Zoltan Hudak / CRC16

Implementation of CRC16 using polynomial 0x8005 = X^16 + X^15 + X^2 + 1

Dependents:   Manchester_Transmitter Manchester_Receiver ManchesterUART_Transmitter ManchesterUART_Receiver

Fork of CRC16 by Emilie Laverge

Files at this revision

API Documentation at this revision

Revision 3:3f5622979e77, committed 2017-09-03

Comitter:
hudakz
Date:
Sun Sep 03 08:28:01 2017 +0000
Parent:
2:a01521fb2fe1
Commit message:
Function parameter added for setting initial CRC value. Defaults to 0x0000.

Changed in this revision

CRC16.cpp Show annotated file Show diff for this revision Revisions of this file
CRC16.h Show annotated file Show diff for this revision Revisions of this file 
--- a/CRC16.cpp	Mon May 22 09:32:41 2017 +0000
+++ b/CRC16.cpp	Sun Sep 03 08:28:01 2017 +0000
@@ -1,6 +1,8 @@
 /*
  * This is a fork of the CRC16 library COPYRIGHT(c) Emilie Laverge
  * published at [https://developer.mbed.org/users/EmLa/code/CRC16/]
+ * using the polynomial 0x8005: X^16 + X^15 + X^2 + 1.
+ * Default initial CRC value = 0xFFFF
  *
  * Modified by Zoltan Hudak
  */
@@ -44,13 +46,14 @@
     0x8213, 0x0216, 0x021C, 0x8219, 0x0208, 0x820D, 0x8207, 0x0202
 };
 
-unsigned short CRC16::calc(char input[], int length) {
-    unsigned short  result = 0;
+unsigned short CRC16::calc(char input[], int length, unsigned short crc /*=0x0000*/) {
     for(int i = 0; i < length; i++) {
-        unsigned short  tableValue = TABLE[((result >> 8) ^ *(char*)input++) & SHIFTER];
-        result = (result << 8) ^ tableValue;
+        unsigned short  tableValue = TABLE[((crc >> 8) ^ *(char*)input++) & SHIFTER];
+        crc = (crc << 8) ^ tableValue;
     }
 
-    return result;
+    return crc;
 }
 
+
+

--- a/CRC16.h	Mon May 22 09:32:41 2017 +0000
+++ b/CRC16.h	Sun Sep 03 08:28:01 2017 +0000
@@ -1,6 +1,8 @@
 /*
  * This is a fork of the CRC16 library COPYRIGHT(c) Emilie Laverge
  * published at [https://developer.mbed.org/users/EmLa/code/CRC16/]
+ * using the polynomial 0x8005: X^16 + X^15 + X^2 + 1.
+ * Default initial CRC value = 0x0000
  *
  * Modified by Zoltan Hudak
  */
@@ -14,8 +16,8 @@
     static const unsigned int   SHIFTER;
     static const unsigned short TABLE[];
 public:
-    CRC16(void) { };
-    ~CRC16(void){ };
-    unsigned short  calc(char input[], int length);
+    CRC16(void){};
+    ~CRC16(void){};
+    unsigned short calc(char input[], int length, unsigned short crc = 0x0000);
 };
 #endif // CRC16_H