+ if (length == 0)
+ return (~crc);
+
+ do
+ {
+ for (i=0, data=(unsigned int)0xff & *data_p++;
+ i < 8;
+ i++, data >>= 1)
+ {
+ if ((crc & 0x0001) ^ (data & 0x0001))
+ crc = (crc >> 1) ^ POLY;
+ else crc >>= 1;
+ }
+ } while (--length);
+
+ crc = ~crc;
+ data = crc;
+ crc = (crc << 8) | (data >> 8 & 0xff);
+ crc = crc ^ 0xBC3;
+ return (crc);
+}