/* adbfcrc.c */

/*
addbfcrc() accepts a buffer address and a count and adds the CRC for
all bytes in the buffer to the global variable crccode using
CRC-16.

CRC computation algorithm taken from source code for ARC 5.12, which
in turn took it from an article by David Schwaderer in the April 1985
issue of PC Tech Journal.

I claim no copyright over the contents of this file.

                                    -- Rahul Dhesi 1986/12/31
*/

unsigned int crccode;
unsigned int crctab[] = {
   0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241, 0xc601, 
   0x06c0, 0x0780, 0xc741, 0x0500, 0xc5c1, 0xc481, 0x0440, 0xcc01, 0x0cc0, 
   0x0d80, 0xcd41, 0x0F00, 0xcFc1, 0xce81, 0x0e40, 0x0a00, 0xcac1, 0xcb81, 
   0x0b40, 0xc901, 0x09c0, 0x0880, 0xc841, 0xd801, 0x18c0, 0x1980, 0xd941, 
   0x1b00, 0xdbc1, 0xda81, 0x1a40, 0x1e00, 0xdec1, 0xdF81, 0x1F40, 0xdd01, 
   0x1dc0, 0x1c80, 0xdc41, 0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0, 
   0x1680, 0xd641, 0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081, 
   0x1040, 0xF001, 0x30c0, 0x3180, 0xF141, 0x3300, 0xF3c1, 0xF281, 0x3240, 
   0x3600, 0xF6c1, 0xF781, 0x3740, 0xF501, 0x35c0, 0x3480, 0xF441, 0x3c00, 
   0xFcc1, 0xFd81, 0x3d40, 0xFF01, 0x3Fc0, 0x3e80, 0xFe41, 0xFa01, 0x3ac0, 
   0x3b80, 0xFb41, 0x3900, 0xF9c1, 0xF881, 0x3840, 0x2800, 0xe8c1, 0xe981, 
   0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41, 0xee01, 0x2ec0, 0x2F80, 0xeF41, 
   0x2d00, 0xedc1, 0xec81, 0x2c40, 0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 
   0xe7c1, 0xe681, 0x2640, 0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0, 
   0x2080, 0xe041, 0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 
   0x6240, 0x6600, 0xa6c1, 0xa781, 0x6740, 0xa501, 0x65c0, 0x6480, 0xa441, 
   0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaF01, 0x6Fc0, 0x6e80, 0xae41, 0xaa01, 
   0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840, 0x7800, 0xb8c1, 
   0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41, 0xbe01, 0x7ec0, 0x7F80, 
   0xbF41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40, 0xb401, 0x74c0, 0x7580, 0xb541, 
   0x7700, 0xb7c1, 0xb681, 0x7640, 0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 
   0x71c0, 0x7080, 0xb041, 0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0, 
   0x5280, 0x9241, 0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 
   0x5440, 0x9c01, 0x5cc0, 0x5d80, 0x9d41, 0x5F00, 0x9Fc1, 0x9e81, 0x5e40, 
   0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841, 0x8801, 
   0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40, 0x4e00, 0x8ec1, 
   0x8F81, 0x4F40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41, 0x4400, 0x84c1, 0x8581, 
   0x4540, 0x8701, 0x47c0, 0x4680, 0x8641, 0x8201, 0x42c0, 0x4380, 0x8341, 
   0x4100, 0x81c1, 0x8081, 0x4040 
};

int addbfcrc(buffer,count)
char *buffer;
int count;

{
   register unsigned int localcrc;
   register int i;
   localcrc = crccode;

   for (i=0; i<count; i++)
      localcrc = (localcrc>>8) ^ crctab[(localcrc ^ (buffer[i])) & 0x00ff];
   crccode = localcrc;
}