Diff: crc.h

Revision:

0:b5b370873460

Child:

1:df31097c8442

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/crc.h	Wed Apr 15 10:43:22 2015 +0000
@@ -0,0 +1,43 @@
+#define WIDTH 16
+#define TOPBIT (1 << 15) 
+#define POLYNOMIAL 0x1021
+
+class CRC{
+private:
+    typedef unsigned short int crctype; 
+public:
+    // no need of intializer
+    crctype crcGenerate(const char message[], int nBytes){
+        crctype remainder = 0xffff;
+        int byte;
+        char bit;
+        
+        for( byte = 0 ; byte < nBytes ; byte++ ){
+            /*
+            Bring the data byte by byte
+            each time only one byte is brought
+            0 xor x = x
+            */
+            remainder = remainder ^ ( message[byte] << (WIDTH-8) );
+            
+            for( bit = 8 ; bit > 0 ; bit--){
+                /*
+                for each bit, xor the remainder with polynomial
+                if the MSB is 1
+                */
+                if(remainder & TOPBIT){
+                    remainder = (remainder << 1) ^ POLYNOMIAL;
+                    /*
+                    each time the remainder is xor-ed with polynomial, the MSB is made zero
+                    hence the first digit of the remainder is ignored in the loop
+                    */
+                }
+                else{
+                    remainder = (remainder << 1);
+                }
+            }
+        }
+        
+        return remainder;
+    }
+};
\ No newline at end of file